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52
Wind Power Machines / Re: Interfacing wind turbines to the grid
Last post by SparWeb -
Quote from: bigrockcandymountain – on
What if all you did was add a very large capacitor (or a few of them) with a resistor in series to limit charge /discharge amps between positive and negative between the ssr and the micro inverter? Would it smooth the dc power enough that the micro would be happy? Would it store enough that when the mppt swept up it would drop a bit of amps and mimic a solar panel?

Funny you mentioned the SSR just when I was getting frustrated with designing my circuit with a MOSFET, and tonight I've been replacing it with a SSR.

I think I have the microcontroller signals figured out.  What's really bothering me now is that I've made some assumption about the inverter and I don't like the way things go bad if I am wrong.  I've been using Falstad's site to simulate this, and it suggests I will be blasting the 0.5 ohm power resistor with brief bursts of 90 amps.   Probably just something I have simulated wrong, but...

To your suggestion BRCM, yup, a big capacitor soaks up a lot of nuisance noise.  You just have to make sure it doesn't drown out the signal you want to measure.  Circuits that combine resistors and capacitors have a "time constant".  If the constant is long (in the electronics world 1 millisecond is long) then the time for the capacitor to charge up is longer than the time for a 1 kiloHertz signal to arrive, and you probably won't measure the signal.  On the other hand, if the capacitor is too small or ineffective, then the microcontroller is measuring pulses and it may pick up the pulse on the Hi during one reading, and on the Lo on the next.  From the microcontroller's perspective, the signal went from on to off, and in a sense, it would be right.  But in another sense it failed to detect what the power resistors are doing.  It missed the next Hi peak which has a different voltage than the last Hi peak, and that was the information it's looking for.  So there's a balance, when Goldilocks finds the right oatmeal.

Quote from: bigrockcandymountain – on
It sounds like a thread hijack when I read through it, but it kind of applies to sparweb's setup too.

Nah, you're forgiven
53
Wind Power Machines / Re: Interfacing wind turbines to the grid
Last post by SparWeb -
Quote from: bigrockcandymountain – on
...my diversion load is a 500hz 12v signal that goes to a ssr and dumps the 48v battery voltage through an approx 10ohm resistor (water heater element) I assume the 48v comes out of the ssr at 500hz, not exactly as dc.

48v/10 ohms = 4.8 Amps
60v/10 ohms = 6.0 Amps

Hmm surely you'd dump more than that?  I think your WT is bigger than mine is, and I need a 2kW diversion load (and I admit mine turns out to be only 1.8kW).  It may not matter in your case if you're using your batteries most of the time.
55
Wind Power Machines / Re: Interfacing wind turbines to the grid
Last post by SparWeb -
Quote from: MaryB – on
Feed it thru a rectifier and monitor the DC current via your micro... a full wave bridge with electrolytic has 1.4 times the voltage output so some math involved...

For now, I'm monitoring DC current, which is pulsed.  Where I tap off the power resistors with a voltage divider determines the scaling factor I need to satisfy the microcontroller's ADC input.  I figured out that a 1 to 10 uF capacitor is all I need, and doesn't have too slow a time constant for these devices.
56
General Discussion / Re: How is everyone surviving the cold and snow?
Last post by SparWeb -
When the Germans "went solar", they soon encountered the winter doldrums which get cold and dark, and then sometimes even the wind stops...  ...so they came up with a word for it:  Dunkelflaute

There's always a long Dunkelflaute here, where we get virtually no sun or wind for about a week.  Solar panels covered in snow makes it worse, but there's not even any point brushing them off.  Last December, about Christmas-time, the temps were -20C for a week.

In early January both the weather and I perked up, and I got in a lot of skiing.  Since then, it warmed up, melted the good snow, and turned the rest into ice. So much for skiing around the house.
58
Wind Power Machines / Re: Interfacing wind turbines to the grid
Last post by bigrockcandymountain -
I looked at your circuit diagram and read the explaination, and I'm trying to picture exactly how it would all work and i think i see some light.  I have "Electronics for Dummies" open in my lap right now.  That helps too. 

I have something I'm wondering about and I'm sure someone will explain to me why it won't work. 


In my case, my diversion load is a 500hz 12v signal that goes to a ssr and dumps the 48v battery voltage through an approx 10ohm resistor (water heater element) I assume the 48v comes out of the ssr at 500hz, not exactly as dc.

If I swapped the water heater element for a grid tied micro inverter it would get fed messy 500hz and would blow something up likely. 

What if all you did was add a very large capacitor (or a few of them) with a resistor in series to limit charge /discharge amps between positive and negative between the ssr and the micro inverter? Would it smooth the dc power enough that the micro would be happy? Would it store enough that when the mppt swept up it would drop a bit of amps and mimic a solar panel?

I get the feeling the magic smoke would come out somewhere, and i don't even have the grid here, so it's all academic.  I just can't picture in my head what would happen, and i was hoping to learn something by asking.

It sounds like a thread hijack when I read through it, but it kind of applies to sparweb's setup too. 

59
General Discussion / How is everyone surviving the cold and snow?
Last post by MaryB -
Second morning of -20f, thankfully the wind died down so the house is warmer! Yesterday's high temp was -9f!

Seems like more normal weather patterns are back, Minnesota usually sees a week or two of deep cold in January/early February then spring starts to creep in...