alaskanassassin
Member
- Location
- Fairbanks, Alaska
Can someone tell me what the difference is please? It is in reference to a power generation system. When would you use either one and why? Thanks Doug
Isoch vs droop
- Thread starter alaskanassassin
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ohmhead
Senior Member
- Location
- ORLANDO FLA
Well Isochronous speed control mode is better done off line or off grid by a good operator manual operation .
fundamental difference is maintaining speed to load of turbine to generator and doing this to parallel generators or kinda the grid .
Droop speed control mode is done on grid or line it varys the load but will not hold the frequency . Thats as good as its gets its all voltage regulators and hydrolic gov to control and adjust speed automatically .
Last edited:
nawao
Member
- Location
- Abuja - Nigeria
Isoch vs droop
Isoch is used to parallel generators in island mode. Droop is necessary to parallel them to the grid.
Isoch is used to parallel generators in island mode. Droop is necessary to parallel them to the grid.
Cold Fusion
Senior Member
- Location
- way north
Bob's link is excellent. Here is some of the simplified concepts that may help. My comments are limited to 300kw to 2mw recips and 400kw to 10mw turbine gens
Isoc:
Strictly a governor function. The governor feedback loop watches the frequency and sets the throttle to keep the frequency at setpoint. The Voltage Regulator function is completely separate.
Generally, Isoc is used in one of two ways:
1. Single generator islanded. The governor setpoint sets the throttle to hold the frequency and the VR function sets the DC field drive to the rotor to hold the voltage at setpoint.
2. Multiple generators with load share and var share lines. The load share lines modify the input to each generator governor to pull the throttle to share the load. The var share lines set DC field current to the the rotor to keep the voltage at set point and share the vars
Two generators in isoc with no other feedback:
They will be fighting. One will always be a slightly higher setpoint will go to wide open throttle in an attempt to hold the frequency up. The other will pull the throttle clear back in an attempt to keep the frequency down.
The voltage regulator settings don't have much to do with frequency (power/throttle setings). Rather, the VR setting will control the VAR sharing. The one with the higher VR setpoint will hog all of the VARS even to the point of sending the other gen to leading and putting out vars.
Two gens in isoc, without load share or var share, is not a recognized operating mode.
Frequency Droop:
As the linked article showed, this is a control function that links load and frequency. The governor feedback is set to let the frequency drop as the load increases.
Normally this is accompanied with voltage droop. As the load increases, the VR drops the rotor current linear with the load. In single generator (island) mode, this drops the voltage. In parallel operation mode, this drops the var output.
Examples:
In single generator operation, either isoc or droop will work. Droop gives terrible voltage regulation. Isoc would always be used is available.
For parallel operation, several modes are available: (The modes discussed here are for generators in close proximity. Paralleling with a grid is a different matter)
1. One in isoc, the others is droop works fairly well if the power swing is small. However, if the power swing is too far, then auto-starting/loading is necessary.
2. All in isoc with load share and var share lines works really well. Most any generator capabile of parallel operation can do this. The technology has been around since the mid 70s. This would be the prefered mode.
3. All in droop gives really poor regulation. Normally this is used only when the generators do not have load/var share available. Usually because the gens are far apart, but most often because the machines are not setup correctly. Although, turbines are notorius for poor governor-reaction/frequency-stability. Even when in isoc, they react like they are in droop:roll:
There was a pretty good post sometime back about generator controls, field drive, voltage regulation, throttle, governor - I'll look for it.
cf
Isoc:
Strictly a governor function. The governor feedback loop watches the frequency and sets the throttle to keep the frequency at setpoint. The Voltage Regulator function is completely separate.
Generally, Isoc is used in one of two ways:
1. Single generator islanded. The governor setpoint sets the throttle to hold the frequency and the VR function sets the DC field drive to the rotor to hold the voltage at setpoint.
2. Multiple generators with load share and var share lines. The load share lines modify the input to each generator governor to pull the throttle to share the load. The var share lines set DC field current to the the rotor to keep the voltage at set point and share the vars
Two generators in isoc with no other feedback:
They will be fighting. One will always be a slightly higher setpoint will go to wide open throttle in an attempt to hold the frequency up. The other will pull the throttle clear back in an attempt to keep the frequency down.
The voltage regulator settings don't have much to do with frequency (power/throttle setings). Rather, the VR setting will control the VAR sharing. The one with the higher VR setpoint will hog all of the VARS even to the point of sending the other gen to leading and putting out vars.
Two gens in isoc, without load share or var share, is not a recognized operating mode.
Frequency Droop:
As the linked article showed, this is a control function that links load and frequency. The governor feedback is set to let the frequency drop as the load increases.
Normally this is accompanied with voltage droop. As the load increases, the VR drops the rotor current linear with the load. In single generator (island) mode, this drops the voltage. In parallel operation mode, this drops the var output.
Examples:
In single generator operation, either isoc or droop will work. Droop gives terrible voltage regulation. Isoc would always be used is available.
For parallel operation, several modes are available: (The modes discussed here are for generators in close proximity. Paralleling with a grid is a different matter)
1. One in isoc, the others is droop works fairly well if the power swing is small. However, if the power swing is too far, then auto-starting/loading is necessary.
2. All in isoc with load share and var share lines works really well. Most any generator capabile of parallel operation can do this. The technology has been around since the mid 70s. This would be the prefered mode.
3. All in droop gives really poor regulation. Normally this is used only when the generators do not have load/var share available. Usually because the gens are far apart, but most often because the machines are not setup correctly. Although, turbines are notorius for poor governor-reaction/frequency-stability. Even when in isoc, they react like they are in droop:roll:
There was a pretty good post sometime back about generator controls, field drive, voltage regulation, throttle, governor - I'll look for it.
cf
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