Performance Improvement of Unified Power Quality Conditioner Under Various Load, Source, and Line Conditions Using A New Control Method

A unified power quality conditioner (UPQC) is introduced and designed in this paper, which is capable of dealing with multiple power quality issues simultaneously. The mentioned UPQC consists of two active power filters (APF), one of which is placed series with the line, and the other one is parallel to it. Two control systems are developed for each of the UPQC sections. The series APF is controlled by a carrier-based pulse width modulation (PWM) generator, which enables it to follow the reference voltage. Furthermore, a direct-quadrature-zero (dq0) transformation is utilized to generate the most proper current reference signal in order to minimize harmonics in the current waveform and maximize the power factor. Then, a hysteresis controller is used to build command signals for shunt APF. The proper functionality of introduced UPQC and its control system is verified in cases of most common power quality problems such as voltage sag, voltage swell, single-phase fault, three-phase fault, reactive power compensation, current harmonic compensation of nonlinear loads, and unbalanced load by performing extensive simulations in MATLAB Simulink.