Multilevel current source converters for high power medium voltage applications

In medium voltage high power applications, multi-level current source converters (CSCs) are good candidate to increase system power region, reliability, and the quality of output waveforms. Compared with widely researched voltage source multi-level converters (MLCs), the current source MLCs have the advantages of inherent short-circuit protection, high power capability and high quality of output current waveforms. The main features of MLCs include reduced harmonics, lower switching frequency and reduced current stress on each device which is a particularly important for high power application with low voltage and high current requirements. This paper conducts a general review of the current research about MLCs in higher power medium voltage application. The different types of parallel structure based MLCs and the modulation methodologies will be introduced and compared. Specifically, the circuit analysis of the common-mode (CM) loop for parallel structures will be conducted, the common-mode voltage (CMV) and circulating current suppression methods developed on the base of multilevel modulations will be addressed.