Active Control of Variable DC-Link for Maximum Efficiency of Traction Motor Drives

Modern electric vehicles often interpose a DC/DC converter between traction battery and inverter, boosting the supply voltage of the drive. The power losses in the two converters and in the electric motor significantly vary with the DC-link voltage amplitude. In this work, a novel control algorithm is proposed to adapt online the DC-link voltage during vehicle operation, pursuing the maximum efficiency of the DC/DC converter and traction inverter without affecting the motor control dynamic. The key principle of the proposal, suitable for 3-phase and multi-three-phase drives, relies on the DC-link voltage minimization on varying the drive operating conditions. Among its advantages, the proposed variable DC-link control is independent of the motor parameters, the adopted torque/speed control strategy and the number of 3-phase sets of the drive. Although originally developed for electric vehicles, it can be adopted in a wide number of applications. Straightforward calibration roles are also provided. The proposed algorithm is deeply validated in simulation and experiments using a full-scale 135 kW 6-phase traction motor drive at TRL6.

Automated summary

Modern electric vehicles often use a DC/DC converter to increase the supply voltage and improve efficiency. This study proposes a novel control algorithm to adjust the DC-link voltage during vehicle operation, maximizing the efficiency of the converter and inverter without impacting motor control. The algorithm is independent of motor parameters and can be applied to various applications. Validation is done using a 135 kW 6-phase traction motor drive.