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Design of Self-Tuning PI Controller forSTATCOM using Bats Echolocation

Algorithm

Presented by: Mr.G.Kumaravel

Assistant Professor-EEE

Arunai Engineering College

Tiruvannamalai

Guided by: Dr.C.Kumar,B.E.,M.Sc(Engg).,Ph.D.

Director-Academics

SKP Engineering College

Tiruvannamalai

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Abstract

A Static Synchronous Compensator (STATCOM) is a typical Flexible AC Transmission (FACTS) device, play a vital role in stability of a power system under small and large disturbances.

This paper deals with, Design and Evaluation of a Bats Echolocation Algorithm (BEA) for self-tuning PI controller of STATCOM.

The proposed BEA shows very good performance in non linear load.

The effectiveness of the proposed Bats Echolocation Algorithm is evaluated by computer simulation. Simulations are carried out using MATLAB/SIMULINK software.

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Power System Configuration with STATCOM

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The load impedance is estimated from load voltage and load current.

Based on the estimated system load impedance, The Bats Echolocation algorithm optimize the PI controller gains.

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Principle of STATCOM

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Voltage Source Inverter is the core element of the STATCOM , which is in general converts a DC voltage into an AC output voltage at power frequency, with controllable amplitude and phase angle.

This paper proposes a self-tuning PI controller ,to maintain the magnitude of the bus voltage by controlling the magnitude and phase shift of the output voltage (Vp) of the VSC.

Under steady state, there is no real power transfer occurs via coupling transformer

If Vs>Vp,the VSC draws reactive power from the AC bus. Whereas if Vs<Vp , it supplies reactive power to the AC system

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Fixed – Gain PI Controller for STATCOM

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Fixed gain PI controllers are normally used to regulate a load bus voltage under disturbance conditions

The d-axis and q-axis current regulators regulate ipd and ipq in order to get desired ipdref and ipqref by adjusting the epd and epq values.Inorder to compute the phase angle α as phase angle difference of Vt and Vs.

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Bats Echolocation System

• Bats emits ultrasonic sound of 5 to 20ms duration at a rate of 10Hz, while looking for prey, by measuring the time of flight, bats estimate their distance from the target.

• When the single pulse repetition rate increases up to 200Hz.bats enter the approach phase to prey.

• By means of this, bats avoid overlapping of pulses which results in loss of resolution

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Bats Echolocation Algorithm

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Digital SIMULINK model of system with STATCOM

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Digital SIMULINK model of VSI with self tuning PI controller using Bats Echolocation Algorithm.

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Digital Simulink model of Non linear load

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System parameters

Source voltage (Erms(p-p)) =25(kV), source x/r ratio=7, F=50(Hz), Load resistance in the non linear load (Rl) = 3000Ω, filter L=0.1(H),C=250μF, capacitor value on DC side of VSI=1mF

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Stable Regions of Kp and Ki values

KP KI Load-20 -10 Light Load

15 + j30Ω.-15 -30-10 -40-15 -10 Medium Load

8+ j15Ω.-10 -30-5 -55-10 -10 Heavy Load

3 + j7Ω.-7 -20-5 -20

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Digital Simulation Results

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Dynamic response of system for non linear load with fixed gain PI controller

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Dynamic response of system for non linear load with self tuning PI controller using BEA

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Dynamic response of source current for non linear load

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Dynamic response of DC capacitor voltage for non linear load

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Response of q-axis current of STATCOM controller

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Digital Simulation Results

In fixed gain PI controller, Kp and Ki values are selected as 0.01 and 0.1 respectively for non linear load with 3kΩ.

The dynamic response of system for non linear load with fixed gain PI controller shows the stability in load bus voltage is obtained in 0.017 seconds.

The dynamic response of system load bus voltage for non linear load with self tuning PI controller using BEA shows the stability is obtained within 0.0012 seconds.

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Conclusion

The fast dynamic response obtained in system load bus when self tuning PI controller using Bats Echolocation algorithm is used as a STATCOM controller as compared with fixed gain PI controller.

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References

1. Grady, A. Mansoor, E. F. Fuchs, P. Verde, and M. Doyle, “Estimating the net harmonic currents produced by selected distributed single-phase loads: Computers,televisions, and incandescent light dimmers,” in Proc. IEEE Power Eng. Soc. Winter Meeting,Jan. 2002,vol. 2,pp. 1090–1094.

2. M. Uzunoglu, C. Kocatepe, R. Yumurtaci, “Voltage Stability Analysis in the Power Systems Including Non-Linear Loads”European Transactions on Electrical Power, Volume 14, Issue 1,Date: January/February 2004, Pages: 41-56.

3. N.G.Hingorani and L.Gyugi, Understanding FACTS. New York: IEEE Press, 2000.

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4. T.J.E.Miller, Ed., Reactive Power Control in Electric Systems. New York: Wiley, 1982.

5. B.S.Chen and Y. Y. Hsu, “An analytical approach to harmonic analysis and controller design of a STATCOM,” IEEE Trans. Power Del., vol. 22,no. 1, pp. 423–432, Jan. 2007.

6. JI-CHANG LE and YA-HU KUO, Decoupled fuzzy sliding-mode control, IEEE Trans. On Fuzzy Systems, Vol. 6, 1998.

7. Hung-Chi Tsai; Chia-Chi Chu; "Nonlinear STATCOM Controller using Passivity-Based Sliding Mode Control" IEEE APCCAS, 4-7 Dec. 2006 Page(s):1996 – 1999.

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8. Yazdani, A.; Crow, M.L.; Guo, J.; "A comparison of linear and nonlinear STATCOM control for power quality enhancement" IEEE Power and Energy Society General Meeting - onversion and Delivery of Electrical Energy in the 21st Century, 20-24 July 2008 Page(s):1 –6.

9. Allen, G. M. (1940), Bats, Harvard University Press.

10. Griffin, D. R. (1944), ‘Echolocation in blind men, bats and radar’, Science 100, 589–590.

11. Souvik Chattopadhyay and V. Ramanarayanan, “A Voltage Sensorless Current Shaping Method for Balancing the Input Current of the Three Phase Three Wire Boost Rectifier Under Unbalanced Input Voltage Condition,” accepted for publication in IEEE Power Electronics Specialists Conference ’02, 23-27 June, 2002, Cairns, Australia.

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THANK YOU