The Current Synchronous Detection Method Combined with Positive Sequence Detector for Active Power Filters

The Current Synchronous Detection (CSD) method for active power filters (APF) is an average power theory (APT) that can control power source current to balanced sinusoidal waveforms even under three-phase unbalanced power source conditions But, in the CSD method, when three-phase power source voltage is distorted, voltage information is used as it is to extract the active current component of the nonlinear load current, and thus the compensated power source current is also distorted. Therefore, in this study, a CSD method combined with a Positive Sequence Detector (PSD) that can control the current in a balanced and sinusoidal waveform was proposed even under unbalanced and distorted power source conditions. In order to verify the validity of the method presented in this study, experiments were performed under unbalanced and distorted three-phase 110 V/60 Hz power source conditions, and the CSD method and the proposed method were compared and discussed under state and transient conditions. As a result, it was proven that the proposed method can control the current in a balanced sinusoidal waveform even in a power source with severe distortion and unbalance. The validation of the proposed method is not based on the conventional Total Harmonics Distortion% (THD%) analysis that evaluates the distortion level of the three-phase waveform for each phase, but is based on the α-β-phase trajectory analysis that comprehensively evaluates the distortion and unbalance of the three-phase waveform.