Fast initial position estimation for IPMSMs at standstill using comb filters

This paper proposes the fast initial position estimation of IPMSMs (Interior Permanent Magnet Synchronous Motors), based on intentional pulse voltage injection and comb filters. Generally, the rotor position can be estimated by detecting high-frequency current caused by injected high-frequency voltage because its response includes inductance information due to saliency. In general, sinusoidal current, sinusoidal voltage and pulse voltage are utilized for saliency excitation. Methods based on sinusoidal current and voltage, however, require a shorter control period for precise signal injection, making methods based on pulse voltage injection more desirable. Methods based on pulse voltage injection generally utilize the amplitude or differential value of high-frequency current. The algorithms used to calculate the current´s amplitude or differential value, however, are complex and unsuitable for improving the response of position estimation. Especially, algorithms for calculating amplitude values require low-pass filters (LPFs), with the low cut-off frequency utilized for the amplitude calculation. This process degrades the response of the initial position estimation. In order to overcome this problem, this paper proposes a new algorithm using comb filters which can rapidly calculate the amplitude value of high-frequency current and improve the initial position estimation performance.