Homebrewed Electricity > Solar
Grid Tie, Oh My
OperaHouse:
You have to have guts to plug one of these in! Got my grid tie inverter arrived yesterday.
It was the typical ebay "Works, just missing a screw." It was in like new condition and rattled.
Never did find out what that was. No obvious shorts or burnt components. Someone tried to
fix it, but they never got as far as lifting the board. Almost a virgin. Notice long black
vertical blobs from lower left of the transformer and fan. This is where a 4,700uf 50V
capacitor should be. Reports are these blow all the time since they are no bigger than your
pinkie. They tried surface soldering some wires from the board to a replacement cap and insulating
them with this goop. That cap was nowhere to be found. Pretty bad job of soldering.
Not shown in the photo, hard to see even with the naked eye, is a #30 wire grounding the copper
shield on the transformer. Wire this small is hard to use in manufacturing. Cost is not likely the
reason. It probably acts like a fuse should insulation break down from a lightning surge on the
power line.
I just bought 400 electrolytic power capacitors. I'm waiting for those to show up. They are triple
the physical size and 1/4 the capacitance. Two in parallel will perform much better than what
was in there. It will take a couple of days anyway to get the courage to plug this into the grid.
OperaHouse:
Well that wasn't fun. I temped in a capacitor and hooked it up to the grid with my XANTREX HPD30-10. Seemed to be operating normally. At about 29V and 5.9A the power supply started buzzing and then dies. Must have sent something nasty back down the line. You can short this supply forever at 10A and not do any damage.
OperaHouse:
Got my two SUNIVA 280W solar panels today. Been buying up broken grid tie inverters and sine wave inverters. Now I can start doing experiments with water heating and feeding power to the house when energy use is sufficient. Don't want to set off any alarms by feeding energy to the grid. Don't know how smart my meter is, but it is internet connected. Will be developing a grid tie controller to switch the GTI on and off. With the number of cheap GTI out there that have gone bad, they don't seem like a good investment for most people.
clockmanFRA:
Hi Opera House,
Its good to see another using old GTI's.
It will be interesting to see how you control yours.
Here in Europe there are good quality used/second hand working GTI's for sale, around the $40 to $200 depends on the kW. Folk here upgrade to a bigger PV system and hence their old GTI is just scrap value as it can not be used on another official system
I tend to go for the LF types, has a toroid inside, and a certain brand as I have the internal parameter re-set codes. Re-set mine so they start up within a 10 second period, so my batteries take the short time loads.
My 4 GTI's, under 3kW rating, are operating on my OzInverter Mini Grid, and I allow a little feedback from the GTI's to backcharge through the OzInverter to my battery bank.
When the AC voltage, domestic house supply, on my mini grid climbs to a pre-set selected voltage, ie I am not using the power produced, each of my GTI's shut down in sequential order.
So you will need to really carefully monitor the Incoming AC grid and constantly compare with what you are actually using.
At ..... http://www.thebackshed.com/forum/forum_posts.asp?TID=9903 several methods are being used with the GTI's, and some experiments by 'madness' regards controlling the HF, high frequency, no torroid, GTI, and some interesting Blow Ups!.
1. My method which is bang bang when the AC voltage rises on each GTI, although with the latest OzInverter AC control, this may not work as the AC is now rock steady!.
2. Controlling the DC from the PV panels coming into the GTI by monitoring the DC battery voltage, ie a battery charger.
3. Monitoring the AC voltage and allowing certain amount of power back to the AC mini grid.
4. Monitoring the DC voltage and allowing certain amount of power back to the AC mini grid.
As you can see with the Backshed forum guys, they are heavily into using Arduino/Mega coded systems.
Hopefully some of the comments may help you.
My coding skills are non existent, yes I can change the speed of the blink, but that's it, so I will watch your endeavours with great interest.
Would be nice to see a simple, robust, cost effective GTI controller out of the box, so to speak.
OperaHouse:
Mistakes will be made. Lessons will be learned. Good thing these broken ones are so cheap. Managed to fix everyone so far. I find the idea exciting that I can put a GTI right at the solar panel and send high voltage 160 feet to the garage and minimize losses. There will likely be problems having multiple GTI on just a 300W sine wave inverter with very little load, even with automatic dump load.
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