Reliable winding-based DC-Bus capacitor discharge technique over full-speed range for IPMSM drive in electric vehicles without position sensor

When electric vehicles encounter emergency, the dc-bus capacitor voltage in the motor drive system needs to be reduced as quickly as possible to prevent the passengers from secondary electrical injury. For the purpose of compactness and low cost, a novel discharge scheme by using the machine windings has come forth. Yet, the relevant research works are incomprehensive without considering the standstill cases and sensor fault issues. This article proposes a position sensor fault-tolerant winding-based dc-bus capacitor discharge method over the full-speed range. To achieve voltage discharge at high speed without using position sensor, an improved second-order sliding-mode observer based on continuous sigmoid function is presented. Moreover, an adaptive sine-wave-based position observer with high immunity to voltage change is proposed for discharge in the low and zero speed cases. In terms of the discharge procedures, deceleration-based and acceleration-based algorithms are designed and optimized aiming at the spinning and standstill situations, respectively. More specifically, they include voltage, current, and speed regulation methods. The proposed fault-tolerant discharge technique is verified by both simulation and experiments, which are conducted on a three-phase interior permanent magnet synchronous machines drive system.