Steady State Comparative Performance Analysis Of ILBC UPQC System With PI And PR Controllers

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Steady State Comparative Performance Analysis Of

ILBC-UPQC System With PI And PR Controllers

G.V. Prasanna Anjaneyulu

, Dr.P. Sangameswara Raju

1_{Associate Professor,} 2_{Professor (Retd)}

Electrical & Electronics Engineering, Tirumala Engineering College Narasaraopet, Andhra Pradesh, India Electrical & Electronics Engineering, S.V.University College of Engineering, Tirupathi Andhra Pradesh, India

[email protected], [email protected]

Abstract:Unified Power Quality Conditioner (UPQC) is an useful FACTS controller in power system network for improvement of voltage quality. The objective of this work is to improve the steady state response of ILBC-UPQC using suitable controller. This work gives selection of suitable controller for improved steady state performance of ILBC-UPQC system. The steady state responses with Proportional Integral PI and Proportional Resonant PR controllers are presented in this paper. The MATLAB results of Proportional Integral PI based ILBC-UPQC system are compared with those of Proportional Resonant PR controlled ILBC-UPQC system. The comparison is done in terms of steady state error. MATLAB results shows that improved steady state performance with Proportional Resonant PR controller of ILBC-UPQC system.

Keywords—Unified Power Quality Conditioner (UPQC); PI Controller; PR Controller;

1. INTRODUCTION disconnection of large industrial loads and reactive power compensating capacitors; and 3) voltage and/or current harmonic distortion due to the UPQC unified power quality conditioner has superior performance and the capacity to reduce almost all major PQ problems. UPQC is the most attractive system for PQ improvement in spite of its high cost, complex structure, and control [1]-[3]. The basic structure of a UPQC is shown in Figure.1.

Figure 1: Basic Structure of UPQC

Generally, the voltage sags and swells are short duration PQ problems. Thus, in UPQC-P and UPQC_Q, series inverter VA loading will only be utilized for short durations. On the other hand, the shunt inverter VA rating is fully utilized thorough out the operation, due to continuous load reactive power support and current harmonic compensation. To enhance the utilization of series part of UPQC during steady state, part of load reactive power is

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84 reduction in the percentage of swell compensation

capability.

2. PROPOSED SYSTEM CONFIGURATION

The block diagram of proposed closed loop PI/PR fed Inter Leaved Boost Converter

(ILBC) fed UPQC system is shown in Figure 2. The capacitor of UPQC is charged by the output of Inter Leaved Boost Converter (ILBC). The output voltage of PV is boosted using Inter Leaved Boost Converter (ILBC). For ILBC the modified pulse width signals are fed from feedback obtained via closed loop controllers. Here feedback is collected from load voltage.

Figure 2: Block Diagram of proposed closed loop PI/PR fed ILBC-UPQC system

A. Mathematical Analysis for Proportional Integral Controller

As the name suggests it is a combination of proportional and an integral controller. The output (also called the actuating signal) is equal to the summation of proportional and integral of the error signal. Now let us analyze proportional and integral controller mathematically. As know in a proportional and integral controller output is directly proportional to the summation of proportional of error and integration of the error signal, writing this same mathematically

𝐴(𝑡) ∞ ∫ 𝑡

𝑑𝑡 + (𝑡) (2.1)

Removing the sign of proportionality,

𝐴(𝑡)=𝐾i∫ 𝑡

𝑑𝑡+𝐾𝑃 (𝑡)

(2.2)

Here, Ki and Kp Proportional constant and Integral

constants respectively.

B. Mathematical Analysis for Proportional Resonanant Controller

As the name suggests it is a combination of Proportional and Resonant controller. The output of PR controller is as follows

VO(S) = E(S)

[K1+ ] (2.3)

Here K1, K2 are Proportional and Resonant

constants of PR controller.

3. IMPLEMENTATION OF PROPOSED SYSTEM

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Table 1: Parameters for PI and PR colosed loop systems

PARAMETERS VALUE

R1, R2, R3 0.1Ω, 0.5Ω,0.8Ω

L1, L2,L3 3mH, 30mH, 40mH

Cin 50µF

Cb 9000µF

Ro, Lo 200Ω, 100mH

A. Implementation of Proportional Integral (PI) Controller

The closed loop PI fed ILBC-UPQC system is simulated in MATLAB. Simulated diagram of closed loop ILBC - UPQC system with PI

controller is shown in Figure 3.1. Load voltage is rectified and converted in to an analog signal. It is compared with the reference voltage. The error is applied to a PI controller. The output of PI controller is applied to pulse generator.

Figure 3.1: Simulation Diagram of proposed closed loop PI fed ILBC-UPQC system

B. Implementation of Proportional Resonant (PR) Controller

The closed loop PR fed ILBC-UPQC system is simulated in MATLAB. Simulated diagram of closed loop ILBC - UPQC system with PR controller is shown in Figure 3.2. Load voltage

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Figure 3.2: Simulation Diagram of proposed closed loop PR fed ILBC-UPQC system

4. SIMULATION RESULTS

The closed loop PI fed ILBC-UPQC system is simulated in MATLAB/SIMULINK..

RMS value of receiving end voltage is shown in figure 4.1. The steady state error is 5.3 V in PI controller.

Figure 4.1: Receiving end voltage RMS value

The closed loop PR fed ILBC-UPQC system is simulated in MATLAB/SIMULINK. RMS value of

receiving end voltage is shown in figure 4.2. The steady state error is 1.8 V in PR controller.

Figure 4.2: Receiving end voltage RMS value

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Table 1: Comparison of Steady State Error for PI and PR controllers fed ILBC-UPQC system

Controller Steady State Error

PI 5.3

PR 1.8

5. SIMULATION RESULTS

Proportional Integral PI and Proportional Resonant PR controller based ILBC-UPQC systems are modeled and simulated using MATLAB/SIMULINK and steady state performance i.e. steady state error is analyzed. The results indicated that the steady state error with Proportional Resonant controller is very less than that of Proportional Integral PI Controlled ILBC-UPQC system. The steady state error is reduced by 3.5 Volts by replacing Proportional Integral PI controller with Proportional Resonant PR Controller. The contributions of the present work are as follows: Proportional Resonant PR controller is proposed to decrease the Steady state error.The disadvantage is that the hardware of ILBC becomes twice that of SBC.

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BIBLIOGRAPHY OF AUTHORS

G.V. Prasanna Anjaneyulu has completed his B.E in 2005 from Andhra University and M.Tech in 2009 from NIT, Calicut. He has a teaching experience of twelve years. Presently, he is a Research Scholar at S.V. University college of Engineering, Tirupathi, India. His research area is on Power Quality improvement in multibus systems. Mail-Id:[email protected].