Setting of PFC

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AG_Serad
Level 4
Level 4
First solution authored 25 replies posted 25 sign-ins

Hello,

 

I don't know if there is a link with the phenomen I described here:

https://community.infineon.com/t5/iMOTION-controller-driver-IPM/IMC102T-Shunt-PFC-resistor-explosed/...

But sometime, the PFC voltage not regulate to the TargetVoltage (400V) and overPass the OverVoltage critical threshold to 440V.

I don't explain why.

- Have you some literature indicate how set the PFC parameters (Kp/Ki current/Voltage Loop)?

- What could happen, becaus anytime the PFC votlage is Ok, reaction is ok, but sometime, (1 time after, one or two day of running) the OverVoltage error occurs. Are they other parameter than Kp/Ki which could explain this critical fault?

Regards

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1 Solution

Hello,

Now the situation is stabilized.

When tuning other motor, I seen the Vdc crasy increase can be caused when motor R parameter is bad tune. (To high)

Maybe this can be the rootcause? (because Vdc increase whenever PFC is running...)

Vac filter capacity was changed from 4.7nF to 47nF to avoid PFC AC frequency fault. Now, the system not trig error on EMI discharge up to 5Kv.

 

View solution in original post

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psb
Moderator
Moderator
Moderator
250 sign-ins 25 solutions authored 100 replies posted

Hello @AG_Serad ,

   Is this issue occurring at some particular conditions only ?  Going through the mce wizard files shared, it doesn't look like it randomly occurs.  

Best Regards,
Sai
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AG_Serad
Level 4
Level 4
First solution authored 25 replies posted 25 sign-ins

Hello,

I observed this on POwer ON (when I start the PFC on startup).

But I also seen the problem in runing. So I try to reproduce it with the MCEDesigner Trace to see when this occurs. 

But at this time, problem not occurs again with the trace activated. I continue to catch it.

You said "it doesn't look like it randomly occurs.  " What is your thought?

 

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psb
Moderator
Moderator
Moderator
250 sign-ins 25 solutions authored 100 replies posted

But sometime, the PFC voltage not regulate to the TargetVoltage (400V) and overPass the OverVoltage critical threshold to 440V.

This might happen due to either incorrect tuning of Kp, Ki, feedforward values or any other parasitic noise in the system or if inverter is turned off suddenly for sometime or if the response of the system is very slow.

Request you to monitor and then capture at around the OV condition and send us the following waveforms so that we can get to the root cause. 
output voltage
gate pulses of the PFC switch
inductor current
VCE of the PFC switch

If this is occurring always at startup, I recommend to slowly increase the input voltage to the PFC and check. If this problem doesn't occur then it is due to the incorrect tuning of the control loop. 

Best Regards,
Sai
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AG_Serad
Level 4
Level 4
First solution authored 25 replies posted 25 sign-ins

Hello

Thank for your back.

I try to slowly increase the input voltage when PFC was started, without reproduce the problem.

But, I find a way to reproduce the PFC over voltage. I don't know if the root cause is the same than my original problem!...

Please find the attached documentation. The way is to start the PFC, then decrease the Vac input voltage (50V). PFC stay On and output voltage stay to 400V (No current need)

I start the motor, then current need increase. PFC current increase to compensate the lack of voltage. Then OCP (Cycle-By-Cycle) is running. This lead to Vdc increase.

Maybe in this particular case (Vac very low), this is normal? Or maybe  this step to reproduce can help us to set the PFC?

Because on my original problem, the PFC OVP occurs on PowerOn the board, when the script started immediatly the PFC, also in running when motor move (The PFC was Off/On according motor or generation phase in which we link a discharche resistor to control the DCBus increase)

Note: I try with PFC_AcDcScale set to 1454 (80%) and also with 300 (16%) with the same issue.

 

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Hello,

Have you a target date where you think have a feedback?

In waiting this, COuld you say me where find the doncumentation explaining how setting the PFC parameters (Ki/Kp...)?

Regards

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psb
Moderator
Moderator
Moderator
250 sign-ins 25 solutions authored 100 replies posted

Hello, 

 I have seen that you have changed the Kp, Ki values. Have you changed them after changing the shunt resistor from the previous one ?
Also, the shunt resistor  exploding, PFC overvoltage and change of shunt resistor related .. as in they have happened simultaneously ?

Regarding the change in Kp, Ki values, they shall be done by deriving the transfer function of the PFC and following the control loop given in section 2.2 of https://www.infineon.com/dgdl/Infineon-MCESW-RM-UserManual-v01_03-EN.pdf?fileId=5546d462719b59230171...

Best Regards,
Sai
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AG_Serad
Level 4
Level 4
First solution authored 25 replies posted 25 sign-ins

Hello

Iwill try to summer the differents step:

 

- First we observe the PFC overVoltage, mainly in deceleration phase, when motor is on regeneration phase. We drive an R load 2K2 10W resistor when Vdc >410V.

I supposed the PFC not apreciate the regenerating mode. SInce, I switch off the PFC before ask motor reduce speed.

2) Problem seems disapears. 

3) We perform the PFC due to audible noise. We change the PFC shunt from 11mohm to 50mohm. IMC102T was changed according this.

4) Our customer come back to use because PFC overVoltage Occurs.

5) Our customer comeBack to us because PFC shunt was explosed on 230V Power On

-> At this Stage, the PFC was started on startup of the script. Now I change it to wait the Inrush relay was driven, And I wait some time to be sure all is ok and stable. I change the PFC OVC from Latch to Cycle-By-Cycle. Since I never seen other PFC shunt Explosed. THe future will say us if it is of for this point.

-> For PFC overVOltage, I try to set the PFC parameter. I observed the Vdc. Target was 400V, and I seen 398V->402V sinusoidale. Then I tune the PFC to have 399.5V-> 400.5V.

But this was done with PFC no load!..... I'm currently trying to set the PFC with a fixed load (75ohm 8KW under 400V) and after check if Ok with motor running (5A in acceleration, 2.5A in stabilized max speed).

 

In the same time, customer indicate to me some noise error (AC underVOltage and FaultFrequency). It is why I want Try to change the Vac input capacity filterof 13K/4.7nF (like eval board) to 15K/10nF (Fc 2.2KHz -> 1Kz). Pfc running at 35KHz, Input can vary from 50Hz/60Hz => 100Hz/120Hz

PLease, could you confirm change filter has no impact on the PFC control?

I will back here to show you the PFC reaction according my setting in load.

 

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AG_Serad
Level 4
Level 4
First solution authored 25 replies posted 25 sign-ins

Hello,

So I revert PFC parameter like given on Evaluation borad exemple.

The votage ripple is higher but I will accept it. I hope by this, the PFC will me more stable and will not goes to overvoltage...

- First, data are get by charging the VDC with 8KW 75ohms resistor.

-Second, data are get with the real motor running

-Third: Script activated: Control of RBrake to control Vdc and swithc Off the PFC on regeneration phase (Deceleration)

 

Questions that we can see in the attached document:

- On "Command = 0" with the motor runing and PFC running, the Vdc voltage increase fastly. Is it normal? Can we adjust PFC to limit that?

- Can we change Vac filter capacity from 4.7nF to 10nF? 

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psb
Moderator
Moderator
Moderator
250 sign-ins 25 solutions authored 100 replies posted

Hello @AG_Serad ,

  Thanks a lot for sharing all the information. Will analyze and get back to you with the root cause. 

Best Regards,
Sai
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Hello,

Now the situation is stabilized.

When tuning other motor, I seen the Vdc crasy increase can be caused when motor R parameter is bad tune. (To high)

Maybe this can be the rootcause? (because Vdc increase whenever PFC is running...)

Vac filter capacity was changed from 4.7nF to 47nF to avoid PFC AC frequency fault. Now, the system not trig error on EMI discharge up to 5Kv.

 

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