Direct Model Predictive Control without Steady-State Error proposed for a Cascade H-Bridge Multilevel Inverter to operate in a Microgrid

Cascade H-bridge multilevel (CHB-ML) inverters are an excellent alternative to supply power to the ac micro-grids since they have high reliability and achieve an acceptable quality of voltage at their output terminals. On the other hand, the standard direct model predictive control (MPC) scheme is a very intuitive strategy to control this type of converters, but in general, has a steady-state error when operates with low sampling frequencies and/or if the parameters of the predictive model are different in the real system. In this paper, a CHB-ML inverter that injects power to a micro-grid using a new improved direct MPC scheme is proposed. The proposed strategy eliminates the steady-state error in the MPC operating with low sampling frequencies, also maintaining a correct operation when occurring a change in some parameter of the system. Simulated results will demonstrate the feasibility of the proposal.