Analysis of a Modular Multilevel Inverter Under the Predicted Current Control Based on Finite-Control-Set Strategy

This paper introduces a method for the precise control of (un)balanced load currents in Modular Multilevel Converter (MMC). The algorithm is based on the Finite-Control-Set Model Predictive Control (FCS-MPC) which is a promising predictive control approach for power converters to minimize the circulating currents inside the converter legs, achieve the voltage balance in the capacitors and load current control. The grid-connected MMC topology, its analytical modeling and the controller design procedure are described and design example is studied. Developed predictive control is also employed to reduce sensitivity of the converter output voltage to disturbances in load side and measurement noise. In addition, system stability has been analytically verified in terms of model uncertainties. Simulation results are included to validate the proposed controller especially for good load current reference tracking and disturbance rejection properties despite the variations in the system parameters.