In the field of electrical drives, finite control set model predictive control (FCS-MPC) scheme is widely used due to its fast dynamic response and superior ability to handle nonlinear constraints. However, the typical practical switching frequency of FCS-MPC is relatively lower than its sampling frequency, which limits the improvement of power density and efficiency. This problem becomes more pronounced when implementing FCS-MPC to parallel-connected converters with LC output filter, where the heavy calculation burden imposes limitations on employing high sampling frequency. To effectively suppress circulating currents, a higher switching frequency is desirable. In this work, an improved multi-rate FCS-MPC scheme is proposed, where the increase of switching frequency is realized with two aspects. First, the control set is simplified by categorizing the control variables into two groups, so exhaustive enumeration of all possible switching states is avoided. Second, multi-rate technique is integrated, where multiple control cycles are inserted within one sampling interval. Experimental results verify the effectiveness of the proposed scheme.
