Multirate FCS-MPC for Parallel Dual-Converter-Fed PMSM Drives With Reduced Circulating Currents

When implementing finite control set model predictive control (FCS-MPC) schemes in parallel converters sharing a common dc link, circulating currents become prominent due to the relatively low switching frequency. Although the multirate technique was proposed later to enhance the calculation efficiency, it is complex in parallel converters due to the numerous switching states and strong coupling between control variables. This article presents a multirate FCS-MPC method for permanent magnet synchronous machine (PMSM) drives fed by parallel converters. Reduced circulating currents are achieved from two primary aspects. First, the equivalent multilevel model of parallel converters is integrated with a multirate structure. This fully utilizes the redundancy in switching states, thus simplifying the calculation and enabling a higher equivalent control frequency. Second, the regulation of circulating currents is decoupled from the motor-side variables, allowing for precise regulation of circulating current and easy design of cost functions. In contrast to conventional modulation-based schemes, the proposed scheme ensures superior stator current performance and fast dynamic response under all operating conditions. The effectiveness of the proposed method was validated through experiments.