Reactive Power Compensation and Resonance Damping for Three-Phase Buck-Type Dynamic Capacitor

摘要

Dynamic capacitor (D-CAP) is able to provide dynamic reactive power and harmonic compensation for industrial plants. Previous papers have introduced the principles and control strategies of D-CAP. However, there is no paper to focus on resonance conditions of D-CAP. In this paper, based on three-phase Buck-type D-CAP, basic structure and principle are introduced. Then, through the modeling of D-CAP impedance and grid impedance, the reason of resonance is analyzed, and the corresponding resonance points are calculated. In order to suppress the harmonics near the resonant frequency, this paper presents an active damping method that the capacitance voltage of D-CAP is detected as feedback quantity to solve this problem. At last, a hybrid control strategy for reactive power compensation, harmonic suppression and resonance damping is proposed. Through this strategy, grid current harmonic distortion obtains good inhibition and its THD meets the IEEE std519-1992. The experimental results verify the validity of the theoretical analysis.