Reliable voltage balancing control based on hybrid algorithm for modular multilevel converter

摘要

Modular multilevel converter (MMC) has great potential in medium voltage power transmission. However, the large capacitor voltage would ripple at low frequency. In order to achieve the balance of the capacitor voltages of sub modules (SMs), the hybrid algorithm combined Sorting-Carrier Phase Shifted-Pulse Width Modulation (S-CPS-PWM) algorithm and cyclic modulation algorithm is proposed. The principle of the S-CPS-PWM algorithm is that the sorting method is used to determine the SMs that need to be bypassed or inserted after determining the number of SMs that need to be inserted. The performance of proposed algorithm is analyzed through simulation results with medium voltage. In addition, the effect of the algorithm is verified by the simulation results and experimental results, of which the RL load is working at 50 Hz and 30 Hz.