What if active power reach inverter limit and I want to adjust the reactive power too

[Spanky007]

Hi everyone, I just curious when I adjust the reactive power (via power factor, etc) and at noon the PV array will generate the full power that reach the limit MVA of inverter.

For example
PV array at 1 MW and inverter limit at 1 MVA
if I adjust the pf to 0.9 what the result can be at noon?

1. The active power will be 1 MW and reactive power will be 0 or
2. The active power will be 0.9 MW and reactive power will be 0.** (something) or
3. It can adjust both results

If it (2) where the different active power go away?

 

[Gavin A]

Re: What if active power reach inverter limit and I want to adjust the reactive power

what are you trying to achieve there, and what inverter are you using?

It looks from the wording like you might be using SMA, in which case I'd strongly suggest you contact their technical department, as adjusting the PF settings on a 1MW system doesn't sound like a sensible idea unless you really know what you're doing and why.

 

[Spanky007]

Re: What if active power reach inverter limit and I want to adjust the reactive power

I just research the operation of inverter and I has seen the operation to adjust reactive power by inverter, so I just curious about how it will doing in that case.

 

[jason121]

Re: What if active power reach inverter limit and I want to adjust the reactive power

Unless you know the difference of KW, KVA, KVAr and have HNC in electrical dont bother

 

[Spanky007]

Re: What if active power reach inverter limit and I want to adjust the reactive power

I know the different, I just don't know the working of grid-tie inverter to provide the reactive power to the gird.

 

[Gavin A]

Re: What if active power reach inverter limit and I want to adjust the reactive power

I know the different, I just don't know the working of grid-tie inverter to provide the reactive power to the gird.

My advice stands - if this is a 1MW system then you need to contact SMA serviceline and discuss this with their technical support team as they have a lot of experience of this in different countries - assuming this is SMA, if not then contact the technical support line of your inverter manufacturer.

This is not the level of advise that you're going to get from this forum.

If it is SMA though, then I do have a relevant document I can email you that might either help or confuse you on this subject.

 

[ian.settle1]

Re: What if active power reach inverter limit and I want to adjust the reactive power

As the op is in Thailand he would need to speak to someone local rather than post on a UK forum.

 

[Spanky007]

Re: What if active power reach inverter limit and I want to adjust the reactive power

Ah, thank Gavin A, can you send your document to my e-mail?
As I said before I just research the operation of inverter, I'm not install the PV system or anything.

As far as I research (SMA) they say that if inverter reach it limit the active power will decrease to (as example) 0.9 MW to create the Q for pf=0.9

Just curious that can the inverter provide full P (1MW) and not create Q (0MVar) for maximum power inject to the grid.

 

[Gavin A]

Re: What if active power reach inverter limit and I want to adjust the reactive power

ok, if it's just for research purposes then I suppose a theoretical discussion won't hurt.

first of all though I need to confirm what you're meaning by some of the terms you're using, as you're discussing the pf, which in the UK usually stands for the power factor, but I get the impression that you might actually be just using it to mean that the inverter limits to 90% of its rated output, which would be a far less complex thing to discuss.

 

[Spanky007]

Re: What if active power reach inverter limit and I want to adjust the reactive power

It a power factor (as far as I know the inverter can create Q by adjust the power factor isn't it?)
The meaning is if PV array can create 1 MW.
The inverter output is 1MVA. And adjust power factor of inverter to 0.9 what will happen?

 

[Gavin A]

Re: What if active power reach inverter limit and I want to adjust the reactive power

It a power factor (as far as I know the inverter can create Q by adjust the power factor isn't it?)
The meaning is if PV array can create 1 MW.
The inverter output is 1MVA. And adjust power factor of inverter to 0.9 what will happen?

Well, it'll alter the power factor at which the inverter is feeding power in to the grid, which can be a useful thing to do if you're trying to balance the local power factor eg on a factory where there was lots of heavy machinery that was creating issues with the power factor on site.

So essentially if you have a reason for wanting to output at a different power factor to the standard 1 (ish), and the grid operator is happy with this, then fair enough, if not then don't go messing with it.

 

[Spanky007]

Re: What if active power reach inverter limit and I want to adjust the reactive power

Is the active power decrease when adjust the pf?

 

[Gavin A]

Re: What if active power reach inverter limit and I want to adjust the reactive power

Is the active power decrease when adjust the pf?

erm, there are multiple ways this can work, but to be honest, I haven't really got my head around it all properly myself yet, these are pretty none standard settings.

Again though, it'd help if you'd explain exactly what it is you're trying to achieve.

 

[SpitfireW'sale]

Re: What if active power reach inverter limit and I want to adjust the reactive power

The active power P is changing when adjust the pf and it's always getting lower PF<=1. S(apparent) = P / cosφ => P= S * cosφ where cosφ = power factor.

I would recommend you not change the pf. The grid network is designed to accept up to a certain amount of reactive power (either lagging or leading) based on demand and DNO has given the connection agreement to connect your system taken into account Power Factor close to unity (1). If you export lots of reactive power to the grid, there should be some imposed fines to you by the DNO.

In addition, your FIT is based on the active power not the apparent or reactive power. So by decreasing the pf, you loosing money.

 

[Gavin A]

Re: What if active power reach inverter limit and I want to adjust the reactive power

The active power P is changing when adjust the pf and it's always getting lower PF<=1. S(apparent) = P / cosφ => P= S * cosφ where cosφ = power factor.

I would recommend you not change the pf. The grid network is designed to accept up to a certain amount of reactive power (either lagging or leading) based on demand and DNO has given the connection agreement to connect your system taken into account Power Factor close to unity (1). If you export lots of reactive power to the grid, there should be some imposed fines to you by the DNO.

In addition, your FIT is based on the active power not the apparent or reactive power. So by decreasing the pf, you loosing money.

he's in Thailand.

But yes, unless there is a specific reason for it, and the grid operator is happy with thie being done, then PF correction settings should be left well alone.