I would like to implement a boost PFC stage for an alternator that has a large leakage inductance (~40mH). When looking at the schematic, we can see that the boost inductance Lb and the alternator inductance La are connected in series (through the diodes D1 or D2, depending on the half-cycle), and that the large value of La means that it cannot be ignored (and that Lb is useless and can be removed).


In theory we need to measure the instantaneous alternator voltage Va, in order to shape the alternator current Ia waveform the same way (scaled with the error on output voltage Vo). This is clearly impossible as Va and La are intrinsically the same component, so Va+ is not available.

At first I was planning to measure the current and rectified voltage Vr (as should be done in the absence of leakage inductance La), and to compute what Va should look like, knowing the value of La. But then I realized that as soon as I will start switching M1, I will alter Ia and Vr (it is the purpose), so I can't use them anymore.

I have a few ideas in mind about how to workaround this, but they all seem quite impractical (like measuring the derivative of the current Ia when M1 is closed). In addition I was thinking that this problem should be classical, for instance in wind turbines, but I did not manage to find information about this on the web.

Is this a known problem, or is La usually insignificant and ignored? Does a robust solution exist to implement a proper PFC in this situation?


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