Computationally Efficient Optimal Switching Sequence Model Predictive Control for Three-Phase Vienna Rectifier Under Balanced and Unbalanced DC Links

Abstract

Unbalanced dc links usually occur when a Vienna rectifier is used as a charger for series-connected battery packs. The redundant vector preselection optimal switching sequence model predictive control (OSS-MPC) scheme does not require weighting factor tuning and is applicable to unbalanced dc links. However, its use is complicated for switching sequence selections and duty cycle calculations. Therefore, this article proposes a computationally efficient OSS-MPC scheme for three-phase Vienna rectifier operating under balanced and unbalanced dc links. The scheme achieves the same performance as that achieved by the redundant vector preselection OSS-MPC scheme, however, its execution is significantly more efficient. In the proposed method, an unbalanced factor is proposed by considering unbalanced dc links, and a look-up table is derived to describe the equivalence relation among the six feasible switching sequences. Then, duty cycles are calculated for only one switching sequence, and the OSS and its duty cycles are reconstructed based on the predefined table. Unlike the redundant vector preselection OSS-MPC scheme, the enumeration process is eliminated in the proposed method, thus, the computational burden is significantly reduced. Experimental results are provided to validate the effectiveness of the proposed method. This article is accompanied by a PDF demonstrating the look-up tables.