FOC PMSM with Hall Sensor Queries

Dear Community,

I am refering https://in.mathworks.com/help/mcb/gs/foc-pmsm-using-hall-sensor-example.html for my motor control application using FOC FOR IPMSM. I am stuck with below queries.

1. PI Controller: How to decide saturation upper(1) and lower(-1) limits values?
2. How to decide D-Q Limiter block saturation limit value?
3. PWM Duty cycle not changing after changing referance speed.
4. Wrap on overflow error. "Current Control/Input Scaling/Read_Sensor (sim)/Subsystem/Speed Measurement/PositionToCount'
5. Torque-speed characteristics: For my application V=60V, I=48A,Torque=20Nm. After updating motor parameters, I am not getting expected values on graph.(Attached snapshot for ref.)
6. mcb_getCharacteristics: Are values shown in graph are in PU_System units or SI units. Please clarify.

Thanks in Advance.

.

Answer 1

[Shivaprasad Narayan]

1. The upper and lower saturation for the PI controller is decided based on the units used in succeeding control logic and safe operating conditions for the motor.
2. Speed PI controller limits must be configured such that the resulting currents are less than the rated motor current. If the control is modelled in SI units, the limits would be '+/- rated motor current'. If it is Per-unit, the limits would be '+/- rated motor current / Per Unit base current'.
3. If the control algorithm is going to be deployed on to an embedded target, the final output of the current controller would be PWM duty cycles. Hence, the current PI controller limits can be set to +/- 1. In all the above cases the PI controller gains must be computed based on the range of output expected from the PI controller.
4. For an ideal system, the DQ limiter saturation can be 100%. Since the model is to be deployed on to an embedded target, 0% and 100% duty cycles are not feasible due to hardware limitations such as PWM dead time. The DQ limiter saturation must be set considering these hardware limitations. Most of the example models in motor control blockset are configured to 95% by default.
5. The PWM duty cycles do not change when the PI controllers are saturated or feedback values ( position and/or current) are not correct.
6. The speed measurement block uses the wrap on overflow as a design choice to keep the output in the range. This warning can be ignored.
7. The characteristics plot are in SI unit. The plot depends entirely on the motor and inverter parameters. Make sure these are updated correctly.