Online current cut-off frequency self-tuning active damping speed controller for permanent magnet synchronous motors

This study suggests a dynamic current cut-off frequency-based pole-zero cancellation speed controller for permanent magnet synchronous motors (PMSMs). The proposed self-tuning algorithm automatically increases the current cut-off frequency during only the transient periods and restores it as approaching the steady-state operation. The outer loop control injects the active damping effect, resulting in a closed-loop order reduction by pole-zero cancellation from the particularly structured feedback gain. These two benefits contribute to the following advantages: (a) lowering the steady-state current cut-off frequency to improve the relative stability margin and (b) securing the capability of assigning the desired cut-off frequency to both the inner and outer loops in the first-order low-pass filter form. A 500-W PMSM experimental prototype platform confirms the effectiveness of the proposed controller.