Initial rotor position estimation for sensorless interior PMSM with signal injection

An improved initial rotor position estimation method based on signal injection for position sensorless interior permanent magnet synchronous motor (PMSM) at standstill is presented. In first step, high-frequency rotating voltage signal is injected into stator wingding to obtain magnetic pole position. A PI tracing observer is used to regulate the error signal containing magnetic pole position information. When the error signal is regulated to zero, magnetic pole position can be estimated. In second step, in order to identify magnet polarity more easily, two pulse voltage vectors are injected based on the obtained position information in first step. By comparing d-axis stator current values, magnet polarity can be identified. Then the position estimated in the first step can be compensated according to the magnet polarity information. The validity of the proposed estimation scheme is verified by a 22 kW interior PMSM. Experimental results show that the method can achieve acceptable estimation accuracy.