TMS320F28388D: CCS/TMS320F28388D Build3 Torque Control Example, Current Sine Wave is distorted

Build level 3 is torque loop and you cannot perform this test without any load on the motor. IF you tried to increase the current reference, then it will attempt to raise it but then without load, it will reach full speed and the inner loop will saturate. 

Thank you Ramesh.

I already use TMS320F28069 with Motor Drive, it is no problem. good.

but it's old and low performance device, so we move to F28388D Drive.

(Both board inverter circuits are the same (DRV8323RS)

As your advice, I Re-test with Motor Dynamo Test Device

The Below Picture is that,

Figure 1.

- Test Environment

Figure 2. 

- Test Motor is torque  control based on F28388D Drive and Opposite  Motor(Dynamo Motor) is Speed Control

-  Test Motor's torque is 0 Amp and Dynamo Motor is running 1,900 RPM, the operation OK.

Figure 3.

- Test Motor's Torque is 1.1A and Dynamo Motor is running 1,900 RPM, The operation is abnormal.

  that is, Top FET Gate Signal is missed on 2 cycle, when 3 Phase Current Signal is bounced abnormally

  I guess that the bemf will affect. 

( I test same environment, only change motor drive based on TMS320F20869 DSP, it's operation is ok)

Figure 4. 

- Test Motor's Torque is 37 A (Motor Max Current), and Dynamo Motor is running 950 RPM, the operation is ok

but over the 950 RPM, the abnormal state is occurred.

Figure 5.

- The motor's Spec

In the low speed rpm, the Motor is normally operation, but in the high speed rpm test is not normal.

is it related with bemf?

Please give me your advice

Thanks you

< Figure 1. Motor Test Environment with Motor Dynamo Device>

Dynamo Motor is panasonic servo Motor

<Figure 2. Injection Torque 0 A, with Dynamo Motor running RPM 1900>

Oscilloscope channel Description

- Ch1 : U-Phase Top FET GATE Signal

- CH2 : U-Phase Current (scale = 0.1V/A)

- CH3 : V-Phase Current (scale = 0.1V/A)

- CH4 : W-Phase Current (scale = 0.1V/A)

<Figure 3. Injection Torque 1.1A, with Dynamo Motor running RPM 1900>

<Figure  4. Injection Torque 37A, with Dynamo Motor running RPM 950>

< Figure 5. Test Motor Spec >

Check if over current protection is kicking in to mess up the pulse.

Secondly, with FCL, there is a limit on max duty cycle that you can use. It basically limits the max speed of operation. If you increase the DC bus voltage, and you are able to run to the same high speed without any problem, it means that you are running into dutycycle limit of FCL. You may have to add some additional code to address this issue. Find out the value of D and Q voltage inputs to PWM generator at the time of this event.

Hi, Ramesh

Thank you for reply

As your advice. i test.

first. over current protection is not kicking, when the issue is occurred.

second. i change the DC bus Voltage 48V -> 55V(as soon as possible), then the issue is occurred from 2100 rpm to 2350 rpm on torque 0 Amp.

above picture is tested on torque 1.1A and 1900 rpm

if torque 0A, then the issue is occurred on 2100rpm .

so i test torque 0A, DC bus voltage 48V, 55V

48 V : 2100rpm  <- the issue is occurred.

55 V : 2350rpm <- occurred.

depends on DC bus voltage, the rpm is moved from 2100 to 2350 rpm.

and i test anther environment.

all of the above test is done on PWM Freq 10KHz.

PWM Frequency Change

PWM : 10KHz -> 5KHz  (ISR Freq also 5KHz)

DC Voltage : 48V

Torque : 0 A

the issue is not occurred on 2800 rpm (Max Motor RPM)

would tell me what is the duty cycle limit of FCL, which you said above.

is it means that the PWM duty cycle or another?

and if i can modify the duty cycle limit of FCL?

at last. " some additional code"  is where part. ? 

thanks

A certain amount of computation time is needed to calculate the new values of duty cycle of A, B and C, and this time is lost for new PWM cycle, and hence reduced max duty cycle. When you go lower in PWM frequency, you get a higher dutycycle as the percentage of lost time is smaller in a lower frequency PWM. Conversely, if you increase the pwm frequency, you lose more dutycycle.

Additional code - you may try to play around with the max values of Vd or Vq - both controller outputs and net compensated max Vd, Vq. See if this helps. To do this, just watch the value of these parameters in the debug window. Whichever is hitting the limit first, try to increase the limit of this one. Just make sure that the vector sum of Vd and Vq is not more than a limit (say 95% or lower). 

in the above.

Is the limit, which you said, means the sum of max Vd and Vq value ?

if then, how do i decide and increase the limit value ?

thanks.

I attached the figure 8-1, which is in the Quick Response Control of PMSM Using Fast Current Loop.pdf

I can't the Vd and Vq Variable in the source code of the fcl_cpu_code.c.

but the pi_id.out, pi_iq.out is there

what variable should I check?

Thanks Ramesh.

pi_id.Max/Min and pi_iq.Max/Min

Hi Ramesh.

i test the pi_id.Max/Min and pi_iq.Max/Min with change the limit value up/down

but the issue is not resolved.

so i tried to another test

that is change the TBPRD, which is one of the EPWM Regs.

when the issue is occured with motor rpm 2100, TBPRD Value is 0x1388( 5000 decmal), 

the follow figure is the TBPRD 0x1388 Scope screen, Tpwm : 99.52us 

#define PWM_FREQUENCY           10   // in KHz

and change the TBPRD Value 0x1500(5376 decimal)

the follow figure is the TBPRD 0x1500 Scorp screen, Tpwm : 107.5us

#define PWM_FREQUENCY           10   // in KHz ( the define value is same above)

in this case FCL Torque mode is operation normaly, when MOTOR RPM 2400.

is it correct?

finally. i find the follow figure 

i wonder that FCL Library is include the Feed-forward Decoupling function?

tthanks.

I think the voltage limits are being reached. When you increase the time period, you get a little more time before maxing out on modulation index and due to this incremental jump in modulation index, you are able to get higher speed. If you reduce the frequency further, you may get further higher speed. Well, see what is the max speed you can get without FCL. That can give some clue as to where things are missing.

Btw, the library takes care of decoupling voltages as well.

Thanks Ramesh.

I  need to more test about the Max speed without FCL.

The without FCL Test means Example Build 1 or 2 ?

and would you tell me where the decoupling algorithm source in the library.

comment out FCL_initPWM() in main() and repeat the tests to find out max speed.

Pls step through the code to understand the details. You may need to spend some time to understand the code organization and logistics. That will help you answer many queries on your own.