I am sayin tha PMS can be not well setted for frequency control mode..
Grid frequency unstable - potential problems?
- Thread starter gubavac111
- Start date
Okay. I gotta say something here.
"Droop refers to changing the speed and frequency of the generator to proportionally change the load. That is, when the load of the generator increases, the speed or frequency is reduced by simple load feedback."
This is pure, unadulterated bull poop. Pure and simple. When connected to a stable grid, changing the load DOES NOT change the speed of the prime mover OR the generator (unless the two are not directly coupled or are not coupled through a reduction gear). It. Just. Doesn't. Happen. Not no how, Not no way.
It's drivel like this with incorrect terms that are not just misleading, but physically impossible.
Speed (generator speed) and frequency are directly related. If the generator speed (and prime mover speed) change, then the frequency will change. BUT, when a generator is SYNCHRONIZED to a grid with other prime movers and generators, the speed of the generator (and prime mover) CANNOT change. Not no how. Not no way. It. Just. Doesn't. Happen. Not on planet Earth.
It's no wonder people trying to learn Droop Speed Control have such a difficult time trying to understand it and learn the concept.
The concept of Droop Speed Control has been covered ad nauseum on (Speed)Control.com. Droop Speed Control loads a generator and prime mover synchronized to a grid with other generators and their prime movers by changing the prime mover speed reference--NOT the actual speed. (I'm sure that's what the author meant to write--but it's not what was published). And people only get to read what's published--not what was intended. And, most proof-readers and most editors are not technically savvy enough to catch serious mistakes like this. So, drivel gets published--and read--causing confusion.
I'm going to admit, I haven't looked closely at the data that's been provided (it's been a really crappy couple of days--and the crap just keeps on coming, folks). So, I've been just a LITTLE busy. And then I try to relax a little and read this.
As for what's happening in this thread--what is the source of the "shore power"? Other land-based generators and their prime movers? Or a solid, stable, large or "infinite" grid? Because unless the shore power generators are larger than the yacht-based generators and their prime movers, then it's possible there could be grid frequency disturbances.
It would be very informative to know when these frequency variations are occurring, what is the frequency of the voltage in an outlet--on the yacht, and on the dock? Also, what is the prime mover speed doing when these frequency disturbances are occurring?
Also, what is the frequency at an outlet on the shore/dock when the yacht is NOT connected???
But, this--this Droop Speed Control shite is just plain wrong. And, it can't go unchallenged.
"Droop refers to changing the speed and frequency of the generator to proportionally change the load. That is, when the load of the generator increases, the speed or frequency is reduced by simple load feedback."
This is pure, unadulterated bull poop. Pure and simple. When connected to a stable grid, changing the load DOES NOT change the speed of the prime mover OR the generator (unless the two are not directly coupled or are not coupled through a reduction gear). It. Just. Doesn't. Happen. Not no how, Not no way.
It's drivel like this with incorrect terms that are not just misleading, but physically impossible.
Speed (generator speed) and frequency are directly related. If the generator speed (and prime mover speed) change, then the frequency will change. BUT, when a generator is SYNCHRONIZED to a grid with other prime movers and generators, the speed of the generator (and prime mover) CANNOT change. Not no how. Not no way. It. Just. Doesn't. Happen. Not on planet Earth.
It's no wonder people trying to learn Droop Speed Control have such a difficult time trying to understand it and learn the concept.
The concept of Droop Speed Control has been covered ad nauseum on (Speed)Control.com. Droop Speed Control loads a generator and prime mover synchronized to a grid with other generators and their prime movers by changing the prime mover speed reference--NOT the actual speed. (I'm sure that's what the author meant to write--but it's not what was published). And people only get to read what's published--not what was intended. And, most proof-readers and most editors are not technically savvy enough to catch serious mistakes like this. So, drivel gets published--and read--causing confusion.
I'm going to admit, I haven't looked closely at the data that's been provided (it's been a really crappy couple of days--and the crap just keeps on coming, folks). So, I've been just a LITTLE busy. And then I try to relax a little and read this.
As for what's happening in this thread--what is the source of the "shore power"? Other land-based generators and their prime movers? Or a solid, stable, large or "infinite" grid? Because unless the shore power generators are larger than the yacht-based generators and their prime movers, then it's possible there could be grid frequency disturbances.
It would be very informative to know when these frequency variations are occurring, what is the frequency of the voltage in an outlet--on the yacht, and on the dock? Also, what is the prime mover speed doing when these frequency disturbances are occurring?
Also, what is the frequency at an outlet on the shore/dock when the yacht is NOT connected???
But, this--this Droop Speed Control shite is just plain wrong. And, it can't go unchallenged.
These notes are only for informations ...we know that sometimes "litterature " can be wrong/misinterpreted /non appropriated to the field...
One have to read these but get his own opinion by searching crossing references on same subject ...
One have to read these but get his own opinion by searching crossing references on same subject ...
Okay; so the cats procreating woke me up early this morning and I re-read and re-re-read and re-re-re-read the original poster’s comments and I understand the source of my confusion. He is referring to the yacht operating independently of shore power as a “grid”—I was confusing it as the “shore grid.”
So the problem is not that frequency varies when connected to “shore grid” but when the yacht is NOT connected to “shore grid.”
THAT is, as ControlsGuy25 has written, most likely a problem with the programming and/or tuning of the PMS. The PMS is most likely monitoring frequency and sending signals to each of the generator prime mover control systems to change load to control frequency. And it’s not doing a very good job of that; not at all.
What is not known here is what governor mode are the generator prime movers operating in? Droop Speed Control? Or some kind of Isochronous Sharing Load Control? Or some other proprietary name for some sort of load-sharing scheme? If the generator prime mover control systems are themselves interconnected in some kind of load sharing system AND there is also a PMS trying to do something similar the two could be working against each other and causing instability. I have seen that before and it’s very difficult to solve because the PMS programmers don’t really understand AC (Alternating Current) power generation nor do they understand the prime mover control systems and they FIRMLY believe the PMS IS NOT the problem. And they will never be convinced the PMS IS the problem.
PMS’s are usually the result of someone not understanding how Isochronous- and Droop Speed control work. Because people don’t understand Isochronous and Droop Speed control they want to program a system to do what Isochronous and Droop Speed Control does. But there are extremely few people who understand what they do AND can program a system to do that—because it’s very difficult to do. They hire some really talented programmers who can do some really genius programming—but if they really don’t understand AC power generation it’s never going to work very well.
The original poster said the PMS is CIMPLICITY, and while that’s possible it’s more likely that CIMPLICITY is the graphical front end for some PLC (Programmable Logic Controller) or PAC (Programmable Action Controller). And the controller is doing the heavy lifting of PMSing and CIMPLICITY is just the graphical interface to the controller.
SOMETHING is causing a “delay” in changing the load(s) of the generator(s) to maintain frequency closer to the desired 50 Hz. Is that a sloppy deadband (hysteresis) in the PMS? Is it the prime mover control system operating mode or gain too high or too low? Is it that the gain of the PMS is too high causing overshoot—which can appear as a sluggish response without good data?
We don’t know enough about the troubleshooting capabilities of the systems (the speed and trending capabilities) to be able to say how to capture data or if the data is suitable to a proper analysis of the problem. One thing is for sure: The frequency fluctuations are much higher than they should be for a well-tuned system on a yacht. Whoever designed the PMS and whoever programmed it didn’t finish the job properly by tuning it.
It’s also possible the system worked well in the beginning (we don’t know that...) and over time it has deteriorated to it’s present state. That could be a lack of maintenance on the generator prime mover fuel rack(s), hydraulic issues, dirty fuel filters—or some combination of the above. We don’t know. The PMS may be the best PMS, but if the diesel fuel system is incapable of responding quickly enough (or is responding too quickly) then it’s not the PMS. (Though in my experience, PMS’s are not very well programmed and are usually the problem—but convincing people who don’t understand AC power generation of that is next to impossible.)
Lastly, when a generator and its prime mover or two or three generators and their prime movers are operating together (synchronized) to power loads independently of a large grid of many generators and their prime movers, the small “grid” of power generation, transmission and distribution they form is often called a “power island,” or, simply an “island”. A power island or an island can be synchronized with a larger group of generators and their prime movers (a “grid" or an “infinite grid”). But it’s confusing to some to call a shipboard power generation, transmission and distribution system a grid and a shore-based power generation, transmission and distribution system a grid without some clearer method of distinguishing the two. (The original poster did call one a “shore grid.”) Anyway, a yacht or a ship could be considered a “power island.”
That’s me! I’m done here. Wish I could do more, but this is a really difficult problem with a lot of possible causes and solutions. I would like to know how it gets resolved.
So the problem is not that frequency varies when connected to “shore grid” but when the yacht is NOT connected to “shore grid.”
THAT is, as ControlsGuy25 has written, most likely a problem with the programming and/or tuning of the PMS. The PMS is most likely monitoring frequency and sending signals to each of the generator prime mover control systems to change load to control frequency. And it’s not doing a very good job of that; not at all.
What is not known here is what governor mode are the generator prime movers operating in? Droop Speed Control? Or some kind of Isochronous Sharing Load Control? Or some other proprietary name for some sort of load-sharing scheme? If the generator prime mover control systems are themselves interconnected in some kind of load sharing system AND there is also a PMS trying to do something similar the two could be working against each other and causing instability. I have seen that before and it’s very difficult to solve because the PMS programmers don’t really understand AC (Alternating Current) power generation nor do they understand the prime mover control systems and they FIRMLY believe the PMS IS NOT the problem. And they will never be convinced the PMS IS the problem.
PMS’s are usually the result of someone not understanding how Isochronous- and Droop Speed control work. Because people don’t understand Isochronous and Droop Speed control they want to program a system to do what Isochronous and Droop Speed Control does. But there are extremely few people who understand what they do AND can program a system to do that—because it’s very difficult to do. They hire some really talented programmers who can do some really genius programming—but if they really don’t understand AC power generation it’s never going to work very well.
The original poster said the PMS is CIMPLICITY, and while that’s possible it’s more likely that CIMPLICITY is the graphical front end for some PLC (Programmable Logic Controller) or PAC (Programmable Action Controller). And the controller is doing the heavy lifting of PMSing and CIMPLICITY is just the graphical interface to the controller.
SOMETHING is causing a “delay” in changing the load(s) of the generator(s) to maintain frequency closer to the desired 50 Hz. Is that a sloppy deadband (hysteresis) in the PMS? Is it the prime mover control system operating mode or gain too high or too low? Is it that the gain of the PMS is too high causing overshoot—which can appear as a sluggish response without good data?
We don’t know enough about the troubleshooting capabilities of the systems (the speed and trending capabilities) to be able to say how to capture data or if the data is suitable to a proper analysis of the problem. One thing is for sure: The frequency fluctuations are much higher than they should be for a well-tuned system on a yacht. Whoever designed the PMS and whoever programmed it didn’t finish the job properly by tuning it.
It’s also possible the system worked well in the beginning (we don’t know that...) and over time it has deteriorated to it’s present state. That could be a lack of maintenance on the generator prime mover fuel rack(s), hydraulic issues, dirty fuel filters—or some combination of the above. We don’t know. The PMS may be the best PMS, but if the diesel fuel system is incapable of responding quickly enough (or is responding too quickly) then it’s not the PMS. (Though in my experience, PMS’s are not very well programmed and are usually the problem—but convincing people who don’t understand AC power generation of that is next to impossible.)
Lastly, when a generator and its prime mover or two or three generators and their prime movers are operating together (synchronized) to power loads independently of a large grid of many generators and their prime movers, the small “grid” of power generation, transmission and distribution they form is often called a “power island,” or, simply an “island”. A power island or an island can be synchronized with a larger group of generators and their prime movers (a “grid" or an “infinite grid”). But it’s confusing to some to call a shipboard power generation, transmission and distribution system a grid and a shore-based power generation, transmission and distribution system a grid without some clearer method of distinguishing the two. (The original poster did call one a “shore grid.”) Anyway, a yacht or a ship could be considered a “power island.”
That’s me! I’m done here. Wish I could do more, but this is a really difficult problem with a lot of possible causes and solutions. I would like to know how it gets resolved.
Contrôle de la vitesse de chute litterally.. stand for droop mode CSA..
I don't post fiction here I just Support people as best as I can and it works fine...
@ControlsGuy25 and @CSA
Thank you sooo much for your input!
Since I am not on your level of expertise, I will need some time to read several times what you have written and then some time to try to understand it, so I can provide you with the best possible information.
Once again, thank you so much, it means a lot to me!
Thank you sooo much for your input!
Since I am not on your level of expertise, I will need some time to read several times what you have written and then some time to try to understand it, so I can provide you with the best possible information.
Once again, thank you so much, it means a lot to me!
@gubavac111 Thank for your reply..
My advise would be to you to try to understand what the PMS is doing on your site...
The best you learn how it operate the best you can find the solution..
Again without be able to see block diagram of such euipment.. I cannot say more...
Any time!
James.
What is an SOE?
Let's say load sharing scheme is not tuned properly. Would this matter if only one genset is online?
My humble opinion is that load sharing scheme is not important when there is just one genset online because no load is being shared, all the load is taken by one genset. Am I right?
One thing I mentioned in my first post which I believe is important - the more gensets are online, the smaller frequency fluctuation is! So, frequency fluctuation is greatest when there is just one genset online.
And for the SLD observation, you are correct indeed; there should be one Port and one Starboard genset.
SOE stands for Sequence of Event...
Its like report of what happened on the systems ( like alarm, trip , undefrequency/overfrequency....)
If only one genset is online it is about how it is operating (control mode) isochronous or Droop mode ..
Thats why PMS is also operating if only one genset is online ( isochronous mode for example)..
Its like report of what happened on the systems ( like alarm, trip , undefrequency/overfrequency....)
If only one genset is online it is about how it is operating (control mode) isochronous or Droop mode ..
Thats why PMS is also operating if only one genset is online ( isochronous mode for example)..
gubavac111,
IF the PMS is not set up correctly AND it is trying to control frequency when only one genset is online, that could be part of the problem.
Opinions--and ass-u-me-ptions--are worthless when troubleshooting technical issues, and can cause lots of wasted time and effort. If you don't know how the PMS works, you should start finding out how it works, and when.
IF the PMS were NOT working when there was only one genset online, then that genset's governor should be in Isochronous Speed Control Mode. And, if a second genset were to be synchronized to the first, then the one of the gensets should be in Isochronous Speed Control Mode and the other should be in Droop Speed Control mode OR they both should be in Droop Speed Control Mode (or some form of Isoch Load Sharing mode--which is really just de-tuned Isoch, very close to Droop) AND the PMS should be sending signals to one or both gensets to try to control frequency as load changes.
You MUST understand how--and when--the PMS works.
You have also NOT told us if this scheme ever worked properly since sea trials/commissioning, or if it's always behaved this way.
My money is on EITHER poor maintenance of the diesel fuel control rack/system, OR the PMS--and based on my poor experience with many PMSs (especially ones that are custom, one-off systems and not "standard" off-the-shelf systems)--it's more than likely the configuration/programming of the PMS.
There's one fairly simple way to test this--and that's to turn off the PMS and have a well-trained operator or two monitor the gensets. One genset should be in Isoch mode, and any other gensets added to the island (what you want to call a "grid") should be in Droop Speed Control mode. That would be a very simple test. But the operator(s) have to understand how to adjust the gensets in a multi-unit configuration to keep the load on the Isoch unit from being too high or too low as HVACs and other loads on the island are switched on and off.
But, it's not likely that anyone will agree to this test. Because no one thinks the automation (PMS) could be at fault. Not to mention it's kind of risky if the operator makes a mistake (think black-out...).
So, the speculation will continue.
Get familiar with the configuration and programming of the PMS--especially if it's a custom, one-off design. If it's a "standard" off-the-shelf system, get the manual and the drawings (schematics) out and start reading and studying (another reason NOT to go with a custom, one-off PMS: the documentation is usually pretty difficult to find, read, and understand).
Best of luck!
IF the PMS is not set up correctly AND it is trying to control frequency when only one genset is online, that could be part of the problem.
Opinions--and ass-u-me-ptions--are worthless when troubleshooting technical issues, and can cause lots of wasted time and effort. If you don't know how the PMS works, you should start finding out how it works, and when.
IF the PMS were NOT working when there was only one genset online, then that genset's governor should be in Isochronous Speed Control Mode. And, if a second genset were to be synchronized to the first, then the one of the gensets should be in Isochronous Speed Control Mode and the other should be in Droop Speed Control mode OR they both should be in Droop Speed Control Mode (or some form of Isoch Load Sharing mode--which is really just de-tuned Isoch, very close to Droop) AND the PMS should be sending signals to one or both gensets to try to control frequency as load changes.
You MUST understand how--and when--the PMS works.
You have also NOT told us if this scheme ever worked properly since sea trials/commissioning, or if it's always behaved this way.
My money is on EITHER poor maintenance of the diesel fuel control rack/system, OR the PMS--and based on my poor experience with many PMSs (especially ones that are custom, one-off systems and not "standard" off-the-shelf systems)--it's more than likely the configuration/programming of the PMS.
There's one fairly simple way to test this--and that's to turn off the PMS and have a well-trained operator or two monitor the gensets. One genset should be in Isoch mode, and any other gensets added to the island (what you want to call a "grid") should be in Droop Speed Control mode. That would be a very simple test. But the operator(s) have to understand how to adjust the gensets in a multi-unit configuration to keep the load on the Isoch unit from being too high or too low as HVACs and other loads on the island are switched on and off.
But, it's not likely that anyone will agree to this test. Because no one thinks the automation (PMS) could be at fault. Not to mention it's kind of risky if the operator makes a mistake (think black-out...).
So, the speculation will continue.
Get familiar with the configuration and programming of the PMS--especially if it's a custom, one-off design. If it's a "standard" off-the-shelf system, get the manual and the drawings (schematics) out and start reading and studying (another reason NOT to go with a custom, one-off PMS: the documentation is usually pretty difficult to find, read, and understand).
Best of luck!
First of all, I can't believe you are this kind to write in so many details to try to help me. It's just amazing!
I have one small observation that might be helpful:
When observing Local operating panel (the panel where you can operate genset locally and see engine and alternator parameters) of the genset that was online, I could see that the command to INCREASE SPEED or DECREASE SPEED was given every 7-8 seconds, but the frequency was fluctuating just as usual during these 7-8 seconds, going up and down. And the command to increase or decrease speed is, from what I've seen, given by the PMS.
So, it could be that, as you mentioned, there is an issue with the poor maintenance of the diesel fuel control rack/system and perhaps not with the PMS.
That would be great to know OEM controller /type /model..
And if you got that PMS block diagram you can post it...
Then we will in better position to support..
gubavac111,
The problem could be as simple as the length of time the RAISE or LOWER (INCREASE SPEED or DECREASE SPEED) command is sent to the genset controller from the PMS. It could be causing the frequency to be a little higher or a little lower than desired.
This is another one (of the many) problems with a lot of PMS systems--especially the custom, one-off systems. Simply, they weren't--or in some cases, can't be--tuned to prevent over- or under-shoot when making small adjustments to the genset controller(s).
It could also be that the "deadband" in the PMS is too large--meaning it waits too long before a pulse to raise or lower load is given. That's sometimes done when there are large loads with high in-rush currents which can have a short effect on load which reduces after a second or three. If the PMS were constantly changing load based on such load swings it would also be constantly responding to over-shoot or under-shoot caused by the high in-rush currents.
In my personal opinion, a PMS should only be trying to mimic a well-trained operator (which is very difficult to do, even with machine learning and AI (Artificial Intelligence)). It should only be trying to keep the load on the Isoch unit (the unit operating in Isoch Speed Control Mode) from getting too close to some upper or lower limit, based on system characteristics and machine capabilities. When there's only ONE genset operating, the PMS doesn't do anything. It would only start a second genset--in Droop Speed Control mode--when the load was getting too high on the Isoch unit. And, it would use the second genset to keep the load on the Isoch unit within limits (an Isoch unit can't change its load--except in response to changes in frequency). The PMS could be used to change which genset is in Isoch (and which is in Droop).
Many "standard" off-the-shelf PMS (load sharing systems) have the ability to fine tune both the length of pulses as well as the time between pulses; some custom, one-off PMS systems do not.
As ControlsGuy25 has written, if you want better help you need to provide more information. We are not there beside you; we can't see what you see. We can't know what you know--and what you don't know. And, this is VERY important: EVERY PMS AND ISLAND SITUATION IS NOT THE SAME. You want help--we need information. Actionable information. Graphs; time-based data (in spreadsheet form at a minimum). Manufacturer's names and model numbers.
Without more information, it's going to be next to impossible to offer much more help. Honestly, anything more is just speculation, and we have only been able to offer some problems which have been experienced on other islanded systems--none of them yacht-board systems.
And, if you don't really understand Droop- and Isochronous Speed Control it's going to be difficult to explain it so you can quickly pick it up. (And, the drivel which was copied and pasted is just that: drivel; totally under-described and as written--just plain wrong. Except maybe for the engineer at Startech who wrote it, or ran it through a translator program (and even that wouldn't spit out what appears above if the right description was used in the original language it was written in).)
If you had a method to automatically capture data, as you configured the system and looked at the data things would start to become clearer. You might even be able to dig in to the PMS "logic" and begin to see what happening--and why. You could forward it to us and we could also review it and add our comments and analysis. But, that requires "actionable" data--something we can work with. What you have provided is what's called "anecdotal" data--and while that can be helpful sometimes, it's proving not be helpful in this case (at least not for me, and it seems not for ControlsGuy25).
We'd love to follow this problem to its resolution--there's a lot to be learned. But, I'm afraid we've reached the end based on the information provided. Best of luck! Write back to let us know how you fare in solving the problem.
Lastly, often troubleshooting is a process of elimination. When you don't know what the problem is, sometimes you have to use what you do know and start breaking down the problem--and the systems--into likely and unlikely causes. If you do that and you start investigating the likely causes and you reach the end of your list of likely causes, then you start investigating the list of what were considered unlikely causes--until you either find the cause, or you step back and say, "Did I have a good list of likely and unlikely causes to begin with?" and start building a new set of lists. Try not to ass-u-me things (you see how that's spelled? look at it real closely--it is very interesting!!!). When someone ass-u-me-s things it can make an arse (my politically correct spelling for the first three letters of ass-u-me!) of "u" and "me" and that's not good for either of us. Try to base your hunches on what you know. Do you know diesel engine maintenance? Go after what you now about fuel delivery systems, and prove it's either not the diesel fuel delivery system, or it is. And, proceed from there.
And write down three things when you're working on a particular vexing and/or complicated problem: What you tested. How you tested. And what the results were. Because it can get very confusing if the troubleshooting takes a long time, and you're trying to explain it to someone else. If you have to involve someone else but you can't explain how you test this or that--AND what the results were, it's VERY likely you're going to watch that person do the same tests (whilst paying him/her). Just to say, "We tried that, and it didn't work [it didn't solve the problem]!" is meaningless to anyone else who wasn't there.
This is real troubleshooting--and learning!!! Do it enough times, and it becomes second nature--and you will be able to solve many problems other people couldn't or can't. Don't do it, and, ..., well, ..., it's going to be a long (and probably expensive) process to resolve some problems.
The problem could be as simple as the length of time the RAISE or LOWER (INCREASE SPEED or DECREASE SPEED) command is sent to the genset controller from the PMS. It could be causing the frequency to be a little higher or a little lower than desired.
This is another one (of the many) problems with a lot of PMS systems--especially the custom, one-off systems. Simply, they weren't--or in some cases, can't be--tuned to prevent over- or under-shoot when making small adjustments to the genset controller(s).
It could also be that the "deadband" in the PMS is too large--meaning it waits too long before a pulse to raise or lower load is given. That's sometimes done when there are large loads with high in-rush currents which can have a short effect on load which reduces after a second or three. If the PMS were constantly changing load based on such load swings it would also be constantly responding to over-shoot or under-shoot caused by the high in-rush currents.
In my personal opinion, a PMS should only be trying to mimic a well-trained operator (which is very difficult to do, even with machine learning and AI (Artificial Intelligence)). It should only be trying to keep the load on the Isoch unit (the unit operating in Isoch Speed Control Mode) from getting too close to some upper or lower limit, based on system characteristics and machine capabilities. When there's only ONE genset operating, the PMS doesn't do anything. It would only start a second genset--in Droop Speed Control mode--when the load was getting too high on the Isoch unit. And, it would use the second genset to keep the load on the Isoch unit within limits (an Isoch unit can't change its load--except in response to changes in frequency). The PMS could be used to change which genset is in Isoch (and which is in Droop).
Many "standard" off-the-shelf PMS (load sharing systems) have the ability to fine tune both the length of pulses as well as the time between pulses; some custom, one-off PMS systems do not.
As ControlsGuy25 has written, if you want better help you need to provide more information. We are not there beside you; we can't see what you see. We can't know what you know--and what you don't know. And, this is VERY important: EVERY PMS AND ISLAND SITUATION IS NOT THE SAME. You want help--we need information. Actionable information. Graphs; time-based data (in spreadsheet form at a minimum). Manufacturer's names and model numbers.
Without more information, it's going to be next to impossible to offer much more help. Honestly, anything more is just speculation, and we have only been able to offer some problems which have been experienced on other islanded systems--none of them yacht-board systems.
And, if you don't really understand Droop- and Isochronous Speed Control it's going to be difficult to explain it so you can quickly pick it up. (And, the drivel which was copied and pasted is just that: drivel; totally under-described and as written--just plain wrong. Except maybe for the engineer at Startech who wrote it, or ran it through a translator program (and even that wouldn't spit out what appears above if the right description was used in the original language it was written in).)
If you had a method to automatically capture data, as you configured the system and looked at the data things would start to become clearer. You might even be able to dig in to the PMS "logic" and begin to see what happening--and why. You could forward it to us and we could also review it and add our comments and analysis. But, that requires "actionable" data--something we can work with. What you have provided is what's called "anecdotal" data--and while that can be helpful sometimes, it's proving not be helpful in this case (at least not for me, and it seems not for ControlsGuy25).
We'd love to follow this problem to its resolution--there's a lot to be learned. But, I'm afraid we've reached the end based on the information provided. Best of luck! Write back to let us know how you fare in solving the problem.
Lastly, often troubleshooting is a process of elimination. When you don't know what the problem is, sometimes you have to use what you do know and start breaking down the problem--and the systems--into likely and unlikely causes. If you do that and you start investigating the likely causes and you reach the end of your list of likely causes, then you start investigating the list of what were considered unlikely causes--until you either find the cause, or you step back and say, "Did I have a good list of likely and unlikely causes to begin with?" and start building a new set of lists. Try not to ass-u-me things (you see how that's spelled? look at it real closely--it is very interesting!!!). When someone ass-u-me-s things it can make an arse (my politically correct spelling for the first three letters of ass-u-me!) of "u" and "me" and that's not good for either of us. Try to base your hunches on what you know. Do you know diesel engine maintenance? Go after what you now about fuel delivery systems, and prove it's either not the diesel fuel delivery system, or it is. And, proceed from there.
And write down three things when you're working on a particular vexing and/or complicated problem: What you tested. How you tested. And what the results were. Because it can get very confusing if the troubleshooting takes a long time, and you're trying to explain it to someone else. If you have to involve someone else but you can't explain how you test this or that--AND what the results were, it's VERY likely you're going to watch that person do the same tests (whilst paying him/her). Just to say, "We tried that, and it didn't work [it didn't solve the problem]!" is meaningless to anyone else who wasn't there.
This is real troubleshooting--and learning!!! Do it enough times, and it becomes second nature--and you will be able to solve many problems other people couldn't or can't. Don't do it, and, ..., well, ..., it's going to be a long (and probably expensive) process to resolve some problems.
Here's a little example of how a system WITHOUT a PMS might work. (By the way--the original poster has used the terms "PMS" and "load sharing" interchangeably--they might be similar, but we have mostly been talking about frequency control, which is what we have been mostly asking about. Be careful with terms; just like using "grid" to describe the generation/transmission/distribution system on the ship--which is not generally referred to as a grid, like on shore generation/transmission/distribution systems are.)
Let's say the yacht is off shore, admiring the coastline from afar, and is not connected to shore power. It's early morning and the HVAC is not really in use; just some fans and lights and water pumps (bilge pumps; cooling water pumps; RO pumps; espresso machine; and a tea kettle; and the navigation gear). So, only one generator is running, and it is about 50% of rated output and the frequency of the yacht's electrical system is about 50.09 Hz. The final condition is the genset's governor is operating in Isochronous Speed Control mode--meaning that it will change the fuel flow to the diesel to make the frequency stay as close to 50 Hz as possible as long as the total load on the yacht doesn't exceed 100% of the genset's rated capacity, nor fall below 0% of the genset's rated capacity. Isoch Speed Control will do that (maintain 50 Hz)--all by itself. No operator intervention required--as long as the load on the yacht doesn't exceed the limits (0% and 100%) of the genset rating (and that's the PRIME MOVER rating--NOT the generator nameplate rating; gensets are rated based on prime mover capability not generator capability). It's also VERY IMPORTANT that when operating in Isoch mode an operator can't do anything to the genset to change the load on the genset. If the operator clicks on RAISE (or INCREASE) all he/she will be doing is increasing the frequency setpoint--which will raise the generator output frequency and the speeds of the diesel and generator--but the load WILL NOT change. The load will only change as electrical devices (motors; microwaves; navigation gear; lights; HVAC) are turned on or off, which will tend to cause the frequency to change--but Isoch mode won't let it change (as long as the total amount of electrical devices doesn't exceed 100% of the genset rating nor drop below 0% of the genset rating).
As people wake up and start using more electricity the load on the yacht's system will increase. The engineer on watch is monitoring the generator output and the yacht system load and it's starting to increase. As the load approaches 85% of the rating of the genset the engineer's instructions are to start and synchronize a second generator, which he does--and his instructions also say the second genset's governor is to be in Droop Speed Control mode after synchronization with the first genset. Further, his instruction say to then reduce the load on the Isoch genset to 45% of its rated capacity. So, the experienced and well-trained operator increases the load on the Droop genset until the load on the Isoch genset drops to 45% of its rated capacity. (Because one cannot directly change load on a genset running in Isoch mode; so the way to indirectly change the load on an Isoch genset is to change the load on one or more Droop gensets synchronized to the Isoch genset.)
As the sun rises and the below-deck spaces heat up, the HVAC units kick into higher output--raising the load on the yacht's systems. Also, it's decided to raise anchor and motor slowly to another location for the afternoon, so some other electrical devices are started--further increasing the total load on the yacht's system. The engineer on watch is monitoring everything that's going on and notices that the load on the Isoch genset is again approaching 85% of rated, but that the load on the Droop genset hasn't changed (which is as it should be!). So, to reduce the load on the Isoch unit the engineer on watch increases the load on the Droop machine.
Once the new anchorage is reached, and the anchor dropped, and the engines shut off, the load on the yacht's system drops a little, thereby reducing the load on the Isoch genset. The engineer on watch monitors the system and when the load on the Isoch unit gets down to about 15% of rated his operating instruction tell him to increase the load on the Isoch genset--which the engineer on watch does by reducing the load on the Droop genset. The load on the Isoch unit now increases to about 55% of rated, and the load on the Droop unit falls to about 25% of rated or so. (In a small, island system, the load on the Droop genset doesn't change unless the operator changes it. The load on the Isoch genset changes automatically--but only because if it didn't the system frequency would drift away from nominal. It's not the amount of load that's making the Isoch unit change its power output, it's what the amount of load does to the frequency that makes the Isoch unit change its power output. The Droop unit? It's just "along for the ride" (presuming the Isoch governor is working properly); it's load won't change unless an operator changes it. (I'm talking a very small, manually controlled power island. And, it works similarly for larger systems as well, though it's not as easy to understand or explain--but it's still the same principle.)
This is how load is "shared" between gensets in a manual way. (I prefer to call it "load balancing.") Remember: The load of a genset running in Isoch mode can't be directly changed (using the Isoch's governor)--so the only way to change the load on the Isoch genset is to do so indirectly by changing the load on a Droop genset synchronized with the Isoch genset. The Isoch genset governor will sense the change in frequency and will automatically adjust the fuel flow-rate to the Isoch's prime mover to keep the Isoch generator output--and so the that of the yacht's system--at 50 Hz.
There's usually a little "deadband"--sometimes called hysteresis. I'm talking about a difference of approximately +/-0.10% of frequency, so a rather insignificant amount. If you hook up a multimeter capable of reading frequency to a shore-side electrical outlet you will see that over the course of a day, any normal, usual day, the frequency will NEVER stay exactly at 100.0% of rated--it's always a little above or a little below. That's normal, but what the original poster described is not normal and is excessive.
This is what a PMS is supposed to do--look at a set of operating instructions for maintaining the frequency of a small, "islanded" power system, and make the necessary adjustments to make it all happen seamlessly in the background. Need more power? Start and synchronize a second genset. Maintain some kind of balance between multiple gensets (usually there's some kind of table or matrix which defines usage rates/times/capacities for the various generators). Change the "lead" and "lag" generators automatically. And, it's not as easy as a lot of people think it is. Not at all. Especially when all of the genset governors are usually operated in Droop Speed Control or some kind of "Isoch load-sharing" mode. The latter actually complicates things (in my personal opinion--a LOT), but then so does the timing of pulses to change load on multiple machines.
The original poster said his hunch was the PMS wasn't active when only on genset was running. That is an ass-u-me-ption--not a bad one, necessarily, but an ass-u-me-ption nonetheless. Personally, I've only seen a couple of PMSs that will switch genset governor mode between Isoch and Droop--it's just not common, but it does happen. Generally, the implementers of PMSs think the genset governors should always remain in the same mode--AND they think the genset governors are NEVER as capable or intelligent at the PMS so they want the PMS to ALWAYS be in control, whether it's a single genset or two or three or more.
And, it can--and usually does--get very complicated very fast.
Now, imagine what happens to system response when the diesel genset fuel racks/injectors are not being properly maintained. Or the diesel fuel filters get some water or dirt in them, choking the flow through the filter(s)--and they aren't swiftly replaced. Ir the diesel air filters get dirty, or the turbos get worn. People forget how all of these components and systems have to work together. But, because the "control system" has so many wires and LEDs and it's SOOO complicated--well, it just has to be the control system that's the problem. (And in the case of many custom, one-off PMS control systems--they can definitely be the problem, though convincing the supplier is next to impossible--if they're even still in business or still working on PMSs!).
The purpose of a PMS is to do the above--maintain frequency without exceeding the limits (minimum or maximum) of the genset(s), and keep the genset(s) from operating too close to their limits (minimum or maximum). Isochronous and Droop Speed Control can do the first (maintain frequency)--but they require trained and experienced operators to do so, and in the process the operator(s) will also be "sharing" loads between the gensets. Replace the operators with a PMS, and, you damn well better know exactly what the operators would be doing--and change the genset governor modes in the process, and well, you have greatly increased the complexity of the PMS.
Hope this helps! It's just a small window into what goes on all day every day around the world in many places, and at sea.
Let's say the yacht is off shore, admiring the coastline from afar, and is not connected to shore power. It's early morning and the HVAC is not really in use; just some fans and lights and water pumps (bilge pumps; cooling water pumps; RO pumps; espresso machine; and a tea kettle; and the navigation gear). So, only one generator is running, and it is about 50% of rated output and the frequency of the yacht's electrical system is about 50.09 Hz. The final condition is the genset's governor is operating in Isochronous Speed Control mode--meaning that it will change the fuel flow to the diesel to make the frequency stay as close to 50 Hz as possible as long as the total load on the yacht doesn't exceed 100% of the genset's rated capacity, nor fall below 0% of the genset's rated capacity. Isoch Speed Control will do that (maintain 50 Hz)--all by itself. No operator intervention required--as long as the load on the yacht doesn't exceed the limits (0% and 100%) of the genset rating (and that's the PRIME MOVER rating--NOT the generator nameplate rating; gensets are rated based on prime mover capability not generator capability). It's also VERY IMPORTANT that when operating in Isoch mode an operator can't do anything to the genset to change the load on the genset. If the operator clicks on RAISE (or INCREASE) all he/she will be doing is increasing the frequency setpoint--which will raise the generator output frequency and the speeds of the diesel and generator--but the load WILL NOT change. The load will only change as electrical devices (motors; microwaves; navigation gear; lights; HVAC) are turned on or off, which will tend to cause the frequency to change--but Isoch mode won't let it change (as long as the total amount of electrical devices doesn't exceed 100% of the genset rating nor drop below 0% of the genset rating).
As people wake up and start using more electricity the load on the yacht's system will increase. The engineer on watch is monitoring the generator output and the yacht system load and it's starting to increase. As the load approaches 85% of the rating of the genset the engineer's instructions are to start and synchronize a second generator, which he does--and his instructions also say the second genset's governor is to be in Droop Speed Control mode after synchronization with the first genset. Further, his instruction say to then reduce the load on the Isoch genset to 45% of its rated capacity. So, the experienced and well-trained operator increases the load on the Droop genset until the load on the Isoch genset drops to 45% of its rated capacity. (Because one cannot directly change load on a genset running in Isoch mode; so the way to indirectly change the load on an Isoch genset is to change the load on one or more Droop gensets synchronized to the Isoch genset.)
As the sun rises and the below-deck spaces heat up, the HVAC units kick into higher output--raising the load on the yacht's systems. Also, it's decided to raise anchor and motor slowly to another location for the afternoon, so some other electrical devices are started--further increasing the total load on the yacht's system. The engineer on watch is monitoring everything that's going on and notices that the load on the Isoch genset is again approaching 85% of rated, but that the load on the Droop genset hasn't changed (which is as it should be!). So, to reduce the load on the Isoch unit the engineer on watch increases the load on the Droop machine.
Once the new anchorage is reached, and the anchor dropped, and the engines shut off, the load on the yacht's system drops a little, thereby reducing the load on the Isoch genset. The engineer on watch monitors the system and when the load on the Isoch unit gets down to about 15% of rated his operating instruction tell him to increase the load on the Isoch genset--which the engineer on watch does by reducing the load on the Droop genset. The load on the Isoch unit now increases to about 55% of rated, and the load on the Droop unit falls to about 25% of rated or so. (In a small, island system, the load on the Droop genset doesn't change unless the operator changes it. The load on the Isoch genset changes automatically--but only because if it didn't the system frequency would drift away from nominal. It's not the amount of load that's making the Isoch unit change its power output, it's what the amount of load does to the frequency that makes the Isoch unit change its power output. The Droop unit? It's just "along for the ride" (presuming the Isoch governor is working properly); it's load won't change unless an operator changes it. (I'm talking a very small, manually controlled power island. And, it works similarly for larger systems as well, though it's not as easy to understand or explain--but it's still the same principle.)
This is how load is "shared" between gensets in a manual way. (I prefer to call it "load balancing.") Remember: The load of a genset running in Isoch mode can't be directly changed (using the Isoch's governor)--so the only way to change the load on the Isoch genset is to do so indirectly by changing the load on a Droop genset synchronized with the Isoch genset. The Isoch genset governor will sense the change in frequency and will automatically adjust the fuel flow-rate to the Isoch's prime mover to keep the Isoch generator output--and so the that of the yacht's system--at 50 Hz.
There's usually a little "deadband"--sometimes called hysteresis. I'm talking about a difference of approximately +/-0.10% of frequency, so a rather insignificant amount. If you hook up a multimeter capable of reading frequency to a shore-side electrical outlet you will see that over the course of a day, any normal, usual day, the frequency will NEVER stay exactly at 100.0% of rated--it's always a little above or a little below. That's normal, but what the original poster described is not normal and is excessive.
This is what a PMS is supposed to do--look at a set of operating instructions for maintaining the frequency of a small, "islanded" power system, and make the necessary adjustments to make it all happen seamlessly in the background. Need more power? Start and synchronize a second genset. Maintain some kind of balance between multiple gensets (usually there's some kind of table or matrix which defines usage rates/times/capacities for the various generators). Change the "lead" and "lag" generators automatically. And, it's not as easy as a lot of people think it is. Not at all. Especially when all of the genset governors are usually operated in Droop Speed Control or some kind of "Isoch load-sharing" mode. The latter actually complicates things (in my personal opinion--a LOT), but then so does the timing of pulses to change load on multiple machines.
The original poster said his hunch was the PMS wasn't active when only on genset was running. That is an ass-u-me-ption--not a bad one, necessarily, but an ass-u-me-ption nonetheless. Personally, I've only seen a couple of PMSs that will switch genset governor mode between Isoch and Droop--it's just not common, but it does happen. Generally, the implementers of PMSs think the genset governors should always remain in the same mode--AND they think the genset governors are NEVER as capable or intelligent at the PMS so they want the PMS to ALWAYS be in control, whether it's a single genset or two or three or more.
And, it can--and usually does--get very complicated very fast.
Now, imagine what happens to system response when the diesel genset fuel racks/injectors are not being properly maintained. Or the diesel fuel filters get some water or dirt in them, choking the flow through the filter(s)--and they aren't swiftly replaced. Ir the diesel air filters get dirty, or the turbos get worn. People forget how all of these components and systems have to work together. But, because the "control system" has so many wires and LEDs and it's SOOO complicated--well, it just has to be the control system that's the problem. (And in the case of many custom, one-off PMS control systems--they can definitely be the problem, though convincing the supplier is next to impossible--if they're even still in business or still working on PMSs!).
The purpose of a PMS is to do the above--maintain frequency without exceeding the limits (minimum or maximum) of the genset(s), and keep the genset(s) from operating too close to their limits (minimum or maximum). Isochronous and Droop Speed Control can do the first (maintain frequency)--but they require trained and experienced operators to do so, and in the process the operator(s) will also be "sharing" loads between the gensets. Replace the operators with a PMS, and, you damn well better know exactly what the operators would be doing--and change the genset governor modes in the process, and well, you have greatly increased the complexity of the PMS.
Hope this helps! It's just a small window into what goes on all day every day around the world in many places, and at sea.
Wow, what a wealth of information! Please excuse me for not replying quickly. I am quite busy right now as we are entering dry dock tomorrow and will reply as soon as I process your info. Thank you!
gubavac111,
Thanks for writing back to let us know your status. We can probably answer some of the more basic questions you may have about islanded system operation without a PMS (which may help you in trying to understand how the PMS on the yacht works), but there's probably not a lot more we can say about your specific situation since you have decided not to tell us any details about the equipment and the PMS.
I want to add that only ONE PMS that I worked on was capable of switching governor modes for the generators and prime movers it controlled--that's kind of considered to be a very difficult thing to do automatically (or at least it was in the past), and so that's why most PMS systems don't do that and why most generators that PMS systems control are either operated in Droop Speed Control or some kind of Isochronous Load Sharing mode (which is really just a de-tuned Isoch mode which is really just a form of Droop Speed Control with a different name). So, it's probably likely that the PMS on the yacht and the generators and their prime movers it controls are operating in Droop Speed Control mode, and when a single generator is running the PMS isn't really tuned for controlling frequency very well. When two or more generators are running in Droop Speed Control mode they will kind of "support" each other (since that's one of the things Droop Speed Control does all by its lonesome (by itself)), but, again, you are not providing any information about the PMS or the prime mover governors so we can only speculate--and I don't like guessing more than I already have.
Best of luck! It would be great if you would write back to let us know how you fare in understanding the PMS and generator/prime mover configuration on the yacht!
Enjoy drydock!
Thanks for writing back to let us know your status. We can probably answer some of the more basic questions you may have about islanded system operation without a PMS (which may help you in trying to understand how the PMS on the yacht works), but there's probably not a lot more we can say about your specific situation since you have decided not to tell us any details about the equipment and the PMS.
I want to add that only ONE PMS that I worked on was capable of switching governor modes for the generators and prime movers it controlled--that's kind of considered to be a very difficult thing to do automatically (or at least it was in the past), and so that's why most PMS systems don't do that and why most generators that PMS systems control are either operated in Droop Speed Control or some kind of Isochronous Load Sharing mode (which is really just a de-tuned Isoch mode which is really just a form of Droop Speed Control with a different name). So, it's probably likely that the PMS on the yacht and the generators and their prime movers it controls are operating in Droop Speed Control mode, and when a single generator is running the PMS isn't really tuned for controlling frequency very well. When two or more generators are running in Droop Speed Control mode they will kind of "support" each other (since that's one of the things Droop Speed Control does all by its lonesome (by itself)), but, again, you are not providing any information about the PMS or the prime mover governors so we can only speculate--and I don't like guessing more than I already have.
Best of luck! It would be great if you would write back to let us know how you fare in understanding the PMS and generator/prime mover configuration on the yacht!
Enjoy drydock!
@gubavac111 Can you share a quick feedback on the status at site /yacht...Regarding that issue that you posted here.
ControlsGuy25
Hi,
We are currently in the shipyard, connected to shore power because our gensets are being overhauled.
Of course, frequency is now very stable at 50.02Hz.
