IJE Reprint
-
Upload
jeevananthan-seenithangam -
Category
Documents
-
view
235 -
download
0
Transcript of IJE Reprint
-
7/25/2019 IJE Reprint
1/21
Full Terms & Conditions of access and use can be found athttp://www.tandfonline.com/action/journalInformation?journalCode=tetn20
Download by:[1.39.62.56] Date:09 June 2016, At: 09:51
International Journal of Electronics
ISSN: 0020-7217 (Print) 1362-3060 (Online) Journal homepage: http://www.tandfonline.com/loi/tetn20
Development of High Performance SolarPhotovoltaic Inverter with Reduced HarmonicDistortions
Albert Alexander
To cite this article:Albert Alexander (2016): Development of High Performance Solar
Photovoltaic Inverter with Reduced Harmonic Distortions, International Journal of Electronics,DOI: 10.1080/00207217.2016.1196746
To link to this article: http://dx.doi.org/10.1080/00207217.2016.1196746
Accepted author version posted online: 08Jun 2016.Published online: 08 Jun 2016.
Submit your article to this journal
View related articles
View Crossmark data
http://crossmark.crossref.org/dialog/?doi=10.1080/00207217.2016.1196746&domain=pdf&date_stamp=2016-06-08http://crossmark.crossref.org/dialog/?doi=10.1080/00207217.2016.1196746&domain=pdf&date_stamp=2016-06-08http://www.tandfonline.com/doi/mlt/10.1080/00207217.2016.1196746http://www.tandfonline.com/doi/mlt/10.1080/00207217.2016.1196746http://www.tandfonline.com/action/authorSubmission?journalCode=tetn20&page=instructionshttp://www.tandfonline.com/action/authorSubmission?journalCode=tetn20&page=instructionshttp://dx.doi.org/10.1080/00207217.2016.1196746http://www.tandfonline.com/action/showCitFormats?doi=10.1080/00207217.2016.1196746http://www.tandfonline.com/loi/tetn20http://www.tandfonline.com/action/journalInformation?journalCode=tetn20 -
7/25/2019 IJE Reprint
2/21
Publisher: Taylor & Francis
Journal:International Journal of Electronics
DOI: 10.1080/00207217.2016.1196746
Development of High Performance SolarPhotovoltaic Inverter with Reduced Harmonic
Distortions
1Abstract In addition to the focus towards growing demand on electrical energy due to the increase in population,
industries, consumer loads etc., the need for improving the quality of electrical power also need to be considered. The design
and development of solar Photo Voltaic (PV) inverter with reduced harmonic distortions is proposed. Unlike the
conventional solar PV inverters, the proposed inverter provides the advantages of reduced harmonic distortions thereby
intend towards the improvement in power quality. This inverter comprises of multiple stages which provides the required
230VRMS, 50Hz inspite of variations in solar PV due to temperature and irradiance. The reduction of harmonics is governed
by applying proper switching sequences required for the inverter switches. The detailed analysis is carried out by employing
different switching techniques and observing its performance. With a separate mathematical model for a solar PV
simulations are performed in MATLAB software. To show the advantage of the system proposed, a 3kWp photovoltaic plant
coupled with multilevel inverter is demonstrated in hardware. The novelty resides in the design of a single chip controller
which can provide the switching sequence based on the requirement and application. As per the results obtained, the solar
fed multi stage inverter improves the quality of power which makes this inverter suitable for both standalone and grid
connected systems.
Key words- Harmonics, Multilevel systems, Modulation strategy, Photovoltaic systems, Power Quality.
I.
INTRODUCTION
In the present scenario, development of an individual and society is basically depends on the
availability of electrical energy. In India, providing electrical power to all the consumers without
interruption is a major issue. To overcome this, many power plants are installed and proposed in
meeting the demand. For the construction of a power plant it requires thousands of crores as the
investment and also consumes more number of years for its debut power generation. Inspite of this, the
power demand is not met for the growing population.
In the conventional power generation system, it causes problems in terms of fossil fuel
1This work was supported in part by the Department of Science and Technology, Government of India under Technology System Development SchemeGrant (Ref. No.DST/TSG/NTS/2009/98).
-
7/25/2019 IJE Reprint
3/21
exhaustion and drastic effects in environment. To overcome these problems, renewable energy sources
are in high demand. It has been estimated by Cecati, Ciancetta, and Siano (2010) that the energy
generated by non conventional energy sources is estimated to quantify 50% of the total power demand
in 2050. But quality of power from these sources has to be improved to protect the loads connected in
the system and also to enable the continuity of supply to the consumers without any disturbances. Power
quality refers to maintaining near sinusoidal voltage to a bus at rated voltage and frequency. In addition
to the focus towards growing demand on electrical energy due to the increase in population, industries
and consumer loads, the need for improving the quality of electrical power also to be considered
seriously.
There are major considerations over the deviation of voltage, current and frequency in an
electrical system when connected to the load and also to the grid. This affects the entire system and
possesses major problems in connecting the non conventional energy sources towards the common grid.
It is not only the technical problem, it also exhibits financial problem. In USA, poor quality of power
results in economic loss of $120 billion/year as estimated by Electric Power Research Institute (EPRI,
2004). Hence the combination of power quality and power quantity will certainly result in providing
clean power from green energy sources. The discrimination of POWER QUANTITY or POWER
QUALITY results in acceptance of both the parameters. In Indian sub continent, power quality is a
major issue which needs to be addressed in creating a healthy and reliable power grid and utility
enhancing productivity and Gross Domestic Product (GDP) growth.
The proposed work enlists both the extremes such that the solar Photo Voltaic (PV) postulated
towards quantity and the inverter design with switching sequence controller approximated with quality.
To meet the objective, a power electronic interface with harmonic reduction capability needs to be
connected between the source and load. Unlike conventional inverters, the Multi Level Inverter (MLI)
is recommended by Rahim, Mohamed Elias, and Hew (2013) as the high quality outputs obtained from
the multilevel inverter overcomes the system size and filter requirements. The proposed inverter
provides the advantage of reduced harmonic distortions which intend towards the improvement in
power quality. This inverter comprises of multiple stages which provides the required 230VRMS, 50Hz
inspite of variations in solar PV due to temperature and irradiance. The switching sequence for the MLI
is controlled by single chip controller which enables the power quality. The input source considered is
solar PV which intends the power quantity. It is much convenient to both power quality and power
generation in the same system as mulled by Cavalcanti, Farias, Oliveira, Neves, and Afonsa (2012).
Pertaining to power quality, harmonics appear as the waveform distortion of the voltage or
current. The presence of harmonics in inverter output will lead to power supply failure and other system
components. Hence MLIs when compared to conventional two level inverters can be used in diverseapplications which require the quality of electrical power needs to be improved as claimed by Zambra,
Rech, and Pinheiro (2010).
-
7/25/2019 IJE Reprint
4/21
Alexander and Manigandan (2014) compared the various structures of MLI and found Cascaded
Multilevel Inverters (CMLI) utilizes minimum number of switching devices in ahead of other types of
MLIs. In CMLI, each DC link can be fed by an isolated sources hence it does not possess a voltage
unbalance problem as pointed by Kouro et al. (2010). Due to these merits the CMLI based structure can
be used as power conversion unit in renewable energy sources like solar PV as considered by Rahim
and Selvaraj (2010) and fuel cell by Babaei, Alilu, and Laali (2014).
This paper vindicates the performance improvement in CMLI and also addresses the challenges
of it. By eliminating harmonics, utilizing suitable control algorithms and adopting new multilevel
structures the performance can be improved as experimented by Abu-Rub, Holtz, Rodriguez, and
Baoming (2010). Reducing switching frequency and improving quality of power are the challenges of
MLIas pointed byGovindaraju and Baskaran (2011). For eliminating harmonics, the step modulation
proposed by Liu, Hong, and Huang (2009) computes the gating signals but this method cannot be used
for solar PV applications as this method intend towards equal DC sources. Newton Raphson (NR) based
iterative methods depend on the guess value and possess certain discrepancy when the inverter levels
are increased which was analysed by Fei, Du, and Wu (2010). Chiasson, Tolbert, McKenzie, and Du
(2005) found that resultant theory is much complicated and consumes more time which is capable to
calculate only three switching angles for asymmetrical DC and six switching angles for symmetrical DC
sources. For increasing the inverter levels it requires a new expression.
In this paper, a detailed analysis is carried out by employing different switching techniques and
observing its performance. MATLAB/Simulink is used to perform the simulation studies.The paper is
organised as: Section II formulates the problem design considerations and Section III describes the
various modulation strategies. Section IV describes simulation and its corresponding results. Section V
illustrates experimental outcome and some final discussions.
II. PROBLEMFORMULATION
In CMLI H Bridge each cells are referred as stages. The increase in the number of stages
increases the number of levels at the inverter output whose shape approximates near sinusoidal
waveform. It is henceforth considered that the increase in levels intend towards the reduction in Total
Harmonic Distortion (THD) which is the measure that quantifies how close the waveform is to pure
sine. Figure 1 shows the power circuit of a solar PV fed seven stage inverter to achieve a fifteen level
output.
Figure 1 Solar PV fed fifteen level inverter
Figure 1 also shows the phase voltage waveform of a cascaded fifteen level inverter with seven
PV array inputs. The phase voltage is synthesized by the sum of seven inverter outputs given by the
relation: van = va1+va2+va3+va4+va5+va6+va7. Each inverter level can generate three different voltage
-
7/25/2019 IJE Reprint
5/21
outputs, +Vdc, 0 and Vdc by connecting the PV array source to the AC output side by different
combinations of the four switches in the individual inverter stage. As a case, in the first stage of the
inverter, turning switches 1 and 4 ON yields the output +Vdcand turning switches 2 and 3 ON yields the
output Vdc. Turning OFF all the switches provides the output 0. Similarly, the AC output at each level
can be obtained in the same manner. If Nsis the number of input PV sources, the output phase voltage
level is m= 2Ns+1. Thus, a fifteen level cascaded inverter needs seven separate DC sources and seven
full bridges. Controlling the switching angles at different inverter stages can minimize the harmonic
distortion of the output voltage which in turn improves the power quality.
In India, the consumer loads operate at the input supply of 230VRMS (Root Mean Square) with
frequency 50Hz. To achieve this, the design procedure is started from the solar cell modelling. The
system considered is single phase standalone PV system with battery storage which enables it to operate
even during weak weather conditions. The proposed system is application specific especially intended
towards rural areas where there is less concentration of utility grid. Each solar cell of specification
Voc=0.5V, Isc=7A is chosen based on the data sheet of the commercial solar PV specifications. Solar
cells of 24 numbers are connected in series/parallel combinations at standard test conditions (1000W/m2
and 250C) to develop a 12V, 7A which constitutes a single solar module. Solar modules are connected
appropriately to achieve 48V, 7A solar PV array or panel. The series connection of the module is the
same as that of cell. This 48V, 7A solar PV serves as the input source for the single inverter stage. In
the proposed work, seven numbers of such input sources are utilized to power the seven inverter stages,
thereby a fifteen level output waveform is obtained. The following relations given in Equations (1) and
(2) hold for the desired design requirement:
V3367V48Vpeak == (1)
V59.2372
336VRMS == (2)
In order to extend the system for making it suitable for grid connected system, the condition
given in Equation (3) has to meet as indicated by Rahim, Chaniago, and Selvaraj (2011).
dc gridV > 2V (3)
In the proposed design, the total Vdc=336V is greater than the square root of the grid voltage
(230VRMS) as per the condition given in the Equation (3). As the design made for Standard Test
Conditions (STC), it produces the fixed DC output from solar panel without any variations. Most of the
models in various literature deals with the fixed output supply panels. Hence the PV panel model which
-
7/25/2019 IJE Reprint
6/21
exhibits the variations occurring due to temperature and irradiance is required to adhere the real time
specifications. In order to achieve this, a detailed analytical study on temperature and irradiance
variations is undertaken throughout the year by solar PV observatory for the geographic location where
the experiment is conducted. The radiation measurements used are beam and diffuse horizontal surface
radiation gathered with a PV pyranometer. Figures 2 and 3 shows the analysis which depicts the
irradiation and temperature levels measured for the months of January and November. Based on the
analysis it is found that the irradiance varies from 0W/m2to nearly 900W/m2.
The Solectric 9000 model is taken into consideration for modelling which provides 115W of
nominal maximum power and it has 24 numbers of series connected polycrystalline silicon cells for a
single module. It consists of two bypass diodes each of which is connected in antiparallel with 12 series
connected PV cells to protect them against hot spots. For providing a PV array input, 96 series
connected cells are used for modelling. Figure 4 shows the characteristics of modelled solar PV array
which serves as the inverter input.
Figure 2 Solar data for the month of January (Min: 0W/m2, Max: 892W/m2)Figure 3 Solar data for the month of November (Min: 0W/m2, Max: 887W/m2)
Figure 4 (a) V-I and (b) V-P characteristics of solar PV array
III.
MODULATIONSTRATEGIESIn order to improve the modular characteristics and performance of MLIs, unique modulation
techniques, control and protection features are required. A high number of power electronic devices and
switching redundancies bring a higher level of complexity compared with the two level inverters. This
complexity could be used to add additional capabilities to the modulation techniques by reducing the
switching frequency (fs), minimizing the Common Mode Voltage (CMV) and balancing the DC
voltages as studied by Malinowski, Gopakumar, Rodriguez, and Prez (2010).
By using Sinusoidal Pulse Width Modulation (SPWM) techniques, the inverters fundamental
voltage can be controlled and the harmonics will be attenuated. In this method, a carrier signal at the
desired frequency is generated and compared with the modulating voltage signal to generate gating
signals for the switching devices. When the modulating signal is above the carrier, the upper switch is
ON and when below the carrier, the lower switch is ON. Unlike the single carrier used in the SPWM
approach for the two level inverters, multiple carriers PWM with various sequence modifications are
proposed to improve power quality in solar PV fed CMLI. Multiple carrier based PWM has several
triangle carrier signals which can be modified in phase and/or vertical position in order to reduce the
output voltage harmonic content. The frequency of the triangular signal establishes the switching
-
7/25/2019 IJE Reprint
7/21
frequency of the switches and the frequency of the modulating signal determines the inverter output
frequency.
The multiple carrier modulation is classified into vertical and horizontal distribution; in which
vertical distribution of carriers does not increase the equivalent carrier frequency. This technique is
further classified into Alternate Phase Opposition Disposition (APOD), Phase Opposition Disposition
(POD) and Phase Disposition (PD). Mei, Xiao, Shen, Tolbert, and Zheng (2013) found that PD PWM
has voltage balance capability and better output voltage harmonic profile than phase shift PWM.Cougo,
Gateau, Meynard, Rafal, and Cousineau (2012) shown POD is better in terms of differential mode of
phase currents. Figure 5 shows the carrier arrangements for PD, POD and APOD considering a five
level inverter in normal case with equal distribution of carriers without any modification in frequency or
amplitude. The novelty of the work is in achieving all these modulations in a single chip with
movement of carriers above and below the zero reference for solar PV applications.
Figure 5 Carrier arrangements of (a) PD (b) POD and (c) APOD
For an m level inverter, these level shifted modulation schemes require (m-1) triangle carriers,
all having the same frequency and peak to peak amplitude. The (m-1) carriers are vertically disposed
such that the bands they occupy are contiguous. The frequency modulation index (m f) and amplitude
modulation index (ma) are given in Equations (4) and (5).
m
crf
f
f
m = (4)
)1m(V
V2m
cr
ma
= (5)
where fcr and fmare the frequencies of the carrier and modulating signals respectively. Vcr is the peak
amplitude of the modulating signal and Vm is the peak amplitude of each carrier signal.The value of ma
is between 0 to 1, beyond which it is termed as over modulation region which has to be avoided to
achieve better results.
IV.
PROBLEMSTATEMENT
The paper aims at design and implementation of a solar PV fed cascaded fifteen level inverter
with various modulation strategies in order to reduce the harmonic distortions. This includes the
multiple carrier PWM techniques such as APOD, PD and POD along with the SPWM techniques. The
modifications were made in both carrier and reference arrangements to provide the best suited strategy
for solar PV applications in spite of variations in the solar PV input. Appropriate modulation technique
with the choice of various parameters such as modulation index, switching frequency and signal
arrangement will certainly improve the power quality by reducing the harmonics in the system. The
-
7/25/2019 IJE Reprint
8/21
methods considered for each of the multicarrier PWM topologies and analysed from single stage three
level inverter to seven stage fifteen level inverter are: a) Multiple carrier with sinusoidal reference,
b) Multiple carrier of variable frequency, c) Multiple carrier of variable amplitude, d) Multiple carrier
with modified sinusoidal reference, e) Multiple carrier with Trapezoidal Amalgamated Reference
(TAR), f) Phase Shifted Carrier (PSC) and g) Unipolar and bipolar modulations.
SIMULATION AND RESULTS
MATLAB/Simulink software R2010b is used for simulation of all the modulation strategies. The
modelled solar PV panel with the input 48V, 7A depicts as the input for the separate inverter stages of
CMLI. For simulations, parameters used are, amplitude modulation index ma=1, switching frequency
fs=1000Hz as considered by Kouro, Roboelledo, and Rodriguez (2010), inverter output frequency=
50Hz and frequency modulation index mf=20. Zhang, Jouanne, Dai, Wallace, and Wang (2000) have
prescribed that the switching frequency of 1 kHz will be much appropriate for PWM inverters to reduce
the losses which was also analysed by Zhang, Jouanne, Dai, Wallace, and Wang (2000). The load
considered is RL whose values are R=100and L=10mH. For a fifteen level inverter, 14 carrier signals
are required to generate the switching pulses in which seven carriers each are placed above the zero
reference and the remaining seven carriers are positioned below the zero reference. Figure 6 shows the
multi carrier arrangements for APOD, POD, PD, PSC (each carrier signals are phase shifted by 25.71 0),
unipolar modulation (with bias at 3.2V) and inverted sine reference with TAR. Figure 7 shows the
carrier arrangements for APOD in which the modifications are made in frequency and amplitude. The
similar modifications are also considered for POD and PD whose results are given in Figure 8.
Figure 6 Multi carrier arrangements for solar PV fed fifteen level inverter
Figure 7 Modified multi carrier arrangements for solar PV fed fifteen level inverter
The comparisons given in Figure 8 (a) to (h) illustrates the resultant THD obtained from solarPV fed single stage inverter to seven stage inverter with aid of various approaches such as normal,
variable amplitude, variable frequency and modified reference. Based on the results it infers that by
increasing the levels, the harmonic distortions are summarily reduced to a great extent.
Figure 8 Comparison of THD for various modulation strategies
A minimum THD is achieved when the inverter output level reaches fifteen. Further increase in
levels can also be made, but as the design procedures suitable for Indian sub continent is developed for
the fifteen levels, it gets limited with this level. While comparing the THD for the multiple carrier PWM
methods, the lesser THD values are obtained at APOD, PD and POD in variable frequency modes and
PSC in unipolar mode.
-
7/25/2019 IJE Reprint
9/21
V. EXPERIMENTALRESULTS
A 3kWpsolar PV power supply unit is designed and implemented for the seven stage fifteen level
solar fed CMLI with multiple carrier PWM generation in a single chip. Table 1 shows the rating of the
individual solar PV module. Solar panels are connected to the loads in any of three divisions: direct,
standalone and grid connected. For application oriented, the first one is not applicable. In the proposed
set up, stand alone type is used which can also be extended to grid connected systems.
Table 2 reveals the specifications of the entire hardware setup. Figure 9 shows the 3kWp solar
PV plant and Figure 10 shows the complete hardware setup of the proposed CMLI. Here the notation
INV specifies the individual inverter stage. Gu et al. (2013) postulated the necessary to utilize
MOSFETs as a switching device.
The DSP controller is utilized for the generation of switching pulses for the MOSFET switches
based on POD, APOD and PD schemes. The carrier signals are generated and level shifted above and
and below the zero reference to produce the desired pulses. A change over switch is included which will
subsequently make the choice for any of the three schemes.
Table 1 Solar PV panel specifications Table 2 Specifications of experimental set up
Figure 9 Solar PV plant of 3kWp with 28 modules
Figure 10 Experimental setup of the proposed solar fed fifteen level inverter
These carrier signals are level shifted above and below the zero reference as per the program to
achieve PD, POD and APOD signals. Figures 11 to 13 show the carrier arrangements generated by the
controller pertaining to APOD, PD and POD modulation schemes. A DSP based processor for PV
system with tuning parameters for filter design is given by Zhang, Tang, and Yae (2015). Unlike DSP,
an analogue based circuit design for switching function generation in boost converters is investigated by
Cho, Kwak, and Lee (2015). Figure 14 shows output voltage waveform of the proposed solar inverter.
Figure 11 APOD based carrier arrangement
Figure 12 POD based carrier arrangement
Figure 13 PD based carrier arrangementFigure 14 Fifteen level inverter output voltage waveform
Table 3 shows the harmonic analysis conducted for each modulation strategies using Power
Quality Analyser (PQA) WT3000 which depicts both voltage and current THD values. WT3000 is a
high precision analyser which can display 20 parameters along with the THD and the magnitude of
harmonic orders. Based on the results it is found that inspite of variations in solar PV, by using CMLI
the required output of 230VRMS, 50Hz is achieved.
Table 3 Harmonic analysis for APOD, POD and PD
The experimental setup developed for a 3kWp solar PV inverter comprising 28 panels of each
115Wp in a standalone mode, the harmonic measurements are undertaken. The different modulations
-
7/25/2019 IJE Reprint
10/21
given in Figures 11 to 13 are thus obtained based on the shifting mechanism of carrier waveforms above
and below the zero reference with an aid of DSP processor. High care should be ensured that the carrier
shifting remain same for all the stages in both its amplitude and frequency. Deviations if any will results
in the abnormal waveforms across the inverter output. This is due to the consideration that the
comparison of carrier and reference signals will not be the same for all the three methodologies which
can be clearly viewed for the lower modulation index. The detailed information on harmonic analysis
for the proposed inverter is shown in Table 4.
Table 4. Detailed information on harmonic analysis
Voltage regulation is the process of obtaining the required output voltage in closed loop system.
The actual voltage obtained at the CMLI output in aid of solar PV variations is compared with the
required 230V. The error thus obtained is utilized as modulating signal for POD and compared with its
respective carriers. By adopting this technique, the THD is also reduced and adhere to the IEEE
standard 519-1992.
Table 5 shows the comparison of results .Table 6 shows the comparison of results obtained
from other methods in literature with the aid of resultant THD and the number of levels considered.
Table 5 Comparison between simulation and experimental results
Table 6 Comparison with the other methods
The results thus obtained thus indicate that by the appropriate choice of switching schemes will
eventually improves the power quality by reducing the value of THD. Of the three schemes investigates,
POD provides the lesser THD when compared to its counterparts APOD and PD. When comparing withother methods listed in various literatures, much of the methods are proposed for lesser number of
inverter levels and the implementation is not considered for solar PV applications. For the method
proposed, higher number of levels with reduced harmonic distortion is achieved and a single chip
controller for all the modulating strategies for level shifting makes the method unique when compared
to other methods listed in Table 5.
VI. CONCLUSION
A solar fed cascaded fifteen level inverter for power quality improvement is developed. The
multiple carrier PWM techniques are eminently suggested for the reduction of THD in a solar fed
CMLI. In the multiple carriers, the variations are made in both carrier and reference signals and their
performance is analysed from three level to fifteen level solar PV fed inverters. Based on the results, it
is found that POD method provides the least THD when compared to its counterparts. All the methods
considered for comparison deal with low power systems and uses DC power supply as its input source.
An experimental investigation is carried out for a 3kWp solar PV system with DSP based controller ingenerating the switching signals to the MLI. As per the results obtained, the solar fed multi stage
inverter improves the quality of power which makes it inverter suitable for all the systems.
-
7/25/2019 IJE Reprint
11/21
ACKNOWLEDGEMENT
The authors acknowledge and thank the Department of Science and Technology (Government of
India) for sanctioning the research grant for the project titled, DESIGN AND DEVELOPMENT OF
MULTILEVEL INVERTERS FOR POWER QUALITY IMPROVEMENT IN RENEWABLE
ENERGY SOURCES (Ref.No.DST/TSG/NTS/2009/98) under Technology Systems Development
Scheme for completing this work.
REFERENCES
Abu-Rub,H., Holtz,J., Rodriguez, J., & Baoming, G. (2010). Medium-Voltage Multilevel Converters-State of the Art,Challenges, and Requirements in Industrial Applications.IEEE Transactions on Industrial Electronics. 57,8, 2581-2596. doi: 10.1109/TIE.2010.2043039
Alexander,S.A., & Manigandan,T. (2014). Digital Control Strategy for Solar Photovoltaic fed Inverter. Journal ofRenewable and Sustainable Energy, 6, 013128 (1)-(18). doi: 10.1063/1.4863987
Babaei,E., Alilu, S., & Laali, S.(2014). A New General Topology for Cascaded Multilevel Inverters with Reduced Numberof Components Based on Developed H-Bridge.IEEE Transactions on Industrial Electronics. 61,8, 3932-3939.doi:
10.1109/TIE.2013.2286561Cavalcanti,C.M., Farias,M.A., Oliveira,C.K., Neves,A.S.F., & Afonsa,L.J. (2012). Eliminating Leakage Currents in Neutral
Point Clamped Inverters for Photovoltaic Systems. IEEE Transactions on Industrial Electronics. 59,1, 435-443.doi: 10.1109/TIE.2011.2138671
Cecati,C., Ciancetta,F., & Siano,P. (2010). A Multilevel Inverter for Photovoltaic Systems with Fuzzy Logic Control.IEEE Transactions on Industrial Electronics. 57, 12, 4114-4125. doi: 10.1109/TIE.2010.2044119
Cho,H.K., Kwak,S.S., & Lee,S.H., (2015) Fault diagnosis algorithm based on switching function for boost converters.International Journal of Electronics, 102,7, 1229-1243. doi: 10.1080/00207217.2014.966780
Cougo, B., Gateau, G., Meynard,T., Rafal,M.B., & Cousineau, M. (2012). PD Modulation Scheme for Three-PhaseParallel Multilevel Inverters. IEEE Transactions on Industrial Electronics. 59,2, 690-700. doi:10.1109/TIE.2011.2158773
Fei,W., Du,X., & Wu,B., (2010). A Generalized Half-Wave Symmetry SHE-PWM Formulation for Multilevel VoltageInverters.IEEE Transactions on Industrial Electronics.57, 9, 30303038. doi: 10.1109/TIE.2009.2037647
Govindaraju,C., & Baskaran,K. (2011). Efficient Sequential Switching Hybrid-Modulation Techniques for CascadedMultilevel Inverters.IEEE Transactions on Power Electronics. 26,6, 1639-1648. doi: 10.1109/TPEL.2010.2089064
Gu,B., Dominic, J., Lai, J.S., Chen, C.L., La Bella,T., & Chen,B. (2013). High Reliability and Efficiency Single-PhaseTransformer less Inverter for Grid Connected Photovoltaic Systems. IEEE Transactions on Power Electronics.28,5, 2235-2245. doi: 10.1109/TPEL.2012.2214237
Gupta, R., Ghosh, A. & Joshi, A. (2010). Multiband Hysteresis Modulation and Switching Characterization for Sliding ModeControlled Cascaded Multilevel Inverter. IEEE Transactions on Industrial Electronics, 57, 7,.2344-2353. doi:10.1109/TIE.2009.2030766
Kouro,S., Rebolledo , J., & Rodrguez, J., (2007). Reduced Switching-Frequency-Modulation Algorithm for High-PowerMultilevel Inverters.IEEE Transactions on Industrial Electronics. 54,5, 2894-2901. doi: 10.1109/TIE.2007.905968
Kouro,S., Malinowski, K.M., Gopakumar, Pou, J., Franquelo, L.G., Wu,B., Rodriguez, J., Prez, M.A., & Leon, J.I. (2010).Recent Advances and Industrial Applications of Multilevel Converters. IEEE Transactions on IndustrialElectronics.57, 8, 2553-2579.doi: 10.1109/TIE.2010.2049719
Liu,Y., Hong, H., & Huang, A.Q., (2009). Real-Time Calculation of Switching Angles Minimizing THD for MultilevelInverters with Step Modulation. IEEE Transactions on Industrial Electronics. 56, 2,285-293.doi:10.1109/TIE.2008.918461
Malinowski, M., Gopakumar,K., Rodriguez, J., & Prez, M.A., (2010). A Survey on Cascaded Multilevel Inverters. IEEETransactions on Industrial Electronics.57,7, 2197-2206.doi: 10.1109/TIE.2009.2030767
Mei,M.,Xiao,B.,Shen,K.,Tolbert, L.M., & Zheng, J.Y., (2013). Modular Multilevel Inverter with New Modulation Methodand its Application to Photovoltaic Grid-Connected Generator. IEEE Transactions on Power Electronics. 28,11,5063-5073.doi: 10.1109/TPEL.2013.2243758
Rahim,N.A., & Selvaraj,J. (2010). Multistring Five-Level Inverter with Novel PWM Control Scheme for PVApplication.IEEE Transactions on Industrial Electronics.57, 6, 2111-2123.doi: 10.1109/TIE.2009.2034683
Rahim,N.A., Chaniago,K., & Selvaraj,J. (2011). Single-Phase Seven-Level Grid-Connected Inverter for PhotovoltaicSystem.IEEE Transactions on Industrial Electronics. 58, 6, 2435-2443. doi: 10.1109/TIE.2010.2064278
Rahim,N.A., Mohamed Elias, F.M., & Hew, W.P. (2013). Transistor-Clamped H-Bridge Based Cascaded Multilevel Inverter
with New Method of Capacitor Voltage Balancing. IEEE Transactions on Industrial Electronics.60, 8, 2943-2956.doi: 10.1109/TIE.2012.2200213
The CEA (2015). Executive summary of power sector in India for the month of May 2015. Retrieved fromhttp://www.cea.nic.in/reports/monthly/executive_rep/may15.pdf
-
7/25/2019 IJE Reprint
12/21
The EPRI (2004). What is Power Quality?. Retrieved from http://www.epri.comZambra,A.B.D., Rech,C., & Pinheiro,J.R. (2010). Comparison of Neutral-Point-Clamped, Symmetrical, and Hybrid
Asymmetrical Multilevel Inverters. IEEE Transactions on Industrial Electronics. 57,7, 2297-2306.doi:10.1109/TIE.2010.2040561
Zhang, H., Jouanne,A.V., Dai, S., Wallace, A.K., & Wang, F. (2000). Multilevel Inverter Modulation Schemes to EliminateCommon-Mode Voltages.IEEE Transactions on Industry Applications. 36, 6, 1645-1653.doi: 10.1109/28.887217
Zhang, N., Tang, H. & Yae, C (2015). Analysis of Active Damping of LCL Filter Used In Single-Phase PV System inDiscrete Domain.International Journal of Electronics, 102,6, 1022-1043. doi: 10.1080/00207217.2014.954637
Zhao,Z., He,X., & Zhao,R. (2010). A Novel PWM Control Method for Hybrid-Clamped Multilevel Inverters. IEEETransactions on Industrial Electronics, 57, 7, 2365-2373. doi: 10.1109/TIE.2009.2027915
Figure 1 Solar PV fed fifteen level inverter
-
7/25/2019 IJE Reprint
13/21
Figure 2 Solar data for the month of January (Min: 0W/m2, Max: 892W/m2)
Figure 3 Solar data for the month of November (Min: 0W/m2, Max: 887W/m2)
(a) (b)
Figure 4 (a) V-I and (b) V-P characteristics of solar PV array
.
(a) (b) (c)
Figure 5 Carrier arrangements of (a) PD (b) POD and (c) APOD
-
7/25/2019 IJE Reprint
14/21
(a) APOD (b) POD
(c) PD (d) PSC
(e) Unipolar with bias (f) TAR
Figure 6 Multi carrier arrangements for solar PV fed fifteen level inverter
(a) Variable amplitude (b) Variable frequency
-
7/25/2019 IJE Reprint
15/21
(a) Modified reference
Figure 7 Modified multi carrier arrangements for solar PV fed fifteen level inverter
(a) APOD: Comparison for voltage THD (b) APOD: Comparison for current THD
(c) POD: Comparison for voltage THD (d) POD: Comparison for current THD
(e) PD: Comparison for voltage THD (f) PD: Comparison for current THD
-
7/25/2019 IJE Reprint
16/21
(g) PSC: Comparion of voltage and current THD (h) Dual reference and TAR: Comparison
Figure 8 Comparison of THD for various modulation strategies
Figure 9 Solar PV plant of 3kWp with 28 modules
-
7/25/2019 IJE Reprint
17/21
-
7/25/2019 IJE Reprint
18/21
Figure 11 APOD based carrier arrangement
Figure 12 POD based carrier arrangement
-
7/25/2019 IJE Reprint
19/21
Figure 13 PD based carrier arrangement
Figure 14 Fifteen level inverter output voltage waveform
-
7/25/2019 IJE Reprint
20/21
Table 1 Solar PV panel specifications Table 2 Specifications of experimental set up
Table 2 Specifications of experimental set up
Parameter Value
Model Solectric 9000
Pmpp 115Wp
Voc 21.2V
Isc 7.4A
Vpm 16.5V
Ipm 6.95A
Max system voltage 540V
Tolerance at peak power 5%
Number of panels 28
Total power 3220Wp
Parameter Rating
Charge Controllers (CC)
Make Sukaam
V-I Rating 48V,10A
Number of CC 7
Battery bank
Make & Model EXIDE 6LMS100L
Rating 12V, 100Ah
Number of batteries 28
Power circuit
Semiconductor devices MOSFET IRF 840
Number of devices 28
Switching sequences APOD, POD, PD
Control circuit
Controller DSP - TMS320F2812
Measuring Instruments
Power quality analyser Yokogawa WT3000
Oscilloscope Tektronix
Logic Analyser 0+ LOGIC CUBE 32128
-
7/25/2019 IJE Reprint
21/21
Table 3. Harmonic analysis for APOD, POD and PD
Method VRMS IRMS P1 S1 Q1 VTHD ITHD PTHD
APOD 229.05 2.140 439.419 439.429 0.873 8.813 7.740 2.168
POD 229.45 2.294 439.524 439.534 0.871 7.955 7.851 2.206
PD 229.95 2.619 495.398 415.391 0.713 9.514 9.526 2.400
Table 4.Detailed information on harmonic analysis
Or. U1 [V] hdf[%] I1 [A] hdf [%]
Tot. 230.611 2.843
dc --------------- ----------------- ---------------- -----------------
1 228.488 99.079 1.247 99.092
2 0.127 0.055 0.136 0.079
3 27.670 1.999 0.606 1.922
4 0.207 0.090 0.145 0.084
5 10.994 0.767 8.153 0.717
6 0.176 0.076 0.136 0.0797 7.289 0.161 5.422 0.137
8 0.369 0.160 0.238 0.137
9 1.433 0.621 1.063 0.615
10 0.120 0.052 0.087 0.050
11 3.566 1.546 2.649 1.533
12 0.410 0.178 0.292 0.169
13 1.795 0.779 1.316 0.761
14 0.917 0.398 0.673 0.389
15 0.536 0.232 0.369 0.213
16 0.395 0.171 0.294 0.170
17 0.877 0.380 0.648 0.375
18 0.176 0.076 0.141 0.081
19 1.556 0.675 1.152 0.66620 0.360 0.156 0.240 0.139
Table 5 Comparison between simulation and experimental results
S.No. ModulationSimulation Experimental
VTHD (%) ITHD (%) VTHD (%) ITHD (%)
1. APOD 8.98 7.23 8.813 7.740
2. POD 7.84 5.63 7.955 7.851
3. PD 8.04 5.96 9.514 9.526
Table 6 Comparison with the other methodsAuthors Levels Methodology THD (%) Application to solar PV
Zhao, He, and Zhao (2010). 5 PD 38.73
Malinowski, Gopakumar,
Rodriguez, and Prez (2010)
5
5
7
PSC
Bipolar
Bipolar
30.2
29.9
21.8
Gupta, Ghosh, and Joshi (2010) 5 Multiband 27.0
Zambra, Rech, and Pinheiro
(2010)
9 PD 8.29
Proposed 15 POD 7.9
PLL U1
Freq 49.667 Hz
U1 230.611 V
I1 2.843 A
P1 639.8497W
S1 639.8548 VA
Q1 -0.6372 var
1 0.99987
1 D 0.916Uthd1 3.539%
Ithd1 3.445%
Pthd1 1.805%