Gas Turbine Free Governor Mode of Operation

Thanks CSA. I will most certainly carry out test when suits operators and post the results.

Thanks for your reply.
Thanks to CSA for the comment.

It takes time to read the explaination but it worth spending my weekend.

From the explanation, droop and FGMO is the same.

Preselected load is a mode where we keep the active power constant when connected to utility, regardless how is the grid frequency behaves. There is outer loop which is responding to "fight" with the droop loop to drive the TNR lower and hold the active power.

That is what I understand from the explanations.

But I can't see how this scheme actually works without numerical example between droop/FGMO and PSL.

If this PSL is banned & we must use the traditional droop control, why does the OEM keep coming with this mode with various other name?

Could you explain why Var/PF also bad?

I think you are abbreviating Pre-Selected Load Control as PSL.?.?.? (But you didn't explain that...)

Yes, for all intents and purposes Free Governor Mode and Droop Speed Control are the same. And, I get comments like this all the time:

>If this PSL is banned & we must use the traditional droop
>control, why does the OEM keep coming with this mode with
>various other name?

So, this particular OEM has realized the error of their way (that Pre-Selected Load Control doesn't allow the unit to respond to grid frequency disturbances properly) and has a new option--that people can PURCHASE (to correct what is a programming error from the OEM!)--called 'Primary Frequency Response.' It's yet another version of Pre-Selected Load Control that monitors frequency and when the frequency deviates from rated by more than a certain amount allows the unit to change load to respond as if only Droop Speed Control were active, then when the grid frequency disturbance is over returns the unit to the Pre-Selected Load Control setpoint--all without any manual intervention from the operator (whose job it is to properly recognize and respond to upsets in operation, but everyone expects the control system to do that instead!).

It's all about automating turbine and generator operation so that operators have less and less to do, and can be paid less and less and don't require as much training (which costs more money), and can eventually be replaced by AI (Artificial Intelligence).

Everyone would like numerical examples of every control function. But, that takes time and are very difficult to do on because we can't post images or graphs or tables very easily. (Actually, everyone these days would like YouTube videos of every control function.) I also believe that people should use the tools available to them to research the answers to some of their questions themselves. For example, you can configure the Mark VI Trend Recorder to get some excellent data--very easily--but most people are terrified to use it, even though it CANNOT cause the turbine to trip (which is why most people won't touch it--they falsely believe it will cause the turbine to trip, and they will lose their job if the turbine trips). I don't know if you're an operator or a technician or an engineer (it would help to know) but based on the questions you are asking it would be best if you could get access to Toolbox to start looking at running values and signals and trends. ANYONE can use Toolbox without the possibility of tripping the turbine--to trip the turbine when in Toolbox one would have to be forcing logic without understanding the knock-on effects of what they are doing, or they are changing Control Constants without understanding the knock-on effects of what they are doing, or downloading I/O Configuration or application code changes without understanding the knock-on effects of what they are doing.

And, ALL of those operations (forcing logic, changing Control Constants, and making and downloading I/O Configuration or application code changes) requires the use of a password--which if the passwords are not given out means the operations can't be done. And, there is another method of preventing making or saving unintended changes--by setting the 'Read Only' attribute of the Toolbox .m6b file to prevent any modifications from being made/saved.

The point is: It's possible to use Toolbox to troubleshoot and understand turbine operation without upsetting turbine operation or tripping the turbine. And, using Toolbox by operators and technicians <i>WHILE THE TURBINE IS RUNNING</i> should be encouraged in order to help them understand what is happening and how it's happening in the mythical and magical Mark VI. (It's neither mythical nor magical--it's just poorly documented, and there are LOTS of false beliefs and tribal knowledge (much of which is also false) that is spread about the Mark* and becomes gospel for many people.)

VAr/Power Factor control adjusts generator terminal voltage (by adjusting excitation being applied to the generator rotor) to maintain either a VAr or Power Factor setpoint. When there is a grid voltage disturbance (primarily voltage disturbances) that requires generators to maintain grid voltage VAr or Power Factor control will try, instead, to adjust their terminal voltage to maintain a VAr or Power Factor setpoint instead of a voltage setpoint. This is opposite of what grid regulators want generators to do during a grid disturbance. So, many grid operators/regulators are or are in the process of banning the use of VAr or Power Factor Control. This means the operators have to monitor the VArs being carried by their generator, or the Power Factor of their generator, and make manual adjustments to excitation to maintain a setpoint. Why do they have to do this? Because during the course of the day and over the week and months grid voltage varies--and that causes the generator VArs/Power Factor to vary. Which requires either manual intervention (the operators' job, essentially) or some kind of automatic control (VAr or Power Factor control).

The control system manufacturers are trying very hard to come up with more automatic control methods and schemes to prevent operators from having to make manual adjustments that are acceptable to grid operators and regulators. It's coming, it's just hasn't arrived yet. In the interim, operators are going to have to monitor VArs or Power Factor and make manual adjustments (which is really part and parcel of power plant operation).

Hope this helps! I strongly encourage you to get access to Toolbox and start to use and become familiar with Trend Recorder--at least. You can also create Watch Windows where you can put multiple signals to monitor (but not trend) to observe operation and response. They are both very powerful and useful troubleshooting and educational software tools--especially Trend Recorder. Also, learning to use Toolbox to observe sequencing and logic and algorithms is very valuable--and not difficult with a little practice.

A few sites (power plants) do allow their operators to have access to Toolbox--and it has made those operators and those power plants much more reliable and efficient. People are naturally curious, and without Toolbox passwords they can't hurt anything (or trip the turbine)--BUT they can learn and help troubleshoot issues and help others learn and become better operators and technicians. Many plants have HMIs designated as "engineering workstations" which are not in the Control Room and can be used by technicians, and even operations supervisors!, to learn and troubleshoot. There are some sites where this will never happen--but, it should--and those plants have more problems than they realize (because people don't properly respond to alarms and

And, if you have questions and need clarification--we at are always here to help!