Analytical and Experimental Efficiency Evaluation of a Voltage Balancer Based Three-Phase Unfolding EV Powertrain

Three-phase unfolding based converters have emerged as promising solutions for achieving two-stage dc to three-phase ac conversion, particularly for electric vehicle (EV) powertrains. This paper presents a comprehensive loss model of a novel non-isolated buck-boost three-phase unfolding based powertrain. The proposed converter incorporates a voltage balancer circuit in the dc-dc stage to generate the required varying dc-link voltages, subsequently unfolded by the unfolder stage operating at motor fundamental frequency. The paper outlines the analytical characterization of the system currents, followed by detailed calculations of semiconductor and inductor losses. Experimental measurements conducted on a hardware prototype affirm the accuracy of the analysis, demonstrating peak efficiencies surpassing 98% for power levels up to 5 kW.