Two-Phase DC Charging Method for Improved Efficiency and Zero Torque in Motor-Integrated Charger

Recently, the battery voltage of electric vehicles (EVs) has almost doubled for faster charging. However, it is difficult to charge these EVs with existing low-voltage fast chargers. To solve this issue, boost charging topology using the motor drive system has been introduced and applied to commercial EVs. These motor-integrated chargers are controlled as three-phase interleaved boost converters. Since they use low-zero-sequence inductance for boosting, they could generate larger ripple currents and higher losses. This article analyzes the losses and finds a solution for increasing the charging efficiency and eliminating the torque to avoid rotation. Unlike the conventional method using the zero-sequence inductance, it considers the differential-mode inductance by two-phase conduction of the motor. This results in a significant reduction in current ripple, improving the efficiency. In addition, a position controller is proposed to suppress the rotation explicitly. The feasibility of this work is theoretically assessed, and the experimental results conducted in the reduced scale setup demonstrate the effectiveness of the proposed strategy.