Space-Vector Current Control Of Cascaded Half-Bridge Three-Phase Three-Wire Voltage Source Inverter

Current controllers for voltage source inverters give better control of current waveform and also provide compensation for load transients and non-linearities. Despite the increasing employment of multilevel inverters in high-power medium voltage applications and its superior performance compared to two-level inverters, the extension of hysteresis current controllers to multilevel voltage source inverters is much less established. In this study, a current error space vector-based hysteresis controller is implemented on a three-phase cascaded half-bridge voltage source inverter. The vector-based method measures the current error in a space vector form and keeps the error within the assigned tolerance region. It has been observed from the simulation tests and experimental verifications that the implemented current regulator maintains the load current as close as possible to the set reference current with a significantly minimised error. Another attractive feature in the implemented closed-loop current controller is that the number of voltage levels is maintained as the output of the inverter with a fast dynamic response.