auto run

grant@msew · May 20, 2008

hello

i have two gen sets i need to run in auto if the load of a town is greater than what they are contracted for. if this happens the operator types in a set point in KW he wants the engines to run at if the load is two small for both to run i just need on to carry the load and ramp up or down depending on what the load does or share the load if both are needed. i have a watt var transducer bringing a 4-20ma signal to a IF4/b Analog card in a L32E Compact logic controller but i have a 0-5v output to the gen sets my problem is that the load jumps up and down so i need a bandwith to regulate things and i can't figure out how to or what instuction to use to make the gen sets ramp up or down only if the load goes out of the bandwith and convert in to a 0-5v signal as it leaves the plc the math is done for the conversion

Can someone help me

BobB · May 20, 2008

Buy a generator controller that will take up all load but not export. It is not good to use a generator to just take 'the top off' the load as the generator will run very inefficiently and oil up. Generators should be loaded generally to at least 40% of their capacity but ideally 90-95%.

Don't try and re-invent the wheel when there is a ready made solution available at reasonable cost. Have a talk to Woodweard Governor Company for starters.

By the way, generators are a big part of my business and I do not have time to fiddle about with home grown solutions and would not anyway when there is so much good stuff out there that makes life easy and works really well at reasonable cost.

The generator controllers are set with with multiple PID loops to take care of the normal load bumps - just set them up and walk away.

Mickey · May 20, 2008

BobB said:
Buy a generator controller that will take up all load but not export. It is not good to use a generator to just take 'the top off' the load as the generator will run very inefficiently and oil up. Generators should be loaded generally to at least 40% of their capacity but ideally 90-95%.

Don't try and re-invent the wheel when there is a ready made solution available at reasonable cost. Have a talk to Woodweard Governor Company for starters.

By the way, generators are a big part of my business and I do not have time to fiddle about with home grown solutions and would not anyway when there is so much good stuff out there that makes life easy and works really well at reasonable cost.

The generator controllers are set with with multiple PID loops to take care of the normal load bumps - just set them up and walk away.

Ditto,Ditto
Take Bob's advice. I have seen this done with a PLC5 and four generators. They used the PLC's standard PID loop with load sharing modules. I was not there but watched from afar. It took months to tune. I was involved in a simalar project, same gen set but used woodward govenors. Took a couple of days to tune. Save yourself the grief, Woodward has what you need.

http://www.woodward.com/

grant@msew · May 20, 2008

this is for peak shaving only they are going to be running in parallel with the utilty if the utility tie trips the gen sets ignore my program and do there own thing this just needs to work while running during peak days to load and unload as the utility tie changes

BobB · May 20, 2008

My comments stand. Peak shaving in Ozz loads the generators to 90-95% of their capacity without export so that the engines run efficiently and do not oil and carbonise up. Small loads are definately not advisable if they want the engines to have a reasonably long life.

Trying to tune PIDs in a PLC to cover all eventualities would be an absolute nightmare. For example, a generator controller I use here regularly has separate PID loops for starting and ramping up, idling, running at speed, running synchronised with other sets and running against the mains. I do not even try to tune these things myself. I pay the manufacturer to do it as they do it much better and in 1/4 the time because they are doing it all the time for a living.

leitmotif · May 20, 2008

grant@msew said:
this is for peak shaving only they are going to be running in parallel with the utilty if the utility tie trips the gen sets ignore my program and do there own thing this just needs to work while running during peak days to load and unload as the utility tie changes

As a US Navy trained electrician who did parallel to utility to take on shorepower it does not matter what you parallel to utility another generator etc. BUT you must have adequate droop matching, voltage regulation, adequate speed (load) control, VAR control
AND they must match
OR you are going to get all screwed up.

I recommend you really listen to the guy in the business. Either get equipment designed for the need OR manually parallel and manually control. So your cost is going to be
1. Properly designed equipment meant for the purpose
2. Manual operation with full time operator
3. Damaged equipment.

Dan Bentler

BobB · May 21, 2008

BUT you must have adequate droop matching, voltage regulation, adequate speed (load) control, VAR control
AND they must match

I must admit I assumed they have a droop CT in the alternator and that droop % can be set on the existing AVR. Most Woodward controllers can drive 0-5 volts and they certainly interface well with Basler AVRs.

Just designing a job at the moment - 480 volts 60 hZ. 1 power station being replaced and has to interface with a second power station. Having to use Woodward EGCP3 controllers in Woodward DSLC mode (restricted functions) so that a Woodward LSIM (load share interface module) can be used to tie the new digital stuff together with the old analogue stuff. Will have to use cross current compensation for var sharing. HORRIBLE!!!! They do not have the dough at the moment to update both power stations.

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grant@msew

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