Power flow control in low voltage networks

[Adam1980]

Dear members,

i am designing a system for a building which recieves its main supply from a wind turbine.

The building is still connected to the grid in order to provide a stable operation for the wind turbine (IG).

The utility however prevents injecting active power into the grid.

Other than regulating the active power produced by the wind turbine through pitch/yaw control or using dummy loads are there any available technologies in the market which regulates power transfer on low voltage grids?

Thank you

 

[7anoter4]

If the Building is still connected to the Grid that means you need the Grid just in case the wind is not available. In this case you may
"accumulate" the wind using a kind of water tower and fill it with a pump with the remaining unused power and use the water gravity potential
acting a turbine-generator as an alternative source when the wind is not available.

 

[dpc]

Welcome to the real world. Wind turbine output cannot be regulated to fit the building's power demand profile. The concept that a building will "receive its main supply from a wind turbine" is inherently incorrect and the source of your dilemma. A wind turbine can help offset the power being used by the building, but it can't be the main supply.

The pumped storage mechanism mentioned is one option as would be large battery bank that could be charged when there is excess power being generated.

 

[Adam1980]

Hello thanks, for your replies.

What is the solution if this storage is full ?
any other ideas/innovations?!

Thank you.

 

[davidbeach]

What is the solution if this storage is full ?

It wasn't sized large enough. Or, the building load was sized too small, or the wind turbine was sized too large. You have to be prepared, some how, to spill wind and not generate.

 

[dpc]

Make the building bigger?

I'm curious about the utility's refusal to allow export of power. Is this in the US?

 

[davidbeach]

Well, if "low voltage networks" in the thread title means network systems, particularly spot networks, then the prohibition on export is absolute and absolutely necessary. On the other hand, the locations with spot networks, or area networks for that matter, don't coincide will with areas of significant wind generation.

 

[odlanor]

davidbeach,
I guess this applied to any distributed generation.

 

[davidbeach]

Not necessarily. We have no problems with power exported from the customer back to the distribution system except for the network areas downtown. The network protector will trip instantaneously for reverse power and the whole building will go black.

 

[odlanor]

I mean , producer can export only in parallel with distribution system ,never isolated.

 

[LionelHutz]

I think dpc gave the correct answer. I personally don't believe it is possible to combine the wind and utility on a common AC bus and not back-feed the utility.

You could possibly do it by rectifing the incoming utility and wind generator onto a single DC bus feeding a large cap bank. Run the building via a large UPS powered by the DC bus and/or directly off the DC bus. Put a load dump on the DC bus that operates when the voltage reaches a certain threshold which is capable of absorbing the excess load from the wind generator. You could possibly use feed-back from this load dump to control the pitch/yaw of the wind generator.

 

[rasevskii]

What sort of power levels are we talking about here? Is it tens of kW or a couple MW? What is the interconnection voltage level? Is it MV or LV like 220/380 or 480V...

Why does the utility not agree to backfeed? prc above gave the best answer: you cannot do it, the utility has to provide the stability and frequency regulation.

Unless it is a very small system (some few kW) all storage options are impractical and/or outrageously expensive.

rasevskii

 

[FreddyNurk]

I don't believe that pitch/yaw control of the turbine is going to be fast enough to prevent dynamic export onto the grid for short periods of time.

There is a solution on the market for similar applications, though whether its applicable to your situation is another thing entirely.

I don't currently work for the company in the link, but it may be worth looking into.

 

[DTR2011]

How much is this system going to cost($/kW)?

 

[Adam1980]

The building is in Russia and for some reason they have that requirement. Between the wind turbine and the battery storage already designed the system will be expensive but the client is asking for innovation in design since it will be a pilot project.

 

[waross]

How about feeding loads directly.
Heating is a good choice. You can feed electric heaters with as much energy as is available and reduce your heating costs.
It has been suggested that feeding the DC bus of an inverter is a way to avoid back-feeds to the utility. You may consider driving the AC systems with VFDs and feed solar energy to the DC bus.
There may be times when you have excess energy.
Storage systems such as flywheels, pumped storage or batteries will be expensive to start with in smaller sizes and will be an excellent example of the law of diminishing returns as the size increases.
One use of storage may be to save excess energy in gusting conditions. The combination of demand on the solar system and overproduction of energy during high gusting winds make this a small window.
The cost per KWHr of a storage system will be very high.
My suggestion:
1st; Electric heating.
2nd; Feed the DC bus of VFDs.
3rd; Don't try to save energy for future use. If you must waste energy as part of your control scheme, boil water.


Bill
--------------------
"Why not the best?"
Jimmy Carter