An Optimal Current Controller Design for a Grid Connected ...

Research ArticleAn Optimal Current Controller Design fora Grid Connected Inverter to Improve Power Qualityand Test Commercial PV Inverters

Ali Algaddafi Saud A Altuwayjiri Oday A Ahmed and Ibrahim Daho

Electrical Electronics Engineering Department Sirte University Sirte Libya

Correspondence should be addressed to Ali Algaddafi alisirteyahoocom

Received 19 December 2016 Revised 1 March 2017 Accepted 2 April 2017 Published 30 April 2017

Academic Editor Chi-Wai Chow

Copyright copy 2017 Ali Algaddafi et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Grid connected inverters play a crucial role in generating energy to be fed to the grid A filter is commonly used to suppress theswitching frequency harmonics produced by the inverter this being passive and either an L- or LCL-filterThe latter is smaller in sizecompared to the L-filter But choosing the optimal values of the LCL-filter is challenging due to resonance which can affect stabilityThis paper presents a simple inverter controller design with an L-filter The control topology is simple and applied easily usingtraditional control theory Fast Fourier Transform analysis is used to compare different grid connected inverter control topologiesThe modelled grid connected inverter with the proposed controller complies with the IEEE-1547 standard and total harmonicdistortion of the output current of the modelled inverter has been just 025 with an improved output waveform Experimentalwork on a commercial PV inverter is then presented including the effect of strong and weak grid connection Inverter effects onthe resistive load connected at the point of common coupling are presented Results show that the voltage and current of resistiveload when the grid is interrupted are increased which may cause failure or damage for connecting appliances

1 Introduction

Understanding the grid code requirements is very importantin grid connected inverter A grid connected inverter is a solarsystem that works in parallel with the grid [1] The electricitythat is generated by photovoltaic (PV) panels can be exportedto the grid or used by the local load A storage using forexample batteries is not included with clear cost benefitsover stand-alone renewable installations PV generation isbecoming increasingly widespread According to the authorsin [1 2] a solar PV system is the third most important ofrenewable energy after hydro- and wind power WorldwidePV capacity was approximately 70GW in 2011 Europe is thelargest PV energy producer with capacity 51 GW followed byJapan (5GW) and then the USA (44GW) China (31 GW)Australia (13 GW) and India (0466GW) [1 2] PV gener-ation has been implemented in many developing countriesThose regions have a large subbelt and could have 1100GWinstalled capacity by the year 2030 [3] As PV generationcapacity increases guidelines or standards will be needed

to govern the import and export of power to and from thegrid and their importance will increase Many organisationsare dealing with PV codes and safety standards such asthe Institute of Electrical and Electronic Engineering stan-dard (IEEE-1547) and the International Electro-TechnicalCommission standard (IEC-61727) In this paper the gridconnected inverter is used to connect solar panels to the gridIn other words inverters form a crucial link in renewableenergy systems between the generating components suchas wind turbines solar photovoltaic and the rest of thegrid Full bridge DCAC topologies are commonly used ingrid connected inverters with a high switching frequency(eg 15000Hz) The harmonics generated by high switchingfrequency however limit the efficiency of grid connectedinverters An LCL-filter is usually used to mitigate the lim-itations and satisfying required grid standards [4] Howeverthe virtual impedance of the grid network and the interactionbetween the main elements of the LCL-filter make designingan effective controller challenging due to high peak gainat the resonant frequency Some methods and techniques

Hindawie Scientific World JournalVolume 2017 Article ID 1393476 13 pageshttpsdoiorg10115520171393476

2 The Scientific World Journal

were developed to overcome this issue and to improve thesteady state and the transient response of the grid connectedinverter including repeat control proportional resonant anddeadbeat control [4ndash7] Channegowda and John [8] used adamping resistor to reduce LCL-filter resonance althoughthis was successful damping resistor power losses were highenough to affect inverter efficiency The upshot being that atthe time of wiring the LCL-filter in this application still haspoor dynamic performance

PV inverters should have certain design features intrin-sically included such as Maximum Power Point Tracking(MPPT) anti-island power factor correction harmonicreduction and fault ride through [4] Solar PV generationoffers clear environmental advantages being almost com-pletely pollution-free at the point of generation and unlikesome other forms of renewable generation is silent makingit eminently suitable for residential areas too [1] Distributedgeneration using PV system is also advantageous in countrieswhere traditional heavy grid infrastructure is not in placeThe requirement for small distributed power generationsystems is low cost high efficiency and tolerance for a widerange of input voltage variations The inverter can be a singlestage or multiple stages Single stage inverters convert DCdirectly to AC with no intermediate stage Two-stage invert-ers take the form of a DC-DC converter followed by aDC-ACinverter [9ndash12] Single stage inverters offer simple structureand low cost but multiple stage inverters can accommodate awider range of input voltages For multiple (eg DCDC andDCAC converter) stages inverters complexity and cost areincreased and efficiency is lower [1 9]

The L-filter is suitable for an inverter with a high switch-ing frequency this being a first-order filter with 20 dBdecadeoverall frequencyThe dynamic interaction between invertersthat use L-filters is less than it is between the inverterswith LC- or LCL-filters Also variation in environmentalconditions can result in the generation of a nonsinusoidalcurrent to the network that may cause a voltage drop anddistortion across it Liang et al presented voltage distortionanalysis [13] however their study did not include analysisof current at the point of common coupling (PCC) ThePV inverters are limited by several factors including theweak grid connection island mode connection and theinteraction between different PV inverters The island modeconnection can be dangerous to utility workers and mayprevent utility interface with G59 protection to reconnect thenetwork with the PV system This requires developing ananti-islanding mode connection to stop producing power tothe main grid However the anti-islanding mode connectionmay cause events of the power shortage (a blackout) Abackup inverter can overcome this limitation The backupinverter is used to supply the critical load and does notfeed the grid This is because the utility interface with G59protection contains a Voltage Monitoring Detection (egVMD460) relay which is an external network and systemprotection This relay is used to disconnect the public gridwith the PV generator in events of unacceptable thresholdvalues The VMD460 relay is a device that monitors the gridvoltage and frequency and when the voltage and frequencyof the source energy are in the acceptable threshold then

the VMD460 relay allows reconnecting with the public gridHowever an interaction is likely to occur if multiple PVinverters are connected Therefore the AC Mini-Grid canbe used to improve the performance of the system whichincludes multiple PV inverters Harmonic interference oflarge population of inverters was analysed by Enslin et al [14]The resonance between the PV inverter and existing networkcomponents was discussed It was found that the outputinverter impedance should be high since it is a functionof frequency and it gives an unpolluted sinusoidal currentwaveform The study assumed that most house applianceswould be capacitive loads and these tend to be inductive Xueet al provided an overview of future development trends forinverters [15] Taking that case reliability improvements willbe needed It wasmentioned that in the future the PV invert-ers are required to power ancillary service in the distributiongrid In general PV inverter design criteria will includeflicker mitigation unbalanced compensation active loadbalancing power active filter harmonic filtering voltage sagand swell mitigation control voltage Anti-island detectionwas also identified as a challenge and it should be possible todistinguish between permanent power outages and transientfalls and provide an appropriate response in each caseThe limitations of these studies were presented with criticalreviews by Algaddafi et al [16] A new method to determinethe inverter output impedance and grid impedance waspresented by Sun [3] who argued that high output impedancefor a grid connected inverter enables successful operationwith a wider range of grid impedances Other issues whichwould also be important include grid parallel inverter controloutput filter anddamping themethodof synchronising to thegrid and optimising output impedance

In recent a multiple inverter using Nortonrsquos equivalentcircuits was modelled by He et al [17] discussing theinteraction of parallel inverters The multiple PV inverterbased Micro-Grid system presented a more challenging pic-ture where the PV inverters interaction will cause complexresonance at various frequencies so the output current willbe distorted even when the control design and filter circuitare accurately designed for a single inverter

A physical PV array has several limitations as it dependson the weather conditions for outdoor testing and requiresa large space and cooling system for indoor testing A PVarray emulator (PVAE) with a fast response offers a potentialsolution The currently available power electronic PVAEshave a slow response time This can be overcome by using aseries regulator with a robust control The nonlinearity of theCurrent-Voltage (I-V) and Power-Voltage (P-V) curve gen-erator of a PVAE is also challenging and the characteristicsof this will vary with solar insolation ambient temperatureand output voltage [12] This can be overcome by using ananalogue computation circuit as presented in [18] Howeverthe PVAE that presented in [18] requires a cooling systemwhere with high load or high power the system may beunstable and the performance of PVAE will deteriorateTherefore the PVAE is unsuitable to operate Sunny Boy(SB 1700E) at the present time even though it can be usedwith small power such as Sunny Boy 700 inverter For thesimplicity and availability the commercial PV inverter which

The Scientific World Journal 3

minusminus

inv grid

iout

++

L

(a)

훿

VL

Vinv

Vgrid

Iout

(b)

Figure 1 Grid connected inverter (a) equivalent circuit and (b) phasor diagram

is SB 1700E inverter was initially tested with a Theveninsource in this paperTheoperation of the single phase inverteris described as an equivalent circuit of the grid connectedinverter which helps to understand the behaviour of the PVinverter The dynamic model of the inverter does not appearto be adequately discussed to date Equation (1) is commonlyused to study the behaviour of the PV inverter and to find thephase angle [19]

100381610038161003816100381610038161198812119871 10038161003816100381610038161003816 = 100381610038161003816100381610038161198812inv10038161003816100381610038161003816 + 100381610038161003816100381610038161198812grid10038161003816100381610038161003816 minus 2 10038161003816100381610038161003816119881grid10038161003816100381610038161003816 1003816100381610038161003816119881inv1003816100381610038161003816 cos 120575 (1)

where 119881119871is the voltage drop on the inductor 119881inv is the

inverter voltage 119881grid is the grid voltage and 120575 is the loadangle Figure 1 shows the equivalent circuit of the inverterconnected to the main grid and a phasor diagram of the gridconnected inverter The phasor diagram is used to explainthe circuit performance of the PV inverter When the loadangle (120575) is equal to zero the grid voltage is equal to theoutput inverter voltage Thus the active power will be zeroTherefore the amplitude of the inverter voltage should behigher than the utility network voltage The load angle (120575) isused to control the active power (119875) and the reactive power(119876) injected into the grid per (2) and (3) below [20]

119875 = 119881grid119908119871 (119881inv sin 120575) (2)

119876 = 119881grid119908119871 (119881inv cos 120575 minus 119881grid) (3)

119881119871= 119895119908119871119868

119900 (4)

where 119908 = 2120587119891119871 is the reactance of the inductor connectedbetween the grid and the inverter The power factor (PF)which is cos120593 is affected by three elements including theload angle the inverter voltage and the voltage drop on theinductor119881inv sin 120575 = 119881119871 cos120593 if the PF approaches one knownas the unit PF the output voltage and the output currentwill be in phase This analysis assumes no losses in switchingpower electronic whichmeans ideal switchesMany invertersintend to operate at unity PF The modulation index ratiocould be calculated by dividing the output inverter voltage by

the DC input voltage The modulation index (119898) is definedas the ratio between the fundamental components of theinverter voltage (119881inv) and theDC input voltage of the inverter(119881DC) This can be given by [18]

119898 = 119881inv119881DC (5)

The phase difference between119881inv and119881grid is the angle 120575Theinverter voltage and the load angle can be estimated by using(6) and (7) respectively under the condition of inverter workat unity power factor [18]

119881inv = radic(1198812119871 + 1198812grid) (6)

120575 = tanminus1 ( 119881119871119881grid) (7)

This mathematical approach and theory will help to designopen loop grid connected inverter To summarise in generalthe harmonic components are required to be filtered whetherby using the passive filter or the active filter The latteruses extra switches and may bring extra loss and also itis a complex [21ndash23] The passive filters could be L-filterLC-filter LCL-filter and LLCL-filter The higher order suchas LCL-filter or LLCL-filter may suffer from the resonanceoscillation [21 24ndash26] Therefore in order to overcome theabove limitations this paper presents a simple method todesign an optimal control of a grid connected inverter withan L-filter It is organised as follows a configuration andthe numerical modelling of the grid connected inverter withoptimal design control are discussed in Section 2 In additionSection 2 presents the simulation and experimental setupto investigate the grid connected inverter for a weak gridcompared to a strong grid connection Section 3 discusses theacquired numerical and experimental resultsThe last sectiondraws the conclusions and future work

2 Configuration and Modelling ofthe Grid Connected Inverter

It is necessary to consider the requirements of the gridand how a single connected inverter interacts with this


ScopeCurrent

1 2

From

g

A

B

DCAC inverter

Goto

Linear transformer

[PWM]

[PWM]

SPWM generator

Pulses

minus+

minus

+i

DC = 300 v10mH amp 033Ω

Grid = 230V (Vrms)

+

+ +

+

+

Figure 2 Open loop circuit diagram of the DCAC grid connected inverter

A mathematical modelling of a grid converter which wasfollowed by designing an optimal controller to improveoverall power quality was developed Experimentation forthis work was carried out using a commercial PV inverterin this case the Sunny Boy 1700E inverter was utilised

21 Simulation Part The simulation section includes a nu-merical model of grid connected inverter with open loopcircuit and then designing the optimal controller of the samecircuit of grid connected inverter

211 Grid Connected Inverter in the Open Loop Circuit Theinverter can be configured as a stand-alone inverter supplyinga local load a grid connected or a bidirectional inverter Thegrid connected inverter is considered in this paperThe utilitynetwork is defined as the infinite busbar which has a constantvoltage and a constant frequency The grid synchronisationis very necessary for the grid connected inverter It can beachieved by using a phase locked loop [4] In this study thedesired current 119868ref is given in

119868ref = 12 sin (wt) (8)

The open loop control of the grid connected inverter wasmodelled theoretically and simulated in Simulink accordingto the assumptions listed in Table 1 with the theory describedin the previous section The voltage drop on the inductor Lwas calculated by (4) The modulation index was determinedby dividing the inverter voltage by the DC input voltageaccording to (5) The inverter voltage was estimated by (6)Load angle was calculated by (7) The outcomes of theseequations are as follows the modulation index = 0658 theload angle 120575 = 659∘ and the inductor voltage 119881

119871= 37V

These results were calculated theoretically thus the sim-ulation model should provide the same results to validatethe model The modelling of the power circuit consistsof a constant DC source a universal bridge an L-filter

Table 1 Assumption to model grid connected inverter

Electrical parameters ValueDC voltage source 300VAC voltage source 230V 50HzSwitching frequency 15 kHzInductor 10mHOutput current 12 AParasitic resistance 033ΩTurn ratio of linear transformer 06

a linear transformer and an AC voltage source The lineartransformer has two features Firstly it provides galvanicisolation of the DC components and secondly it can boostthe voltage level to match the grid voltageThe control circuitused a pulse width modulation generator block which wasinserted into the modulation index the carrier frequencythe phase angle 120575 and the output grid frequency Thepredicted inverter output voltage and the inductor voltagewere acquired between terminals A and B of the universalbridge as shown in Figure 2 By using Fast Fourier Transform(FFT) analysis the fundament inverter voltage was foundto be 197V whereas the inductor fundamental voltage wasfound to be 37V

Figure 3 shows the predicted output current of theinverter where the current value is nearly 12 A and thefrequency is 50Hz This can validate the open loop controlof the grid connected inverter where the output current issymmetrical to the assumed reference current

The following section focuses on the design of the controlsystem for the grid connected inverter using the single-inputsingle-output in MATLAB This is done by assuming idealswitching of the full bridge converter where the L-filterwith its parasitic resistance is used to design the optimalcompensator


003 004 005 006 007 008002Time (s)

minus15

minus10

minus5

0

5

10

15

Curr

ent (

A)

Figure 3 Output current of the DCAC grid connected inverter

212 Proposed Grid Connected Inverter with L-Filter andFeedback Controller Here the grid connected inverter alongwith its controller design is modelled numerically andProportional-Integral-Derivative (PID) methods are inves-tigated The aim is to find the optimal controller methodby observing the resultant total harmonic distortion (THD)Figure 4 shows the modelled grid connected inverter witha feedback controller The output current was comparedwith the reference current and then passed through the PIDcontroller blockThe reference currentwas set to 12A at 50Hzand the phase offset was set to zero In the same manner thegrid voltage the frequency and the phase offset were set to230V 50Hz and 0 respectively As a result the referencecurrent is in phase with the grid voltage It is assumed thatthe grid is a strong grid with no harmonic generated by thegrid impedance

213 L-Filter An L-filter is suitable for inverters which havehigh switching frequency It can be designed easily accordingto

119875119900= 119881grid119883L radic119881

2

dc minus 1198812grid (9)

where 119875119900is the output power 119881dc is the voltage DC link119881grid is the grid voltage for the single phase and 119883L is the

reactance of the L-filter which determines the value of theinductor according to the switching frequency The ripplecurrent injected into the gridmust be less than 3of the ratedcurrent

An L-filter can be readily optimised according to (9)The impact of variation of DC voltage and inductor on thepower of the inverter is shown in Figure 5 where this figurepresents the output power as a function of DC voltage andinductor inductanceTherefore the selected L-filter is a trade-off between the harmonic required cost and required outputpower

22 Experimental Part The experimental work presents asimple procedure to test a commercial PV inverter andimpact of interrupt network and SB 1700E inverter on the

resistive load along with testing the speed response of PVinverter

221 Requirements to Test the SB 1700E Inverter Experimen-tally and Testing a Weak Grid Connection A PV inverterrequires the real PV array and themain gridHowever the useof the real PV array in the laboratory may be impractical dueto limitations mentioned above Ideally a PVAE is requiredto operate the PV inverter at the maximum power point(MPP) A Thevenin voltage source was initially used to testSB 1700E inverter Thevenin source is a voltage source and aseries resistor as shown in Figure 6 The PV inverter can beconnected between the terminals A and B in order to test theinverter experimentally

The SB 1700E inverter was connected to the Theveninsource to investigate the behaviour of the inverter and alsothis experiment aimed to understand the equipment perfor-mance and connection devices such as the series resistance(119877119904) DC supply voltage and the power system analyser

(PA2100) The SB 1700E inverter was tested when the inputvoltage 119877

119904 and the additional inductor line were varied

According to the manual description of the SB 1700E inverter[27] when the grid impedance is higher than 125Ω orthe grid voltage exceeds the range between minus15 and +10of the nominal grid voltage or the grid frequency exceedsthe range of 02Hz the SB 1700E inverter is disconnectedfrom the main grid within 02 sec Inverter limitations weretested experimentally as follows A variable inductor wasused to create a weak grid The weak grid could also beachieved by using a synchronous generator with a VARcontrollerHowever itmay be regarded as an overly expensivemethod Hence the variable inductor is used to create a weakgrid SB 1700E inverter documentation states that if the lineimpedance exceeds 125Ω the inverter will switch off Thuswhen the reactance of the additional inductor is greater than125Ω then the grid connection is referred to as a weak gridconnection Strong grid connection tests were carried outfirst followed by weak grid experiments

The SB 1700E inverter has an internal resistance (119903) andit is operated in the range of DC voltage 139ndash400V thenominal operating voltage is 180V and the maximum DCcurrent is 126 A The AC side (grid connected) has 230Voperating voltage 1500W power 85 A maximum outputcurrent and 50Hz nominal frequency In order to test the PVinverter with the DC supply voltage 119877

119904is used 119877

119904contains 3

banks (a b and c) each consisting of 8 resistors connectedin parallel each resistor being switchable in or out of thecircuit as appropriate and each rated at 228Ω and 250WThe conducted experiments used eight resistors connected inparallel to give 285Ω or 12 resistors to give 19Ω Apparatusconsisted of a DC source supply series resistor banks acommercial inverter such as the SB 1700E inverter a PowerAnalyser (PA2100) and a switch connected in parallel to theadditional inductor as shown in Figure 7 to toggle betweenthe weak and strong grid connections

Weak grid connection may cause instability increase theharmonic components and cause distortion in the output


Current

[Current]

[Current]

Desired current

1 2

From

g

A

B

DCAC inverter

Goto

From 1

PID controller

Goto 1

Linear transformer

[PWM]

[PWM]

PWM generator

Pulses

minus

minus

++

minus

+

i

DC = 300 v

Grid = 230V

10mH

PID(s)Signal(s)

DSP

+ + +

+

+

Figure 4 DCAC grid connected inverter with L-filter used a unit proportional gain controller

959858757656555

570565

560555

550

Voltage (V)

10

Inductance (mH)

1

15

2

25

Pow

er (W

)

times105

Figure 5 Characteristics of the L-filter

Voltage source

Series resistor

B

A

minus

+

Figure 6 Thevenin source implemented to test SB 1700E inverter

waveforms The DC source voltage was set to 300V and theinductor was varied and observed

The weak grid has properties of a low short circuit powerand high grid impedance The Short Circuit Ratio (SCR) isgiven by [23]

SCR = 119878SC119878119899

(10)

where 119878119899is the rated power of the PV inverter and 119878SC is the

short circuit at the PCC The grid is considered as a strong

grid when the SCR is above 20 and as a weak grid when theSCR is below 10 according to Etxegarai et al [28]

222 Impact of the Network Interruption with the SB 1700EInverter on the Resistive Load The aim of this experiment isto test the impact of the SB 1700E inverter on the resistiveload when the grid is interrupted Experimental setup of thistest is as follows the push button momentary was used toconnect the network distribution with the SB 1700E inverterand supplied the resistive load while the normal close switchwas used to disconnect the system from the main grid Thecontactor 55 kW was used along with the momentary switchand normal close switch A DC source voltage was connectedto the SB 1700E inverter via a series resistance A resistive loadvalue of 228Ω was connected to inverter output which wasconnected in parallel to the main grid through the contactoras shown in Figure 8 The results of this experiment arepresented in Section 322

223 The Response of the SB 1700E Inverter to Change ofthe MPP The PV inverter needs to disconnect from thenetwork in cases of abnormal grid conditions in terms ofthe voltage and the frequency This provides safety of theutility maintenance workers and public network and avoidsdamaging elements of the PV system which are connectedto the PV system [4] This function of the PV invertercan be used to test the response of the SB 1700E inverterexperimentally

This test was used to find the response of the SB 1700Einverter to the change in the series resistor This can help todesign the PV array emulator in accordancewith the responseof the SB 1700E inverter The series resistor 28Ω was perma-nently connected in series between the DC source voltageand the DC side of the inverter as shown in Figure 9 An


DC

ACr

DC power supply

Switch

Utility network

Line impedance

+minus

Rs

Figure 7 Testing the impact of the weak grid connection on the SB 1700E inverter by adding an additional inductor

Load

Push button

Switch off

Contactor

436587109

12

Series resistorDC powerUtility network

Sunny Boy inverter 1700E

AC side

DC side

minus

+

supply

228 Ohm

28 Ohm

Figure 8 Circuit diagram of the SB 1700E inverter connected in parallel to grid and load 228Ω

additional resistance value was 56Ω which was connectedin parallel with the series resistor 28Ω via a momentaryswitch and a contactor The DC source voltage was set to300V and the oscilloscope (MDO3024) was triggered for2 sec The results and discussion of this test are presented inexperimental work results

3 Results and Discussion

Numerical model results are presented first in this sectionfollowed by experimental work results In the numericalmodel of grid connected inverter an FFT analysis was usedto evaluate the performance and efficiency of the proposedcontrol system

31 Simulink Results In this section the acquired resultsare displayed and discussed in detail Figure 10 depicts thegrid voltage and the output current of the modelled gridconnected inverter It can be seen that the voltage and currentare in phase Thus the modelled inverter operates at unitypower factor

Figure 11(b) illustrates the waveform of the modelledinverter output current and its FFT analyses Using a unitproportional gain controller the output current decreasedfrom 12A to 113 A although some ripple remains whichcould be removed Even though the THD is larger thanthe optimal controller it is still acceptable and does satisfythe required IEEE-1547 standard An optimal controllereliminates the current ripple and improves the output currentwaveform as depicted in Figure 11(a) In the case where the

unit proportional gain controller is used the third currentharmonic is the dominant harmonic while the fifth currentharmonic is the dominant harmonic when the optimalcontroller was modelled It can be seen that the optimalcurrent controller has reduced the current harmonic value by165The proportional gain of an optimal current controllerwas found 18 the integral gain was found 222324 while thederivative was set to zero

Due to the nonlinearity of switching power electronicsof the grid connected inverter a trial and error (manual)methodology was adopted by Elsaharty and Ashour [29] toobtain the value of the L-filter and the LCL-filter to complywith the standard IEEE-1547 Their acquired filter value wasvery large whichwill increase the cost and size of the inverterTherefore this paper proposes a control method to improvethe efficiency of the grid connected inverter with a reducedcost and size

32 Experimental Results Acquired results of testing a com-mercial PV inverter are given as follows

TheAC side was directly connected to the grid without anadditional inductorThe connected DC source voltage variedbetween 150 and 300V in cases where the series resistanceis 119877119904= 28Ω as listed in Table 2 Those results are measured

by Power Analyser System (NORMA D6000) This table isused to describe the behaviour of SB 1700E inverter The fifthcurrent harmonic in Figure 12(b) is the dominated harmonicon the other handwhen an additional inductorwas increasedthe current harmonic was reduced as shown in Figure 12(a)This occurs because the additional inductor acts as a filter forthe output current This improves the current waveform


Table2Syste

mconfi

guratio

nactsas

astro

nggrid

totestthep

erform

ance

oftheS

B1700Einverter

underv

arying

theD

Cvoltage

Num

ber

Actual 119877 119904

Internalresistor

ofinverter

Reading119877 119904Ω

Vdc (V)

I1 (A)

V1

(V)

P1 (W)

I2 (A)

V2

(V)

P2 (W)

S2 (VA)

Efficiency

PF

DCsid

eAC

side

1315

323

28300

47

152

727

29

229

675

689

093

098

2310

357

28280

42

150

634

26

229

590

601

093

098

3320

351

28260

387

136

544

22

228

500

510

092

098

4312

415

28240

33

137

451

19228

420

430

093

098

5311

504

28220

27

136

369

157

228

340

350

092

097

6320

680

28200

2136

278

12228

250

280

09

089

7338

1046

28180

13136

182

087

228

160

206

088

078

8359

2141

28160

064

137

8806

228

70140

08

050

90

028

140

Theinverterswitcheso

ff


DC side

Utility network

DC power supply


AC side

Push button

Switch off

Contactor

43

65

87

109

12

Series resistor

Series resistor

minus

+

56 Ohm

28 Ohm

Figure 9 Circuit diagram for testing the MPPT and the speedy response of the SB 1700E inverter

CurrentVoltage

minus400

minus200

0

200

400

Volta

ge (V

)

minus20

minus10

0

10

20

Curr

ent (

A)

003 004 005 006 007 008002Time (s)

Figure 10Output voltage and current of the grid connected inverterworks at unity power factor

The parameters of frequency and voltage setting of theSB 1700E inverter were changed to values different from thedefault values The voltage range varied in 180ndash260V andthe frequency range plusmn45Hz (starting from 50Hz) This hasbeen done to allow the SB 1700E inverter to operate witha bidirectional inverter (SUNNY ISLAND60H inverter)which will design a novel ACMini-Grid systemThe THD ofthe output current was measured using the Power Analyser(PA2100) Figure 13 depicts the output voltage waveform ofthe SB 1700E inverter along with its FFT analysis at theweak grid and the strong grid connections The third voltageharmonic is dominant for the harmonic in the case of the

Table 3 THD of the output voltage current and PF of the SB 1700Einverter

Total harmonic distortion(THD) () 300VDC 200VDC 160VDC

Additional inductorCurrent 74 2003 478Voltage 2 218 24Power factor (PF) 0994 091 054

Without additional inductorCurrent 59 18 44Voltage 24 235 22Power factor (PF) 0996 091 054

weak grid connection The THD of the output voltage at thestrong grid connectionwas 25The SB 1700 inverter voltagefor the weak grid has a distinct distortion near the voltagezero crossing as shown in Figure 13(a)

Table 3 depicts the total harmonic distortion of the outputvoltage and current of the SB 1700E inverter at three differentlevels of DC source voltage 300V 200V and 160V for boththe strong grid and the weak grid connection It can be seenthat at 160V the total harmonic distortion is roughly 47and the PF is reduced This will not meet with the IEEE-1547standard [4] Therefore the grid connected inverter requiresfurther study where next publication will propose a newsystem that can be integrated with existing PV inverter toimprove power quality of old PV inverter such as SunnyBoy 700 inverter and Sunny Boy 1700E inverter This systemis called AC Mini-Grid system that includes a bidirectionalinverter with battery storage


0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)

5 10 150Harmonic order

Fundamental (50Hz) = 12 THD = 025FFT analysis

(a) Optimal PID controller


0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)


(b) Unit proportional gain

Figure 11 FFT analysis of the output current of the grid connected inverter and its frequency spectrum as in (a) and (b)

Time (10msdiv)

500mVminus300div

VerticalMab

Curr

ent (

2A

div

)

4

M

(a) Weak grid and THD = 24

Time (10msdiv)

Curr

ent (

2A

div

)

4

M

500mVminus300div

VerticalMab

(b) Strong grid and THD = 98

Figure 12 Output current waveform and its FFT analysis at varying inductor as in (a) and (b)

2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab


2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab


Figure 13 Output inverter voltage waveform and its FFT analysis as in (a) and (b)

321 Network Interruption of the SB 1700E Inverter with theResistive Load The result was obtained by using a Tektronixoscilloscope (MDO3024) The voltage and the current on theresistive load were measured in two methods The first test iswhen the SB 1700E inverter was connected to the main gridwhich was interrupted Second test is when the main gridsupplied the resistive loadwithout connecting to the SB 1700E

inverterThe comparison between these two connections wasshown in Figure 14

The results show that the resistive load connected to themain grid with the inverter has a significant effect on themeasured voltage and current as shown in Figure 14(a) Inboth cases the load was 228Ω and the grid voltage was230V thus the current is approximately 1 A However when


Curr

ent

Increment in voltage and current by blue arrow

4

3

04183712 Apr 2015400V 200mV 400ms 250kSs

10k points 000V3 34

(2A

div

)Vo

ltage

(400

Vd

iv)

Time (40msdiv)

(a) Inverter connected

Volta

ge

Curr

ent

3

04211112 Apr 2015400V 200mV 400ms 250kSs

10k points 000V33 4

(1A

div

)(400

Vd

iv)

Time (40msdiv)

4

(b) Supply load without inverter

Figure 14 Waveforms of the load voltage in pink colour [10VDiv] and the current in green colour [10ADiv]

a b

b

200V 200mV400ms 250kSs

10k points 132V

minus4956 s 2000 Vminus7760 Vminus3944 s

Δ1012 s Δ9760 Vminus9644 Vs

1 2

2

1 8 May 2015003002

Cursors linked

a

dVdt1

Figure 15 Input voltage trace 1 [200VDiv] and input current in trace 2 [10ADiv] at connecting the additional resistor

the inverter was connected to the main grid and then themain grid was interrupted the load voltage increased overthe rated voltage and the load current increased over the ratedcurrent

This test provides a framework for the exploration ofthe effect of the SB 1700E inverter on the resistive load Itwas interesting that the voltage and the current waveformssharply increased overrating of the voltage and the currentThis increment in the voltage and the currentmay damage theconnected appliances The explanation of this increment inthe load voltage and current could be due to the transformeror the filter of the SB 1700E inverter or its properties

322 Results of SB 1700E Inverter to Change of the MPPThe input voltage and current of the SB 1700E inverter wereobserved using the oscilloscope The results were shown inFigure 15 The results show that the voltage is disturbed by

connecting the additional series resistor and taking approxi-mately 1012 sec to settle to the level of the voltage Howeverthe input current was changed according to the change inthe resistive load and has also taken 1012 sec in both casesof the additional series resistor connected and disconnectedTherefore the SB 1700E inverter requires a PV array emulatorwith a fast response higher than 1012 sec in order to study theperformance and behaviour of MPPT of PV inverter

Figure 16 shows the response of the SB 1700E inverterto change the series resistor from 20Ω to 28Ω and viceversa The open voltage may not change when the seriesresistance was changed but the voltage at the maximumpower point has a small change Perhaps the SB 1700E invertermay work in the line between the open voltage and themaximum power point Consequently the input current hasa large variance according to the variation of the additionalseries resistorTheMPP is produced by multiplying the input


Maximum current

1

2

3

4

5

6

Curr

ent (

A)

100 150 20050Voltage (V)

Figure 16 The response of the SB 1700E inverter to change of theadditional series resistor

voltage and current The curve represented the maximumpower as shown in Figure 16

4 Conclusion

The paper studies a method to reduce the signal distortionusing L-filter and PID feedback control technologies Adetailed review of the technologies is performedThe charac-teristics of a commercial inverter (SB 1700E) are also studiedbesides this paper describes the behaviour of SB 1700Einverter A grid connected inverter has been modelled withan L-filter in the open loop circuit The optimal controller ofthe inverter helps to attenuate the harmonic components Inaddition the size of the filter with a good design controllercan be reduced with the PID controller but it has beenselected to be 10mH to easily describe the open loop circuitThis model can be used to connect any DC link inverter tothe utility network In addition the proposed model can beused to connect a storage battery which is charged by therenewable energy to the grid A simple procedure to test aSunny Boy 1700E inverter is developed The impact of theweak grid connection has been investigated by implementingthe variable inductor that is available at the laboratory of theDepartment of Engineering at the University of Leicester Itcan be concluded that when the additional inductor valueincreases the output voltage distortion increases and thecurrent improves as the harmonic distortion is reduced Thespeedy response of a commercial PV inverter is determinedFuture work will focus on improving the power quality andthe stability of the solar PV system in rural areas and designwork for solar PV systems with attached storage that canimprove the reliability and efficiency The future work willalso be considered designing a superior controller for thenonlinear model of the grid connected inverter with parasiticelements that were presented by Algaddafi in [30]

Conflicts of Interest

The authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

The experimental work presented in this paper was con-ducted at the Department of Engineering University ofLeicester UK Ali Algaddafi would like to thank Dr HansBleijs for supporting in the past when he came to the UK

References

[1] B Alajmi Design and control of photovoltaic systems in distrib-uted generation [PhD thesis] University of Strathclyde 2013

[2] EPIA ldquoGlobal market outlook for photovoltaics until 2016rdquohttpwwwsolarifyeuwp-contentuploads201205EPIA_Global-Market-Outlook-2016pdf

[3] J Sun ldquoImpedance-based stability criterion for grid-connectedinvertersrdquo IEEE Transactions on Power Electronics vol 26 no11 pp 3075ndash3078 2011

[4] R TeodorescuM Liserre and P RodrıguezGrid Converters forPhotovoltaic andWind Power Systems JohnWiley amp Sons 2011

[5] T T Leong and D Ishak ldquoDeadbeat-based PI controller forstand-alone single-phase voltage source inverter using batterycell as primary sourcesrdquo in Proceedings of the IEEE 1st Confer-ence on Clean Energy and Technology (CET rsquo11) pp 87ndash92 June2011

[6] F Cao W Li J Wu and X He ldquoEffect of connection cableimpedance on multi-inverter parallel system and an optimizedcontroller with zero steady circulating currentrdquo in Proceedingsof the 34th Annual Conference of the IEEE Industrial ElectronicsSociety (IECON rsquo08) pp 2314ndash2319 November 2008

[7] W Yao Z Lu H Long and B Li ldquoResearch on grid-connectedinterleaved inverter with L filterrdquo in Proceedings of the 1stInternational Future Energy Electronics Conference (IFEEC rsquo13)pp 87ndash92 November 2013

[8] P Channegowda and V John ldquoFilter optimization for gridinteractive voltage source invertersrdquo IEEE Transactions onIndustrial Electronics vol 57 no 12 pp 4106ndash4114 2010

[9] Y-H Chang and Y-K Lin ldquoA closed-loop high-gain switched-capacitor-inductor-based boost DC-AC inverterrdquo in Proceed-ings of the International MultiConference of Engineers andComputer Scientists (IMECS rsquo15) pp 694ndash699 March 2015

[10] J C Lima J M Corleta A Medeiros et al ldquoA PIC controllerfor grid connected PV system using a FPGA based inverterrdquo inProceedings of the IEEE International Symposium on IndustrialElectronics (ISIE rsquo00) pp 169ndash173 December 2000

[11] S Samerchur S Premrudeepreechacharn Y Kumsuwun andK Higuchi ldquoPower control of single-phase voltage sourceinverter for grid-connected photovoltaic systemsrdquo in Proceed-ings of the IEEEPES Power Systems Conference and Exposition(PSCE rsquo11) pp 1ndash6 Phoenix Ariz USA March 2011

[12] A Datta G Bhattacharya D Mukherjee and H Saha ldquoAnefficient technique for controlling power flow in a single stagegrid-connected photovoltaic systemrdquo Scientia Iranica vol 21no 3 pp 885ndash897 2014

[13] J Liang X Zhou X Jin Y Tong and R Cai ldquoAnalysis ofvoltage distortion for parallel PWM inverters with L filterrdquo inProceedings of the IEEE 7th International Power Electronics andMotion Control ConferencemdashECCE Asia (IPEMC rsquo12) pp 1588ndash1593 June 2012

[14] J H R Enslin W T J Hulshorst A M S Atmadji et alldquoHarmonic interaction between large numbers of photovoltaicinverters and the distribution networkrdquo in Proceedings of the


IEEE Bologna PowerTech Conference vol 3 pp 75ndash80 BolognaItaly June 2003

[15] Y Xue K C Divya G Griepentrog M Liviu S Suresh andMManjrekar ldquoTowards next generation photovoltaic invertersrdquo inProceedings of the 3rd Annual IEEE Energy Conversion Congressand Exposition (ECCE rsquo11) pp 2467ndash2474 San Jose Calif USASeptember 2011

[16] A Algaddafi K Elnaddab and M Khoja ldquoReview gridconnected inverter with its filter and providing suggestionsfor designing transformerless inverterrdquo in Proceedings of the5th International Conference on Power Science and EngineeringIEEE Venice Italy 2016

[17] J He Y W Li D Bosnjak and B Harris ldquoInvestigation andresonances damping of multiple PV invertersrdquo in Proceedingsof the 27th Annual IEEE Applied Power Electronics Conferenceand Exposition (APEC rsquo12) pp 246ndash253 February 2012

[18] A Algaddafi N Brown R Gammon S Altuwayjiri A Rahiland S Ali ldquoAn analogue computation based photovoltaicemulator for realistic inverter testingrdquo in Proceedings of the3rd International Conference on Energy Engineering (ICEE rsquo15)Aswan Egypt December 2015

[19] L Hassaine E Olıas J Quintero and A Barrado ldquoDigital con-trol based on the shifting phase for grid connected photovoltaicinverterrdquo in Proceedings of the 23rd Annual IEEE Applied PowerElectronics Conference and Exposition (APEC rsquo08) pp 945ndash951February 2008

[20] V K Mehta and R Mehta Principles of Electrical Engineering SChand amp Company Limited 2005

[21] N A Ashtinai S M Azizi and S A Khajehoddin ldquoControldesign in 120583-synthesis framework for grid-connected inverterswith higher order filtersrdquo inProceedings of the IEEE Energy Con-version Congress and Exposition (ECCE rsquo16) pp 1ndash6MilwaukeeWis USA September 2016

[22] F Huerta D Pizarro S Cobreces F J Rodrıguez C Gironand A Rodrıguez ldquoLQG servo controller for the currentcontrol of LCL grid-connected Voltage-Source ConvertersrdquoIEEE Transactions on Industrial Electronics vol 59 no 11 pp4272ndash4284 2012

[23] K H Ahmed A M Massoud S J Finney and B WWilliams ldquoA modified stationary reference frame-based pre-dictive current control with zero steady-state error for LCLcoupled inverter-based distributed generation systemsrdquo IEEETransactions on Industrial Electronics vol 58 no 4 pp 1359ndash1370 2011

[24] E Twining and D G Holmes ldquoGrid current regulation of athree-phase voltage source inverter with an LCL input filterrdquoIEEE Transactions on Power Electronics vol 18 no 3 pp 888ndash895 2003

[25] M Huang X Wang P C Loh and F Blaabjerg ldquoActivedamping of LLCL-filter resonance based on LC-trap voltage orcurrent feedbackrdquo IEEE Transactions on Power Electronics vol31 no 3 pp 2337ndash2346 2016

[26] W Wu Y Sun M Huang et al ldquoA robust passive dampingmethod for LLCL-filter-based grid-tied inverters to minimizethe effect of grid harmonic voltagesrdquo IEEE Transactions onPower Electronics vol 29 no 7 pp 3279ndash3289 2014

[27] Sunny Boy 1700E Technical Description httpfilessmadedl5671SB1700E-11-EE4403pdf

[28] A Etxegarai P Eguia E Torres and E Fernandez ldquoImpact ofwind power in isolated power systemsrdquo inProceedings of the 16thIEEE Mediterranean Electrotechnical Conference (MELECONrsquo12) pp 63ndash66 March 2012

[29] M A Elsaharty and H A Ashour ldquoPassive L and LCL filterdesign method for grid-connected invertersrdquo in Proceedings ofthe IEEE Innovative Smart Grid TechnologiesmdashAsia (ISGT Asiarsquo14) pp 13ndash18 May 2014

[30] A Algaddafi Advanced Modelling and Designing of an OptimalController Converter LAP Lambert Academic Publishing 2016

TribologyAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FuelsJournal of


Journal ofPetroleum Engineering


Industrial EngineeringJournal of


Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

CombustionJournal of


Journal of


Renewable Energy

Submit your manuscripts athttpswwwhindawicom


StructuresJournal of

International Journal of

RotatingMachinery


EnergyJournal of


Hindawi Publishing Corporation httpwwwhindawicom

Journal of

Volume 201Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal of


Nuclear InstallationsScience and Technology of


Solar EnergyJournal of


Wind EnergyJournal of


Nuclear EnergyInternational Journal of


High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


were developed to overcome this issue and to improve thesteady state and the transient response of the grid connectedinverter including repeat control proportional resonant anddeadbeat control [4ndash7] Channegowda and John [8] used adamping resistor to reduce LCL-filter resonance althoughthis was successful damping resistor power losses were highenough to affect inverter efficiency The upshot being that atthe time of wiring the LCL-filter in this application still haspoor dynamic performance

PV inverters should have certain design features intrin-sically included such as Maximum Power Point Tracking(MPPT) anti-island power factor correction harmonicreduction and fault ride through [4] Solar PV generationoffers clear environmental advantages being almost com-pletely pollution-free at the point of generation and unlikesome other forms of renewable generation is silent makingit eminently suitable for residential areas too [1] Distributedgeneration using PV system is also advantageous in countrieswhere traditional heavy grid infrastructure is not in placeThe requirement for small distributed power generationsystems is low cost high efficiency and tolerance for a widerange of input voltage variations The inverter can be a singlestage or multiple stages Single stage inverters convert DCdirectly to AC with no intermediate stage Two-stage invert-ers take the form of a DC-DC converter followed by aDC-ACinverter [9ndash12] Single stage inverters offer simple structureand low cost but multiple stage inverters can accommodate awider range of input voltages For multiple (eg DCDC andDCAC converter) stages inverters complexity and cost areincreased and efficiency is lower [1 9]

The L-filter is suitable for an inverter with a high switch-ing frequency this being a first-order filter with 20 dBdecadeoverall frequencyThe dynamic interaction between invertersthat use L-filters is less than it is between the inverterswith LC- or LCL-filters Also variation in environmentalconditions can result in the generation of a nonsinusoidalcurrent to the network that may cause a voltage drop anddistortion across it Liang et al presented voltage distortionanalysis [13] however their study did not include analysisof current at the point of common coupling (PCC) ThePV inverters are limited by several factors including theweak grid connection island mode connection and theinteraction between different PV inverters The island modeconnection can be dangerous to utility workers and mayprevent utility interface with G59 protection to reconnect thenetwork with the PV system This requires developing ananti-islanding mode connection to stop producing power tothe main grid However the anti-islanding mode connectionmay cause events of the power shortage (a blackout) Abackup inverter can overcome this limitation The backupinverter is used to supply the critical load and does notfeed the grid This is because the utility interface with G59protection contains a Voltage Monitoring Detection (egVMD460) relay which is an external network and systemprotection This relay is used to disconnect the public gridwith the PV generator in events of unacceptable thresholdvalues The VMD460 relay is a device that monitors the gridvoltage and frequency and when the voltage and frequencyof the source energy are in the acceptable threshold then

the VMD460 relay allows reconnecting with the public gridHowever an interaction is likely to occur if multiple PVinverters are connected Therefore the AC Mini-Grid canbe used to improve the performance of the system whichincludes multiple PV inverters Harmonic interference oflarge population of inverters was analysed by Enslin et al [14]The resonance between the PV inverter and existing networkcomponents was discussed It was found that the outputinverter impedance should be high since it is a functionof frequency and it gives an unpolluted sinusoidal currentwaveform The study assumed that most house applianceswould be capacitive loads and these tend to be inductive Xueet al provided an overview of future development trends forinverters [15] Taking that case reliability improvements willbe needed It wasmentioned that in the future the PV invert-ers are required to power ancillary service in the distributiongrid In general PV inverter design criteria will includeflicker mitigation unbalanced compensation active loadbalancing power active filter harmonic filtering voltage sagand swell mitigation control voltage Anti-island detectionwas also identified as a challenge and it should be possible todistinguish between permanent power outages and transientfalls and provide an appropriate response in each caseThe limitations of these studies were presented with criticalreviews by Algaddafi et al [16] A new method to determinethe inverter output impedance and grid impedance waspresented by Sun [3] who argued that high output impedancefor a grid connected inverter enables successful operationwith a wider range of grid impedances Other issues whichwould also be important include grid parallel inverter controloutput filter anddamping themethodof synchronising to thegrid and optimising output impedance

In recent a multiple inverter using Nortonrsquos equivalentcircuits was modelled by He et al [17] discussing theinteraction of parallel inverters The multiple PV inverterbased Micro-Grid system presented a more challenging pic-ture where the PV inverters interaction will cause complexresonance at various frequencies so the output current willbe distorted even when the control design and filter circuitare accurately designed for a single inverter

A physical PV array has several limitations as it dependson the weather conditions for outdoor testing and requiresa large space and cooling system for indoor testing A PVarray emulator (PVAE) with a fast response offers a potentialsolution The currently available power electronic PVAEshave a slow response time This can be overcome by using aseries regulator with a robust control The nonlinearity of theCurrent-Voltage (I-V) and Power-Voltage (P-V) curve gen-erator of a PVAE is also challenging and the characteristicsof this will vary with solar insolation ambient temperatureand output voltage [12] This can be overcome by using ananalogue computation circuit as presented in [18] Howeverthe PVAE that presented in [18] requires a cooling systemwhere with high load or high power the system may beunstable and the performance of PVAE will deteriorateTherefore the PVAE is unsuitable to operate Sunny Boy(SB 1700E) at the present time even though it can be usedwith small power such as Sunny Boy 700 inverter For thesimplicity and availability the commercial PV inverter which


minusminus

inv grid

iout

++

L

(a)

훿

VL

Vinv

Vgrid

Iout

(b)






119875 = 119881grid119908119871 (119881inv sin 120575) (2)


119881119871= 119895119908119871119868

119900 (4)



119898 = 119881inv119881DC (5)


119881inv = radic(1198812119871 + 1198812grid) (6)

120575 = tanminus1 ( 119881119871119881grid) (7)





ScopeCurrent

1 2

From

g

A

B

DCAC inverter

Goto

Linear transformer

[PWM]

[PWM]

SPWM generator

Pulses

minus+

minus

+i

DC = 300 v10mH amp 033Ω

Grid = 230V (Vrms)

+

+ +

+

+





119868ref = 12 sin (wt) (8)


119871= 37V








003 004 005 006 007 008002Time (s)

minus15

minus10

minus5

0

5

10

15

Curr

ent (

A)




119875119900= 119881grid119883L radic119881

2













119904is used 119877

119904contains 3




Current

[Current]

[Current]

Desired current

1 2

From

g

A

B

DCAC inverter

Goto

From 1

PID controller

Goto 1

Linear transformer

[PWM]

[PWM]

PWM generator

Pulses

minus

minus

++

minus

+

i

DC = 300 v

Grid = 230V

10mH

PID(s)Signal(s)

DSP

+ + +

+

+


959858757656555

570565

560555

550

Voltage (V)

10

Inductance (mH)

1

15

2

25

Pow

er (W

)

times105


Voltage source

Series resistor

B

A

minus

+




SCR = 119878SC119878119899

(10)








DC

ACr

DC power supply

Switch

Utility network

Line impedance

+minus

Rs


Load

Push button

Switch off

Contactor

436587109

12



AC side

DC side

minus

+

supply

228 Ohm

28 Ohm













Table2Syste

mconfi

guratio

nactsas

astro

nggrid

totestthep

erform

ance

oftheS

B1700Einverter

underv

arying

theD

Cvoltage

Num

ber

Actual 119877 119904

Internalresistor

ofinverter

Reading119877 119904Ω

Vdc (V)

I1 (A)

V1

(V)

P1 (W)

I2 (A)

V2

(V)

P2 (W)

S2 (VA)

Efficiency

PF

DCsid

eAC

side

1315

323

28300

47

152

727

29

229

675

689

093

098

2310

357

28280

42

150

634

26

229

590

601

093

098

3320

351

28260

387

136

544

22

228

500

510

092

098

4312

415

28240

33

137

451

19228

420

430

093

098

5311

504

28220

27

136

369

157

228

340

350

092

097

6320

680

28200

2136

278

12228

250

280

09

089

7338

1046

28180

13136

182

087

228

160

206

088

078

8359

2141

28160

064

137

8806

228

70140

08

050

90

028

140


ff


DC side

Utility network

DC power supply


AC side

Push button

Switch off

Contactor

43

65

87

109

12

Series resistor

Series resistor

minus

+

56 Ohm

28 Ohm


CurrentVoltage

minus400

minus200

0

200

400

Volta

ge (V

)

minus20

minus10

0

10

20

Curr

ent (

A)

003 004 005 006 007 008002Time (s)










0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)





0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)




Time (10msdiv)

500mVminus300div

VerticalMab

Curr

ent (

2A

div

)

4

M


Time (10msdiv)

Curr

ent (

2A

div

)

4

M

500mVminus300div

VerticalMab



2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab


2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab







Curr

ent


4

3

04183712 Apr 2015400V 200mV 400ms 250kSs

10k points 000V3 34

(2A

div

)Vo

ltage

(400

Vd

iv)

Time (40msdiv)


Volta

ge

Curr

ent

3

04211112 Apr 2015400V 200mV 400ms 250kSs

10k points 000V33 4

(1A

div

)(400

Vd

iv)

Time (40msdiv)

4



a b

b

200V 200mV400ms 250kSs

10k points 132V



1 2

2

1 8 May 2015003002

Cursors linked

a

dVdt1








Maximum current

1

2

3

4

5

6

Curr

ent (

A)

100 150 20050Voltage (V)



4 Conclusion




Acknowledgments


References



































FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of



Journal of















minusminus

inv grid

iout

++

L

(a)

훿

VL

Vinv

Vgrid

Iout

(b)






119875 = 119881grid119908119871 (119881inv sin 120575) (2)


119881119871= 119895119908119871119868

119900 (4)



119898 = 119881inv119881DC (5)


119881inv = radic(1198812119871 + 1198812grid) (6)

120575 = tanminus1 ( 119881119871119881grid) (7)





ScopeCurrent

1 2

From

g

A

B

DCAC inverter

Goto

Linear transformer

[PWM]

[PWM]

SPWM generator

Pulses

minus+

minus

+i

DC = 300 v10mH amp 033Ω

Grid = 230V (Vrms)

+

+ +

+

+





119868ref = 12 sin (wt) (8)


119871= 37V








003 004 005 006 007 008002Time (s)

minus15

minus10

minus5

0

5

10

15

Curr

ent (

A)




119875119900= 119881grid119883L radic119881

2













119904is used 119877

119904contains 3




Current

[Current]

[Current]

Desired current

1 2

From

g

A

B

DCAC inverter

Goto

From 1

PID controller

Goto 1

Linear transformer

[PWM]

[PWM]

PWM generator

Pulses

minus

minus

++

minus

+

i

DC = 300 v

Grid = 230V

10mH

PID(s)Signal(s)

DSP

+ + +

+

+


959858757656555

570565

560555

550

Voltage (V)

10

Inductance (mH)

1

15

2

25

Pow

er (W

)

times105


Voltage source

Series resistor

B

A

minus

+




SCR = 119878SC119878119899

(10)








DC

ACr

DC power supply

Switch

Utility network

Line impedance

+minus

Rs


Load

Push button

Switch off

Contactor

436587109

12



AC side

DC side

minus

+

supply

228 Ohm

28 Ohm













Table2Syste

mconfi

guratio

nactsas

astro

nggrid

totestthep

erform

ance

oftheS

B1700Einverter

underv

arying

theD

Cvoltage

Num

ber

Actual 119877 119904

Internalresistor

ofinverter

Reading119877 119904Ω

Vdc (V)

I1 (A)

V1

(V)

P1 (W)

I2 (A)

V2

(V)

P2 (W)

S2 (VA)

Efficiency

PF

DCsid

eAC

side

1315

323

28300

47

152

727

29

229

675

689

093

098

2310

357

28280

42

150

634

26

229

590

601

093

098

3320

351

28260

387

136

544

22

228

500

510

092

098

4312

415

28240

33

137

451

19228

420

430

093

098

5311

504

28220

27

136

369

157

228

340

350

092

097

6320

680

28200

2136

278

12228

250

280

09

089

7338

1046

28180

13136

182

087

228

160

206

088

078

8359

2141

28160

064

137

8806

228

70140

08

050

90

028

140


ff


DC side

Utility network

DC power supply


AC side

Push button

Switch off

Contactor

43

65

87

109

12

Series resistor

Series resistor

minus

+

56 Ohm

28 Ohm


CurrentVoltage

minus400

minus200

0

200

400

Volta

ge (V

)

minus20

minus10

0

10

20

Curr

ent (

A)

003 004 005 006 007 008002Time (s)










0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)





0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)




Time (10msdiv)

500mVminus300div

VerticalMab

Curr

ent (

2A

div

)

4

M


Time (10msdiv)

Curr

ent (

2A

div

)

4

M

500mVminus300div

VerticalMab



2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab


2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab







Curr

ent


4

3

04183712 Apr 2015400V 200mV 400ms 250kSs

10k points 000V3 34

(2A

div

)Vo

ltage

(400

Vd

iv)

Time (40msdiv)


Volta

ge

Curr

ent

3

04211112 Apr 2015400V 200mV 400ms 250kSs

10k points 000V33 4

(1A

div

)(400

Vd

iv)

Time (40msdiv)

4



a b

b

200V 200mV400ms 250kSs

10k points 132V



1 2

2

1 8 May 2015003002

Cursors linked

a

dVdt1








Maximum current

1

2

3

4

5

6

Curr

ent (

A)

100 150 20050Voltage (V)



4 Conclusion




Acknowledgments


References



































FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of



Journal of















ScopeCurrent

1 2

From

g

A

B

DCAC inverter

Goto

Linear transformer

[PWM]

[PWM]

SPWM generator

Pulses

minus+

minus

+i

DC = 300 v10mH amp 033Ω

Grid = 230V (Vrms)

+

+ +

+

+





119868ref = 12 sin (wt) (8)


119871= 37V








003 004 005 006 007 008002Time (s)

minus15

minus10

minus5

0

5

10

15

Curr

ent (

A)




119875119900= 119881grid119883L radic119881

2













119904is used 119877

119904contains 3




Current

[Current]

[Current]

Desired current

1 2

From

g

A

B

DCAC inverter

Goto

From 1

PID controller

Goto 1

Linear transformer

[PWM]

[PWM]

PWM generator

Pulses

minus

minus

++

minus

+

i

DC = 300 v

Grid = 230V

10mH

PID(s)Signal(s)

DSP

+ + +

+

+


959858757656555

570565

560555

550

Voltage (V)

10

Inductance (mH)

1

15

2

25

Pow

er (W

)

times105


Voltage source

Series resistor

B

A

minus

+




SCR = 119878SC119878119899

(10)








DC

ACr

DC power supply

Switch

Utility network

Line impedance

+minus

Rs


Load

Push button

Switch off

Contactor

436587109

12



AC side

DC side

minus

+

supply

228 Ohm

28 Ohm













Table2Syste

mconfi

guratio

nactsas

astro

nggrid

totestthep

erform

ance

oftheS

B1700Einverter

underv

arying

theD

Cvoltage

Num

ber

Actual 119877 119904

Internalresistor

ofinverter

Reading119877 119904Ω

Vdc (V)

I1 (A)

V1

(V)

P1 (W)

I2 (A)

V2

(V)

P2 (W)

S2 (VA)

Efficiency

PF

DCsid

eAC

side

1315

323

28300

47

152

727

29

229

675

689

093

098

2310

357

28280

42

150

634

26

229

590

601

093

098

3320

351

28260

387

136

544

22

228

500

510

092

098

4312

415

28240

33

137

451

19228

420

430

093

098

5311

504

28220

27

136

369

157

228

340

350

092

097

6320

680

28200

2136

278

12228

250

280

09

089

7338

1046

28180

13136

182

087

228

160

206

088

078

8359

2141

28160

064

137

8806

228

70140

08

050

90

028

140


ff


DC side

Utility network

DC power supply


AC side

Push button

Switch off

Contactor

43

65

87

109

12

Series resistor

Series resistor

minus

+

56 Ohm

28 Ohm


CurrentVoltage

minus400

minus200

0

200

400

Volta

ge (V

)

minus20

minus10

0

10

20

Curr

ent (

A)

003 004 005 006 007 008002Time (s)










0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)





0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)




Time (10msdiv)

500mVminus300div

VerticalMab

Curr

ent (

2A

div

)

4

M


Time (10msdiv)

Curr

ent (

2A

div

)

4

M

500mVminus300div

VerticalMab



2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab


2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab







Curr

ent


4

3

04183712 Apr 2015400V 200mV 400ms 250kSs

10k points 000V3 34

(2A

div

)Vo

ltage

(400

Vd

iv)

Time (40msdiv)


Volta

ge

Curr

ent

3

04211112 Apr 2015400V 200mV 400ms 250kSs

10k points 000V33 4

(1A

div

)(400

Vd

iv)

Time (40msdiv)

4



a b

b

200V 200mV400ms 250kSs

10k points 132V



1 2

2

1 8 May 2015003002

Cursors linked

a

dVdt1








Maximum current

1

2

3

4

5

6

Curr

ent (

A)

100 150 20050Voltage (V)



4 Conclusion




Acknowledgments


References



































FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of



Journal of















003 004 005 006 007 008002Time (s)

minus15

minus10

minus5

0

5

10

15

Curr

ent (

A)




119875119900= 119881grid119883L radic119881

2













119904is used 119877

119904contains 3




Current

[Current]

[Current]

Desired current

1 2

From

g

A

B

DCAC inverter

Goto

From 1

PID controller

Goto 1

Linear transformer

[PWM]

[PWM]

PWM generator

Pulses

minus

minus

++

minus

+

i

DC = 300 v

Grid = 230V

10mH

PID(s)Signal(s)

DSP

+ + +

+

+


959858757656555

570565

560555

550

Voltage (V)

10

Inductance (mH)

1

15

2

25

Pow

er (W

)

times105


Voltage source

Series resistor

B

A

minus

+




SCR = 119878SC119878119899

(10)








DC

ACr

DC power supply

Switch

Utility network

Line impedance

+minus

Rs


Load

Push button

Switch off

Contactor

436587109

12



AC side

DC side

minus

+

supply

228 Ohm

28 Ohm













Table2Syste

mconfi

guratio

nactsas

astro

nggrid

totestthep

erform

ance

oftheS

B1700Einverter

underv

arying

theD

Cvoltage

Num

ber

Actual 119877 119904

Internalresistor

ofinverter

Reading119877 119904Ω

Vdc (V)

I1 (A)

V1

(V)

P1 (W)

I2 (A)

V2

(V)

P2 (W)

S2 (VA)

Efficiency

PF

DCsid

eAC

side

1315

323

28300

47

152

727

29

229

675

689

093

098

2310

357

28280

42

150

634

26

229

590

601

093

098

3320

351

28260

387

136

544

22

228

500

510

092

098

4312

415

28240

33

137

451

19228

420

430

093

098

5311

504

28220

27

136

369

157

228

340

350

092

097

6320

680

28200

2136

278

12228

250

280

09

089

7338

1046

28180

13136

182

087

228

160

206

088

078

8359

2141

28160

064

137

8806

228

70140

08

050

90

028

140


ff


DC side

Utility network

DC power supply


AC side

Push button

Switch off

Contactor

43

65

87

109

12

Series resistor

Series resistor

minus

+

56 Ohm

28 Ohm


CurrentVoltage

minus400

minus200

0

200

400

Volta

ge (V

)

minus20

minus10

0

10

20

Curr

ent (

A)

003 004 005 006 007 008002Time (s)










0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)





0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)




Time (10msdiv)

500mVminus300div

VerticalMab

Curr

ent (

2A

div

)

4

M


Time (10msdiv)

Curr

ent (

2A

div

)

4

M

500mVminus300div

VerticalMab



2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab


2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab







Curr

ent


4

3

04183712 Apr 2015400V 200mV 400ms 250kSs

10k points 000V3 34

(2A

div

)Vo

ltage

(400

Vd

iv)

Time (40msdiv)


Volta

ge

Curr

ent

3

04211112 Apr 2015400V 200mV 400ms 250kSs

10k points 000V33 4

(1A

div

)(400

Vd

iv)

Time (40msdiv)

4



a b

b

200V 200mV400ms 250kSs

10k points 132V



1 2

2

1 8 May 2015003002

Cursors linked

a

dVdt1








Maximum current

1

2

3

4

5

6

Curr

ent (

A)

100 150 20050Voltage (V)



4 Conclusion




Acknowledgments


References



































FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of



Journal of















Current

[Current]

[Current]

Desired current

1 2

From

g

A

B

DCAC inverter

Goto

From 1

PID controller

Goto 1

Linear transformer

[PWM]

[PWM]

PWM generator

Pulses

minus

minus

++

minus

+

i

DC = 300 v

Grid = 230V

10mH

PID(s)Signal(s)

DSP

+ + +

+

+


959858757656555

570565

560555

550

Voltage (V)

10

Inductance (mH)

1

15

2

25

Pow

er (W

)

times105


Voltage source

Series resistor

B

A

minus

+




SCR = 119878SC119878119899

(10)








DC

ACr

DC power supply

Switch

Utility network

Line impedance

+minus

Rs


Load

Push button

Switch off

Contactor

436587109

12



AC side

DC side

minus

+

supply

228 Ohm

28 Ohm













Table2Syste

mconfi

guratio

nactsas

astro

nggrid

totestthep

erform

ance

oftheS

B1700Einverter

underv

arying

theD

Cvoltage

Num

ber

Actual 119877 119904

Internalresistor

ofinverter

Reading119877 119904Ω

Vdc (V)

I1 (A)

V1

(V)

P1 (W)

I2 (A)

V2

(V)

P2 (W)

S2 (VA)

Efficiency

PF

DCsid

eAC

side

1315

323

28300

47

152

727

29

229

675

689

093

098

2310

357

28280

42

150

634

26

229

590

601

093

098

3320

351

28260

387

136

544

22

228

500

510

092

098

4312

415

28240

33

137

451

19228

420

430

093

098

5311

504

28220

27

136

369

157

228

340

350

092

097

6320

680

28200

2136

278

12228

250

280

09

089

7338

1046

28180

13136

182

087

228

160

206

088

078

8359

2141

28160

064

137

8806

228

70140

08

050

90

028

140


ff


DC side

Utility network

DC power supply


AC side

Push button

Switch off

Contactor

43

65

87

109

12

Series resistor

Series resistor

minus

+

56 Ohm

28 Ohm


CurrentVoltage

minus400

minus200

0

200

400

Volta

ge (V

)

minus20

minus10

0

10

20

Curr

ent (

A)

003 004 005 006 007 008002Time (s)










0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)





0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)




Time (10msdiv)

500mVminus300div

VerticalMab

Curr

ent (

2A

div

)

4

M


Time (10msdiv)

Curr

ent (

2A

div

)

4

M

500mVminus300div

VerticalMab



2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab


2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab







Curr

ent


4

3

04183712 Apr 2015400V 200mV 400ms 250kSs

10k points 000V3 34

(2A

div

)Vo

ltage

(400

Vd

iv)

Time (40msdiv)


Volta

ge

Curr

ent

3

04211112 Apr 2015400V 200mV 400ms 250kSs

10k points 000V33 4

(1A

div

)(400

Vd

iv)

Time (40msdiv)

4



a b

b

200V 200mV400ms 250kSs

10k points 132V



1 2

2

1 8 May 2015003002

Cursors linked

a

dVdt1








Maximum current

1

2

3

4

5

6

Curr

ent (

A)

100 150 20050Voltage (V)



4 Conclusion




Acknowledgments


References



































FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of



Journal of















DC

ACr

DC power supply

Switch

Utility network

Line impedance

+minus

Rs


Load

Push button

Switch off

Contactor

436587109

12



AC side

DC side

minus

+

supply

228 Ohm

28 Ohm













Table2Syste

mconfi

guratio

nactsas

astro

nggrid

totestthep

erform

ance

oftheS

B1700Einverter

underv

arying

theD

Cvoltage

Num

ber

Actual 119877 119904

Internalresistor

ofinverter

Reading119877 119904Ω

Vdc (V)

I1 (A)

V1

(V)

P1 (W)

I2 (A)

V2

(V)

P2 (W)

S2 (VA)

Efficiency

PF

DCsid

eAC

side

1315

323

28300

47

152

727

29

229

675

689

093

098

2310

357

28280

42

150

634

26

229

590

601

093

098

3320

351

28260

387

136

544

22

228

500

510

092

098

4312

415

28240

33

137

451

19228

420

430

093

098

5311

504

28220

27

136

369

157

228

340

350

092

097

6320

680

28200

2136

278

12228

250

280

09

089

7338

1046

28180

13136

182

087

228

160

206

088

078

8359

2141

28160

064

137

8806

228

70140

08

050

90

028

140


ff


DC side

Utility network

DC power supply


AC side

Push button

Switch off

Contactor

43

65

87

109

12

Series resistor

Series resistor

minus

+

56 Ohm

28 Ohm


CurrentVoltage

minus400

minus200

0

200

400

Volta

ge (V

)

minus20

minus10

0

10

20

Curr

ent (

A)

003 004 005 006 007 008002Time (s)










0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)





0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)




Time (10msdiv)

500mVminus300div

VerticalMab

Curr

ent (

2A

div

)

4

M


Time (10msdiv)

Curr

ent (

2A

div

)

4

M

500mVminus300div

VerticalMab



2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab


2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab







Curr

ent


4

3

04183712 Apr 2015400V 200mV 400ms 250kSs

10k points 000V3 34

(2A

div

)Vo

ltage

(400

Vd

iv)

Time (40msdiv)


Volta

ge

Curr

ent

3

04211112 Apr 2015400V 200mV 400ms 250kSs

10k points 000V33 4

(1A

div

)(400

Vd

iv)

Time (40msdiv)

4



a b

b

200V 200mV400ms 250kSs

10k points 132V



1 2

2

1 8 May 2015003002

Cursors linked

a

dVdt1








Maximum current

1

2

3

4

5

6

Curr

ent (

A)

100 150 20050Voltage (V)



4 Conclusion




Acknowledgments


References



































FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of



Journal of















Table2Syste

mconfi

guratio

nactsas

astro

nggrid

totestthep

erform

ance

oftheS

B1700Einverter

underv

arying

theD

Cvoltage

Num

ber

Actual 119877 119904

Internalresistor

ofinverter

Reading119877 119904Ω

Vdc (V)

I1 (A)

V1

(V)

P1 (W)

I2 (A)

V2

(V)

P2 (W)

S2 (VA)

Efficiency

PF

DCsid

eAC

side

1315

323

28300

47

152

727

29

229

675

689

093

098

2310

357

28280

42

150

634

26

229

590

601

093

098

3320

351

28260

387

136

544

22

228

500

510

092

098

4312

415

28240

33

137

451

19228

420

430

093

098

5311

504

28220

27

136

369

157

228

340

350

092

097

6320

680

28200

2136

278

12228

250

280

09

089

7338

1046

28180

13136

182

087

228

160

206

088

078

8359

2141

28160

064

137

8806

228

70140

08

050

90

028

140


ff


DC side

Utility network

DC power supply


AC side

Push button

Switch off

Contactor

43

65

87

109

12

Series resistor

Series resistor

minus

+

56 Ohm

28 Ohm


CurrentVoltage

minus400

minus200

0

200

400

Volta

ge (V

)

minus20

minus10

0

10

20

Curr

ent (

A)

003 004 005 006 007 008002Time (s)










0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)





0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)




Time (10msdiv)

500mVminus300div

VerticalMab

Curr

ent (

2A

div

)

4

M


Time (10msdiv)

Curr

ent (

2A

div

)

4

M

500mVminus300div

VerticalMab



2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab


2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab







Curr

ent


4

3

04183712 Apr 2015400V 200mV 400ms 250kSs

10k points 000V3 34

(2A

div

)Vo

ltage

(400

Vd

iv)

Time (40msdiv)


Volta

ge

Curr

ent

3

04211112 Apr 2015400V 200mV 400ms 250kSs

10k points 000V33 4

(1A

div

)(400

Vd

iv)

Time (40msdiv)

4



a b

b

200V 200mV400ms 250kSs

10k points 132V



1 2

2

1 8 May 2015003002

Cursors linked

a

dVdt1








Maximum current

1

2

3

4

5

6

Curr

ent (

A)

100 150 20050Voltage (V)



4 Conclusion




Acknowledgments


References



































FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of



Journal of















DC side

Utility network

DC power supply


AC side

Push button

Switch off

Contactor

43

65

87

109

12

Series resistor

Series resistor

minus

+

56 Ohm

28 Ohm


CurrentVoltage

minus400

minus200

0

200

400

Volta

ge (V

)

minus20

minus10

0

10

20

Curr

ent (

A)

003 004 005 006 007 008002Time (s)










0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)





0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)




Time (10msdiv)

500mVminus300div

VerticalMab

Curr

ent (

2A

div

)

4

M


Time (10msdiv)

Curr

ent (

2A

div

)

4

M

500mVminus300div

VerticalMab



2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab


2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab







Curr

ent


4

3

04183712 Apr 2015400V 200mV 400ms 250kSs

10k points 000V3 34

(2A

div

)Vo

ltage

(400

Vd

iv)

Time (40msdiv)


Volta

ge

Curr

ent

3

04211112 Apr 2015400V 200mV 400ms 250kSs

10k points 000V33 4

(1A

div

)(400

Vd

iv)

Time (40msdiv)

4



a b

b

200V 200mV400ms 250kSs

10k points 132V



1 2

2

1 8 May 2015003002

Cursors linked

a

dVdt1








Maximum current

1

2

3

4

5

6

Curr

ent (

A)

100 150 20050Voltage (V)



4 Conclusion




Acknowledgments


References



































FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of



Journal of















0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)





0

005

01

015

02

025

Mag

( o

f fun

dam

enta

l)




Time (10msdiv)

500mVminus300div

VerticalMab

Curr

ent (

2A

div

)

4

M


Time (10msdiv)

Curr

ent (

2A

div

)

4

M

500mVminus300div

VerticalMab



2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab


2

M

Time (10msdiv)

Volta

ge (2

00

Vd

iv)

200mVminus300div

VerticalMab







Curr

ent


4

3

04183712 Apr 2015400V 200mV 400ms 250kSs

10k points 000V3 34

(2A

div

)Vo

ltage

(400

Vd

iv)

Time (40msdiv)


Volta

ge

Curr

ent

3

04211112 Apr 2015400V 200mV 400ms 250kSs

10k points 000V33 4

(1A

div

)(400

Vd

iv)

Time (40msdiv)

4



a b

b

200V 200mV400ms 250kSs

10k points 132V



1 2

2

1 8 May 2015003002

Cursors linked

a

dVdt1








Maximum current

1

2

3

4

5

6

Curr

ent (

A)

100 150 20050Voltage (V)



4 Conclusion




Acknowledgments


References



































FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of



Journal of















Curr

ent


4

3

04183712 Apr 2015400V 200mV 400ms 250kSs

10k points 000V3 34

(2A

div

)Vo

ltage

(400

Vd

iv)

Time (40msdiv)


Volta

ge

Curr

ent

3

04211112 Apr 2015400V 200mV 400ms 250kSs

10k points 000V33 4

(1A

div

)(400

Vd

iv)

Time (40msdiv)

4



a b

b

200V 200mV400ms 250kSs

10k points 132V



1 2

2

1 8 May 2015003002

Cursors linked

a

dVdt1








Maximum current

1

2

3

4

5

6

Curr

ent (

A)

100 150 20050Voltage (V)



4 Conclusion




Acknowledgments


References



































FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of



Journal of















Maximum current

1

2

3

4

5

6

Curr

ent (

A)

100 150 20050Voltage (V)



4 Conclusion




Acknowledgments


References



































FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of



Journal of


































FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of



Journal of














An Optimal Current Controller Design for a Grid Connected ...

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