IV Curve with MPPT Charge Controller

[Sunking]

I love this thread. I always go to the plots first then guess what the discussion will be. Not doing as well as I would have hoped. Once I read the discussion I go back to the plots and say 'of course it is'. I'm glad I do not have access to this testbed. I would sit and stare at it like a little kid watching Saturday cartoons. I can't imagine how many things I would stick out the window to produce controlled partial shade. Light from the window? Full moon? Yee-haw.

I got some paint you can watch dry, or some grass you can watch grow.

Where I live a lot of folks like to watch grass grow. Especially a variety called Panama Red. Looks more purple than red to me.But it is kind of pretty flowers.

[AzRoute66]

I know you see substrings overcome the bypass diodes every day, but it was new for me.

[BackwoodsEE]

I know you see substrings overcome the bypass diodes every day, but it was new for me.

I still get a kick out of seeing the bypass diodes do their thing, and then being able to look out the window and see the shading on the panels.

When I had the real-time capacitor-switching box included in the circuit, my software was set to trigger a new IV sweep whenever the latest voltage and current reading (done once per second) deviated too far from the last IV curve. I could put the plot display on my iPad and then walk in front of the array and see how the IV curve changed from shading in real time. Now that, for a EE geek, was definitely cool to watch. Sort of like a real-life engineering video game.

[sensij]

I still get a kick out of seeing the bypass diodes do their thing, and then being able to look out the window and see the shading on the panels.

When I had the real-time capacitor-switching box included in the circuit, my software was set to trigger a new IV sweep whenever the latest voltage and current reading (done once per second) deviated too far from the last IV curve. I could put the plot display on my iPad and then walk in front of the array and see how the IV curve changed from shading in real time. Now that, for a EE geek, was definitely cool to watch. Sort of like a real-life engineering video game.

The really hard question to answer, then, is how does the Morningstar controller compare to your sweep box, or a truly ideal mppt controller. You've shown us that when it runs a sweep, it correctly identifies the maximum point. Rhetorically, how much power or energy is lost because it doesn't run a sweep every second of every day? One clue might be the difference in power before and after each sweep. A first order estimate of energy lost might be
Sum throughout the day of [(power change induced by current sweep * time since last sweep) / 2] + [time required to complete current sweep * current power]

The more sweeps that it runs, the more power is lost to the sweeping action (relative to holding at the power point). Interesting optimization problem...

[bcroe]

I got some paint you can watch dry, or some grass you can watch grow.
Where I live a lot of folks like to watch grass grow. Especially a variety called Panama Red.

I think that is what we in the country did, before there was the ability to monitor
the output of every panel, every 5 minutes.

Yes the MPPT controllers do their job. The details have been pretty much a trade secret up until now, but
certainly the methods can be measured. If this catches on, it will be another subject for comparisons. My
approach might be, frequently iterate a small amount around the latest MPPT point. If power drops,
immediately iterate in the other direction, expecting first a small rise and eventually a drop. This would not
take significant power away from normal operation. A full scan could be done rather infrequently, or when
iteration has tracked a significant drop.

I have had occasions for bypass diodes to operate, but it was from weak sections in a no name panel, not
shade. I swapped some out to keep the rest at best efficiency. While the shade issue is interesting, its
regarded as a definite negative here, an opportunity to improve the system. Still trying to find an app to
keep those orphan panels in useful service. My options are run at full voltage but reduced peak current,
or short out the bypassed section and put them in series with a full current string. That would cost me
some mounting hardware, to put 11 panels in a 10 panel string. Bruce Roe

[littleharbor]

I got some paint you can watch dry, or some grass you can watch grow.

Where I live a lot of folks like to watch grass grow. Especially a variety called Panama Red.

He'll steal your woman, then he'll rob your head.......

[PNPmacnab]

Here is my whole house control panel. It is fun to watch and nothing Micky Mouse about it.

[SunEagle]

He'll steal your woman, then he'll rob your head.......

At least put quotes around that part of the song.

[littleharbor]

At least put quotes around that part of the song.

I need to figure out how to get those musical note symbols instead of quotation symbols. I don't even know how to get the comic sans font

[SunEagle]

I need to figure out how to get those musical note symbols instead of quotation symbols. I don't even know how to get the comic sans font

When you make a post there is a button on the right with the capital letter A. Click on that and it brings down a horizontal tool box.

In that group of tools is a big button labeled Font. Click on that and it gives you drop down menu of different font types.

[littleharbor]

Well that was easy, Thanks SunEagle. I learned something today.

[SunEagle]

Well that was easy, Thanks SunEagle. I learned something today.

You are welcome. Glad to have helped.

[AzRoute66]

Hope that didn't dead end the thread. Can I get a couple dozen more pictures of panels and MPPT algorithms doing fun things? The paint is dry and the grass needs cutting.

[BackwoodsEE]

Hope that didn't dead end the thread. Can I get a couple dozen more pictures of panels and MPPT algorithms doing fun things? The paint is dry and the grass needs cutting.

Here you go. Battery is about halfway discharged, about 100W inverter load and bulk charging. Hazy sunshine, bright enough to still cast a faint shadow on the ground. The panels are producing at about 25% the highest I've ever seen from them, and the charge controller is taking everything it can get. Capture.PNG

The dots are from real-time IV readings that occur after the MPPT sweep. Note how the voltage stays fixed and the charge controller just draws more or less current from the PV array as the sun brightens and dims. This makes sense, since the MPPT point only decreases slightly in voltage with lower insolation.

[BackwoodsEE]

We are in the thick of the smoke from British Columbia's forest fires right now. The max power from my three panels is about half what they'd be capable of in full sun.

Capture.PNG