Simplified Model Predictive Control of Multilevel Converters With Internal Identical Structure

Model predictive control (MPC) is a promising control scheme for multilevel converters as the multiple control objectives in multilevel converter can be achieved using a single cost function. However, the computational burden of MPC is heavy when it is applied to multilevel converters as the number of switching states in the multilevel converter is very large. On the other hand, an internal cascaded or parallel identical structure is extensively employed in multilevel converters as the voltage level increases. This paper proposes a simplified MPC for multilevel converters by fully utilizing the feature of the internal structure in the multilevel converter. In the proposed MPC, a series of switching states are modeled as a single virtual switching state, and the multiple vector MPC is adopted to generate the duty cycle for the virtual switching state. The duty cycle obtained by the multiple vector MPC is applied to each switching state in the internal identical cell using phase-shifted pulse-width-modulation (PS-PWM). The flying capacitor voltage balance or the circulating current suppression is achieved by slightly regulating the duty cycle among each switching state in the internal identical cells. Comparative experimental results with a linear controller with PS-PWM are presented to validate the effectiveness and superiority of the proposed MPC method.