Forced angle mode current

Yichao Zhang

Other Parts Discussed in Thread: DRV8301, MOTORWARE

Hi,

We are using drv8301 and motorware as a current source to do some test. The goal is to supply various frequency 3ph current. I notice that I can set the USER_ZEROSPEEDLIMIT at my desired frequency. I also need to set motor max current in user motor parameter to my desired current magnitude. So the code is always in the forced angle state.

It works at high frequency like >15Hz. I noticed at low frequency <10Hz. The current magnitude is a lot lower than the max current. Since I cannot see the forced angle code， I am not sure what happened. Is there anything I can do to increase the forced angle current at low frequency?

Yichao

over 8 years ago

0 ChrisClearman over 8 years ago

TI__Guru** 118350 points

since you aren't really trying to control a motor - don't need FOC - why not just create (or change the MotorWare code) to do open loop?
I posted on here some time ago about how to change the CTRL to allow you to set a fixed frequency. Let me see if I can find it.

0 ChrisClearman over 8 years ago in reply to ChrisClearman

TI__Guru** 118350 points

here you go
e2e.ti.com/.../1458092

0 Yichao Zhang over 8 years ago in reply to ChrisClearman

Intellectual 495 points

Thank you, Chris. I cannot do voltage open loop. I need current loop.

0 ChrisClearman over 8 years ago in reply to Yichao Zhang

TI__Guru** 118350 points

what are you controlling the current of? is there even a motor attached to the inverter?

when ForceAngle is active, while you are doing forward Iq/Id control, the modulation is controlled by the estimated rotor flux angle. with forceangle this isn't a real estimation, it is completely fixed/forced. So you aren't really controlling the current as you suspect.

0 Yichao Zhang over 8 years ago in reply to ChrisClearman

Intellectual 495 points

We connect three battery at the terminal. So we want to inject different frequency ac current to battery... My understanding is that the forced angle generate a fixed speed . So the current vector follow this angle. It works! my problem is that when the frequency is lower than 10Hz. The current magnitude cannot be controlled to my setting value.

0 ChrisClearman over 8 years ago in reply to Yichao Zhang

TI__Guru** 118350 points

the current magnitude shouldn't really be able to be controlled at higher frequencies either.
you're setting an Iq_Ref? or just a speedRef equivalent to the frequency you want?

I don't really understand trying to use InstaSPIN for this purpose. I am hoping it was just a quick way to try to get this functionality

0 Yichao Zhang over 8 years ago in reply to ChrisClearman

Intellectual 495 points

It is a quick way to do my test. If I have more time, I would write a current reference and current regulator.

I try to take advantage of the forced angle when starting a motor. So I set USER_ZEROSPEEDLIMIT to my desired frequency.

0 ChrisClearman over 8 years ago in reply to Yichao Zhang

TI__Guru** 118350 points

the frequency is actually set by
#define USER_FORCE_ANGLE_FREQ_Hz (2.0 * USER_ZEROSPEEDLIMIT * USER_IQ_FULL_SCALE_FREQ_Hz)

USER_ZEROSPEEDLIMIT sets the frequency where the ForceAngle stops being used and FAST is used.

For YOUR case, and never for actual InstaSPIN operation, I would try setting something like
#define USER_FORCE_ANGLE_FREQ_Hz (DESIRED_FREQ_Hz)

#define USER_ZEROSPEEDLIMIT (500.0 / USER_IQ_FULL_SCALE_FREQ_Hz) // this will keep the ForceAngle active til 500 Hz; set it as high as you require

0 Yichao Zhang over 8 years ago in reply to ChrisClearman

Intellectual 495 points

Thank you, Chris. I did similar to yours.

I just don't know why the current magnitude is a lot lower than my setting at low frequency. Could it be possible that at low frequency it somehow use lower current magnitude reference for forced angle?

0 ChrisClearman over 8 years ago in reply to Yichao Zhang

TI__Guru** 118350 points

how are you setting the current magnitude?

0 Yichao Zhang over 8 years ago in reply to ChrisClearman

Intellectual 495 points

I use USER_MOTOR_MAX_CURRENT to set the current magnitude

0 ChrisClearman over 8 years ago in reply to Yichao Zhang

TI__Guru** 118350 points

USER_MOTOR_MAX_CURRENT only sets the maximum limit on the output of the speed controller.

0 Yichao Zhang over 8 years ago in reply to ChrisClearman

Intellectual 495 points

So, which parameter determines the current magnitude during the forced angle mode? Especially at low frequency. Does machine parameter also determine the current magnitdue?

0 ChrisClearman over 8 years ago in reply to Yichao Zhang

TI__Guru** 118350 points

the target current magnitude will be given by the IqRef_A, which is the output of the Speed controller.
but the orientation of the stator field - which governs the ability to maximize torque - still depends on the angle.

C2000™︎ microcontrollers

C2000 microcontrollers forum

Forced angle mode current