Seeking Guidance on Transitioning FOC Model from Star to Delta Connection for an IPMSM plant model

I hope this message finds you well. I am currently working on a plant model of an IPMSM with a FOC algorithm implemented. My objective is to transition my plant model from a star configuration to a delta configuration.

Here's a brief overview of my situation:

1. I have utilized the Simscape Electrical Motor model for my simulation, a snapshot of which is attached. I have changed the motor model from Wye wound to Delta wound.
2. During simulation runs, I've encountered a discrepancy in the achieved torque values. While aiming for a torque of 60 Nm, I'm only attaining approximately 25 Nm.
3. I undertook an approach to address this by dividing my line current by the square root of 3 (√3) and give it as feedback to (FOC) 'Park transform' block to derive feedback currents, which increased my torque output to 49 Nm. However, this still falls short of my target torque of 60 Nm.

Given the complexity of transitioning from a star to a delta connection and the apparent lack of pertinent examples or content online, I am seeking guidance from the experienced members of this community. Could you kindly assist me in refining my approach to accurately transition my model and achieve the desired torque output? Any insights, suggestions, or references to relevant resources would be greatly appreciated.

Thank you for your time and expertise.

[Mohamad Nazir]

Have you tried to run the motor mechanically and check if the the back-emf amplitude corresponds to the datasheet? Basically you run the motor at any mechanical speed within its range and calculate the expected back-emf value using the back emf constant and check if the measured value corresponds to that calculation (you would have to eliminate the whole electrical part and just put an open-circuit with a voltage sensor at the motor electrical windings)

If this yields the expected result you will know that the plant is correct so you will only have to tune the controller to attain the reference torque

[Aditya]

Thank you for your reply! And I did! The B-EMF more or less matches the target value. I just realised that since it's a Delta motor, I had to multiply the line current by a value of 1/sqrt(3) before giving it back to the Park transform block to generate feedback Id, and Iq values. I also offset my measured 'theta' values by -30 radians. Doing both of this has helped me reach my torque tagret for most of the operating range of the motor.

I plan on using the 'FOC Autotuner' block to tune gains as suggested by you. Hopefullly I am able to meet my target values. Just curious, have you used the FOC Autotuner app? Do you have any material thet you could post here that would help me in tuning gains?

Thanks again for your recommendations!

[Mohamad Nazir]

Sorry I just noticed your reply. Glad you reached your target. I have never personally used the 'FOC Autotuner' block but Akshat's answer seems to cover it, you could try those examples and keep us up to date.

[Aditya]

Dear Mr. Nazir,

I have a very quick question for you if that's alright.

I have a torque control model with a delta wound motor. I am using the 'MTPA Reference' block and 'IPMSM Control Reference' block for reference Id and Iq generation. The Id and Iq reference values generated by the blocks are not on the MTPA curve except the first operating point!. The Ld, Lq and flux that I use in the blocks are from electromagnetics software designed for Delta motor. These blocks work perfectly for me when I use them for other star connected motor in torque control.

Any clue why this is the case? Thank you so much for your reply! (I have attached images of the blockset)

If I am not able to use the block, I am in the process of generating my own Id and Iq, I have completed for MTPA, I am having difficulty in computing the base speed and Flux weakening zone. Do you have any material that I could refer to that would help me??

[Raghunath Rachabattuni]

This question is discussed at the folloiwng link.

Challenges with Delta Wound Motor in Torque Control: Seeking Guidance on MTPA Reference Block for reference Id and Iq generat... - MATLAB Answers - MATLAB Central (mathworks.com)

Answer 1

[Akshat Dalal]

Hello Aditya,

I hope Nazir’s comment helped you in transitioning your IPMSM plant from star to delta configuration.

You can refer to the following documentation to learn more about the “Field Oriented Control Autotuner” block: https://in.mathworks.com/help/mcb/ref/fieldorientedcontrolautotuner.html

You can also refer the following examples to understand more:

1. https://in.mathworks.com/help/mcb/gs/tune-pi-controllers-using-foc-autotuner.html
2. https://in.mathworks.com/help/mcb/gs/tune-pi-contollers-using-foc-autotuner-real-time-systems.html

[Aditya]

Dear Mr. Dalal,

I have a very quick question for you if that's alright.

I have a torque control model with a delta wound motor. I am using the 'MTPA Reference' block and 'IPMSM Control Reference' block for reference Id and Iq generation. The Id and Iq reference values generated by the blocks are not on the MTPA curve except the first operating point!. The Ld, Lq and flux that I use in the blocks are from electromagnetics software designed for Delta motor. These blocks work perfectly for me when I use them for other star connected motor in torque control.

Any clue why this is the case? Thank you so much for your reply! (I have attached images of the blockset )

If I am not able to use the block, I am in the process of generating my own Id and Iq, I have completed for MTPA, I am having difficulty in computing the base speed and Flux weakening zone. Do you have any material that I could refer to that would help me??

[Raghunath Rachabattuni]

This question is discussed at the following link:

Challenges with Delta Wound Motor in Torque Control: Seeking Guidance on MTPA Reference Block for reference Id and Iq generat... - MATLAB Answers - MATLAB Central (mathworks.com)