Coupled Inductor Analysis and Design for Flying-Capacitor Passive Cross-Connected Arms Modular Multilevel Converter (FC-MMC) for PMSM Drive Application

Modular Multilevel Converters (MMC) are becoming increasingly popular in Medium Voltage drive applications. Voltage ripple on submodule (SM) dc bus capacitor banks is an issue that can be overcome with modified topologies, such as Flying-Capacitor Passive Cross-Connected arms MMC (FC-PCC MMC), exploiting high-frequency voltage and current injection for active SM capacitor voltage balancing. The arm inductors perform a key role in the overall converter operation and integrity, hence their proper design is crucial to decrease the overall converter size, weight and cost. An in-depth analysis of all the different coupling configurations among the sub-arm inductors of the same phase-leg is provided in this paper. A novel solution, based on the magnetic coupling between sub-arm inductors, is proposed and fully analyzed including a preliminary evaluation of the size and weight. The effectiveness of the solution is demonstrated by accurate simulation of the overall converter, which feeds a Permanent Magnet Synchronous Machine (PMSM). The model includes the distributed control timing and the scheduling of the measurement and controller execution.