Improved Fast Method of Initial Rotor Position Estimation for Interior Permanent Magnet Synchronous Motor by Symmetric Pulse Voltage Injection

The precise information of initial rotor position is very important to high performance Interior Permanent Magnet Synchronous Machine (IPMSM) adopting incremental encoder, which can normally be obtained by the high-frequency (HF) rotating or pulsating voltage injection methods. However, the demodulation procedure may confront with the challenge of constrained stability and limited accuracy. For improving estimation accuracy, an improved impulse injection method with merits of simple and fast is proposed. It is carried out by generating a series of phase-axial injections to calculate the probable rotor position, then injecting two reciprocal voltage pulses to obtain the rotor polarity, and finally injecting iterative voltage vectors to obtain the real position rapidly. During the estimation process, the filters to extract the high frequency current signals are not needed. The method effectiveness is validated by the measured results of IPMSM test platform. In the same time, its application limitation is deduced by comparison with the measured results between IPMSM and surface-mounted PMSM (SPMSM). It is shown that the estimation algorithm is compatible with motor parameter differences and can reduce the influence of inductance saturation and nonlinear voltage error. Therefore, the proposed method not only improves the accuracy and robustness of the PMSM sensorless startup control, but also ensures the fast response.