In a Solar System, how can I obtain the MPP of solar cells meanwhile I control the output voltage and I set it in 24 V DC?.
My main issue is that my converters is configured to work in the MPP and the Voltage is not steady in noone value, because it ascend to the maximum value of voltage of the panel (45 V) and descend to the minimum value of the panel, but I want keep it around of 24 V DC.
This simulation is done under Simulink.
If you prescribe the voltage of your panels, you cannot expect to keep the panels at MPP; this is physically impossible. However, at the output side of the converter there usually isn't a DC but an AC voltage. So, what kind of converter do you use? And, what kind of application do you have in mind -- to charge batteries?
Dear Tony adding to Dr. Wagner,
It is assumed that your system is composed of a pv generator which is connected to a DC to DC converter. There are two types of DC/DC converters, Boost and buck converters or a combined one according to the relation between the output and input voltage. Its operation is based on transferring the maximum power from the PV generator to the load by adjusting the transformation ratio between the input and output such that the pv sees the matched load and works at its maximum power point.
The output voltage may change if the load resistance is kept constant.
Then you may require to add a voltage regulator stage to keep the output voltage constant. You may use switching type voltage regulator. Or a low drop out voltage regulators. The important point here is that you operate the DC/DC converter to control the maximum point of the PV generator while delivering a nominal voltage to the load. If you want to keep the output voltage constant you have to further regulate it.
I think that the maximum point operating voltage odes not vary much with the incident solar radiation since the array voltage varies logarithmatically with the incident solar radiation. It may then that your controller do not execute a maximum power point tracking algorithm.
More information is needed to precise the comments.
Best wishes
Hello,
Under uniform distribution of the solar irradiance over an array, the MPP voltage changes over a very narrow bandwidth, and it is nearly constant. Therefore, appropriately used DC-DC converter controlled to follow the MPPT will also provide nearly a constant voltage. You may refer to the relevant chapter in the following book.
https://www.researchgate.net/publication/307926879_Dynamic_Security_of_Interconnected_Electric_Power_Systems_-_Volume_2_Dynamics_and_stability_of_conventional_and_renewable_energy_systems
If the changes in the output voltage are not acceptable, a shunt capacitor or regulator may be used.
The following article includes an improved MPP algorithm for better stabilization of the tracking process.
https://www.researchgate.net/publication/322022340_Reduced_order_modelling_of_solar-PV_generators_for_small-signal_stability_assessment_of_power_systems_and_estimation_of_maximum_penetration_levels?_iepl%5BviewId%5D=Zl0YYbsY7DqTzfFtTUSBID7m&_iepl%5BprofilePublicationItemVariant%5D=default&_iepl%5Bcontexts%5D%5B0%5D=prfpi&_iepl%5BtargetEntityId%5D=PB%3A322022340&_iepl%5BinteractionType%5D=publicationTitle
In my system have connected a Buck converter among the generation side (PV cells) and the consumption (Load) and accumulation (Batteries) side. My doubt Dear Doctors is how implement in Matlab&Simulink this necessary stage.
This Buck converter operate under a MPPT Algorithm such as Incremental conductance or Perturb and Observe, and the converter its function is to charge the batteries and also when the energy surpluses are generated it divide the current flows for supply energy power to the Load.
At this point I've gotten a problem in order to keep my voltage rated output in a value around 24 V (+/- 10 % of tolerance). I have to pinpoint that my Load is variable.
I hope both of you get a wider idea of the problem that I try to solve. If you need some more information just ask it, for you be able to help me to solve my trouble efficiently.
As far as I remember, there is already a demo file in the simpowersystems toolbox entitled smart grid or so contains the models you need. In addition, the 'mathworks file exchange' website contains numerous modeling examples added by users without verification from the mathworks. Good luck in your study
May I show why the output voltage of a generator cannot be varied independently while keeping it at maximum power point?
Let the generator have a source voltage of E and an internal resistance of R (Solar panels will not show a constant R with E but this does not change the basic argument).
Let it be connected to a load r.
Then the current through the circuit = E / (R + r) and the power generated in the LOAD = (E / (R + r))^2 * r = (E^2 * ( R + r) ^-2 * r
If we are at maximum power point this is stationary with respect to R, so
differentiating, with E and r constant we get the condition that for maximum power transfer R = r.
Now the output voltage of the panel = e - internal voltage drop
= E - E / (R + r) * r = E * (1 - R / (R+r))
But if we make this a constant which is not that value where R = r, then we can't have R and r being anything we like, and we are immediately off maximum power point.
Hope this clarifies matters!
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