Direct predictive current control of grid connected neutral point clamped inverter for wave power extraction

In consequence of the generic irregularity of wave energy, it is difficult to envisage the performance of a grid connected wave energy converter without simulations. This paper details a study on directly driven, linear, permanent magnet generator based, wave energy extraction scheme provided with grid-connected three phase neutral point-clamped three level inverter. The linear permanent magnet generator is driven by a magnetic translator undergoing reciprocating motion with the floating buoy according to wave movement. It converts the mechanical power to three phase AC power. The converter-inverter system provides a fast, dynamic power balancing from generator to grid. The predictive current controller is used to control the three phase neutral point clamped inverter which calculates the inverter voltage required to force the load current to follow the reference. Simulation model of the system is implemented in Matlab/Simulink. The DC-link voltage is regulated by the converter. Neutral point voltage balancing is achieved through proper selection of inverter switching states. Three phase balanced current injection to the grid at unity power factor has been attained. The results obtained validate effectiveness of the predictive method of current control.