Hi Jian,
Frequency response estimation can be slow especially if you are using sinestream perturbation signals for power electronics application like power factor correction. This can depend on factors such as sample time of the model, number of frequency points for your estimation. Recently we have introduced PRBS perturbation signals which lead to faster estimation times, specifically for such power electronics applications. Please see if you you can get good results by using this signal compared to sinestream signals. Having the sinestream results can be a good sanity check to compare your PRBS estimation results.
Some useful documentation that you might find helpful to start:
https://www.mathworks.com/help/slcontrol/ug/prbs-input-signals.html?s_tid=srchtitle
https://www.mathworks.com/help/slcontrol/ug/frequency-response-estimation-for-power-electronics-model-using-prbs.html?s_tid=srchtitle
HTH,
Sid
