Grid-Connected PV System

Matlab/Simulink Help

Your diagrams are not readable.

If you want them to be readable you must put just one screen at a time, that doubles height & width.

I insert pictures into blank lines between lines with text like AA, just to make sure they are not "side by side".

Also, selecting just the part with the diagram in Paint or other image editor would help, leaving out the menus.

CR4 seems to shrink images to fit, with lower definition.

Hi 67model,

I'm sorry about the previous pictures which is not readable.I tried to upload again with double the size and height. Unfortunately,it still look the same in the preview. Is that possible if you give me your email so that I can send it to you or perhaps the model can be found in this provided link http://www.mathworks.com/matlabcentral/fileexchange/39408-grid-connected-pv-system-with-mppt] Sorry for the troubles. Many thanks.Looking forward for your reply and guidance.

I am sure that what Subsystem1 and the current source are doing is simulating the Solar panel output I-V curve at the point VM1 is monitoring [Uout]. I guess S and T are solar intensity and temperature values input to subsystem1.

I still struggle to read the subsystem1 & MPPT blocks. On the website I can get the overall diagram but not the subsystem drawings. If you have the matlab files, can you export them as jpg or png type file?

I note on the website that others have queried the program and cannot get the blocks to work.

67model

Thanks for readable diagram, JermPV. I will just comment on your MPPT queries for now.

i) My interpretation is that the Vn, In blocks are sampling the PV volts and amps at regular intervals.
Vfilter and Ifilter are to stop a spike [say a flock of geese flying low over the panels] at the sample instant putting a big spurious error into the control.
The Vb and Ib blocks are delaying samples, so that the Pn and Pb values are present and previous states whose difference identifies a change (and its size).
In theoretical analysis, present and previous samples are commonly put as Pn for current sample and Pn-1 for the preceding sample.
So I think the Pn - Pb block is doing a "Pn - Pn-1" job.

ii) Why DeltaP/DeltaV?

Diversion..... it was not a very good way to label DeltaP*DeltaV on the diagram, because the Pn-Pb and Vn - Vb block outputs are not labelled Delta P and Delta V and could be misunderstood as power and volt changes.
DeltaI in place of DeltaP would be better, perhaps the font for "capital i" did not look nice, so "I" was changed to "P".

Confusion aside, if DeltaP = 0 and Delta V = 0, then what is 0/0?? It is undefined by mathematicians and computer chips and operating systems are set to flag errors, else the system could go into a perpetual unsolvable loop. Which is what the hero does to the megalomaniac supercomputer in the drama "It does not compute...AAAAArg...dies (quietly)".

DeltaI * DeltaV (I just changed the font to Times New Roman in the hope it will get through the web - did not, but CR4 has a good font) has the merit that when both change by 0.5 you get 0.25, while if both change 2 you get 4. So big changes give a big error (for quick action) compared to small changes.

I wonder if there is a problem here, MatLab follows correct mathematical rules, so +.+ =+ and -.- = +. This means that volts and amps both falling has the same sign as volts and amps both rising - not very good for a loop error number.

iii) Delta D duty ratio?? No, I think it is just an error scaling factor, so you compare "cm with cm not metres with centimetres".

67model

FORGET the Diversion, the bit about "i" and the "wonder if there is a problem". Just me getting a wrong idea! My answers to your questions are otherwise correct. The MPPT block does work!

A comment on iii) is that duty cycle modulated switching pulses appear at D. It is the level at the output of the "Add" block (unhelpfully NOT labelled) which sets the duty cycle at D, which controls the IGBT switch following L on the main diagram and changes the load on the solar cells.

Ref. the subsystem block, its purpose is indeed to simulate the PV cell current as a function of solar strength, cell temperature and cell DC output terminal voltage. I have not looked at that block to see how it works yet - do you have any other questions about it?

Note the "Maximum power" cell terminal voltage varies little with solar strength.

67model

Noted. Sorry for the late reply. I was busy with my finals preparation previously. Thank you for the explicit explanations on the model. I've now completely understand what's going on. Your precious time and efforts are much appreciated. Many thanks for helping me once again.

Regards,

Jeremy

Thanks for clearing some of my doubts but some things are still creating problem for me like

i)after simulation if u see the output then it is not approaching to maximum power instead it shows way less than the maximum power after the output gets settled.

ii)in mppt subsystem why is there a repeating sequence block used for comparison and how are its parameters decided same for the saturation block.

iii)and pls can u tell the equations used for the pv cell panel.