An Improved Model Predictive Control for a Novel Flying-Capacitor Five-Level Converter With Reduced Switching Devices

The five-level converter is a promising topology for industrial applications. In this article, a novel flying-capacitor (FC) five-level topology with reduced switching devices (RSD-FC5L topology) and its corresponding control scheme are designed. Compared with conventional topologies, the RSD-FC5L topology has a lower total blocking voltage (TBV) and only requires balancing the FC voltages without considering the neutral-point voltage (NPV) control, which reduces the complexity of control technology. To operate the RSD-FC5L topology properly, an improved model predictive control (IMPC) scheme is proposed. First, the space vector diagram is normalized and an easy judgment can realize accurate current tracking. Then, in order to balance the FC voltages, the space vector diagram is redivided into new candidate hexagons consisting of various vectors. During the entire control process, the cost function is avoided and the weighting factor is eliminated thereby, which further reduces the control complexity. The effectiveness of the proposed topology and IMPC scheme is verified by the simulation and experiment.