Hello everyone. I have designed Indirect vector control for induction machine which is supposed to run at 10000RPM.I have designed all components based on equations.
Problem I am facing is that my controller doesn't follow ref. speed values and motor is running at its rated speed and torque. What could be wrong.
Your help will be much appreciated as It has been more than 8 months I am stuck in this problem.
Power systems in any country in the world can operate with either 50 or 60 Hz. knowing that, 2-pole induction motors can operate with maximum speed of 3000 rpm or 3600 respectively. Motors with poles more that 2 have maximum speed less than the above values. Speed is related to frequency as below:
Speed (rpm) =(60*f)/(P/2), f: frequency, P nbre of poles.
You want to make your motor runs at 10000 rpm, that is beyond that base or rated speed. It is possible as long as you feed your motor using a PWM inverter. I guess that your problem of control is due to the one of the follwoing reasons :
1. Beyond base speed, the motor operates in the constant power region, consequently, the flux must be weakened according to the value of speed:
flux *=(rated flux*rated speed)/actual speed,
2. Furthermore, at speed of 10000 rpm the operating frequency is important, thus iron or core loss component is important too. This alters the performance of vector controller. You have to use the modified FOC to get motor decoupled an controlling speed easily.
3. If you have got a problem of steady state speed error, try to tune correctly your PI controller, particularly the integral action.
Hopefully my answer is useful.
Thank you very much Aissa Kheldoun you answer helped a lot.
Also, all parameters of induction machine are from manufacturer and I am supplying with operating frequency of 334Hz. and my PI controllers are also based on machine parameters.
Now, my controller is following my ref. values but speed is slowly dropping down and when I put some load torque then speed drastically decreases and comes to zero?
Would you please answer this, I hope if these are cleared then I would get through.
Thanks
Abid
Hello Memet Rida Tur, thanks for offering a help.
It would be much appreciated if you please answer my above question.
Dear Abid Soomro,
I suppose this motor is designed for EV applications. Plz find attached a paper that presents a more accurate vector controller and suitable for high speed induction motors. These motors are characterized by their very low magnetizing inductance. Furthermore, you can make you control more robust by employing fuzzy logic based PI controller instead of conventional one.
Good luck
Dear Aissa Kheldon,
Thanks for your answer I am modelling for flywheel energy storage system.Do you think that speed droping problem is due to PI controllers? shall I tune gains of my PI?
Thanks
Dear Abido;
Yes I think so, PI parameters can affect the speed regulation but it is one of many reasons. Can you tell me how the speed drops .
Does it drop without load too? or only when you apply the laod on your motor?. Are, you sure that your motor can handle the load in your application?
With regards
Hi Aissa Kheldon, thanks for your response. Your answers are leading me to corrections in my model.
No, at no load motor operates at command value of speed (up-to 14000 RPM) but when I apply some load torque (from 0 to 100 N.m) then motor doesn't behave well and up to 3 minutes and after few seconds it goes up to commanded speed value.
I don't understand dynamics of this behavior.
Also, when I increase inertia of the motor (which is same like to add flywheel of same inertia on shaft, inertia in my case is 9.8) then speed drastically drops to few hundred RPMs.
Regards,
Abid
Dear Abido,
I think there's a problem of load matching. To this and in order to check this whether your problem is due to load, I need you to send me the ratings of your motor.
regards
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