Power Quality Improvement Using Unified Power Quality Conditioner

Abstract

Power quality can be defined as any power problem faced in the frequency, current or voltage deviation which leads to mal-operation of the customer’s equipment. It has been always difficult to maintain the quality of electric power so as to keep it within the acceptable limits. Mainly the use of power electronics devices that acts as the nonlinear load is responsible for the degradation in the poor power quality. Poor power quality results in various problems in the distribution systems like higher power losses, harmonics, sag and swells in the voltage, poor distortion and displacement factor. The recent developments in communications, digital electronics, and control system have rapidly increased the number of sensitive loads that require ideal sinusoidal supply voltage for their proper operation. So it became necessary to include some sort of compensation in order to meet limits proposed by standards. Here Unified power quality Conditioner (UPQC) has been used to overcome the power quality problem. UPQC which is a combination of back to back connected series and shunt APFs through a common DC link voltage, the two APFs function differently. The shunt active filter is mainly advantageous in removing the current related problems and the improvement of power factor and regulation of DC link voltage. Whereas the series APF helps in correction of voltage related problems by acting as a controlled voltage source. Two control strategies has been described here i.e. the UVTG (unit vector template generation) and the synchronous reference frame, P-Q technique. UVTG is used for the control of both series and shunt active power filter whereas in the other method synchronous reference frame method is used for the control of SAF and the P-Q method is used for the control of shunt APF.