Hi all ,
System and Motor Parameters:
Bus Voltage: 24V
Rated Current: 40A
PWM Frequency: 40kHz
Phase Resistance (Rs): 0.1Ω
Phase Inductance (Ls): 0.03mH
BEMF Constant (Ke): 1.1 Vrms/kRPM
Max Application Speed: 12000 RPM
Estimator & PLL Parameters:
Speed Estimator:
G1 (C1): 552
G2 (C2): 592
PLL Kp: 500
PLL Ki: 100
I am currently using sensorless FOC control. When the motor reaches around 6000 RPM, I observe that the motor noise becomes noticeably sharp, and current feedback (monitored via oscilloscope) shows increasing oscillation. Eventually, it triggers an over-voltage (OV) protection error.
Based on my understanding, I suspect the angle estimation error increases with speed, causing misalignment between the control and actual rotor position. This might lead to excessive back-EMF, resulting in bus voltage overshoot and an OV fault.
I’ve tried adjusting G1/G2 and PLL Kp/Ki via Motor Pilot, but the issue persists.
Additional Question:
When I reduce Max Application Speed from 12000 RPM to 7000 RPM, the error changes from OV to a speed feedback error.
Does the Max Application Speed parameter affect any internal estimator limits or protection logic, besides just defining the operational speed range?
Besides tuning G1/G2 and PLL Kp/Ki, could this issue be due to insufficient estimator bandwidth or controller update rate, especially at high speeds? Or Could back-EMF approaching the bus voltage or estimation lag directly cause instability and trigger OV?
If anyone has any ideas or suggestions, please feel free to share. Thank you!
