A Grid-Connected Current Controlled Granular Multilevel Converter

This paper proposes a current controlled Granular Modular Multilevel Converter (GMC). The Ramp Current Control (RCC) technique is utilized due its simplicity. Besides controlling the output currents, the proposed control system for the GMC regulates the submodules capacitors voltages at their desired settings. A proper switching state is selected to keep the submodule capacitors voltages based on hysteresis capacitor voltages controllers, the required phase voltage level, and the sign of the output current. The reference phase voltages are determined using the RCC to control the d- and q-current components of the GMC in the synchronous frame. These current components are set using two Proportional-Integral (PI) controllers to manage the active and reactive powers fed to grid. Simulations results, using EMTDC/PSCAD, are presented to evaluate the dynamic performance of the proposed system under different operating conditions.