Power loss analysis and measurement of a high efficiency DC-DC converter for EV traction AC drives

Previous works have shown the power design effectiveness of novel H-bridge-based DC-DC boost conversion structure, as well as the feasibility of real-time DC-link voltage adaptation to inverter load, in battery-supplied AC motor drives. In this paper a novel test bench has been developed, suitable for power loss measurements in high-efficiency bi-directional DC-DC converters. In order to allow for quasi-direct measurement of the lost power, the concept is to operate the converter by input current having constant module, handling alternating energy flow between two large capacitor banks at given input/output DC voltages. Accordingly, the input current reference is a low frequency (65 Hz) rectangular-wave, whose duty-cycle is regulated by suitable voltage loop due to constant module operation. Except for added large capacitor banks' losses and other secondary effects related to 65 Hz operation, the input DC power supply is shown equivalent to conversion losses at given DC working point. The results point-out the high efficiency of the conversion structure well matched with simple analytical models.