The paper looks at the harmonic interaction between series and parallel power quality conditioner compensation. The voltage power quality conditioner DVR and parallel APF are taken as examples, and an analysis is carried out on the harmonic effect caused by the nonlinear nature of delayed effects. Simplified equivalent impedance models based on DVR and APF are built, potential parallel resonance is analyzed, and several solutions are presented. For the harmonic compensation of normal important loads, the features and suitable occasions of single/array APF are also analyzed and compared. For the operating losses of array APF, a centralized control mode based on the equal loss incremental rate compensation strategy is proposed, and then an engineering study related to array APF is carried out. This work is supported by the National Key Research and Development Program of China (No. 2019YFE0123600).