Position Sensorless Control of PMSM Based on Frequency Decoupled Complex Coefficient Filter with Frequency Locked Loop

Frequency adaptive filters (FAF) are commonly utilized in phase-locked loop (PLL) to reduce harmonics in the estimated rotor position of sensorless control for permanent magnet synchronous motors (PMSM). Nonetheless, the frequency coupling caused by this type of filter is always disregarded. This paper accurately analyzes the PLL with a FAF and develops a small-signal model that encompasses the frequency coupling loop. The small-signal model demonstrates that the FAF can be equivalent to a low-pass filter because of the presence of the frequency coupling loop, which degrades the dynamic performance and reduces the stability of PLL. To address this issue, a frequency-locked loop (FLL) is introduced to eliminate the frequency coupling between the FAF and the PLL, thereby enhancing the stability and dynamic performance of the position sensorless control system.