Investigation of signal processing for high frequency signal injection based rotor position estimation with 20 kHz square wave voltage

With an inverter consisting of Gallium Nitride semiconductors, the opportunity is offered to increase the frequency of the high-frequency (HF) voltage used for the rotor position estimation of permanent magnet synchronous motors. The increase of the HF voltage frequency can not only improve the dynamic performance of the sensorless control, but also eliminate the audible noise, if the frequency is increased above 20 kHz. However, the increase of the HF voltage frequency requires an improvement of the signal processing for the rotor position estimation. On one side, the effect of the hardware delay and software delay must be taken into consideration and eliminated to ensure the performance of the position estimation algorithm. On the other hand, if the amplitude of the HF voltage is kept constant, the amplitude of the HF current response decreases, which results in the reduction of signal-noise ratio (SNR) and makes the signal processing more difficult. In this paper, the rotor position estimation for an interior permanent magnet synchronous motor (IPMSM) is carried out with a 20 kHz HF voltage. Compared to the existing result with HF voltage of lower frequency, the signal processing is further improved so that the position can be estimated well even with a small amplitude of the HF voltage.