TMS320F28379S: Current sampling in FOC with overmodulation with low-side current senses

Adam

Part Number: TMS320F28379S
Other Parts Discussed in Thread: C2000WARE

Hello,

In PMSM FOC control application I would like to use overmodulation.

Because of that there will be period when Low-Side Mosfet is not switching (High-Side Mosfet Turned on for several PWM Periods).

I have for that 3 low side current senses hovever now can not solve the problem how to figure out in the algorythm which two of them are showing correct current value and take only them into account for further calculation.

So in each moment of time i need to somehow decide which two od 3 ADC current sensed values take into account and how to do that. Any ideas?

I dont want to use in-line sensing, so is there any method to do it with low-side senses?

Regards,

Adam

7 months ago

0 Yanming Luo 7 months ago

TI__Guru** 110630 points

You have to implement the current re-construction method when using overmodulation. You may take a look at chapter "is08_overmodulation – Space Vector Over-Modulation" in InstaSPIN lab user's guide. If you want to get a better performance, you may have to use the inline current sensing mode.

The InstaSPIN lab user's guide can be found in the folder of motor control SDK as below if you installed the software.

\ti\c2000\C2000Ware_MotorControl_SDK_<version>\solutions\common\sensorless_foc\docs\labs

The Motor Control SDK software can be download as the link below.

C2000WARE-MOTORCONTROL-SDK: http://www.ti.com/tool/C2000WARE-MOTORCONTROL-SDK

0 Adam 7 months ago in reply to Yanming Luo

Expert 1110 points

Thank you

0 Adam 7 months ago in reply to Adam

Expert 1110 points

When using overmodulation to about m=1.3 so that near 6-step commutation can I use still SVM method or some other one will be better?

0 Adam 7 months ago in reply to Adam

Expert 1110 points

Also, the "is08_overmodulation – Space Vector Over-Modulation" chapter says m index=1/sqrt(3) is max undistorted sinus voltage, and m=2/3 is 6-step trapezoidal commutation.

While theory says 2/sqrt(3) (famous 1.15 Vdc) is the max SVM modulation index for non distorted sinus. (like here:https://www.pscad.com/webhelp/Master_Library_Models/HVDC_and_FACTS/Space_Vector_Modulation/SVM_Theory.htm)

Can you tell why in TI code the modulation index is 1/sqrt(3) not 2/sqrt(3)?

+1 Yanming Luo 7 months ago in reply to Adam

TI__Guru** 110630 points

Actually, both are the same concept that is related to the PWM duty calculation method using -0.5~0.5 or -1.0~1.0

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TMS320F28379S: Current sampling in FOC with overmodulation with low-side current senses