weressl
Esteemed Member
I was trying to be nice.........
I am not under such gentlemanly obligation, I am not British. :bye: I mean I should be, but somewhere along the line I stopped giving a flying.....:rotflmao:
I was trying to be nice.........
In this particular instance, he has little or no useful knowledge.
Grid-tied systems have requirements that are intrinsically hard to satisfy because the equipment is designed very carefully to NOT connect to something that isn't the electric grid.
The indication that he had no clue was suggesting that the 50Hz power be rectified and then converted back to 60Hz with a 4 quadrant VFD. That =can= be done, but controlling how much power is converted becomes its own problem. In particular, there still has to be a 50Hz signal that behaves sufficiently like the electric grid (or is stout enough that it can't be "moved" by the anti-islanding logic in the inverter) to keep the inverter from disconnecting.
A far simpler solution, and one that's guaranteed to work is to set the system up for AC coupling. Inverters that can AC couple are readily available and solve all the problems with a minimum amount of equipment and handle the change in the direction the power is flowing very automatically. They're also listed for the purpose and meet the appropriate UL and IEEE standards.
A far simpler solution, and one that's guaranteed to work is to set the system up for AC coupling. Inverters that can AC couple are readily available and solve all the problems with a minimum amount of equipment and handle the change in the direction the power is flowing very automatically. They're also listed for the purpose and meet the appropriate UL and IEEE standards.
Thank you for that,kwired.Why are you asking questions if you already have (or think you have) the answers? If you disagree with something give us logical reasons and don't just tell someone they don't know what they are talking about. He may not be all up to speed specifically with PV systems, but he does understand electricity and especially inverters.
tall -...A far simpler solution, and one that's guaranteed to work is to set the system up for AC coupling. Inverters that can AC couple are readily available and solve all the problems with a minimum amount of equipment and handle the change in the direction the power is flowing very automatically. They're also listed for the purpose and meet the appropriate UL and IEEE standards.
tallgirl from post 1 said:We have a growing amount of 50Hz 230 volt power (single phase of a 230/400 volt system) that's being produced at the office. Right now it is all being turned into heat courtesy of a rather large dump load.
The way things are wired right now, there is a several KW 50Hz power supply that is providing a grid reference to what I think is a 2 or 3KW solar array that is powering 50Hz microinverters. The microinverters are back-feeding the supply, which has its output paralleled with the dump load. So, if the sun isn't shining, the dump load is turning most of that 50Hz power into heat. And if the sun is shining, even more of it is turned into heat.
What are the code issues that might be associated with actually =doing= something useful with that power?
tallgirl from post 7 said:When the EE's were originally setting up the testing system, my proposal was a quad stack of OutBack gear -- a twin stack of 50Hz grid-interactive inverters, and a twin stack of 60Hz grid-interactive inverters, with batteries in the middle. Controlling the output of the 50Hz array with a contactor, with the coil power from the 60Hz grid, would have been fairly easy.
...I'm not completely privy to all the decisions, but my understanding is that the batteries were the deal-breaker. ...
...It's a lot easier and cheaper to just turn the electricity into heat -- I think we average 3 to 5KW on a 24 hour basis. That's $0.50 / hour, or $12 / day at residential energy rates. ....
You probably void your own product warranty in the process. But if it works, you could be the first company to plant a flag in ac coupled micro space.
tall -
I had to look up "AC coupled". Is this what you have in mind?
http://lses.org/version1/AC%20Coupling%20WHT%20Paper%20(2).pdf
If so, the output to the utility is 50 Hz. I read all nine pages. It appears you are looking for a method to use the excess energy to power 60hz equipment - not 50hz.
Or perhaps you were thinking the second inverter (the one tied to the mains) the be a 50hz input from the micro inverters and then 60hz output to the utility. I did not see any inverters that were "readily available" that will do this.
It certainly sounds like you are saying the existing test setup has micro inverters driving into a stable 50hz grid that has an integrated load bank. Or you are saying the micro inverters can drive the load bank directly and don't need a stable 50hz grid.
Which might it be? There has been enough wobbling I can't tell what the equipment is capable of and what you are trying to do. The posts leave me uncertain.
ice
Curiousity about the existing test setup: What is providing the stable external signal 50hz signal?...The current configuration is what you described at first -- a stable 50Hz supply feeding an array on the roof with a paralleled load bank. The microinverters can't operate, with the current firmware, without an external 50Hz signal due to anti-islanding requirements.
Of course, AC coupling (as currently defined here) to transfer power from 50 hz micro inverters to a 60Hz system is not possible, and you didn't like any of the profered solutions, so your original queries of how to use the waste heat power is no longer the topic?...A far simpler solution, and one that's guaranteed to work is to set the system up for AC coupling. Inverters that can AC couple are readily available and solve all the problems with a minimum amount of equipment and handle the change in the direction the power is flowing very automatically. They're also listed for the purpose and meet the appropriate UL and IEEE standards.
...What are the code issues that might be associated with actually =doing= something useful with that power?
Curiousity about the existing test setup: What is providing the stable external signal 50hz signal?
An over-sized power supply fed from the grid.
............And yes, the motor-generator would be an awesome solution.
I'm assuming that this is part of a testing process, so you need a consistent load, otherwise I would say power a motor/generator set, or something similar to convert it back to 60hz to recoup some of the power loss. Otherwise, plenty of hot water for the cafeteria?:lol: On a serious note, maybe a steam turbine/generator set? Don't know how much heat you are producing, so I don't know if that's viable. I have heard of "Tornado" type generating stations that use the heat rise to spin a turbine, which should have smallest effect on the load bank.
Really.............seems like something similar was suggested early on in the postings, just not selling it back to the POCO, utilizing the power on site.:roll:
For a synchronous set, little regulatory circuity needed. Set both sides up for a 1.0pf. Power should transfer di-directionally. Which ever side has the leading power angle will transfer power to the other side. That's the beauty of what one might call mechanical feedback. Gets rid of a cubic foot (or cubic yard) of electronics....If you do come up with a way to transfer the dumped power back to the 60 Hz grid, you will need additional regulatory circuitry to control the amount of power backed, or else set it up for a constant maximum back feed, just as you would use a constant high power dump load.
I could see this being a problem with the MG set. (And the MG itself would not necessarily be stable enough and appropriately UL listed for grid feed.) ....
...Unless you are generating a really substantial amount of power from your 50 Hz GTI, I am not sure that it would be economical, regardless of the gut aversion to wasting the power.
Which can be replicated using solid-state power electronics.And yes, the motor-generator would be an awesome solution.
It's sort of a different way of stating what my mom is fond of saying: No drop of water blames itself for the flood.Best signature line I've read in a long time, Ice man. Thanks.