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Modelling and Simulation of FLC based PV Integrated

Unified Power Quality Conditioner

S Neeraja1, Pydisetty Maheswara Rao2, Dr. B Srinivasa Rao3

1, PG Scholar, Department of Electrical and Electronics Engineering

2, Asst. Professor , Department of Electrical and Electronics Engineering 3, Professor , Department of Electrical and Electronics Engineering

Vishaka Institute of Engineering Technology, Narava, Vishakapatnam (Dt), AP, India.

[email protected]

Abstract—

This paper presents a fuzzy logic controller (FLC) technique insolar PV system for improving

the power quality (PQ) with incorporated to UPQC-P (SPV-UPQC-P) in distribution

network. Various loads such as non-linear and critical loads are connected across the solar

system for enhancing the power quality at various circumstances. The proposed system is

investigated during sag/swell situations as well as the PV based compensator can contribute

the injected voltage at different conditions. in this study, for compensating the power quality

difficulties, the voltage generated by the PV system and it is fed to DC link. The system is

carried out under different functioning conditions. The proposed system is examined on

MATLAB/Simulink environment under irradiance, sag/swell and step change in load

conditions.

Key Words: Solar PV module, MPPT, UPQC, Power Quality, Fuzzy logic controller.

1. INTRODUCTION

Power quality disturbances in power system have increased the difficulties of the consumer

by affecting to the sensitive loads. Issues related to power quality such as voltage and current

quality issues have been focused on by Subjak and Mcquilkin (1990), Salmeron and Litran

(2010) and Tey et al. (2005). In addition to this, non-conventional energy sources such as

solar power and wind generated electrical power have shown their effectiveness over

conventional energy sources. Thereby, solar as well as wind energy sources have been

adopted at the distribution level for clean energy generation. However, there is requirement

of power electronic converters/ inverters for the grid penetration of renewable energy system

[1].

The single phase system as well as three phase systems require UPQC as power conditioner.

The issues related to voltage and current such as voltage sags, swells, unbalances and current

harmonics are more significant in single phase systems [3]. Although UPQC is not a new

topic, PV fed UPQC has not gained saturation among researchers, as in India there are very

few working in this field and until now it has not been in practical implementation or

commercially used for the power network. As PV grid integration has gained its popularity

Journal of Information and Computational Science

Volume 9 Issue 9 - 2019

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based on various innovative topologies associated with it are only concentrate on elimination

of current quality issues. Therefore, PV fed UPQC system has been selected by the authors of

the paper to evaluate the performance based on a new controller under highly distorted grid

condition. Furthermore, various single phase grid connected PV systems have been studied,

which are dedicatedly operated for current quality issues elimination (Tuyen and Fujita,

2015). Various innovative topologies have been reported for PV grid integration with single

phase system, but PV grid integration through UPQC for single phase systems have not been

studied and implemented so far. Therefore, the authors have proposed single phase system

where PV has been connected to the grid through UPQC in the present paper. Depending

upon the location of the series active filter part and shunt active filter part of UPQC, it has

been classified into different categories: in UPQC-L topology (left shunt connected UPQC),

where shunt inverter is present at grid side and UPQC-R topology (right shunt connected

UPQC), where shunt active filter of UPQC is found to be present at load terminal [4]. The

mechanism of voltage injection angle for UPQC also presents classification of UPQC, such

as UPQC-Q, UPQC-S and UPQC-P. The requirement of quadrature component and its

injection to the grid is handled by UPQC-Q topology. The UPQC-P type of conditioner has a

characteristic; where the series inverter provides voltage signal in phase with grid voltage

signal [5]. The fault ride through operation along with voltage and current quality issues have

been discussed in [6]. Efficient controllers for grid connected PV systems have been studied

and utilized, developed specially for elimination of current quality issues. Thereby

simultaneous mitigation of voltage and current issues are focused on in this paper by the

implementation of 1 f PV tied UPQC system. The performance enhancement of UPQC can

be achieved by utilization of efficient controllers (Dash and Ray, 2017a). Unit vector

template generation (UVTG) scheme has been also adopted for control of both shunt inverter

part and series inverter part of UPQC system. It is studied from the literature that the

aforementioned controller has been employed for conventional power system. In addition,

there are very few papers that report on the controllers for PV tied UPQC system.

In this paper, the operation of SPV-UPQC-P is examined in detail. To interface solar oriented

PV cluster with DC-connection of UPQC-P,a Boost DC-DC converter is utilized alongside

performing MPPT operation. The dynamic power from the solar based PV exhibit is infused

into the lattice by means of the shunt converter. The receptive part of the heap control is

provided by the shunt compensator, in this way keeping up solidarity control factor at the

network side. The DVR infuses a voltage amid voltage sag/swell in phase with the

framework current which brings about least voltage infusion by the DVR to make up for the

droop or swell in the lattice voltage.

2. SYSTEM OUTLINE & DESIGN

The setup of the SPV-UPQC-P is appeared in Fig1. The fundamental subsystems in the

UPQC are as per the following:

1) It comprises of a shunt VSC and an arrangement VSC with a common DC-transport. The

shunt VSC is associated over the heap. The arrangement VSC is associated in arrangement

with network.



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2) Interfacing Inductors are associated with each VSC for interfacing with network.

3) Ripple channels are utilized for bypassing high recurrence sounds created because of

exchanging.

4) An infusion transformer is utilized for infusing the voltage created by the arrangement

VSC into the system.

5) A lift DC-DC converter is utilized for interfacing the PV cluster to the DC-connection of

SPV-UPQC-P and for most extreme control point following (MPPT) [13].

The phasor graph of SPV-UPQC-P is shown in Fig2. The subscript 1 shows the qualities

previously droop and subscript 2 is for hang condition. The voltage of DVR (VDV R) is

infused in stage with the network voltage (VS2). The DSTATCOM current (Ish) is mix of

dynamic current Iash which is corresponding to PV exhibit power and Irsh which is relative to

the heap receptive power. It can be seen when the PV exhibit control surpasses that of the heap

necessity, the

Fig1. System outline of SPV UPQC-P

Network current relative to the overabundance control streams into the framework.

Subsequently, matrix current (IS1) before sag, (IS2) amid droop is inverse in stage to that of

load dynamic current.



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Fig2. Phasor diagram of SPV UPQC-P

2.1. SYSTEM DESIGN

The outline of SPV-UPQC-P includes determination of proper greatness of DC-transport

voltage, measuring of DC-transport capacitor, interfacing inductor for DVR and

DSTATCOM, outline of support DC-DC inductor, arrangement infusion transformer and

measuring of solar based PV exhibit. The plan perspectives are additionally explained as

follows:

a) Magnitude of DC-Bus voltage: The size of DC link Voltage Vdc relies upon the profundity

of balance utilized also, per-stage voltage of the framework. The DC-interface voltage

greatness should dramatically increase the pinnacle of per-stage voltage of the three stage

framework [10]. The size of DC Bus voltage is given as

𝑉𝑑𝑐 =2√2𝑉𝐿𝐿

√3m (1)

Where profundity of regulation (m) is taken as 1 and VLL is the network line voltage. For a

line voltage of 415V, the base esteem DC-transport voltage is 677.7V. Along these lines, the

DC-transport voltage is set at 700V.

b)DC Bus Capacitor: The DC capacitor is outlined depending upon control necessity and in

addition size of DC-transport voltage. The vitality adjust condition for the DC-transport

capacitor is given as

1

2𝐶𝑑𝑐[Vdc2 − Vdc12] = 3kaVphIt (2)

where Vdc is the reference DC transport voltage, Vdc1 is the most reduced required estimation

of DC-transport voltage, the over-burdening factor is taken as 1, Vph is per-stage voltage, t is

the base time required for accomplishing consistent incentive after an aggravation, I is per-

stage current, k factor considers variety in vitality amid flow and is taken as 0.1. The base

required DC-interface voltage is Vdc1 = 677.69 V as acquired from (2), Vdc = 700 V, Vph=

239.60 V, I= 36.9 A, t= 20ms, a = 1.2, and for dynamic vitality change = 10%, k= 0.1, the

estimation of Cdc is acquired as 4000μF. The rating of capacitor is chosen as 5000μF.



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c)Interfacing Inductor of DSTATCOM: The DSTATCOM interfacing inductor esteem relies

on the swell current, converter exchanging recurrence and DC-connect voltage. The

articulation for the interfacing inductor is as,

𝐿𝑓 =√3mVdc

12afsIcr,pp (3)

where m is profundity of regulation, an is pu estimation of most extreme over load ,fs is the

exchanging recurrence , Icr,pp is the inductor swell current. Here, m=1, a=1.2, fs=10 kHz,

Vdc=700V, one gets 2.3mH as esteem. The estimation of inductance is chosen as 3.5mH.

d)Series Injection Transformer: For a PWM VSC ,a DC link voltage of 700V DC gives415V

line voltage. As the most extreme voltage droop/swell is 0.3pu i.e. 71.88V, the required

voltage to be infusion is just 71.88V which brings about low tweak file at 700V DC-interface

voltage. With a specific end goal to keep tweak file of arrangement VSC close to solidarity,

one may utilize a arrangement transformer with a turns proportion,

𝐾𝐷𝑉𝑅 =VVSC

VDVR (4)

The esteem got for KDVR is 3.33. The esteem chose is 3. The rating of DVR arrangement

infusion transformer is given by

𝑆𝐷𝑉𝑅 = 3𝑉𝐷𝑉𝑅𝐼𝐷𝑉𝑅 (5)

As the DVR is connected in arrangement with the framework, the DVR current is same as

framework current. For a 15kVA load at 0.8pf, with 30% list and 25kW contribution from PV

cluster, the VA rating of infusion transformer accomplished is 5.5kVA

e)Interfacing Inductor of DVR: The DVR interfacing inductor esteem relies on the swell

current at swell condition, exchanging recurrence and DC-connect voltage. Its esteem is

communicated as,

𝐿𝑓 =√3𝑚𝑉𝑑𝑐𝐾𝐷𝑉𝑅

12𝑎𝑓𝑎𝐼𝑟 (6)

where m is the profundity of tweak, a is the pu estimation of greatest over-burden, fs is the

exchanging recurrence, Ir is the inductor current swell, which is taken to be 20% of lattice

current under swell condition. Here, m=1, a=1.2, fs=10 kHz, Vdc=700V and 20% swell

present, one gets 6.3mH as esteem. The chose esteem is as 6.3mH

f)Boost Inductor: The lift inductor articulation is given as,

L = 𝑉𝑝𝑣(𝑉𝑑𝑐−𝑉𝑝𝑣)

𝛻𝐼𝐿𝑓𝑉𝑑𝑐 (7)

For the given framework, Vpv=555V Vdc=700V, f=20 kHz, ΔI=6.75A. The estimation of

inductor acquired is 851.9μH The esteem chose in re-enactment is as 1mH.



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g)PV Array Sizing: The PV array open circuit voltage is chosen as 700V which is same as the

estimation of wanted DC bus voltage of the UPQC. Its measuring is done keeping in mind the

end goal to work the lift converter at bring down obligation proportion and lower current for

a given power level. This outcomes in bring down conduction misfortunes in the lift

converter when contrasted with a PV exhibit structure with bring down voltage and higher

current for the power rating. The PV cluster details are given in Table-I

3. CONTROL SCHEME OF SPV-UPQC-P

The SPV-UPQC-P has three noteworthy subsystems. They are DSTATCOM, DVR and lift

DC-DC converter. The DSTATCOM keeps up the DC-connect voltage alongside adjusting

for receptive power and infusing dynamic power from the PV exhibit. The DVR comes into

operation amid lattice voltage list/swell conditions and the lift converter performs MPPT

operation separating greatest power accessible from PV cluster also, infusing into the DC-

connection of shunt VSC and arrangement VSC.

a)Control of Boost Converter

The boost converter is controlled by MPPT algorithm. The MPPT calculation [12] produces

fitting obligation proportion based on the PV exhibit voltage and current esteems to work the

exhibit at its most extreme power point. Some of MPPT strategies announced in writing [11]

incorporate annoy and watch (P&O), incremental conductance (INC), and different

calculations utilizing neural systems, pilot cells and so on.In this work, MPP is followed

utilizing P&O calculation. The obligation proportion at guaranteed moment is refreshed in

view of the adjustment in control which is given as

D(n) = D(n-1) + ∇D.sgn(∇P) (8)

Where D(n) is available obligation proportion, D(n−1) is past obligation proportion, ΔD is

obligation proportion step estimate, ΔP is change in PV exhibit control.

Two vital parameters in MPPT control are step estimate of obligation proportion and

examining time of MPPT calculation. A bigger step size of obligation proportion prompts

quick response in variable illumination condition. Be that as it may, it prompts steady state

misfortunes once the MPP has been achieved. So also the voltage and current ought to be



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inspected with the end goal that the enduring state motions at MPP are lessened and MPPT

calculation does not react to homeless people. Investigation of step size of the obligation

proportion and testing time of MPPT calculation is given in [12].

b)Control of DSTATCOM

The DSTATCOM plays out the elements of receptive power control and also infusing the

power from PV cluster into the framework. A portion of the control strategies revealed in the

writing are instantaneous responsive power theory(IRP) [13], synchronous reference outline

(SRF) hypothesis [14], prompt symmetrical segment hypothesis [15] and so on. For this

work, DSTATCOM is controlled by changing over the prompt estimations of voltages and

streams into d-q-0 area utilizing SRF hypothesis. The control structure of DSTATCOM is

appeared in Fig.3. The format for the reference network streams are removed from the

network voltage (Vs) utilizing a three phase stage bolted circle (PLL). The three stage stack

currents components are changed over to d-q-0 area as,

The d-hub segment which is the dynamic current is passed through a low pass channel. The

DC-transport voltage is managed at set-point esteem utilizing a corresponding Fuzzy logic

based controller (FLC). The yield of DC-interface voltage controller is included with the d-

hub current alongside PV cluster current to from the reference d axis current for the lattice

streams. The PV cluster current term is a sustain forward term which empowers speedy

reaction of the DC-interface voltage controller. The references of matrix streams are

contrasted and the detected framework streams and essential gating signals are

producedutilizing the hysteresis controller.



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Fig3. Control Scheme of DSTATCOM

c) Control of DVR

The DVR is controlled in such a way, to the point that the infused voltage is in same stage as

that of network voltage, which brings about least infusion voltage by the DVR. The control

structure of DVR is appeared in Fig.4

Fig4. Control Scheme of DVR

In this setup, the voltage over the heap is in an indistinguishable stage from that of the lattice

voltage. The key segment of framework voltage is separated utilizing 3-stage PLL for

creating the reference pivot in d-q-0 area. The matrix voltage, stack voltage and reference

stack voltage are changed over into d-q-0 area with stage and recurrence being acquired from

matrix voltage. The mistake between the reference stack voltage and load voltage gives the

DVR voltage reference. The blunder between the heap voltage and lattice voltage will give

genuine voltage DVR. The contrast between the DVR reference and DVR voltage is gone

through a Fuzzy based logic controller(FLC) for both d-pivot and q-hub signals. The yield

flag of FLC is the flag for DVR which is looked at with real DVR voltages and afterward is

sentthrough hysteresis controller which creates fitting gating signals for the DVR.



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d) Fuzzy Logic Controller

This section employs the technique of FLC theorem to design the FLC controller, including:

1) fuzzification (FI), 2) decision-making logic (DML), 3) defuzzification (DFI), and 4)

knowledge base (KB). This paper utilizes the Sugeno-type fuzzy inference system since it

works well with linear, optimization, and adaptive techniques. Seven linguistic variables for

each input variable are used. These are NB (Negative Big), NM (Negative Medium), NS

(Negative Small), ZR (Zero), PS (Positive Small), PM (Positive Medium), and PB (Positive

Big). The control rules subject to the two input signals and the output signal are listed in

Table 2.

4. SIMULATION RESULTS & ANALYSIS

The model of SPV-UPQC-P was produced in Matlab-Simulink condition utilizing SimPower

Systems tool kit. The created MATLAB model of the framework is utilized to re-enact its

conduct. Different states of operation, for

Table 2 Control Rules of the Studied FLC

Ee NB NM NS ZR PS PM PB

E

NB NB NB NB NB NM NS ZE

NM NB NB NB NM NS ZE PS

NS NB NM NS NS ZE PS PM

ZR NB NM NS ZE PS PM PB

PS NM NS ZE PS PS PM PB

PM NS ZE PS PM PM PB PB

PB ZE PS PM PB PB PB PB

Example, hang what's more, swell in the lattice voltage, illumination variety and load variety

are mimicked. The solver step estimate utilized for the reproduction is 1e-6s.

a)Performance of SPV-UPQC-P under Varying Irradiance

The execution of solar based PV coordinated UPQC-P at different sun based light is appeared

in Fig.5. As the framework is adjusted, just a single period of detected signs are appeared.

The detected signals are network line voltage (Vs), matrix line current (Is), stack voltage

(VL), stack current(IL), DSTATCOM current (Ish), DC link voltage (Vdc) and illumination



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(G). The sun powered light is differed from 1000W/m2 at 0.5s to 200W/m2 at 0.6 s. The

matrix current bearing is at first streaming into the matrix as the power from PV cluster

surpasses that of load dynamic power. As the sun powered light abatements, the PV exhibit

yield control diminishes. Subsequently the network current alters its course to supply the

required dynamic energy of the heap. The DC-transport voltage is kept up at wanted set point

of 700V.

b)Performance of SPV-UPQC-P under Sag and Swell in Supply Voltage

The dynamic reaction of UPQC-P under droop and swell in network voltage is appeared in

Fig.6. The irradiation (G) is at 1000W/m2. The signs indicated are framework voltages (VS),

network currents (IS), stack voltages (VL), stack streams (IL), DSTATCOM current (ISH),DC-

connect voltage (VDC),DVR voltages (VDVR). At 0.4s, there is a voltage sag of 0.2pu and at

0.5s there is voltage swell of 0.2pu. The DVR makes up for the lattice voltage list/swell by

infusing a voltage VDVR in inverse stage with the matrix voltage individually, in this manner

keeping up the stack voltage at evaluated voltage condition.

c) Performance of SPV-UPQC-P under step change in load conditions

The dynamic execution of the SPV-UPQC-P under load step-aggravation condition is

appeared in Fig.7. The solar oriented illumination is kept at STC conditions. The signs

indicated are three stage matrix voltages (VS), stack voltages(VL), DC-connect voltages

(VDC), network currents(IS), stack streams (IL), DSTATCOM streams (ISH).At t=0.41s, the

heap is given a stage change at of half from 15kVA 0.8pf to 7.5kVA 0.8pf. It is to be noted

that the DC transport voltage is directed at 700V at this condition furthermore, the framework

is steady. As the shunt inverter gives dynamic control from the solar based cluster the

framework streams into the lattice are expanded to direct DC-connect voltage at reference

esteem.



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Time(s)

Fig. 5 Varying Irradiance condition



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Time(s)

Fig.6 Voltage sag(0.4-0.5sec)& swell(0.5-0.6) conditions



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Time(s)

Fig.7 step change in load conditions

5. CONCLUSIONS

In this study, the power quality of the system is mainly affected with voltage sag/swell.

Which leads to the system become unstable. Thus, SPV UPQC P are used to compensate the

power quality difficulties and enhanced the system stability and reliability. The UPQC P can

compensate sag/swell circumstances with an improved power factor. Introduction of PV

system in UPQC at DC link can fed the supply voltage to link capacitor as well as fed power



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to the loads. Introduction of FLC based controlling for UPQC control can enhance the

stability of the system and reduces the harmonics compared with conventional PI controller.

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[15] U. Rao, M. Mishra, and A. Ghosh, “Control strategies for load compensation using

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