Droop Mode & Isochronous Mode 2

[kimseunghee]

I have experiened Droop mode in general, but didn't ISO mode. Why is ISO mode adopted ? Anybody explain two different modes, application, and effect on governor. welcome to tell me website.

 

[itsmoked]

I believe Droop is tailored to allow different size generators(same size too!) to balance a load between themselves based on their individual abilities.

ISO is for a lead generator or single generator to run at a fixed speed, that is, frequency. It will control the governor to maintain that speed, regardless of the load.

If you have a single islanded generator you would typically desire ISO.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[byrdj]

In droop, if the load increases, the freq droops and the generator will increase load propertial to the droop (regulation). But the frequency will remain below 60.000hz. It is now up to the operator to increase generaotr output more to bring the frequency back 60.000hz.

This is the norm for units connected to the grid and dispatch then varies generator outputs to keep frequency.


ISO just does the "correction" for the generator to return frequency back to 60.000hz. the control algorithim will be a combination of droop with a time constaint on how fast to make the correction to bring frequency back

 

[waross]

Actually many generators are set at 61.8 HZ at no load. They drop to 60Hz at full load.
An ISO set may have a droop governor with reset added.
The ISO set will be set to 60Hz. When the load changes (up or down) the frequency changes slightly as it does in droop mode. The reset function detects the error or frequency change and "Resets" the governor back to 60Hz. ISO sets don't play well with others. If a droop mode set is paralleled with an ISO set, The ISO set may end up motoring under light load.
The modern answer is to use a load control panel with ISO capability. The load control panel controls the throttle settings, of all the sets under its control. It will control both load sharing and frequency including frequency correction.
For the younger set;
Early process controllers were referred to as proportional proportional plus reset, and proportional plus reset plus pre-act.
They are ow called;
P Proportional or droop if installed on a gen-set.
PI Proportional plus Integral or isochronous if installed on a gen-set, and
PID Proportional plus Integral plus Derivative.
Droop controllers are P.
ISO controllers are PI and possibly PID.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[oldfieldguy]

Easy answer: One generator, all alone, by itself: Isochronous mode. Its governor will chase the setpoint frequency.

More than one generator, tied to the grid: Run in 'droop' mode. Governor adds or subtracts energy to the prime mover to maintain power output at the setpoint. The grid determines frequency.

Droop mode also applies to all the generators except one if you have a multi-generator power system separate from the grid.

During Hurricane Rita, one of my clients had a fine multi-generator power system tied to the utility grid. Hurricane damage took the grid down, removing his frequency reference and one generator after another shut down on the resulting frequency excursions. Nobody thought to switch anything to Isochronous because they'd NEVER run like that. It's part of the emergency procedures now.

old field guy