Initial rotor position estimation for interior permanent magnet synchronous motor

In order to resolve the starting problem for position sensorless interior permanent magnet synchronous motor (IPMSM), an improved initial rotor position estimation based on hybrid signal injection is proposed. Firstly, high-frequency rotating voltage signal is injected into stator wingding to obtain magnet pole position. A PI tracing observer is designed to adjust the constructed error signal containing rotor position information. When the error signal is adjusted to zero, magnet pole position can be obtained. It reduces the algorithm complexity. To identify the magnet polarity more simply and effectively, two voltage pulse vectors are injected into stator winding according to the obtained position information in the first step. By comparing d-axis stator currents, the magnet polarity can be identified easily. Then the position estimated in the first step can be compensated according to the magnet polarity information. The proposed estimation method was experimented at a 22 kW IPMSM. The experimental results show that the average of estimation error is 4.6 electrical degrees.