Optimized Distributed Digital Control and Communication Architecture for Flying Capacitor Modular Multilevel Converter Based PMSM Drives

An optimized digital architecture exploiting dis-tributed and multilayer hierarchical control and real-time communication for Flying Capacitor Passive Cross-Connected arms Modular Multilevel converter (FC-PCC MMC) based drive systems is proposed, designed and validated. The proposed solution, relies on two fundamental components: a Multi-Point Low Voltage Differential Signaling (M-LVDS) bus and a bi-directional optical wireless transceiver, recently introduced to the market. As a result, the necessary isolation barrier between ground and each Sub-Module (SM) can be crossed at a very high data rate. The real-time constraints and requirements have been analyzed and discussed in order to design a control strategy and communication infrastructure for proper, safe and reliable converter operation. Based on this analysis, a distributed control algorithm and the related communication infrastructure are proposed in this paper. Moreover, an innovative isolated communication bus is adopted, which aims at reducing the overall system size and cost. The effectiveness of the proposal is demonstrated by accurate simulation of a 22 kW Permanent Magnet Synchronous Machine (PMSM) drive, including the effect of communication and processing latency. The results show that proper operation is obtained even at rated torque from zero to rated speed, while the voltage ripple across the SM capacitors is kept limited thanks to the optimized control strategy proposed in [1]. A prototype of the converter has been designed and is ready to be manufactured.