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Madhumathi. P et.al; International Journal of Advance Research, Ideas and Innovations in Technology

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(Volume 4, Issue 2) Available online at: www.ijariit.com

Power Quality Compensation by using UPFC

P. Madhumathi

[email protected]

Vivekanada College of Engineering

for Women, Tiruchengode - TK,

Tamil Nadu

V. Lavanya

[email protected]



Tamil Nadu

K. Thamaraiselvi

[email protected]



Tamil Nadu

ABSTRACT

This paper deals with the performance of UPFC to the power quality in the electrical system. UPFC is used to improve the

transient stability in the power system. UPFC can control the power flow in the electrical power system. Unified Power Flow

Controller can easily control the real and reactive power flow. For getting without significant losses in the function of the

electrical system to synchronization of voltage frequency and phase. The following factors are affecting the power quality in the

electrical system they are voltage sag, voltage variation, interruption, swells, brownout, distortion, harmonic noise, voltage spikes,

voltage flicker etc. Comparing to normal standards these factors can produce the deviation in the power. UPFC can control the

parameters like series impedance, shunt impedance, line voltage, current, active power, reactive power, oscillation damping etc.

UPFC is able to control the parameters affecting power flow simultaneously or selectively. Power factor is increased by using

UPFC instead of STATCOM. By installing UPFC in the system we can improve the reliability and quality of power supply.Using

inverter and rectifier the circuit model is developed. Simulation and Matlab results are given to validate the performance of

UPFC.

Keywords: UPFC, Power Quality, STATCOM, Simulation, and Matlab.

1. INTRODUCTION

Nowadays due to increased power quality problems by using of switch off/on introduction loads, nonlinear load and induction motor

etc in domestic and industries, power-quality (PQ) problems, such as harmonics, flicker, and imbalance have become serious

concerns. In addition, lightning strikes on transmission lines, switching of capacitor banks, and various network Faults can also

cause PQ problems, such as transients, voltage sag/swell, and interruption. On the other hand, an increase of sensitive loads involving

digital electronics and complex process controllers requires a pure sinusoidal supply voltage for the proper load operation. To meet

power quality to the standard limits need some sort of compensation. In a few years back to mitigate the power quality problems in

the distribution system by using passive filters like capacitor banks. Now, these research going very fast to mitigate the power

quality problems with help of power conditioning devices [7]. The power conditioning devices are dynamic voltage restorer (DVR),

static compensator (STATCOM), and unified power-quality conditioner (UPQC)(custom power devices)[1]. A static synchronous

compensator (STATCOM), also known as a "static synchronous condenser" ("STATCOM")[2], is a regulating device used on

alternating current electricity transmission networks. It is based on a power electronics voltage-source converter and can act as either

a source or sink of reactive AC power to an electricity network. If connected to a source of power it can also provide active AC

power. It is a member of the FACTS family of devices. It is inherently modular and electable. The proposed HCC [3] method has

many advantages such a being robust, having a very fast response time and being independent of nonlinear loads. Usually, a

STATCOM is installed to support electricity networks that have a poor power factor and often poor voltage regulation. There are

however, other uses, the most common use is for voltage stability. A STATCOM is a voltage source converter (VSC)-based device,

with the voltage source behind a reactor. The voltage source is created from a DC capacitor and therefore a STATCOM has very

little active power capability. However, its active power capability can be increased if a suitable energy storage device is connected

to the DC capacitor. The aim of this project is the STATCOM-based control scheme for power quality [5] improvement in grid-

connected wind generating system [4][8] and with the nonlinear load. The power quality issues [6] and its consequences on the

consumer and electric utility. Combining the STATCOM and the SSSC into a single device with a common control system

represents the third generation of FACTS known as Unified Power Flow Controller (UPFC). It has the unique ability to control real

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and reactive power flow independently. The first utility demonstration of a UPFC is being constructed at the Inez substation of

American Electric Power in 1998. Recently, 80 MVA UPFC is being constructed at Gangjin substation in South Korea.

Figure: Basic circuit diagram of Unified Power Flow Controller

1.1 OPERATION OF UPFC

Operation of the UPFC from the standpoint of conventional power transmission based on reactive shunt compensation, series

compensation, and phase shifting, the UPFC can ful fill these functions and thereby meet multiple control objectives by adding the

injected voltage Vpq, with appropriate amplitude and phase angle, to the terminal voltage Vo. Using phasor representation, the basic

UPFC power flow control functions are illustrated in Figure.2. Terminal voltage regulation, similar to that obtainable with a

transformer tap-

injected in-phase (or anti-phase) with Vo [ 4 ]. Series capacitor compensation, is shown at (b) where Vpq =Vc is in quadrate with

the line current I. Transmission angle regulation, (phase shifting) is shown at (c) where Vpq=Vo is injected with angular relationship

with respect to Vo that achieves the desired s phase shift (advance or retard) without any change in magnitude.

Figure: (a) -voltage regulation, (b) line impedance compensation, (c)-phase shifting,(d)-simultaneous control of voltage

,impedance and angle.

1.2 MODELLING OF UPFC

The control system was derived by assuming that the series and parallel converters are treated as ideal controllable voltage sources,

that the values of the fundamental components of the line currents are locally available. The UPFC is modeled by combining the

shunt and series branches coupled by the DC voltage control branch.Local load is added at port 1 of the UPFC. The Organization

of UPFC modeling blocks are shown in below figure.




Figure: Modelling of UPFC Blocks

Table: Facts Controllers

Shunt Capacitor 8/kVar

Series Capacitor 20/kVar

SVC 40/ kVar controlled portions

TCSC 40/ kVar controlled portions

STATCOM 50/ kVar

UPFC SERIES PORTIONS 50/ kVar through power

UPFC SHUNT PORTIONS 50/ kVar controlled

2. SOURCES AND EFFECTS OF POWER QUALITY PROBLEMS

The distortion in the quality of supply power can be introduced/ enhanced at various stages; however; some of the primary sources

of distortion [2] can be identified as below:

A. Power Electronic Devices

B. IT and Office Equipments

C. Arcing Devices

D. Load Switching

E. Large Motor Starting

F. Embedded Generation

G. Electromagnetic Radiations and Cables

H. Storm and Environment Related Causes etc.

Some of the common power quality issues and their prominent impact are

2.1 Harmonics

Excessive losses and heating in motors, capacitors and transformers connected to the system.

2.2 Flicker

Visual irritation, introduction of many harmonic components in the supply power and their associated equipment.

2.3 Transients

Tripping, components failures, flashover of instrument insulation hardware booting, software glitches, poor product quality etc.

2.4 Voltage sag

Devices /process down time, effect on product quality, failure / malfunction of customer equipments and associated scrap cost, clean

up costs, maintenance and repair costs etc.

3. SIMULATION RESULTS

Simulation are done using the Matlab and presented here. Two bus system without compensation is shown in Fig . Sag is produced

when an additional load is added. Voltage across loads 1 and 2 are shown in Fig 2a. The real power and reactive power waveforms

are shown in Figures 2b and 2c respectively. UPFC using voltage and current sources are shown in Fig. Converter 1 is represented

as a shunt current source and converter 2 is represented as a series voltage source. Load voltage and current waveforms are shown

in Fig 3a. Real and reactive powers are shown in Fig 3b. Variation of powers with the variation in the angle is given in table 1. The

real and reactive powers increase with the increase in the angle of voltage injection.




Figure: 1(a) Voltage across Load1 and Load2

Figure: 1(B) Real Power

Figure: 2(A) Voltage across Load 1 And 2




Figure: 2 (B) Real Power

Figure: 2(C) Reactive Power

Figure: 4(A) Load Voltage and Current Waveform




Figure: 4(B) Real and Reactive Power

4. EXPERIMENTAL RESULTS

Laboratory model of UPFC was designed and fabricated. It is tested in the laboratory to obtain the experimental results. Experimental

set up is shown in Fig. The hardware consists of control circuit and power circuit. The control board generates the pulses required

by the MOSFETs. They are generated by the 8 bit microcontroller. They are amplified by using IR2110. The power circuit consists

of rectifier and inverter system. AC input voltage is shown in Fig . Rectifier output voltage is shown in Fig . Driving pulses are

shown in Fig . Load voltage after compensation is shown in Fig . From the figures, it can be seen that the simulation results coincide

with the experimental results.

Figure: Experimental Set

Figure: AC Input Voltage




Figure: Rectifier Output Voltage

Figure: Driving Pulse for Inverter

Figure: Load Voltage after Compensation




5. CONCLUSION

This paper presents the control & performance of the UPFC used for power quality improvement. Voltage compensation using

UPFC is studied. The real and reactive powers increase with the increase in angle of injection. Simulation results show the

effectiveness of UPFC to control the real and reactive powers. The modelling of UPFC and analysis of power systems embedded

with UPFC has been presented, which is capable of solving large power networks very reliably with the UPFC. The investigations

related to the variation of control parameters and performance of the UPFC on power quality results are carried out. It is found that

there is an improvement in the real and reactive powers through the transmission line when UPFC is introduced. The UPFC system

has the advantages like reduced maintanance and ability to control real and reactive powers. Thus the simulation results matches

with the experimental results.

6. REFERENCES

[1] M L. Crow,"Power quality enhancement using custom power devices, " IEEE Power and Energy Magazine,vol.2,pp.50, April

2004.

[2] Han. A,Huang. Q,Baran. M, Bhattacharya. S and Litzenberger. W, “STATCOM impact study on the integration of a large wind

farm

[3] Mohapatra M. and Babu B.C. 2010. Fixed and sinusoidal-band hysteresis current controller for PWM voltage source inverter

with LC filter. Proceedings of 2010 IEEE Students'

[4] Heier. S, Grid Integration of Wind Energy Conversions. Hoboken, NJ: Wiley, pp. 256– 259, 2007.

[5] Stones and A. Collinson,"Power quality, "Power Eng.Journal, vol.15, pp.58 64, April 2001.

[6] A.ElMofty, K. Youssef,"Industrial power quality problems, " in Proc. on IEE Int. ConfExhib. On1, vol.2, June 2001.

[7] N. G. Hingorani, "Introducing custom power, ” vol.32,pp.41-48,June1995 23.

[8] Mohod. S. W and Aware. M. V, “Power quality issues &it‟s mitigation technique in wind energy conversion,” in Proc. Of IEEE

Int.Conf. Quality Power & Harmonic, Wollongong..
