A Damping Control Strategy to Improve the Stability of Multi-Parallel Grid-Connected PCSs

Abstract

In this study, to ensure stable operation of multi-parallel PCSs, a damping control strategy is adopted to restrain resonance characteristics of a parallel system, and the stability of the system is analyzed. First, the mathematical model of a single PCS is built, the capacitive current feedback-type active damping control strategy is introduced, and the effect of the damping control strategy on a single PCS under proportional-integral (PI) control is analyzed. Then, under the presence of grid impedance, a single PCS model is established and extended to multi-parallel PCSs, where a single PCS is replaced by a Norton’s equivalent circuit. The active damping method is developed, and Bode diagrams are utilized to verify that it can effectively suppress the resonance spikes of a parallel system. Finally, a simulation model of four PCSs in parallel operation is built on the Simulink platform, and the results support the correctness of the theoretical analysis.

Keywords

• power converter system (PCS)
• LCL filter
• PI control
• parallel stability
• active damping