TMS320F280049C: SFRA for plant and open loop data for PFC rectifier

Also attached is the .csv file with the data collected by SFRA.

SFRAData_PFC_I_Loop05092023.csv

Hi Vijay,

I will need to reach out to another expert on SFRA, I will update you as soon as I get more information.

Best,

Ryan Ma

Hi Vijay,

What is the frequency of PWM on which SFRA utility is injecting the disturbance and the resulting samples are collected?

What is the transfer function you are expecting from your design, and can you share the snippet of SFRA GUI boded plot in logarithmic scale?

Regards,

Shashank

Hello Shashank,

The PWM frequency is 20kHz.

Please see the snapshot of the bode plot.

With regards,

Vijay

Hi Vijay,

Can you mention, with what frequency are you using SFRA background tasks and SFRA settings used in your code? 

Are you following the steps present in user guide of SFRA (SFRA Driver or library | TI.com) and taking reference of SFRA example?

(DPSDK/libraries/sfra/examples/example1_stb) 

Hello Shashank,

The task SFRA_F32_runBackgroundTask(&sfra1); is called every 1ms.

We have followed the process given in the documents spruik4a and spruhz5a for integrating SFRA into our application code.

With regards,

Vijay

Hi Vijay,

So, the usage of SFRA utility is correct.

There might be two reasons:

1. SFRA amplitude and frequency from frequency vector, which are injected might affecting output samples- so increase frequency vector width and also SFRA amplitude (decrease and increase observe impacts of both), to get smooth magnitude/phase plots. But please try at low voltage and low power.

2. There might be external signal which may be impacting input of the plant, that you can verify once and no issue with SFRA.

It will be easy for me to understand if you provide details of inputs, you are providing to SFRA_F32_config function (especially magnitude of SFRA amplitude, reference that you are adding this SFRA injection to) and also expected transfer function of plant.

Regards,

Shashank

Hello Shashank,

I will try with some change in the SFRA amplitude.

Currently, the SFRA configuration parameters are as follows:

SFRA (i.e. ISR) frequency: 20kHz

injection amplitude 0.01PU

Number of frequency points: 100

SFRA sweep start frequency: 100Hz

Frequency step multiply: 1.059253

With regards,

Vijay

Hi Vijay,

SFRA settings are configured properly and frequency with which SFRA background task, GUI functions and SFRA inject/collect functions used are correct too.

Did you check the signal given as a reference for SFRA inject and ADC configurations when reading those reference signals?

What is the result of changes asked for increasing width of SFRA injected frequency and magnitude of noise? Did you got smooth boded plots by varying those?

Thanks & Regards,

Shashank