Grid-tied inverter working during a grid shut-down?

jall

New Member
Here in the European Union, people is talking actually more and more that a great grid shut down is coming soon (long enough: several days afecting several countries). Because geopolitical reasons, the supply of liquidfied gas used for the generation plants (comes from Russia or Argelia ) has being "suspiciouslly" reduced what makes also the price of the electric energy today the most expensive ever.
So, a critical event seems to be coming I bet sooner than desired. My question is related to the principle "the grid-tied systems are useless if the grid is off". Have anyone here ever tested to fool a grid-tied inverter simulating the grid with a small (300 w or so) senoidal inverter with a "zero injection Current Transformer" to get the system working with the grid down?
Thanks and regards,

Jose (Madrid)
 

Cheap 4-life

Solar Enthusiast
Here in the European Union, people is talking actually more and more that a great grid shut down is coming soon (long enough: several days afecting several countries). Because geopolitical reasons, the supply of liquidfied gas used for the generation plants (comes from Russia or Argelia ) has being "suspiciouslly" reduced what makes also the price of the electric energy today the most expensive ever.
So, a critical event seems to be coming I bet sooner than desired. My question is related to the principle "the grid-tied systems are useless if the grid is off". Have anyone here ever tested to fool a grid-tied inverter simulating the grid with a small (300 w or so) senoidal inverter with a "zero injection Current Transformer" to get the system working with the grid down?
Thanks and regards,

Jose (Madrid)
They make inverters that are designed to create a mini grid to “fool” grid tie inverters into thinking there’s still grid power.
 

Jordi

Solar Enthusiast
Here in the European Union, people is talking actually more and more that a great grid shut down is coming soon (long enough: several days afecting several countries). Because geopolitical reasons, the supply of liquidfied gas used for the generation plants (comes from Russia or Argelia ) has being "suspiciouslly" reduced what makes also the price of the electric energy today the most expensive ever.
So, a critical event seems to be coming I bet sooner than desired. My question is related to the principle "the grid-tied systems are useless if the grid is off". Have anyone here ever tested to fool a grid-tied inverter simulating the grid with a small (300 w or so) senoidal inverter with a "zero injection Current Transformer" to get the system working with the grid down?
Thanks and regards,

Jose (Madrid)
Hi Jose, a possibility on how to do that is explained here:
https://diysolarforum.com/threads/sola-transformer-to-turn-on-grid-tied-inverter.28849/#post-386213

Pero dicen en las noticias que Espana esta más aislada de la red europea lo que hace que en caso de apagón aún haya menos probabilidades de que llegue a Espana. Los paises más interconectados son Alemania, Holanda, Francia,... y por tanto los que tienen el riesgo más elevado.
 

MurphyGuy

Solar Addict
You need a battery inverter capable of AC Coupling. SMA Sunny Island's can do it, Outback Radians, and I think Sol-Ark can do it as well, but you'll have to check on the Sol-Ark.

I use SMA Sunny Islands, and with the flip of a couple switches, my 11kW grid tied solar system goes into full off-grid mode.
 

DThames

Photon Sorcerer
A good grid tie inverter will be hard to trick. Also grid tie inverters are made to take 100% of available solar power and dump it to the grid. Some systems are made to work with a local grid but there needs to be a way to shut down or throttle the inverter's power output.
 

solar8484

Solar Enthusiast
Here in the European Union, people is talking actually more and more that a great grid shut down is coming soon (long enough: several days afecting several countries). Because geopolitical reasons, the supply of liquidfied gas used for the generation plants (comes from Russia or Argelia ) has being "suspiciouslly" reduced what makes also the price of the electric energy today the most expensive ever.
So, a critical event seems to be coming I bet sooner than desired. My question is related to the principle "the grid-tied systems are useless if the grid is off". Have anyone here ever tested to fool a grid-tied inverter simulating the grid with a small (300 w or so) senoidal inverter with a "zero injection Current Transformer" to get the system working with the grid down?
Thanks and regards,

Jose (Madrid)

I have done it many times. Grid-tied inverters (GTI's) are designed to produce power with any power source that can provide the necessary voltage (waveform, magnitude, frequency) and the ability to absorb the excess power produced by GTI's. AC coupled battery-inverter systems do this all the time with GTI's to form island grids. For most people, the main issues with these systems are complexity and cost. Your idea won't work as GTI's are designed to test the power source is robust (i.e. you need a power source that's similar in power capacity to your GTI system) and you need a way to absorb the varying excess power (i.e. power not used by your loads) up to the full power of your GTI system (i.e. when there is no load) at any moment for stability or the excess power will likely blow up your power source inverter or connected device loads.
 

MurphyGuy

Solar Addict
That was my question that got no response about :cry:
----> https://diysolarforum.com/threads/stupid-question-about-h6-solarcity.24592/
Faking a grid presence; from the response above from solar8484, about 'robustness' seems to be key. But cannot understand the 'power' capacity of the GTI. As long as it supplies the voltage; the "power" would be 'on demand' , wouldn't it ?

Can the 'done it many times' be exposed ?

NO.. The reason it won't work has two parts.. one could be solved, but there is no chance of solving the second.
Part1: You'd have to generate a grid quality signal.. No standard generator system, and even most inverters, won't be able to do this. But it is possible I believe with something as simple as a good Honda inverter type generator or a good quality battery inverter.

Part2: Once you generate that grid signal and the solar array starts making power, it will measure the voltage of the signal you created and then raise the voltage so the current flows into it.. Herein lies the problem that usually results in the magic smoke being released. As the grid tied inverter raises the grid signal, the current starts flowing back into the generator.. which I guess you can surmise, would be very very bad for the generator or whatever other power source you have hooked up...

It gets worse: As the system voltage goes up because the current has no where to go, the grid tied inverter, who's job is to pump current into the system, raises the voltage even higher to overcome the resistance to current flow..

Its a self-reinforcing snowball effect that results in the grid tied inverter causing something else to start smoking.

Battery Inverters capable of AC Coupling overcome this problem by shifting the grid frequency higher, which results in the inverter reducing its output if it is capable of FSPC (Frequency Shift Power Control).. and if it is not, then the battery inverter will eventually reach 62hz, at which point all grid-tied inverters will shut down.

There is one exception to the above:
It is possible to trick a grid tied inverter with a generator (inverter type?) so long as your loads are always greater than the maximum output the grid tied inverter can deliver. In this way, the load on the generator is reduced, but you must always make sure that your loads are always greater than the maximum output of the solar system. If you have 1000 watts of maximum solar output, then you must make sure you have at least 1000 watts of constant loads. If a cloud floats over and the solar dies out, the generator will make up the difference.. under full sun, the generator will just sit there running doing nothing.. There may be problems with this also that I'm not thinking of at the moment.. Truth be told, I'm not risky enough to take a chance on smoking an expensive generator.. and it will smoke if the solar has no where to send power..
 

Texas-Mark

Solar Addict
Its a self-reinforcing snowball effect that results in the grid tied inverter causing something else to start smoking.

Yep. I smoked two battery powered inverters testing different things trying to get this to work (reliably), and as soon as the load was less than the grid-tie was producing - poof went the inverters. Just not worth the risk IMO.
 

sunshine

Solar Addict
poof went the inverters.
A solution that helps @ 12v for over V may be upscaled to higher AC?
I have a cut-off relay on the pv input activated by 14.9v on the inverter side.

A similar HV relay on the PV side activated at a V slightly lower than the grid tied inverters higher V set limit would only replicate cloud cover thus reducing input load and saving the battery inverter.....needs testing!
 

solar8484

Solar Enthusiast
That was my question that got no response about :cry:
----> https://diysolarforum.com/threads/stupid-question-about-h6-solarcity.24592/
Faking a grid presence; from the response above from solar8484, about 'robustness' seems to be key. But cannot understand the 'power' capacity of the GTI. As long as it supplies the voltage; the "power" would be 'on demand' , wouldn't it ?

Can the 'done it many times' be exposed ?

I am not familiar with the H6 but it appears you want zero export limiting likely to avoid penalties from your grid operator. Some GTI's have zero export limiting function by using a CT to monitor grid current and adjust GTI power output to avoid exporting to grid. If the H6 doesn't have this function then you could look at variable power diversion controllers like Immersun. In any case, these things work at much slower time scale to be of use for real-time excess GTI power management in an island grid.
 
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