Could you please explain me how I can adjust settings and parameters of a govenor speed controller for a parallel turbin-generator system?

Here we have three turbin generators (2.2 MW), unfortunately, they work very unstable in parallel mode and so shut down happens very soon. We know system should be in isochronous mode while one generator is used, and if any other generator comes to be paralled with first one should be in droop mode. Our controller System is equipped with a load sharing system, and PLC, but we not sure how to set the parameters of our turbin generator system in PLC.

Could you please help us with some information,

Best Regards,
Mohammad Samie,

 

Can you please explain us how you operate the turbinE-generators? If they are operated to supply an load which is not connected to any other grid, then one turbine would usually need to be operated in Isoch mode and if additional generation is required then they would have to be operated in Droop mode. If the load/turbinE-generators are connected to a grid with other turbinE-generators they all need to be operated in Droop mode.

Now, let's consider an example where the units are supplying a load which is independent of other generation and is 3.5 MW. In this case, two generators would have to be operated in parallel, one of them should be in Isoch mode and the other should be in Droop Mode. The unit which is operating in Droop mode could be loaded up to 2.2 MW, meaning that the Isoch unit would be at 1.3 MW. The third unit could be paralleled in Droop mode and loaded up to 1.3 MW, which would reduce the load on the Isoch unit to 0.0 MW. But, if the load was steady at 3.5 MW, the *total* of the generation cannot exceed 3.5MW *at a stable, steady frequency.*

In the case where all three units were operating and the load was at 3.5 MW, with one of the Droop units at 1.0 MW, the second Droop unit at 1.5 MW, the Isoch unit would be running at 1.0 MW. If the load suddenly increased to 3.9MW, the Isoch unit's load would increase to 1.4 MW, and the loads of the two Droop units would remain unchanged at 1.0MW and 1.5 MW.

The above example presumes there is *NO* external control such as from the PLC and/or load sharing system you "describe." In theory, if programmed properly, the load-sharing system and/or PLC should be able to recognize the operating modes and with some operator input should be able to balance the load as the operator wants it balanced and control frequency and load stably. But, that presumes the devices are configured and programmed properly--which is impossible to know for us.

Now, let's say that the load was at 3.9 MW and one of the Droop units was at 2.2 MW and the other was as 1.5 MW, leaving the Isoch unit at 0.4 MW, and suddenly the load decreased by 0.5 MW. In this case the Isoch unit would drop to 0.0 MW and if the operators took no action the grid frequency would increase above design--until either the load increased to more than 3.7 MW or one of the droop units was reduced by approximately 0.2 MW.

There is this huge misconception that "island" operation (maintaining frequency on a "small" grid independent of a grid with other generators) can be made to be completely automatic and require little or no operator input. There *are* some loads/applications which can be made to operate without trained operators under typical conditions, but those are few and far between. Small loads which can fluctuate or vary 10% of generation require some operator manipulation, and that means trained operators (which are at a premium in the world today, especially in power plants). Maintaining generation on small independent loads is not for the average power plant operator; Droop speed control on a large grid virtually relieves the power plant operator of most of the concerns of operating a power plant. This has lulled even their supervision into thinking, "We can supply power to our Customer (a factory or a manufacturing plant) in the event of a grid separation simply by purchasing a load sharing scheme and a PLC and we don't have to train our operators--the control system will take care of everything!" Unfortunately, there are companies who will sell this equipment to these managers without the proper caveats.

I would recommend you contact the company which supplied the load-sharing device/PLC and consult with them for how the system is capable of being operated versus how it is being operated and how it was programmed to operate. You should be prepared to explain how you operate the units and provide all the drawings and information you have for the site and the conditions of operation.

Now, there may be some droop settings or some exciter settings which could be tuned to help, but we just don't have enough information about the conditions and the equipment to comment.