A Two-Stage Simplified Predictive Control for Modular Multilevel Converter

Abstract

Model Predictive Control (MPC) is rapidly making inroads into power electronics converter control due to its simple and intuitive design and fast transient performance. However issues like heavy computational burden, tedious weights selection process and lack of fixed switching frequency seriously inhibit its application for large systems like the Modular Multilevel Converter (MMC). To tackle this problem, this article proposes a unique simplified two-stage MPC strategy for the Modular Multilevel Converter (MMC) using a simple search algorithm. The proposed technique falls under the category of Modulated MPC. One of the major advantages of this method includes fixed switching frequency for MMC with $2\mathrm{N}+1$ levels in the phase voltage, which is absent in many other MPC techniques in literature. Moreover the circulating current suppression and the output current control are decoupled. The capacitor voltage balancing is carried out using the simple reduced switching frequency type of sorting. It has lower computational complexity and ensures simplified digital implementation. The simulation results carried out using PLECS for 10 SM/0.7 MW MMC connected to a passive load validate the performance of this proposed algorithm.