Model-Predictive Control to realize the Switching-Cycle Capacitor Voltage Control for the modular multilevel converters

This paper presents a Model-Predictive Control (MPC) scheme that can be used in realizing the Switching-Cycle Capacitor Voltage Control (SCCVC) for the power cells of the Modular Multilevel Converters (MMC). The capacitor voltage will follow the reference in one switching cycle by controlling the average currents that flow through the capacitors to zero. The Model-Predictive Control can diminish negative impact brought by the time delay in the digital controller, in which the switching-cycle control cannot be achieved conventionally. The SCCVC with MPC thoroughly decouples the capacitor voltage ripple magnitude apart from the line frequency, which not only provides a significant reduction of the cell capacitance and arm inductance, but also enable the MMC to deliver very low frequency line current without derating.