Sensorless Control of Permanent Magnet Synchronous Motors Based on Low Frequency Signal Injection at Low Speed

Back-emf is usually used to estimate motor speed in the permanent magnet synchronous motor(PMSM) sensorless control methods,but the back-emf is too small to estimate motor speed at low speed and sensorless control can not be realized at low speed.The method of injecting low frequency current signal is used to estimate speed at low speed.In this method,the response of the injection current signal is uses to get estimated speed and the control of PMSM speed estimation at low speed can be realized.Experimental results show the feasibility and validity of this method,the method is insensitive to motor parameter and has wide applicability.