how to say "并网运行的自备电厂" in english?

Hi:

We would like to have more context in order to answer your question. Please post the entire paragraph.

Joe(we'll be waiting)Nation

There is nothing wrong with the statement by itself but joe raises the point we might be able to help more if we have it in context. But by itself it is correct english.
I might have put it thus "a self-contained plant connected to the State/National Power Grid for electricity"
There are other things it needs for operation and we tend to use power supply more locally as in a home or within a factory and talk about the State or national electricity grid for outside those places.

Lots of factories in China have to operate their own electricity generators either because of their remote locations or because their production cannot depend on the - unreliable - national grid. I think what the original poster is trying to express is "a self-contained manufacturing plant connected to the national electricity grid" - which is pretty much what you said. Do you read all the Chinese characters posted in the title, btw?

I surmised (guessed) from my knowledge of China. As for characters I have extensive knowledge of Chinese characters...I know man, woman and Ming, thats all....but I consider it extensive...
You read Chinese characters ???

It's not clear what you intend "self-contained" to mean. I wouldn't say it's commonly used to refer to manufacturing plants. Do you mean that it can generate its own power if it needs to, but usually uses outside power, unless that power goes down? It's not a phrase that's clear in and of itself.