Synchronization of Multiple Generators onto the Grid.

[sykimk]

Hello,

I will do commissioning tests for a plant synchronization system to control a group of turbine generators (2 ~ 3 generators together) to be synchronized onto the grid. FYI, GE CTG rating: 40 MW & Siemens STG rating: 82 MW. For our system, at least 1xCTG, and 1xSTG are to be controlled together for generation bus synchronization with the grid. Of course, the generation bus with multiple generators runs in island mode.

To me, this situation would be quite challenging since CTG & STG controller's responses are not the same. So, I am really concerned if this synchronization would really work although it would take a quite long time.

Do you have any experiences with the synchronization of multiple generators onto the grid? Do you have any thoughts and/or advice? Anything will be very helpful for me.

Thanks in advance.

 

[waross]

1. My first solution would be to synchronize the sets one at a time unless or until some other factor dictated group synchronization.
2.

To me, this situation would be quite challenging since CTG & STG controller's responses are not the same.

This is not so much a synchronization problem as it is a running problem in regards to step or block loads.
When experiencing a step load increase, the generator with the fastest response, that is the ability to increase output the fastest, will hog the load.
As the other sets catch up, they will pick up their share of the load.
And this is not always a controller issue.
Given the same increase in control input, the Steam Turbine Generators will probably pick up the load in initially and then the Combustion Turbine Generators will catch up.
On the other hand we had a plant that started a large motor on two diesel generators in parallel.
One diesel had an electronic governor and the other had a hydraulic governor.
There was no problem synchronizing the generators.
First thing in the morning on a cold start, the electronic governor would hog the load and trip the generator breaker when a motor start was attempted.
After running for 20 or 30 minutes to warm up the oil, the hydraulic governor would respond fast enough to avoid a breaker trip.
I hope that this illustrates some of the difference between control response and prime mover response.


Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[crshears]

What Bill said.

Prime mover / governor / controller response characteristics should as a matter of course be adjusted so that when islanded together as a group [ meaning without grid interconnection ] the units will play well together in the sandbox when it comes to handling step loads etc. In my experience, where this has been done, synchronizing an islanded plant back onto the grid poses no significant problems; a number of our connected customers do so routinely.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]