Effect of BPF Dynamics on Stability of High-Frequency Signal-Injection Sensorless Control

초록

In high-frequency signal injection sensorless control (SISC), a band-pass filter (BPF) is commonly employed to extract the high-frequency current component carrying position information. However, its narrow bandwidth, which is necessary to attenuate the influence of the injected signal on the fundamental current control loop, introduces gain attenuation and phase delay to the baseband signal that contains the position error information, thereby potentially degrading the stability of the position estimation loop. This paper performs a stability analysis of the position estimation loop that incorporates the BPF dynamics, by modeling the effect of the BPF as an equivalent low-pass filter (ELPF). Based on this analysis, a closed-form expression for the minimum BPF bandwidth required to guarantee a desired gain margin is derived as a function of the observer design parameters, providing a systematic guideline for the BPF design. The proposed methodology is validated through both simulation and experiment. © 2026 IEEJ-IAS.

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