A New Approach to Compensating Voltage Unbalance by UPQC-Based PAC

Abstract

This paper proposes a novel algorithm for power angle control (PAC) which aims to simplify the control algorithm and obtain a fast dynamic response. It also extends the capability of PAC to compensate voltage unbalance with or without phase angle jump in a simple way. Using this control strategy, unified power quality conditioner (UPQC) can improve power quality problems such as sag, swell, and unbalances of source voltage, load reactive power and harmonics in distribution systems. The series converter in UPQC is responsible for compensation for voltage-related problems. In PAC method, the series converter also participates in load reactive power compensation which is the superiority of this control strategy. The proposed method uses triangular rules of vector addition/subtraction to determine phase and magnitude of voltage that should be injected by series converter. It reduces the required calculations and hence raises the velocity of compensation. For achieving a better dynamic response, a sliding mode control is used to control DC link voltage instead of conventional PI control. This makes the control algorithm faster and more robust. Simulation results obtained through MATLAB/SIMULINK verify the effectiveness of the proposed method.