Open-Switch Fault Diagnosis for Hybrid Energy Source-Fed Permanent Magnet Synchronous Motor System Based on DC Bus Current

The hybrid energy source-fed permanent magnet synchronous motor (HES-PMSM) system is widely used for electrical vehicles, and it includes two types of the converter, namely two bidirectional DC/DC converters and one voltage source converter, and they are connected through the DC bus. An open-switch fault is one of the most common faults of the converter, posing threats to personal safety and causing significant property damage. However, the existing fault diagnosis methods for bidirectional DC/DC converters or voltage source converter are conducted independently, without adequately considering their coupling relationship. Hence, this paper proposes a unified open-switch fault diagnosis method for HES-PMSM systems based on the DC bus current. In this method, according to the state equations of bidirectional DC/DC converters, the DC bus current is estimated through a sliding mode observer, and the DC bus current residual is calculated by comparing the estimated value with the actual measured value. Meanwhile, the DC bus current is also estimated based on the relationship between the phase current of the PMSM and the trigger signals of the power switches in the voltage source converter and the compensation term, and the DC bus residual is again calculated by comparing the estimated value with the actual measured value. Finally, an evaluation function is constructed based on the residuals from both sides for open-switch fault detection, and the faulty converter side is identified based on the absolute value of the DC bus current residuals on the HES side and the PMSM side. Both the simulation and experimental results demonstrate that this method can effectively detect open-switch faults and identify the specific fault side.