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i have two units one with droop mode and the other with iso mode connected to a grid. and the unit with a droop mode take a trip what will the behavior of the unit with iso mode.
The short answer is that the isoch unit will automatically pick up the load the droop unit was supplying and maintain the frequency. This supposes the isoch unit had the ability to pick up the load without exceeding its rated output <b>and</b> that there is no load sharing or power system monitor connected to and controlling the units. In other words the conditions are just as stated: simply two units supplying a grid, one in isochronous mode and one in droop mode--nothing more, and nothing less in the way of control schemes.
Phil Corso,
I would like to answer your question with a question, because the original poster didn't give us any more information than that there were two generators with their prime movers connected to a grid, failing to note (and I'm sure we'll never know the answer to this question) if there were any other generators connected to the same grid.
So, Phil Corso, what is your supposition regarding the size of the grid?
I didn't suppose anything more than two generators and their prime movers, one being operated in isochronous mode, the other in droop mode, powering an electrical load connected to a distribution system (a grid), and that the generator whose prime mover is in droop mode was suddenly separated from the grid. Just as the original poster had stated. And just as I stated in my response.
What do you suppose I supposed, Phil Corso?
My understanding, however, of a generator with its prime mover running in isochronous mode connected to any grid is that it should respond to a loss of another generator and its prime mover by increasing its power output to make up for the loss, up to its rated power output. As the loss of generation would tend to make the grid frequency decrease the isochronous governor should respond immediately by increasing the torque being produced by the prime mover so as to keep the frequency (prime mover speed) constant. (Of course, this presume the prime mover and generator are mechanically coupled together.)
(I'll admit to supposing you would respond to my response, though, I did suppose it would include at least one exclamation point.)
I would like to answer your question with a question, because the original poster didn't give us any more information than that there were two generators with their prime movers connected to a grid, failing to note (and I'm sure we'll never know the answer to this question) if there were any other generators connected to the same grid.
So, Phil Corso, what is your supposition regarding the size of the grid?
I didn't suppose anything more than two generators and their prime movers, one being operated in isochronous mode, the other in droop mode, powering an electrical load connected to a distribution system (a grid), and that the generator whose prime mover is in droop mode was suddenly separated from the grid. Just as the original poster had stated. And just as I stated in my response.
What do you suppose I supposed, Phil Corso?
My understanding, however, of a generator with its prime mover running in isochronous mode connected to any grid is that it should respond to a loss of another generator and its prime mover by increasing its power output to make up for the loss, up to its rated power output. As the loss of generation would tend to make the grid frequency decrease the isochronous governor should respond immediately by increasing the torque being produced by the prime mover so as to keep the frequency (prime mover speed) constant. (Of course, this presume the prime mover and generator are mechanically coupled together.)
(I'll admit to supposing you would respond to my response, though, I did suppose it would include at least one exclamation point.)
J
joeh4of5
I do not suppose to understand the parameters of the discussion, but this is a subject matter in which I have had a distinct experience with and hope that it is helpful.
This is the situation: a cogen which provides ~15% of thermal and power output to a steam host. The grid becomes separated and the cogen typically trips off, taking all parties black. With some adjustments, the prime mover can switch from droop to isochronous and reject load in a way that maintains the operation for the cogen and steam host. There are provisions for this; controls have to be well coordinated to prevent overspeed/current situations. The residual load has to be substantial.
If you equate this to an island with two generators -- the isochronous machine should maintain the load, provided the controls are well adjusted and the load rejection is not too severe.
This is the situation: a cogen which provides ~15% of thermal and power output to a steam host. The grid becomes separated and the cogen typically trips off, taking all parties black. With some adjustments, the prime mover can switch from droop to isochronous and reject load in a way that maintains the operation for the cogen and steam host. There are provisions for this; controls have to be well coordinated to prevent overspeed/current situations. The residual load has to be substantial.
If you equate this to an island with two generators -- the isochronous machine should maintain the load, provided the controls are well adjusted and the load rejection is not too severe.
This response is really more appropriate to another, current thread:
http://www.control.com/thread/1303904581
As you have stated, we can't know all the particulars of this situation, or if it's just a theoretical question. The poster didn't provide enough information to make any other conclusion or provide any other information.
As you have also stated:
>With some
>adjustments, the prime mover can switch
>from droop to isochronous and reject
>load in a way that maintains the
>operation for the cogen and steam host.
>There are provisions for this; controls
>have to be well coordinated to prevent
>overspeed/current situations. The
>residual load has to be substantial.
Most things are possible with enough tuning and adjustment.
It's just the patience that's required to do the analysis, perform the tuning, and make the adjustments that's the issue at most plants.
Also, many plants were not originally designed for this operation ("islanded"). And the modifications necessary are sometimes quite many, but, it can be done.
http://www.control.com/thread/1303904581
As you have stated, we can't know all the particulars of this situation, or if it's just a theoretical question. The poster didn't provide enough information to make any other conclusion or provide any other information.
As you have also stated:
>With some
>adjustments, the prime mover can switch
>from droop to isochronous and reject
>load in a way that maintains the
>operation for the cogen and steam host.
>There are provisions for this; controls
>have to be well coordinated to prevent
>overspeed/current situations. The
>residual load has to be substantial.
Most things are possible with enough tuning and adjustment.
It's just the patience that's required to do the analysis, perform the tuning, and make the adjustments that's the issue at most plants.
Also, many plants were not originally designed for this operation ("islanded"). And the modifications necessary are sometimes quite many, but, it can be done.
C
CTTech
The simple answer is to consider an iso machine as a zero droop machine. Other than mechanical issues, droop is zero.
