Hello,
I am designing a push-pull converter which source is a PV panel with MPPT algorithm.
I need to have calculation method for the output inductance.
I know the calculation in regular push-pull converter with normal DC source however, PV panel I-V curve changes everythings as i assume.
The output voltage is going to be kept 400V ( for now I am changing the output resistor according to input power).
The rated power is 300W.
The input voltage of the converter is between 25V and 45V.
Finally, I want to keep CCM operation until %10 of the rated power.
I am so confused so far. Amy help would be appreciated a lot.
See the following related books:
Fuchs, Ewald F., and Mohammad AS Masoum. Power conversion of renewable energy systems. Springer Science & Business Media, 2011.
Keyhani, Ali, and Mohammad Albaijat, eds. Smart power grids 2011. Springer Science & Business Media, 2012.
Farret, Felix A., and M. Godoy Simoes. Integration of alternative sources of energy. John Wiley & Sons, 2006.
I think you are seeing difficulties where they don't exist. A PV panel is a very well behaved energy source. It generates a limited voltage and limited current. It can be open circuited AND short circuited safely (try that with a battery - no, on second thoughts DON'T try that with a battery). Just design your converter for the panel nominal output voltage as if it were a battery. You seem to be operating into a low impedance load, otherwise why say you want to operate Constant Current? In such a case you just maximise the current and you have automatically maximised the power. Make sure that the inverter can deliver the power required over the expected input voltage range - by design of the transformers and turns ratios. Best wishes with your research!
Tony Maine thanks for the answer.
I know the behavior of the PV panel and of course not to short circuit the battery :).
But the problem is the Duty cycle values that the MPPT algorithm founds.
Normally and ideally the input-output voltage equation of a push-pull converter is Vout=Vin*2*n*D at CCM operation, where n (let's say n is 16.75) is turn ratio and D is duty cycle.
So if I have a Panel that operates 45V and 6.6 A at the maximum point the required Duty cycle value for having 400V output is 26%. With these conditions, it is easy to calculate required inductance according to given ripple current, etc.
However, when the irradiation reduces so as the panel maximum current value,
the MPPT algorithm reduces the D value in order to get the maximum point.
Then the Vout equation I wrote above is out of order because the output voltage is 400V again (I changed the load resistor in order to keep the voltage constant) and the PV panel voltage is 44V ( a little drop due to irradiation changes)
My goal is, to calculate the required critical inductance( for CCM) for the second situation but I can't estimate the duty cycle that the MPPT algorithm calculates.
I have a detailed Simulink simulation and a real circuit. I am testing these situations in both.
I hope I made it clearer.
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