Impact of SNR on Sensorless Control of PMSMs with PHF Signal Injection

Pulsating High Frequency (PHF) signal injection is a popular sensorless technique used to estimate the rotor position at starting and low speeds of Permanent Magnet Synchronous Motors (PMSMs). However, with the absence of a specific criteria for selecting the frequency and amplitude of the injected High Frequency (HF) signal, implementation of PHF is still a challenge for any given application. Therefore, this paper investigates the impact of Signal to Noise Ratio (SNR) on the error between the estimated and actual rotor position when using the PHF signal injection technique. As SNR depends on the frequency and amplitude of the injected HF signal, an analysis is carried out by varying the injected frequency and the amplitude to determine the minimum SNR to achieve minimum rotor position error is determined. The results of an S-pole, 1 kW PMSM are presented to demonstrate the relationship between the SNR and the rotor position error for different injected HF signals.