Spatial Inductance Estimation for Current Loop Auto-Tuning in IPMSM Self-Commissioning

This paper presents a comprehensive study on current loop auto-tuning for self-commissioning of sensorless interior permanent magnet synchronous machine (IPMSM) drives. Well-tuned current controllers are essential for both high-performance operation and self-commissioning procedure. However, current controller design parameters, i.e., <inline-formula><tex-math notation="LaTeX">$L_{d}$</tex-math></inline-formula> and <inline-formula><tex-math notation="LaTeX">$L_{q}$</tex-math></inline-formula>, are not known at the beginning of the self-commissioning procedure where their estimation also has unique challenges. For example, an initial rotor position to determine the actual <italic>d</italic>- and <italic>q</italic>-axes is not known. Also, feedback controllers cannot be used in the estimation because they are not tuned yet. As a solution, this paper proposes a method to estimate the spatial inductance map by spatially scanning the motor via sinusoidal voltage injection in a controlled manner. Then it uses the estimated inductance values to tune the current controllers. The proposed method identifies <inline-formula><tex-math notation="LaTeX">$L_{d}$</tex-math></inline-formula> and <inline-formula><tex-math notation="LaTeX">$L_{q}$</tex-math></inline-formula> values using open-loop voltage injection without needing actual <italic>d</italic>- and <italic>q</italic>-axis positions. The whole procedure takes around a second. Practical considerations such as an automatic selection of the injection voltage, and digital control and dead-time effects are carefully addressed. The findings are experimentally verified on a 3-phase IPMSM drive. Furthermore, its applicability to different motor types is also demonstrated.