Micro Inverters question

[foggysail]

Mike--thanks for your knowledgeable reply. I have no desire to see solar provided AC power during times of a grid outage.

[Mike90250]

All micro-inverters legally for sale in the USA, have an internal frequency reference, so they can verify the Grid is stable for 5 minutes, before trying to sync and output power to the grid.

"Faking" the grid might work, until the solar puts out more power than your loads, then things start burning up, usually the generator first - because the solar is trying to dump excess power into it. Might work with 100 extra watts, but you are risking your gear and fire insurance policy

[foggysail]

The thing people don't understand with these "create a microgrid island" thoughts is: Where does the power from the solar panels go?
It has to go somewhere or the 240Vac is going to rise up.. There is nothing to regulate it. There has to be a balance between the power coming in and the power going out. A balance between the line and load. The grid has super low impedance(resistance) so that your paltry 7kW has virtually no affect on it.
Your little lithium battery and inverter has no way to absorb power, only put out power. The solar inverter is going to try to make power at 240Vac to match the "island" inverter but it too is only making power. Unless the load is enough to absorb all the solar power and allow the Island inverter to create the rest can it serve as a regulator of the voltage. Ain't gonna work.

OK, I am still wading into this stuff and found this post while searching for possible microinverter recommendations. The purpose of my post is to question how the section I bolded can be real. For example, if a system is operating, producing, and transferring power to a grid when the electrical path to the grid is interrupted by any means such as by the panel's safety disconnect or a circuit breaker it should not allow the inverters to self destruct due to a surge in the output voltage.

I would expect that the lack of a sinewave at an inverter's output will automatically cause the inverter to stop operating. Why would a microinverter have an internal clock when it is designed to operate in sync with an AC load? This is important to me because I need whatever microinverter I end up using to also provide the code's rapid shutdown.

Thx--

[Ampster]

My use of dirty power is to indicate power with quality that does not match what the target device loads expect and frequency variation is a factor (example explanation: http://www.tesengineering.com/electr...s-dirty-power/). If "dirty" is controversial then I would be perfectly happy with "abnormal".

I am happy with any term that you want to use, now that I understand it is fairly common with or without a hybrid inverter. I am not happy with the unreliable and expensive rates for distribution and transmission and other costs from PG & E. I am happy with the energy, benefits and dividend I get from my CCA, Sonoma Clean Power. I am going to run most of my loads and car charging from solar as soon as I get my new pack commissioned.. What extra solar generation I store on the grid I can use at off peak rates to supplement EV charging.

[RKCRLR]

I believe my water iron filter uses frequency to keep track of time. If the power goes out and then comes back on, the time is off by the amount of time the power was out. I didn't think of this until I read this thread. So, I may have a problem there.

[inetdog]

My use of dirty power is to indicate power with quality that does not match what the target device loads expect and frequency variation is a factor (example explanation: http://www.tesengineering.com/electr...s-dirty-power/). If "dirty" is controversial then I would be perfectly happy with "abnormal".

Good idea, to avoid incorrect impressions and associations.

[solardreamer]

My use of dirty power is to indicate power with quality that does not match what the target device loads expect and frequency variation is a factor (example explanation: http://www.tesengineering.com/electr...s-dirty-power/). If "dirty" is controversial then I would be perfectly happy with "abnormal".

[SunEagle]

I guess there are several definitions of dirty power. I always thought most generators put oit dirty power, but what do I know.

Some generators do give out dirty power but based on my experience the majority of offenders are devices; like computers, VFDs, LED lighting, etc that generate harmonics do the most damage.

[Ampster]

I guess there are several definitions of dirty power. I always thought most generators put oit dirty power, but what do I know.

[SunEagle]

Did I miss something ? What is the Dirty Power y'all are talking about ? +- a couple Hz is not "Dirty" Waveform distortion beyond 5% is beginning to get a bit ragged and I doubt most sub $500 UPS would even be able to notice. Often grid power is dirty from the neighbor down the street running a vacuum cleaner or Billy Bob and his arc welder. There's a lot of trash generated in households that radiates out on the power grid all the way to the transformer. I don't see how frequency shifting is getting to the point of dirty power. Heck, light dimmers throw a fair amount of trash on the power line as their triacs start chopping. Modern ones not as bad as the ones from the 70's

Dirty Power is a product of stray harmonics or voltage spikes and dips. Those are created from solid state power supplies that continually switch on and off. Frequency change does not contribute to dirty power.

[NewBostonConst]

I wonder if this 60.5hz frequency change to allow the grid to modulate power was not planned at all and it was an idea they fell into.

I think they haven't used it yet because they can't physically do it. Those greedy power companies do everything they can to stop their competition. DTE in Michigan is a bad company.

Think about the grid being stressed and the power company wanting to raise the frequency to 60.5 They would have to raise the energy to all there generators at the same time to get everything spinning faster. On a macro level that is huge. Wish I had the know how to calculate it.

Then the implications if not all of them do it and two grids are are connected together but not at the same frequency, my guess is something is going to blow. Do we see the next blackout of a whole state the first time they try it? I am ready with my backup power and popcorn in the cabinet.....Life is good.

[Mike90250]

Did I miss something ? What is the Dirty Power y'all are talking about ? +- a couple Hz is not "Dirty" Waveform distortion beyond 5% is beginning to get a bit ragged and I doubt most sub $500 UPS would even be able to notice. Often grid power is dirty from the neighbor down the street running a vacuum cleaner or Billy Bob and his arc welder. There's a lot of trash generated in households that radiates out on the power grid all the way to the transformer. I don't see how frequency shifting is getting to the point of dirty power. Heck, light dimmers throw a fair amount of trash on the power line as their triacs start chopping. Modern ones not as bad as the ones from the 70's

[Ampster]

Okay I understand where you are coming from. When I get my pack reconfigured I will take my system off line to see how bad it is. My guess, correct me if I am wrong, is that the frequency shifting issue only would occur when the GT solar needs to be modulated. It should not be an issue when just running off batteries or when the GT solar is running full bore covering house loads, EV charging and hybrid inverter battery charging. Worse case I will have to charge my EVs when the grid is down to keep from getting that dirrty power if it is a problem for me. That is a good application for the OpenEVSE to modulate my car charging based on my solar production. I have have so time to practice until this Fall before we get more public safety power outages.

[solardreamer]

There should not be "dirty power" under any condition from any UL certified GT or Hybrid inverter. Freq shift from 59-61Hz is not "dirty" and would not affect devices except clocks using power line as a frequency standard. (OK, maybe Aunt Martha's Iron Lung needs precise fq, but it would be on a special UPS circuit anyway) Then you would need hours and hours of shifted frequency to gain or loose a couple minutes. And historically, power companies have done shifting over a period of days but over the long term, they track it and zero out all differences.
Much gear works from 50-60hz. Motors are happiest right at 60hz but +-2hz won't hurt them or else all the folks that have run gear from conventional generators with sloppy B&S engines and weather-vane governors would have burnt up stuff.

Tesla Powerwall is UL listed and its default shifted frequency is 65Hz. Regardless, I have seen reports of things like modern LED light dimmer switches not working even at 62Hz. These are science project problems that average consumers should not have to worry about. Expensive home battery backup systems should always put out normal (traditional best practice 60Hz+/0.5 or at least Rule 21 indefinite 58.5-60.5Hz) to device loads.

[Mike90250]

............................
BTW, I am in the Bay Area and I am all for solar power and even home battery backup system but I just don't think an expensive backup power system should intentionally put out dirty power to loads ever. It's fine if they need shift frequency to modulate grid-tied inverters but just don't put that power out to device loads.

There should not be "dirty power" under any condition from any UL certified GT or Hybrid inverter. Freq shift from 59-61Hz is not "dirty" and would not affect devices except clocks using power line as a frequency standard. (OK, maybe Aunt Martha's Iron Lung needs precise fq, but it would be on a special UPS circuit anyway) Then you would need hours and hours of shifted frequency to gain or loose a couple minutes. And historically, power companies have done shifting over a period of days but over the long term, they track it and zero out all differences.
Much gear works from 50-60hz. Motors are happiest right at 60hz but +-2hz won't hurt them or else all the folks that have run gear from conventional generators with sloppy B&S engines and weather-vane governors would have burnt up stuff.