The Digital Current Control of Single-Phase Cascaded Half-Bridge Voltage Source Inverter

Multilevel inverters MLIs are deeply studied topic due to the integration of power sources in many applications. Mainly, these MLIs are three-phase systems. However, several applications, such as photovoltaic present single-phase configurations. For applications requiring quick response and accurate control, current controlled voltage sources (VSIs) are normally preferred. However, The extension of current controllers to MLVSIs is much less established. This paper presents an asymmetrical single-phase cascaded half-bridge VSIs of controlled load current. The isolated DC-supplies of the presented extendable topology are selected in optimal and applicable strategy. The implemented vector based current controller measures the current error in a vector form and execute the corresponding switching state that keeps the error within the assigned tolerance region. The current regulator maintains the load current as close as possible to the set reference currents with significantly minimized error. Another attracting feature in the implemented closed-loop current controllers is that the number of voltage levels is maintained as the output of the inverter with fast dynamic response. The proposed selection process of the applied vector and the minimization of the error vector was verified through simulation results.