Weak magnetic control of PMSM servo system with high bandwidth current loop

The current sampling and pulse width modulation (PWM) duty cycle update methods currently in use in permanent magnet synchronous machine (PMSM) servo control systems introduce significant delays, thereby impacting the motor’s current loop bandwidth and dynamic characteristics to some extent. In addition, when the motor terminal voltage reaches the maximum output voltage of the driver, the motor operating speed cannot continue to increase. In response to these issues, a current loop bandwidth expansion method was proposed by improving the current sampling and PWM update time. This method reduces the delay between current sampling and the PWM duty cycle update by advancing the timing of the PWM duty cycle update, thereby expanding the closed-loop bandwidth of the current loop control system. Building upon a high-bandwidth current loop, a variable q-axis single current regulator weak field control method is employed to enhance the speed of the PMSM further, ensuring stable operation beyond the base speed. The simulation and experimental results demonstrate that the newly designed bandwidth expansion method exhibits a reduced internal delay in the current loop of the AC permanent magnet servo control system compared to the existing sampling methods. Additionally, it offers a broader bandwidth and faster dynamic response. Combined with the weak magnetic control method, the control system has good stability, accuracy, and speed when operating above the base speed.