DC Voltage Balance Control Strategy for Medium Voltage Cascaded STATCOM Based on Distributed Control

DC bus capacitors of Medium Voltage Cascaded STATCOM are independent. DC side voltage balance control method is the key influencing factor of current control. The imbalance of DC bus voltage increases harmonic current and affects the safety of device. In this paper, the unbalance mechanism of DC side capacitor voltage is analyzed. Based on the unipolar dual frequency and carrier phase-shifted SPWM (CPS-SPWM) modulation algorithms, the distributed control algorithms, which need multiFPGA structure, are proposed. By changing the instantaneous active power input of single module, the voltage balance control strategies of DC bus capacitors are realized. The strategy can be applied in each inverter, respectively. Simulation and experiment results show the feasibility and effectiveness of the strategy.