Research of surge current for PMSM when power down-rejoining on

If the original asynchronous motor of engines is replaced by permanent magnet synchronous motors, the unpredictable surge current will emerge when power down-rejoining on. The causation is the high back EMF of permanent magnet arising from PMSM when engine is passing the switching phase insulator. Aiming at above-mentioned problems, the reasons was analyzed of causing transient surge current based on three-phase PMSM transient mathematical model in the process of power down-rejoining on. The analyzing process is based on the PWM voltage which takes voltage harmonics into account. According to the analyzing results, the control strategies and conditions during the power down- rejoining process were discussed. The control conditions include the given speed, the voltage amplitude and phase of inverter and so on. A control system was designed that makes the transient surge current minimum in the process of power down-rejoining on. By the comparative analysis of simulations and experiments, the validity of analysis for transient surge current mechanism is verified, and the positive function of optimizing control system is illustrated when reducing the transient surge current in power down-rejoining on.