DC-Bus Capacitor Discharge Method Based on Bleeder and Windings for Electric Vehicles in Emergency

Abstract

The bleeding circuit is important for dropping the dc-bus voltage to safe voltage when electric vehicles (EVs) encounter an emergency. However, the bleeding circuit may be bulky and heavy to ensure that the total discharge operation is completed in the specified time (5 seconds). In order to reduce the volume and weight of the bleeding circuit, this paper proposes a maximum discharge power method that can maintain the discharge power of the bleeding resistor at the maximum discharge power. The mechanism and disadvantage of traditional uncontrolled rectification (UR) method is analyzed for illustrating the necessity of reducing the bleeding resistor at first. Then, the proposed maximum discharge power is developed based on the established power flow model. For the sake of improving the tracking performance and dynamic performance of the discharge power, an adaptive sliding mode power control (ASMPC) is proposed with the adaptive reaching law, which can effectively reduce the chatting effect on inner current loop. Finally, the proposed strategy is validated on a permanent magnet synchronous motor drive used for EVs, and the results show that the proposed discharge method can not only reduce the bleeding resistor size and weight but also improve the dynamic characteristics.INDEX TERMS Bleeding resistor, dc-bus capacitor, maximum discharge power, permanent magnet synchronous machine (PMSM), power flow model.