Simplified Model Predictive Control of Four-Leg Inverters for Stand-alone Power Systems

Research coverage of finite control set model predictive control for three-phase four-leg inverter does not include any discussion about the alleviation of the computational burden which is imposed as a result of the additional fourth-leg of the converter to control the zero-sequence component of the current. In this paper a simplified finite control set model predictive control for three-phase two-level four-leg inverter to control the load voltage is presented. The cost function of the proposed FCS-MPC is reformed based on the voltage oriented control to track the desired current reference. With the proposed technique, the prediction process requires the evaluation of only five voltage vectors in the prediction loop compared to the benchmark conventional approach which evaluates all sixteen voltage vectors in the prediction process. Numerical results demonstrate the efficacy of the proposed approach in bringing down the computational burden without any degradation in the converter performance compared to the conventional approach. Moreover, this scheme can eschew the internal current control loops and modulators and thus greatly reduces the complexity.