hello,
I have a PV panel connected to a DC/DC converter and to a resistance load (i am just testing the good working of the PV panel before assembling it with the other microgrid components).
I've put an MPPT algorithm to generate the corresponding duty cycle.
I want to test it while varying the irradiance and also while varying the value of the load.
when the irradiance is 1000w/m2 and the load resistance is equal to the characteristic resistance, the PV panel gives the maximum power corresponding to 1000 w/m2 (using MPPT) but when I vary the value of the load I remarked that the power is no longer the maximum! (in this case(load change) should I get the same max power as before ?) also when I vary the irradiance, it does not give me the max power corresponding to this irradiance!
can I say that there is something wrong with my MPPT algorithm (note: I got it as it is from Matlab).
please help me, if I have my own PV panel and designed converter and load and I just want to add the MPPT part, when I got the ready algorithm from such source, should I vary something ??
Dear Sarah,
I think in order to change the input parameters such as the irradiance G and the temperature of the module T as well as load you must use buck-boost converter.
The boost converter increases the level of the source impedance to the load impedance. While the buck converter matches the smaller loads to that of the source.
In principle such controllers can response only to limited range of parameters variations,
Best wishes
Seyed Majid Hashemzadeh okay you have right, the MPPT should be maintained with irradiance variation, but what about Load variation? MPPT should also be maintained?
Dear Sarah Kassir . MPPT should be maintained with irradiance variation but MPPT should not be maintained with load variation. Load must be according to maximum power. Try to experiment with easy MPPT algurithms like hill climbing algorithm etc.
Afaq Hussain
thank you for your response, but what do you mean exactly by "load must be according to the maximum power".
As I understand that we should connect to the PV a load that supports the power that this PV will give us using MPPT (not to small load then we will have excess power and this is a problem) and (at the same time not too big ), so the load can be within a well-determined range corresponding to the PV array that we have, this is what you meant by this sentence right?
The formula for the calculation of load is R= V_o^2/P_max for MPPT. If the load is lower than R, then you should add battery with its management system to extract the remaining power to achieve MPPT.
Please note that the DC/AC converter with a standard MPPT algorythm usually follows the MPPT for every value of the irradiation by arranging the resistive load on the panel or string of panels (usually by attempts: in the case of a string of panles the MPPT curve can have more than a relative maximum, and the curve has variation with temperature panels temperature). It can also have a "learning" mode that learns the best point of the specific panel string. On the AC side the regulation is according to the characteristics of downstream network to supply in any case the maximum of power to the network (it is an infinite absorber). If you vary only the DC load, it is impossible with only the DC to DC converter to maintain the MPPT in any situation.
It is better to have a constant load while working with MPPT. In my experience MPPT does not work well with varying load, whereas it should be other way around as the load must work based on power generated by MPPT e.g Solar based water pumping system.
You must know that MPPT provided constant current in a specific irradiance condition and if you try to increase load during that time means you are trying to draw more current which is not possible with MPPT, so varying load with MPPT is not a good idea.
Now discussing varying irradiance, with constant load the MPPT should work as it should draw max power from the panel if it does not check your system or codes.
Dear Sarah,
I think in order to change the input parameters such as the irradiance G and the temperature of the module T as well as load you must use buck-boost converter.
The boost converter increases the level of the source impedance to the load impedance. While the buck converter matches the smaller loads to that of the source.
In principle such controllers can response only to limited range of parameters variations,
Best wishes
You can try to use microcontroler just ad Arduino to get better and valid results.
Hello , I think that you should try first with an easy to implement and well-known MPPT algorithm. In the attached link you can find some examples .
https://es.mathworks.com/solutions/power-electronics-control/mppt-algorithm.html
It is in Spanish, so please try to translate to ENG or FR. By the way, the schemes are drawn in ENG.
Please note about the relationship between Conductance (1/R) and Voltage Variation.
Regards
Jorge El Mariachet Carreño
MPPT works well for load variation. However, for any buck or boost converter, MPPT can track a limited range along the I-V curve. In order to cover full I-V curve, CUK or SEPIC converter can be used.
Sarah Kassir In the recent attached link you can find the answer
Article A New MPPT Technique for Fast and Efficient Tracking under F...
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