The Research of Parallel-Connected Power Conversion System Based on Power Series Decoupling

The energy storage system can operate in two modes, including grid-connected mode and islanding mode. The current sharing control of multiple parallel-connected energy storage subsystems is discussed in this paper. Firstly, the circuit configuration of parallel-connected energy storage system based on centralized control is introduced, and the equivalent model is established. Then the expressions of active and reactive circulating current in parallel system are deduced and analyzed. The result shows that the circulating current is related to the output voltage as well as parallel impedance, and can be suppressed by adjusting the output voltage. Moreover, considering the coupling between active and reactive circulation and the static error of impedance, a current sharing control strategy based on power series decoupling is proposed. The decoupling controller is designed and verified to have good robustness. The experimental results show that regardless of various loads, the proposed control method can not only maintain the stability of system voltage and frequency, but also has good static and dynamic current sharing accuracy.