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Rotor Flux Angle Estimation for Vector Control of ACIM

Harsh Suresh
Prodigy 20 points

Good day to all,

Hope I am reaching you in good regards.

I have been working on implementation of Indirect Vector Control of 3-Phase Induction Motor as part of my M.Tech project work. Currently I am facing difficulty in estimating the rotor flux angle which serves as the vital part of the control, as you all are aware of it.

The estimation of motor parameters were done and I believe they are more or less accurate as I have done a comparison with a similar motor data sheet that was available online (from Marathon Electric). 

Currently I am having few queries as follows, 

1. How can the rotor flux angle be estimated from the start up of the motor? 

2. Currently I am starting the motor via autotransformer start and pulses given directly through SVM at 0.8 modulation index. When motor speed reaches 10 rpm switching over to the Vector control algorithm takes place and rotor flux theta calculation begins.For estimating Rotor flux angle , θe= integral(ωr+ωsl)dt,

where, θe=Rotor Flux angle, ωr=Motor speed, ωsl=Slip speed, dt=time of one switching cycle

Considering, ωsl=(Rr/Lr)*(Iq_Ref/Id_Ref)

where, Iq_Ref is obtained as PI Controller output limited to maximum value of Iq of the machine I use and Id_Ref as the reference value obtained via calculation (as mentioned by Dave Sir in reply to a post I found in the forum).

Will this method of approach yield good results?  I strongly believe that the theta i obtain right now is not in sync with actual rotor flux angle because the feedback currents once converted to dq frame with this theta seems wrong (Iq is appearing as negative quantity throughout which i believe should be a +ve quantity) .

I have gone through various posts in the forums and blog through which i understood about the InstaSpin. But Unfortunately I am provided with a different manufacturers ARM CORTEX M-4 32-bit controller and I am expected to develop this drive from the scratch through pure understanding and coding. I have been through many textbooks, scholarly articles and application notes but these queries still remain unanswered.

I will be very thankful if you can spare your valuable time in replying to my query. 

Thanks in advance,

Harsh S Suresh