Optimized Pulse Pattern Modulation for Modular Multilevel Converter High-Speed Drive

The indirect Modular Multilevel Converter (MMC) is an emerging high voltage inverter topology. Off-line Optimized Pulse Patterns (OPP) as investigated in this paper increase the efficiency due to reduced switching and harmonic current losses. This is particularly interesting for applications which demand high output frequencies, such as high-speed motors. Pulse patterns for arbitrary modulation indices and arbitrary numbers of modules per branch are optimized with regard to minimal harmonic distortion of the output voltage. A closed-loop capacitor voltage balancing method that enables distributed modulation is also introduced. Simulation results of a complete drive system show the feasibility of the approach.