A Variable Frequency Voltage Injection Method for Modular Multilevel Converter in Variable Speed Driver
摘要
Modular Multilevel Converter (MMC) is a common multilevel topology for medium voltage motor drives. However, the voltage fluctuation of the sub-module (SM) capacitor is the main obstacle when motor runs at low speed. A variable frequency voltage injection method is recommended in this paper, in which the frequency of the injection voltage changes synchronously with the speed (output frequency) and is permanently guaranteed to be K times of the frequency. The optimal voltage suppression can be achieved at low frequency operation and overmodulation can be effectively avoided. Finally, the availability of the recommended variable frequency voltage injection method is checked with simulation and experimental results.