A Gravitational Search Algorithm Based Static VAR Compensator Switching Function Optimization Technique for Minimum Harmonic Injection

Abstract

Switching function optimization for minimum source harmonic injection for a static VAR compensator is presented. The static VAR compensator is configured with a fixed capacitor and insulated-gate bipolar transistor controlled reactor. The switching function is optimized for minimum source harmonic injection considering the desired fundamental voltage across load terminals. A gravitational search algorithm is employed for this purpose. It is observed that the proposed switching scheme with two different switching angles per half-cycle provides lower source harmonic injection compared to conventional switching, hence improving the source current harmonics. The switching angles are computed off-line using the gravitational search algorithm for varying modulation indices considering the minimum total harmonic distortion of the reactor voltage. The switching angles are stored in a processor as a function of the modulation index for on-line application using a piecewise mixed model approximation technique for low memory usage. It is observed that the proposed switching improves the source current total harmonic distortion on an average of 4 to 5% over most of the operating range compared to conventional switching without optimization. Various simulation and experimental results are presented on different loads to validate the proposed concept.

Keywords:

• static VAR compensator
• gravitational search algorithm
• harmonic distortion
• piecewise mixed model of approximation
• switching function

NOMENCLATURE

C	=	per phase capacitance of fixed capacitor
L	=	per phase inductance of insulated-gate bipolar transistor controlled reactor
PL + jQL	=	phasewise load demand
P L+ jQs	=	phasewise load seen by the source after compensation
Vm	=	peak value of insulated-gate bipolar transistor controlled reactor supply voltage
Z	=	line impedance matrix
α1	=	triggering delay angle for three branches of insulated-gate bipolar transistor controlled reactor
α2	=	extinction delay angle for three branches of insulated-gate bipolar transistor controlled reactor
θ	=	phase angle of insulated-gate bipolar transistor controlled reactor supply voltage

Additional information

Notes on contributors

Sankar Das

Sankar Das received his B.E. and M.E.E., both in electrical engineering, from Vidyasagar University and Jadavpur University, Kolkata, India, in 2002 and 2007, respectively. Currently, he is working as an assistant professor in the Electrical Engineering Department at Jalpaiguri Government Engineering College, India, and is working toward his Ph.D. in the Electrical Engineering Department at Jadavpur University, Kolkata. His research interests include power quality improvement and power electronic devices.

Debashis Chatterjee

Debashis Chatterjee received the B.E. from Jadavpur University, Kolkata, India, in 1990; his M.Tech. from Indian Institute of Technology (IIT), Kharagpur, in 1992; and his Ph.D. from Jadavpur University, Kolkata, in 2005, all in electrical engineering. From 1992 to 2002, he worked as a senior executive engineer at National Radio Electronics Co. Ltd. in drives and automation systems, a development executive at Crompton Greaves Limited in the Industrial Electronics Group, and an assistant manager at R&D in Philips India Ltd. in the Lighting Electronics Division. Currently, he is associate professor in the Electrical Engineering Department at Jadavpur University, Kolkata. His main research interest includes control of electric drives and power electronics, renewable energy generation, and control.

Swapan K. Goswami

Swapan K. Goswami received his B.E. from Tripura Engineering College, Agartala, India, in 1980 and his M.E.E. and Ph.D. from Jadavpur University, Kolkata, in 1982 and 1991, respectively. Currently, he is a professor in electrical engineering, Jadavpur University, Kolkata, India. His current research interests include soft computing applications in power systems, distributed generation, and deregulation.