Parameter Dependency Analysis of Uncontrolled Generation for IPMSMs in Electric Vehicles

Interior permanent magnet synchronous machines (IPMSM) often work under flux weakening state in electrical vehicles for higher speed. But unavoidable faults might occur during that process, after which the power transistors are switched off immediately and the battery packs are charged through the three-phase uncontrolled rectifier composed of six flywheel diodes. That is also renowned as uncontrolled generation (UCG) operation which needs to be well understood to avoid damage to either inverter or battery. In order to achieve more accurate analytical results, this paper proposes an improved steady-state model of the drive system for UCG analysis. On the basis of the model, the parameter dependencies are detailed. The voltage and current characteristics of UCG and the effectiveness of the proposed steady-state model are verified by experimental results.