Fast Finite Control Set Model Predictive Control for Multilevel Inverters

This paper proposes a FCS-MPC strategy for multilevel inverters, called Fast FCS-MPC, that makes use of a coordinate transformation in order to represent the inverter voltage vectors with integer entries. First, it is assumed that the current reference and the actual current at k + 1 are equal, and the voltage reference needed to adequately track the desired current at k+1 is estimated. The voltage reference is then rounded to obtain the nearest inverter voltage vector. In the second step, the voltages of the internal capacitors of the multilevel inverter need to be regulated to their reference values. This is accomplished by solving another optimization problem, considering only the redundancies of the chosen voltage vector. The operation of the proposed Fast FCS-MPC is presented both for linear region and overmodulation. The proposed Fast FCS-MPC does not need weighting factors for the cost function, presents a low computational burden, achieves good steady-state and transient responses, as well as properly balances and regulates the internal capacitor voltages. In order to demonstrate the good performance of the proposed algorithm, Hardware-in-the-Loop results are presented, considering as an example a three-phase grid-tied NPC inverter with L filter.