Say we got a solar array which supply power to battery through a DCDC converter. We want to design two control loops for the converter.
One is the inner(fast) loop which regulates the converter output voltage or current. This loop can be analysis by the traditional converter small signal model.
Another one is outter(slow) loop which is regulate the converter input voltage or current (solar array output voltage or current). How can we analysis the stability for this loop? Do we need to include the small signal module of solar array? If the voltage or current is regulated by some algorithms, how to model the algorithm?
Any tips would be very helpful, thank you
Your's question needs refinement of problem.
What is the outter slow loop?
May be this is a Sun radiation?
Thanks for reply, Maybe I can describe the issue clearer. The outer loop is referring to the control loop for dcdc converter. Because the voltage of battery is relatively stable, the solar array voltage (or you can say working point) can be controlled by adjusting the duty cycle of the converter. During operation, the solar array's voltage and current will be continuously monitored by converter and converter will adjust its duty cycle accordingly to regulate the voltage and current of solar array.
The slow loop controls duty cycle. And what controls fast loop?
I suppose the most of DC-DC controls duty cycle. Wat is the difference - fast loop, slow loop?
You should to place an net-analyser for know the consumpeion and other parameters of the load.
Regards, Hector R.
Hi Bendfeld,
Thanks for the reply. It is true. We can maintain certain inputs (such as battery voltage) within a certain level to keep the PPT control stable. But, from design point of view, we still need to model of the whole control loop. Only by doing so, we can know the stability of PPT before the fabrication of the hardware. Otherwise, we can only know the stability by testing the hardware. Also you will never know how much margin you have.
Hi Somesh,
Thanks for your answer. The difficulty part is we want to know the TF before we building the hardware.
Yes, you need to include the TF of the solar-PV generator for the control design. You may refer to the following model, but it did not include the impacts of batteries.
Article Reduced-order modelling of solar-PV generators for small-sig...
The following book also contains relevant information,
Book Dynamic Security of Interconnected Electric Power Systems - ...
Note, if you could not download the book from the RG, you will find an alternative download link within the page of the book on the RG.
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