Flying Start of Permanent-Magnet-Synchronous-Machine Drives Based on a Variable Virtual Resistance

In this article, a flying start method for sensorless-controlled permanent-magnet-synchronous-machine (PMSM) drives based on a variable virtual resistance is proposed. In the proposed method, the inverter imitates variable resistance, this is used to suppress the inrush current and to regulate the small estimation current. Afterward, the speed and position of the motor are identified using the estimation current based on the fact that the load of the system becomes highly resistive as a result of a certain level of virtual resistance. Since high virtual resistance of the inverter could cause oscillations or instability to the system, we investigate a suitable region of virtual resistance values based on discrete stability analysis. Also, the estimation current controller and speed/position estimator are designed based on a linearized system. Since the proposed method does not require any motor parameters for the estimation process, the accuracy of the estimated position and speed is not affected by parameter variation. The controller design, region of virtual resistance, and facile implementation of the proposed method are shown to be effective by simulation and experiment.