A new phase detecting method for power conversion systems considering distorted conditions in power system

In this paper, a new phase detecting method is proposed for PWM rectifiers and active filters considering distorted utility conditions. The accurate phase angle information of utility voltage is essential to the active power conversion systems tied to the utility line. The angle information can be easily corrupted by the distorted utility voltage such as voltage unbalance and harmonics in the waveform. Thus, large harmonics may be caused in the current or voltage reference signal whose phase angle is based on the detected voltage phase angle. First, focusing on the distorted utility condition, effects of the several phase angle detecting methods on the operation of PWM rectifiers and active filters are investigated. Then a new voltage phase angle detector is proposed using voltage sequence detector and PI controller. The proposed method does not cause harmonics in the reference signal by adequately eliminating unbalance components and high-order harmonic terms in the utility voltage. The basic principle of the proposed method is described in detail. Experimental results prove the feasibility of the proposed strategy compared with the conventional method.