Power Quality Enhancement Using Linear Quadratic Regulator Based Current-controlled Voltage Source Inverter for the Grid Integrated Renewable Energy System

Abstract

This paper presents an optimal control strategy using linear quadratic regulator (LQR) applied in current-controlled voltage source inverter (CCVSI) to control the real and reactive power flow between the renewable energy system (RES) and the grid. It also compensates harmonic current components drawn by the load from the grid terminal. A simplified equivalent circuit is used to develop the reduced order state space model of the three-phase grid connected renewable energy system. This makes the analysis and design of control law simpler by reducing the number of weighing variables used in LQR. The extension real–reactive power (p–q) method implemented in a–b–c frame is used to generate the reference current for controlling the real and reactive power to the grid to minimize the total harmonic distortion (THD) and to achieve unity power factor (UPF) operation at the grid side. The stated technique makes the grid current sinusoidal even under unbalanced grid voltages and the harmonic distortion factors are well within the IEEE limits. The system is simulated under changes in the real power fed from RES to the grid for both balanced and unbalanced grid conditions. The simulation results are validated by the experimental results.

Keywords::

• current-controlled voltage source inverter
• extension p–q method
• hysteresis controller
• linear quadratic regulator

Funding

The authors would like to thank for the financial support through Anna Centenary Research Fellowship, Anna University, Chennai, Tamil Nadu, India.

Additional information

Notes on contributors

Vinifa Rajakumar

Vinifa Rajakumar received the B.E. degree in electrical and electronics from Manonmanium Sundaranar University, Tirunelveli, India, in 2003, and the M.E. degree in power electronics and drives from the College of Engineering, Guindy, Anna University, Chennai, India, in 2013, where she is currently a Research Scholar and working toward to the Ph.D. degree. She has more than 8 years teaching experience. She is a Life Member of Indian Society for Technical Education and Institution of Engineers. Her research interests include renewable energy, power quality, and control systems.

Kavitha Anbukumar

Kavitha Anbukumar received the B.E. (Electrical and Electronics Engineering) degree from Madurai Kamaraj University in 1996, the M.Tech. degree from the Indian Institute of Technology Madras in 2002, and the Ph.D. degree from the College of Engineering Guindy, Anna University, Chennai, India, in 2010. In 1996, she became a Lecturer in St. Peters Engineering College, Chennai. From 2003, she started working as a Lecturer and she is currently an Assistant Professor in Electrical and Electronics Engineering Department, College of Engineering, Guindy, Anna University, Chennai. She has published several papers in reputed international journals. She is a Member of IEEE since 2011 and a Life Member of Indian Society for Technical Education. Her research interests include special electrical machines and drives, DC–DC converters, and renewable energy applications.

Immanuel Selwynraj Arunodayaraj

Immanuel Selwynraj Arunodayaraj received the B.E. (Mechanical Engineering) degree from Manonmanium Sundaranar University in 2001, the M.E. (Thermal Engineering) and Ph.D. degrees from Anna University, Chennai, India, in 2004 and 2015, respectively. He has more than 8 years of teaching experience and 4 years of research experience. He is currently working as an Associate Professor, School of Mechanical Engineering, VIT University, Vellore. He has published several papers in reputed international journals. He is a Life Member of Indian Society for Technical Education. His research interests include renewable energy, solar thermal energy, and energy management.