Deadbeat Control for Circulating Harmonic Currents Suppression of a Level-Increased NLM Based Modular Multilevel Converter

The harmonic components of the circulating current in modular multilevel converter (MMC) can be suppressed to improve the system performance. In this paper, a circulating harmonic currents suppression method based on deadbeat control is proposed for the MMC with level-increased nearest level modulation (NLM). The optimal arm summation voltage to control the circulating current is directly calculated according to the discrete-time mathematical model of the MMC. In order not to affect the output voltage while regulating the circulating current, the adjustment principle of the total arm inserted submodule (SM) number is established. The proposed method offers advantages of simple implementation and high dynamic performance. It can handle large circulating harmonic currents with the extension of the total inserted SM number. Simulation and experimental results verify the validity of the proposed method under steady state and dynamic state conditions.