A PV CONFIGURED UPQC-L FOR POWER QUALITY …

A PV CONFIGURED UPQC-L FOR POWER QUALITY

ENHANCEMENT IN DISTORTED DISTRIBUTION SYSTEM WITH

INDUCTION MOTOR LOAD

Poongothai.S1*, Srinath.S2 1,2Velammal Engineering College, Chennai, India

[email protected], [email protected]

Abstract - The most familiar issues in the power system is the distorted supply in

distribution system and power electronic based loads. One of the most popular custom

power devices, the Unified Power Quality Conditioner with left shunt configuration

(UPQC-L) as well with PV integration is suitably mitigate all quality issues. UPQC-L

generating reference signals without using any transformation by unit vector template

method (UVT). Hysteresis current controller (HCC) creating switching pulses for Active

Power Filters (APF) of UPQC to mitigate load side as well source side disturbances. In

variety of applications induction motor used in huge number which creates dip in voltage.

Along with power quality tribulations and non sinusoidal supply condition, the effect of

voltage dip also successfully defeated and the performance of the proposed system

validated by MATLAB/SIMULINK.

Keywords: Power Quality, Left Shunt-Unified Power Quality Conditioner, Series Active

Power Filter, Parallel Active Power Filter, Photo Voltaic

1. Introduction

Now a days the disturbances in the distribution side, distribution Generation integration and

different kinds of power electronics base loads pollute the power system [1-3]. Due to various fault

the power system may subjected to sag, swell, unbalance and interruption. As a result at a point of

common coupling (PCC) both voltage and current deviates from its original waveform shape [4].

Sensitive loads could seriously affected by quality issues. Active power filters are the best choice to

secure the power system.

Many researchers identify the best performance in UPQC and it has the capability of compensating

voltage, current and power related problems. It has two active power filters connected back to back

via Capacitor. This capacitor denoted as DC link capacitor which maintains the power balance

between two active filters of UPQC. To maintain stable function of active filters a DG can be

integrated across the DC link of UPQC [7-11]. One filter which is connected in shunt with distribution

system at the point of common coupling act as current source, balance current related tribulations and

maintain the voltage across the DC link capacitor [15-16]. It is connected in the left of UPQC called

as left shunt UPQC (LS-UPQC) [17-19]. As well it maintains the reactive power at load. Another

filter connected in series with distribution system at the point of common coupling act as a voltage

source, balance voltage related tribulations [12-14]. Several investigations and methodologies have

been made to generate firing pulses for DC-DC converter to extract the maximum energy from solar

PV [20-22].

Control strategies for active filters of UPQC are discussed in many papers [5-6]. To reduce the

complexity in transformation techniques for generating reference signals, a unit vector template

method used in this paper. Under non sinusoidal supply condition, combined mode control

implemented, PV integrated LS-UPQC could effectively mitigate various quality harms.

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mailto:[email protected]

mailto:[email protected]

Section 2 explores the system design of PV integrated UPQC-L and control strategy of Series

Active Power Filter, Parallel Active Power Filter and boost converter used along with PV array.

Section 3 illustrates quality issues and its compensation retorts and the presentation are assessed in

section 4.

2. Materials and Methods

UPQC has two voltage source inverters suitably for three phase distribution system shown in figure

1. PV integrated to DC link of UPQC via boost converter. At the point of common coupling (PCC)

shunt inverter connected through interconnecting reactive elements and series inverter by transformer.

Self supporting DC link (DG not connected) compensate reactive power, harmonics sag and swell.

But during voltage interruption the voltage across DC link capacitor losses its stability which in turn

the active power filters. But DG integrated DC link withstand its functioning during interruption.

UPQC successfully supports undistorted electrical signals to sensitive loads. Linear RL load

considered as a sensitive load. For distorted supply the inductor with the value of 5mH is connected in

series with supply.

Figure 1. Functional Diagram of PV integrated UPQC-L

2.1. Shunt inverter control

Now a day’s most loads are based on power electronics based loads which pollute the system by

creating harmonics. The harmonics in the system deteriorates the performance of all equipments

which are connected to power system. As well most loads are inductive in nature deviates the system

operating from unity power factor. For the proper function of active power filters of UPQC and to

maintain real power of load the DC link voltage has to be maintaining constant. Above mentioned

problem could effectively overcome by PAPF of UPQC. The control strategy of a Parallel Active

Power Filter (PAPF) shown in figure 2. The supply voltage is sensed and it is multiplied by steady

state desired peak value (Vp) and pass on to Phase locked loop to produce sin term based unit vector

templates with proper delay. The actual DC link voltage (Vdc) is compared with reference voltage

(Vdc*) and it is processed by fundamental component of peak amplitude then it gets multiplied with

unit vector templates to obtain reference current signals.

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Figure 2. Parallel Active Filter Control

The reference current signal compared with actual source current in Hysteresis controller to create

necessary gate signals for PAPF of UPQC. Thus the power quality problems correlate with source

current could effectively overcome by PAPF by reducing current harmonics, balancing reactive

power, maintaining unity power factor and DC link voltage.

2.2. Series inverter control

The power system may subjected to various faults due to which the distorted voltage pattern both

in magnitude and frequency being supplied to all other remaining loads that are connected to the same

power system. The series active power filter (SAPF) of UPQC generates voltage in such a way that

makes the load voltage perfect sinusoidal. Therefore the injected voltage in addition to supply voltage

makes the load terminal voltage ideal.

The control strategy for SAPF has to generate pulses for voltage source inverter of SAPF in such a

way it injects voltage at PCC to formulate the load voltage perfect. Based on Unit vector template

method the SAPF has to generate unit templates to generate reference signal. The supply voltage is

sensed and it is multiplied by steady state desired peak value and pass on to Phase locked loop to

produce sin term based unit vector templates with proper delay as shown in equation.

𝑈𝑎 = sin (𝜔𝑡)

𝑈𝑏 = sin (𝜔𝑡 − 120) (1)

𝑈𝑐 = sin (𝜔𝑡 + 120)

Then it is multiplied with desired load voltage magnitude to obtain the reference load voltage

(𝑉𝐿∗(𝜔𝑡)). Then the generated reference voltage compared with actual load voltage (𝑉𝐿) in Hysteresis

current control to generate gate signal for VSI of SAPF. Thus, the power quality troubles correlate

with supply voltage, for example voltage harmonics, voltage sag/swell/unbalance/interruption will get

compensated indirectly.

Figure 3. Series Active Filter Control

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2.3. Boost converter control

The DC-DC boost converter permits to implement different MPPT control strategies, together with

an interface between Photovoltaic and DC link capacitor of UPQC. The circuit diagram of DC-DC

boost converter is shown in Figure.4. A boost converter consists of an inductor, MOSFET switch,

diode and DC link capacitor (output capacitor).

Figure 4. Schematic block diagram of MPPT control in Boost converter.

The common design equations of the boost converter with PV input is given below

𝑉𝑑𝑐 =𝑉𝑝𝑣

1 + 𝐷 (2)

Where

𝑉𝑑𝑐 = Voltage across DC link capacitor

𝑉𝑝𝑣 = Source Voltage

𝐷 = Duty Cycle

The base inductance L required for continuous conduction mode (CCM) operation. The mathematical

expression of L is

𝐿 = ((1 − 𝐷)2) 𝐷𝑅) 2𝑓𝑠 (3)

Where

𝑓𝑠 = MOSFET switching frequency.

R= Load protection resistance

The Capacitance value has been ready with voltage swell purpose. The capacitor has given the voltage

swelling 𝑉𝑟 as

𝑉𝑟 = 𝐶𝑚𝑖𝑛𝐷

𝑅𝑓𝑠𝑉𝑑𝑐 (4)

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Based on the response of duty cycle the output voltage will changed, which is responsible for a

constant output voltage. The load current Idc also depends on the duty cycle, which is given by

equation (5)

𝐼𝑑𝑐 = (1 − 𝐷)𝐼𝑝𝑣 (5)

Where

𝐼𝑝𝑣 = Source Current in PV

𝐼𝑑𝑐 = Current from Converter

The adjustment in the current ∇𝐼 has the estimation of inductance given as

∇𝐼 =𝑉𝑝𝑣(𝑉𝑑𝑐−𝑉𝑝𝑣)

𝑓𝑠𝑉𝑑𝑐 (6)

To get better the effectiveness of the solar panel MPPT is used. According to maximum power

point theorem, output power of one circuit can be maximize by regulating source impedance equal to

the load impedance, so the MPPT algorithm is the same to the hitch of impedance matching. In

present work, the boost Converter is used as impedance matching device between input and output by

changing the duty cycle of the converter circuit. A major advantage of boost converter is that high or

low voltage obtained from the available voltage according to the application. Output voltage of the

converter is depend on the duty cycle, so MPPT is used to calculate the duty cycle for obtain the

maximum output voltage because if output voltage increases then power also increases. In this work

Perturb and Observe (P&O) and constant duty cycle techniques are used, because these require less

hardware complexity and low-cost implementations.

In this Perturb and Observe method, an inconsequential perturbation of output voltage is generated.

If there is an elevation in output power the similar practice is persistent or else perturbation is

upturned till to gain maximum power. Based on P&O algorithm, the generated pulses applied to

converter switch to extract the maximum energy from PV array.

3. Results and Discussion

In simulation part three phase three wired distorted distribution system is connected to linear as

well induction Motor load. To introduce the distortion a series inductor of 5mH is inserted in series

with supply. When the system is subjected to various faults the voltage and current pattern gets

deviated from ideal pattern. Whereas this kind of distorted pattern should not affect the performance

of linear load and induction motor load. As well the voltage dip due to induction motor start also

should not make any disturbance to sensitive load. All these issues overcome by PV integrated

UPQC-L effectively as follows.

Table 1. Configuration parameters Parameters Values

Frequency 50 Hz

Voltage in RMS 415V

Linear Sensitive Load (per phase) 100+j9.42Ω

Dynamic Load (Induction Motor Load) 5.4HP(4KW),400V,50Hz,1430 rpm

DC-Link capacitor 1000µF

DC-Link Voltage 730V

Inductor in converter L 5mH

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3.1 Disturbance due to Induction Motor load start

Induction motor was favoured as the focus of interest owing to its enormous use in variety of

applications. The distribution system along with DVR provide good voltage profile to induction motor

load when the system experienced with various fault and varying load condition [23,24].During

Induction Motor start a voltage dip occurs which in turn affects the sensitive load. As well the current

also sustain longer in transient state shown in figure 5. Non sinusoidal supply voltage profile is also

depicted in Figure 5.

Figure.5 Voltage dip due to IM start and it mitigation responses in distorted 3 Φ distribution system with PV-UPQC. (a)Voltage at PCC (b) Current at PCC

(c) Load Voltage (d) Load current (e) DC link Voltage.

Figure 5 also depict the load voltage and current. It clearly shows the distortion in supply side voltage

as well the dip in voltage due to Induction Motor start is also clearly eradicated. The load current also

attains the stable state early. It shows the constant DC bus voltage under non sinusoidal supply

condition and voltage dip due to Induction Motor start. Since the supply voltage is 415V the capacitor

voltage is maintained by 730V.

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3.2. Disturbance due to Fault

When the system subjected to various faults, the following responses shows the compensation

responses by PV integrated UPQC-L. The simulation responses are taken up to 0.2Sec. Sag created by

23% in the duration of 20ms to 50ms by introducing three phase fault. The SAPF of UPQC

overcomes it by injecting in phase voltage into the system. Swell created by 38% in the duration of

140ms to 170ms by inserting a series resistance with source. The SAPF of UPQC overcomes it by

injecting out of phase voltage into the system. Voltage unbalance created by 18% in the duration of

80ms to 110ms by introducing double line to ground fault shown in figure 6. It depict that undistorted

voltage and current are supplied to sensitive load and induction motor load.

Figure 6. Power Quality issues and its mitigation responses in distorted 3 Φ distribution system with PV-UPQC. (a) Voltage at PCC (b) Current at PCC

(c) Load Voltage (d) Load current (e) DC link Voltage.

From figure 7 the source voltage interruption occurs at the interval of 0.3S to 0.6S. In this proposed system

UPQC come across the capability of injecting power using PV to sensitive load for the period of source voltage

interruption and DC bus voltage also maintained constant.

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Figure 7. Voltage Interruption and it mitigation responses in distorted 3Φ distribution system with PV-UPQC. (a)Voltage at PCC (b) Current at PCC (c)

Load Voltage (d) Load current (e) DC link Voltage.

4. Performance Evaluation

When UPQC not in operation, the system (non sinusoidal supply) subject to more THD in current

at PCC (28.58%) and load voltage (11.12%) with sensitive RL and Induction Motor load. It is clearly

depict that the system need support to mitigate quality issues. One of the types of UPQC that is

UPQC-L is used with PV integration to mitigate power quality issues (sag/swell/unbalance/THD)

including voltage interruption. Due to PV integration the value of DC link capacitor and its settling

time reduced shown in Table 2. This proposed structure supporting Induction motor load as a dynamic

load as well provides regulated voltage and current profile to sensitive loads. Effect of voltage dip due

to Induction motor start along with power quality tribulations could effectively defeated by UPQC-L.

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The transient state of current profile is also reduced. The shunt active filter of UPQC-L effectively

balances the DC link voltage, reactive power requirement of load and power factor.

An attempt has been made with self supporting UPQC-L to show the effectiveness of PV integrated

UPQC-L. From Table 2 it is clearly depicted that the PV supporting UPQC-L effectively supports for

mitigating voltage interruption, the total harmonic distortion reduction, DC link capacitor value

reduced and the settling time of voltage profile of DC link capacitor is also reduced when compared to

self supporting DC link capacitor. Table 2 clearly shows the benefit of the proposed system and THD

also within the limit of IEEE standard.

Table 2. Compensation Effect of PV integrated UPQC-L

No Power

Quality

Issues

Compensati

on Effect System Configuration

Source

Current

THD %

Load

Voltag

e THD

%

1 Voltage Sag Compensated

Self supporting UPQC-L

configured with Non sinusoidal

source and sensitive RL load

plus Induction Motor Load.

*DC Link Capacitor =

10000µF

*Settling Time (tS) = 2.3mS

4.12 1.9

2 Voltage

Swell Compensated 4.31 1.57

3 Voltage

Unbalance Compensated 4.13 1.49

4 Voltage

Interruption

Partial

Compensatio

n

7.12 4.7

5 Voltage Dip

due IM start Compensated 3.7 1.12

6 Voltage Sag Compensated

PV integrated UPQC-L

configured with Non sinusoidal

source and sensitive RL load

plus Induction Motor Load.

*DC Link Capacitor = 1700µF

*Settling Time (tS) = 1.02mS

2.39 1.6

7 Voltage

Swell Compensated 3.41 1.14

8 Voltage

Unbalance Compensated 2.75 1.7

9 Voltage

Interruption Compensated 4.6 2.2

10 Voltage Dip

due IM start Compensated 2.9 1.02

5. Conclusion

The capability of PV integrated UPQC-L animatedly react to a choice of quality issues has been

analyzed. The proposed system regains the voltage and current pattern both in magnitude and

frequency for linear sensitive load under non sinusoidal supply conditions and Induction Motor load

conditions. Beside the influence of induction motor load, different faults are initiated and the quality

issues like voltage sag, voltage swell, voltage unbalance and voltage interruption owing to the fault

have been mitigated. The simulation results shows that the performance of PV integrated UPQC-L is

satisfactory in elimination of source current harmonics, load voltage harmonics and improving the

input power factor. It is found to be effective to meet IEEE 519 standard recommendation on

harmonic levels. Taking into consideration of rating, cost, voltage pattern and settling time of voltage

of DC link capacitor, the PV integrated UPQC-L is superior option to care for sensitive loads

contrasted with self supporting DC link capacitor left shunt UPQC.

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References

[1] Frede Blaabjerg, Zhe Chen and Soeren Baekhoej Kjaer, “Power Electronics as Efficient Interface in Dispersed Power Generation Systems”, IEEE TRANSACTIONS ON POWER ELECTRONICS. vol. 19, no.5, (2004), pp.1184-1194.

[2] S.Srinath, S.Poongothai and Joyal Isac, “Reliable standalone self sustained power for power quality improvement in grid”, The Institution of Engineers. vol. 40, (2016), pp. 233-238.

[3] H.A.Hejazi, Ali R. Araghi, Behrooz Vahidi, S.H.Hosseinian, M.Abedi and Hamed Mohsenian-Rad, “Independent Distributed Generation Planning to Profit Both Utility and DG Investors”, IEEE TRANSACTIONS ON POWER ELECTRONICS.

vol. 19, no.5, (2013), pp. 1170-1178.

[4] S.H.Laskar and Mohibulla, “Power Quality Issues and Need of Intelligent PQ Monitoring in the Smart Grid Environment”, International Journal of Emerging Technology and Advanced Engineering. vol. 2, no.9, (2012), pp. 63-69.

[5] M. Vishnu Vardhan and P. Sangameswararaju, “ABC and NFC based unified power quality conditioner for compensating power quality problem”, IOSR Journal of Electrical and Electronics Engineering. vol. 7, no.1 (2013), pp. 01-13.

[6] A.JeraldineViji and T. Aruldoss Albert Victoire, “Enhanced PLL based SRF control method for UPQC with fault protection under unbalanced load conditions”, Electrical Power and Energy Systems. vol. 58, (2014), pp. 319-328.

[7] Nirav Kerelia, Amit Vilas Sant and Vivek pandya, “Comparison of UPQC topologies for power quality enhancement in Grid integrated Renewable Energy sources”, IEEE 16th India Council International Conference. Rajkot, India, (2019), December 13-15.

[8] Jian Ye, H.B. Gooi and Fengjiang Wu,”Optimal Design and Control Implementation of UPQC Based on Variable Phase Angle Control Method”, IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS. vol. 14, no.7, (2018), pp. 3109- 3123.

[9] S. Boonachellam, S. Poongothai and S. Srinath, “Power Quality Enhancement Using Distributed Generation integrated Unified Power Quality Conditioner”, International Journal of Applied Engineering Research. Vol. 10, (2015), pp. 9844-9849.

[10] Md. Shafiuzzaman, K. Khadem, Malabika Basu and Michael F. Conlon, “UPQC for power quality improvement in DG Integrated smart grid Network-A review”, International Journal of Emerging Electric Power systems. vol. 13, (2012), pp. 1-13.

[11] S.Srinath and M.P Selvan, “UPS Mode operation of UPQC with Mixed Mode Control”, International Review of Automatic control. Vol.5, no.3, (2012), pp. 342-348.

[12] ChunmingTu, Qi Guo, Fei Jiang, Cheng Chen, Xiaoyun Li, Fan Xiao and JiayuanGao,” Dynamic Voltage Restorer With an Improved Strategy to Voltage Sag Compensation and Energy Self-Recovery”, CPSS TRANSACTIONS ON POWER

ELECTRONICS AND APPLICATIONS. vol. 4, no. 3, (2019), pp. 219-229.

[13] Rodrigo Augusto Modesto, S´ergio Augusto Oliveira da Silva, Azauri Albano de Oliveira and Vin´ıcius D´ario Bacon, “A Versatile Unified Power Quality Conditioner Applied to Three-Phase Four-Wire Distribution Systems Using a Dual Control Strategy”, IEEE TRANSACTIONS ON POWER ELECTRONICS. vol.31, no. 8, ( 2016), pp. 5503-5514.

[14] S. Srinath, S. Poongothai, T. Aruna, “PV integrated shunt active filter for harmonic compensation”, Energy procedia. Vol.117, (2017), pp. 1134-1144.

[15] Sachin Devassy and Bhim Sing,.”Design and Performance Analysis of Three-Phase Solar PV Integrated UPQC”, IEEE

TRANSACTIONS ON INDUSTRY APPLICATIONS. Vol. 54, no. 1, (2018), pp. 73-81.

[16] V. Muneer, Jithin Sukumaran and Avik Bhattachary, ”Investigation on reduced DC link voltage based UPQC for harmonic compensation under unbalanced load”, International conference on technological advancements in power and Energy. Kollam, India, (2017), December 21-23.

[17] Arindam Ghosh and Gerard Ledwich, “Power Quality Enhancement Using Custom Power Devices”, Kluwer’s Power Electronics and Power Systems Series Editor, (2002).

[18] N. G. Jayanti, M. Basu, M. F. Conlon and K. Gaughan, "Performance comparison of a left shunt UPQC and a right shunt UPQC applied to enhance fault-ride-through capability of a fixed speed wind generator," European Conference on Power Electronics and Applications. Aalborg, (2007), pp. 1-9.

[19] Vinod Khadkikar, “Enhancing Electric Power Quality Using UPQC:A Comprehensive Overview”, IEEE TRANSACTIONS ON

POWER ELECTRONICS. vol, 27, no. 5, (2012), pp. 2284-2297.

[20] Xuefeng Hu and Chunying Gong, “A High Voltage Gain DC–DC Converter Integrating Coupled-Inductor and Diode–Capacitor Techniques”, IEEE TRANSACTIONS ON POWER ELECTRONICS. vol. 29, no.2, (2014), pp.5503-5514.

Vol 40, 2020

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ISSN: 0303-6286

[21] Maria C. Mira, Zhe Zhang, Arnold Knott and Michael A.E. Andersen, “Analysis, Design, Modelling, and Control of an Interleaved-Boost Full-Bridge Three-Port Converter for Hybrid Renewable Energy Systems”, IEEE TRANSACTIONS ON POWER

ELECTRONICS. vol.32, no. 2, (2017), pp. 1138-1155.

[22] Jingyang Fang, Hongchang Li, Yi Tang and Frede Blaabjerg, “Distributed Power System Virtual Inertia Implemented by

Grid-Connected Power Converters”, IEEE TRANSACTIONS ON POWER ELECTRONICS. vol. 33, (2018), pp. 8488-8499.

[23] Mohan P.Thakre, S. Prasad, Jagtap and Tejal S. Barhate, “Voltage Sag Compensation of Induction Motor with 6 Pulse VSI based DVR”, Second International Conference on Smart Systems and Inventive Technology. (2019), pp. 493-498.

[24] Navneet Kumar, Thanga Raj Chelliah and S.P. Srivastava, “Voltage Sag Effects on Energy-Optimal Controlled Induction Motor With Time-Varying loads”, IEEE International Conference on Power Electronics, Drives and Energy Systems. Bangaluru, India, (2012), December16-19.

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A PV CONFIGURED UPQC-L FOR POWER QUALITY …