Space vector modulation control of an ac-dc-ac converter with a front-end diode rectifier and reduced dc-link capacitor

In this paper, the control of an ac-dc-ac converter with a front-end diode rectifier and reduced dc-link capacitor based on the space vector modulation strategy is investigated. The modulation index is time-varying and determined by the instantaneous value of the dc voltage measured by a voltage sensor. Using a small bipolar capacitor, instead of a large electrolytic capacitor on the dc-link, increases the lifetime of the converter and reduces its size. The input current quality of this converter has been shown to be superior to that of the conventional ac-dc-ac converter with front-end diode rectifier. The perfectly sinusoidal local average output voltage can still be achieved under unbalanced input voltage condition by implementing a time-varying modulation index. The rule for determining the dc capacitance has also been studied in this paper. The simulation results obtained from PSIM simulation software and experimental, results obtained from the lab prototype are used to verify the theoretical expectations.