instantaneous power control of SCIM by FOC method

Hello. I am simulating the control of a squirrel-cage induction motor with FOC (Field-Oriented Control). When the speed range exceeds a certain threshold, the controller becomes unresponsive and diverges. Please advise🙏

[Epsilon]

Can you share the model please? Without it, it would just be a guess!

[Milad]

Simulink file shared for review.

Answer 1

[Shivam Gothi]

Hello @Milad,

Hello @Milad,

As per my understanding, you are facing an issue with the speed control of Induction Motor when the reference speed exceeds the certain value.

As far as the controllers are concerned, they are designed appropriately and found to be functioning well. The only thing you missed out is putting the saturation limits on the output of “integrator” in the PI controllers “PI(z)” used in your model inside the “Machine Side Converter -> IFOC” subsystem block.

I have fixed this issue and the model is found to be working. Below given is the possible workaround:

• Open the “Block Parameters” of the all the PID controllers i.e “PID controller 4”, “PID controller 1”, “PID controller 2”, “Iq*” and “Id*”, found inside the subsystem block: “Machine Side Converter -> IFOC”.
• Navigate to the “Saturation” tab and click the “Limit Output” check-box found under “Integrator Saturation” property.
• Set the saturation limits for each of the blocks.
• Consider the below figure as an example to set the saturation limits for block “PID controller 1”:

• The saturation limits for other blocks should be set as:

1. “PID controller 2”: “lower limit” = -500; “Upper limit” = 500
2. “PID controller 1”: “lower limit” = -500; “Upper limit” = 500
3. PID controller : “Id*”: “lower limit” = -30; “Upper limit” = 30
4. PID controller : “Iq*”: “lower limit” = -500; “Upper limit” = 500
5. “PID controller 4”: “lower limit” = -200; “Upper limit” = 200

After making the changes, I simulated the model. Below attached is the waveform captured on the scope:

You can notice that we cannot track the reference speed of 105. This is the limitation from the DC link voltage. It shows that the maximum possible line-line voltage is applied on the motor, and we are no longer to be able to increase the “Iq” by further increasing Vq. (Note: Iq is torque producing component of current). You can increase the DC link voltage in the simulation to address this. I have increased the DC link voltage to 800v and got the following output:

I have also attached the modified Simulink model along with this answer.

I hope this helps!

[Milad]

Thanks, your guidance was very helpful. I changed the controller’s saturation limits again to increase the controlled speed range, but I couldn’t control it up to the nominal speed. What do you suggest I do?