A General Position Sensorless Algorithm for <i>LCL</i> -Equipped High-Speed PMSMs

The installation of LCL filter in high-speed motor drives serves to eliminate the excessive <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{dv/dt}$</tex-math></inline-formula> voltage and the motor current harmonics. However, introducing the filter transforms the drive system into a higher-order system, dramatically increasing the complexity of the position sensorless control. This article proposes a general position sensorless algorithm where the feedback state can be either the inverter current or the motor current. Crucially, the effect of the LCL filter on the position estimation is modelled as an equivalent inductance, thereby allowing simpler first-order model-based electromotive force observers to be directly applied. This algorithm simplifies the digital implementation compared with the complicated full-state observers and avoids additional measurement for other system states. Furthermore, a novel equivalent inductance identification algorithm is introduced to provide effective compensation for the position estimation error, addressing a critical gap in the existing literature. Finally, the experimental results demonstrate the superiority of the proposed method.