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VFD as grid forming

Jemsol

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I have 250 kw bluesun module connected to a two Siemens sinamic 160kw vfd and powering two 120 kw water pumps with a 300kw back up generator. VFD has two inputs DC and AC(generator) side. But currently we bought 5*50kw bluesun grid tie inverter. But there is no grid we are living off-grid. We suffering from DC power loss want to use grid tie inverter without grid, please advice me
 
You would need a lot of hybrid inverters capable of AC coupling that much GT capacity. If it were me I would just go with off grid inverters and sell the GT inverters.
 
Currently w
Did I understand correctly that you have five 50kW GT inverter
You would need a lot of hybrid inverters capable of AC coupling that much GT capacity. If it were me I would just go with off grid inverters and sell the GT inverters.
Can put some solar string to VFD via DC input and others via AC input of the VFD?
 
Can't I use vfd as grid forming?
No. The GT grid dependent inverters have a number of tests that they go through to make sure they are connected to a grid and not just a 60Hz signal. A hybrid inverter which can AC couple can pass those tests and perform the necessary frequency Watt shifts to control the output of the GT inverter. That capability costs money, which is why I suggested just using off grid inverters.
How much power do you need? A single 50 kW inverter is over 200 Amps which is larger that most main service panels in homes.
That raises the question about what the use case is for 250 kWs of inverter capacity? Growing vegetables in a warehouse, running a machine shop or Crypto mining?
 
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VFD just delivers PWM, expecting a motor load. I have hooked one up to light bulbs (also a transformer, for some experiments.)
Perhaps with a motor connected the waveform would begin to look like sine wave voltage, which is what GT transformers want. Or a motor-generator.

You may be able to run generator and have GT PV operate in parallel. This could be a problem with the GT PV backfeeding generator, although if it was running no-load up around 63 Hz and under load dropped to 60 Hz, it might interact with a GT PV inverter that does frequency-watts, e.g. UL-1741-SA

After studying Voc and Vmp, you may be able to feed PV into VFD driving pumps. If speed was ramped up and down to keep voltage around Vmp, that would be MPPT operation. If generator feeds VFD, at a moderately low AC voltage (Vpeak similar to PV Vmp), then PV feeding DC rail of VFD should supply what power it is able. May depend on type of VFD, if it is power-factor corrected, etc.

As Ampster said, an AC coupled battery inverter may be a good way. SMA sells one in Europe that is 60kW, uses a 500V or so (expensive?) battery. They also sell 1MW to 4MW units for the US. A Sunny Island multi-cluster could be about 100kW battery inverter, 200kW PV inverter, plus generator (I think.)

Ideally you would get a PV direct VFD. I've seen them advertised for smaller pumps.
 
No. The GT grid dependent inverters have a number of tests that they go through to make sure they are connected to a grid and not just a 60Hz signal. A hybrid inverter which can AC couple can pass those tests and perform the necessary frequency Watt shifts to control the output of the GT inverter. That capability costs money, which is why I suggested just using off grid inverters.
How much power do you need? A single 50 kW inverter is over 200 Amps which is larger that most main service panels in homes.
That raises the question about what the use case is for 250 kWs of inverter capacity? Growing vegetables in a warehouse, running a machine shop or Crypto mining?
We have banana and Cotton irrigation farm land more than 10,000 hectares.
We have three pumping stations of the same size such that. Solar Power 250kw generator 300kw at each pumping stations. Our pump drives are Siemens sinamic 160kw, pump power is 120kw at all the three stations. Use the solar system only for pumping purpose. No other load, we live in off-grid no electrical power. The VFD has two inputs
1. DC input for a solar we are using it
2. AC input for generator we use both input at same time .
Q. Can I use the generator input to actively the GTI? Or
 
I have 250 kw bluesun module connected to a two Siemens sinamic 160kw vfd and powering two 120 kw water pumps with a 300kw back up generator. VFD has two inputs DC and AC(generator) side. But currently we bought 5*50kw bluesun grid tie inverter. But there is no grid we are living off-grid. We suffering from DC power loss want to use grid tie inverter without grid, please advice me
Can you give a link to the inverters you have ?
Is it this hybrid inverter ?

 
I have 250 kw bluesun module connected to a two Siemens sinamic 160kw vfd and powering two 120 kw water pumps with a 300kw back up generator. VFD has two inputs DC and AC(generator) side. But currently we bought 5*50kw bluesun grid tie inverter. But there is no grid we are living off-grid. We suffering from DC power loss want to use grid tie inverter without grid, please advice me

Our pump drives are Siemens sinamic 160kw, pump power is 120kw at all the three stations. Use the solar system only for pumping purpose. No other load, we live in off-grid no electrical power. The VFD has two inputs
1. DC input for a solar we are using it
2. AC input for generator we use both input at same time .
Q. Can I use the generator input to actively the GTI? Or


What do you mean by "suffering from DC power loss"?

Are you referring to a problem with the DC input of VFD, which you were using for solar? And you want to move PV panels from VFD to inverter, using that together with VFD to run pumps?

Or do you want to use solar to power the inverters for a different load?

Can I connect the GTI to the AC side input Port of the VFD

Can't I use vfd as grid forming?

Possibly output of VFD, with motor connected, would form a grid. However, "Variable" frequency drive would be outside the 50 Hz or 60 Hz +/- 0.5 Hz (or so) range GTI inverter accepts under some conditions.

AC side input port of VFD, no grid would be formed. Generator, when running, would form grid, but isn't designed to receive excess power like from GTI inverter. If your GTI inverter can use current transformers for zero export, that might work; up to 100% of available PV would be added to AC power, relieving load from generator. In this case, generator needs to continue delivering frequency in-spec so GTI doesn't go off-line. If GTI performs frequency-watts, that might respond to such frequency variations, an additional way to curtail production in order to match load.


I'm not sure what you're trying to accomplish, since it seemed like generator + solar was meeting pumping needs. A drawing of how you're thinking of connecting equipment and explanation of how you want it to work would help. But probably different equipment designed to be grid-forming would be best.
 
What do you mean by "suffering from DC power loss"?

Are you referring to a problem with the DC input of VFD, which you were using for solar? And you want to move PV panels from VFD to inverter, using that together with VFD to run pumps?

Or do you want to use solar to power the inverters for a different load?





Possibly output of VFD, with motor connected, would form a grid. However, "Variable" frequency drive would be outside the 50 Hz or 60 Hz +/- 0.5 Hz (or so) range GTI inverter accepts under some conditions.

AC side input port of VFD, no grid would be formed. Generator, when running, would form grid, but isn't designed to receive excess power like from GTI inverter. If your GTI inverter can use current transformers for zero export, that might work; up to 100% of available PV would be added to AC power, relieving load from generator. In this case, generator needs to continue delivering frequency in-spec so GTI doesn't go off-line. If GTI performs frequency-watts, that might respond to such frequency variations, an additional way to curtail production in order to match load.


I'm not sure what you're trying to accomplish, since it seemed like generator + solar was meeting pumping needs. A drawing of how you're thinking of connecting equipment and explanation of how you want it to work would help. But probably different equipment designed to be grid-forming would be best.
My accomplishment is to use my new GTI inverters.
Sorry for my language!!!
Only by using solar power which can meet my pump power.
I think to divide my 250kw solar power in to two groups. (120kw- 60kw AC,60kw DC) and (120kw-60kw AC 60kw DC) then separately feed to VFD one for each. Via their respective AC and DC inputs. Just generator for backup use only. Can this way activate my GTI?
 
No, the Grid Tie Inverter can only be activated by the grid. You have no grid. You have wrong inverter for your use case.
Ok thank you. What controller do you recommend me for Pv-genset with GTI?
 
No controller will make a GTI inverter work without grid. You have the wrong inverter for your use case. The Manufacturer may have a suggestionbif one of their hybrid inverters will work.
 
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