A stochastic optimal approach for fundamental frequency modulated modular multilevel converter

This paper presents a fundamental switching frequency strategy for modular multilevel converter (MMC) with PSO based stochastic optimal approach. In case of the number of sub-modules at the upper or lower arm of MMC is not even, a reasonable multilevel modulation mechanism is designed, which is also suitable for non-traditional 2N+1 level modulation application. To calculate switching angle adopted in the modulation method, an appropriate objective function is established; the initial value of the Newton iteration method is investigated by using the stochastic optimization of PSO. Theoretical results are verified by simulations for a 19-level modular multilevel inverter. The effectiveness of proposed control strategy is verified by simulative results.