Voltage Balancing Control Strategy for MMC Based on NLM Algorithm

Abstract

DC/DC converters are a key part of flexible DC distribution networks and have developed rapidly in recent years. In order to expand the voltage level of the original side of the converter, reduce the disadvantages of high manufacturing cost and large unit volume, this paper studies a modular multilevel converter structure. For the new structure, an optimized double phase-shift voltage balancing control strategy is proposed. Under the double phase-shift control, the NLM algorithm is adopted for the high switching frequency of the voltage balancing control. The 5-level single-phase structure MMC simulation model is built by the simulation platform to verify the feasibility of the proposed structure and control scheme for voltage balancing, and the IGBT switching frequency is compared under the two voltage balancing control methods before and after optimization. The results show that the optimized double phase-shift control strategy can effectively reduce the number of IGBT switching and reduce the switching loss under the condition of modular multilevel converter capacitor voltage balancing.