Discrete-time sliding mode direct power control for three-phase grid connected multilevel inverter

This paper presents a novel Direct Power Control strategy for a three-phase grid connected multilevel inverter. The proposed DPC strategy combines discrete-time sliding mode control and predictive control. The active and reactive power are directly controlled by inverter switching states, represented by a switching vector, using the value of the power error computed from samples of phase voltages and currents. An appropriate switching vector is selected for each sampling period to minimize average value of the switching functions on the time interval on three sampling periods. The prediction of phase voltages and currents is necessary for algorithm implementation. The switching frequency is constant, and the digital control implementation is simple. The designed control system is tested using a simulation model of a three-level neutral-point clamped multilevel inverter. Simulation results confirm the design aims.