Reactive Power Compensation Using Induction Motor Driven by Nine Switch AC-DC-AC Converter

Abstract

Induction motors (IM) used for various industrial applications operate with lagging power factor. Electrical distribution agency insists high power factor operation and it gives incentives on operating a system closer to unity. This paper presents a novel reactive power compensation using IM driven by nine switch ac–dc–ac converter for a high power factor operation at the point of common coupling (PCC). The nine switch converter (NSC) with leading power factor operation delivers reactive power to the PCC. Thus, reactive power required for another load at PCC is compensated. Modified sinusoidal pulse width modulation is developed for NSC to operate the active front end rectifier and an inverter simultaneously to feed three-phase IM. A closed loop proportional integral control technique is developed to achieve desired VAR compensation. As per the required VAR compensation, front end rectifier voltage is modified. This is achieved by phase shifting of front end rectifier modulation reference by an angle $\delta$ with respect to utility phase voltage. The PCC phase voltage is continuously sensed to track instantaneous phase angle $\theta$ using synchronous reference frame phase lock loop. The analysis of VAR compensator is presented in the d-q reference frame. The proposed system is simulated in MATLAB for VAR compensation at PCC with 5.4 hp induction motor drive to test the performance of VAR control loop. To validate the feasibility of the proposed system an experimental prototype is developed with 1 hp induction motor drive. Gate pulses are generated using digital signal controller dsPIC33EP256MU810. The simulation and experimental results proved the feasibility of the proposed VAR compensation system.