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From: Badri Pattabiraman on 3 Feb 2010 14:05
Hallo Readers,

I am trying to simulate the process of Synchronization of a Synchronous Generator with an Electrical Grid. One of the condition for this phenomena is to have same phase sequence of both generator and the grid. When the sine wave corresponding to phases a, b and c of the generator are compared with the same of the grid, at certain time they are equal, at least two phases are equal, at this exact moment i close my synchronizing switch. I would like to know, how to make this comparison part.

Thanks and Regards,
Badri
From: Saurabh Mahapatra on 3 Feb 2010 19:51
Hi Badri,

Since I do not know what analysis or modeling you are doing, I would like to ask a clarifying question: if abc and a'b'c' represent the 3-phase sequences, do you consider the following cases as enough for closing the switch to synchronize:

abc AND a'b'c' phase shifted anticlockwise through 120 degrees. So that a corresponds to b', b to c', and c to a'.

All of these should be equivalent cases for synchronization(assuming both the 3-phases are rotating in the same direction) of abc<->(a'b'c'<->b'c'a'<->c'a'b')

Because if that be the case, then you will have to synchronize when any of the above patterns occur. It is not a simple a to a', b to b', and c to c' sync which can be done.

Also, have you thought about the case the syncronization can never happen? The machine's 3-phase moves in opposite direction in comparision to the 3-phase grid. Then, your calculations will wait forever to synchronize.

Thanks,

Saurabh
From: Badri Pattabiraman on 4 Feb 2010 05:47
"Saurabh Mahapatra" <saurabh.mahapatra(a)mathworks.com> wrote in message <hkd5lq$8mg$1(a)fred.mathworks.com>...
> Hi Badri,
>
> Since I do not know what analysis or modeling you are doing, I would like to ask a clarifying question: if abc and a'b'c' represent the 3-phase sequences, do you consider the following cases as enough for closing the switch to synchronize:
>
> abc AND a'b'c' phase shifted anticlockwise through 120 degrees. So that a corresponds to b', b to c', and c to a'.
>
> All of these should be equivalent cases for synchronization(assuming both the 3-phases are rotating in the same direction) of abc<->(a'b'c'<->b'c'a'<->c'a'b')
>
> Because if that be the case, then you will have to synchronize when any of the above patterns occur. It is not a simple a to a', b to b', and c to c' sync which can be done.
>
> Also, have you thought about the case the syncronization can never happen? The machine's 3-phase moves in opposite direction in comparision to the 3-phase grid. Then, your calculations will wait forever to synchronize.
>
> Thanks,
> Saurabh

Hallo Saurabh,

Thanks for your reply.

To start with i am modelling a Synchronous Generator and Electrical Grid. the Synchronous generator is already modelled and Grid is still to be modelled.

Coming to the Topic, the idea is to achieve the process of synchronizing the generator with the Grid.

There are 3 condition for Synchronization
The voltage, the frequency and phase sequence of both generator and grid are to be same.

Having described the background, i would like to come to your clarifying question.

<do you consider the following cases as enough for closing the switch to synchronize: abc AND a'b'c' phase shifted anticlockwise through 120 degrees. So that a corresponds to b', b to c', and c to a'.
>

Yes i consider this case enough to synchronise. You have understood the concept quite clearly. For any of this case of abc<->(a'b'c'<->b'c'a'<->c'a'b'), i have to close the switch and synchronise.

Only when my generator is having a phase sequence abc and the grid is a'c'b'( or anything in that sequence), i cannot synchronise.

Now the question is how to check the phase sequence and realise synchronisation.

would be great to have some ideas or tips or solution for this.

Thanks and Regards,
Badri
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