Operation
057-295 ISSUE: 1
Page 40 of 60
Multiple Generators
In a multiple generator system, the droop on the AVR is working to minimise the alternators kvar
production. If the droop on each AVR is set identically, it balances the kvars between all the
alternators as they each try to produce the minimum reactive power.
This enables a basic form of reactive power (kvar) sharing between connected generators, providing
each AVR is configured to provide the same amount of droop.
However, this has the effect on the alternator output voltage as it varies depending upon the changing
nature of the reactive load.
Where a continuous voltage is required, the use of a generator load share controller with active kvar
sharing and voltage compensation is recommended. Such controllers include the DSE8xxx series of
load share controllers. Contact DSE Technical Support for more information.
To set the droop function for paralleling multiple generators:
NOTE: If it is required that the generator output voltage droops to the nominal voltage,
ensure that Voltage Setpoint is set higher than the nominal by the appropriate amount.
1. With the generator running off load, adjust the
Voltage Setpoint
so that the generator is
providing the desired voltage.
2.
Put the generator to the ‘typical’ reactive load level that the set is to be connected to.
3. Increase the
Droop
setting until the generator output voltage drops by the required amount
(typically 3% to 5%).
4. Ensure all generators in the system are set with exactly the same nominal voltage and droop
setting.
For example:
The generator
off load
is producing 230 V.
Place the generator
on load
at typical load levels and adjust the
Droop
until the output voltage is
218 V. (this is 5% below nominal voltage).
When reactive power is zero (pf 1.0 or unity), the generator output voltage is 230 V.
When reactive power is negative (capacitive or leading pf) the output voltage is raised to increase
inductive current from the generator.
When reactive power is positive (inductive of lagging pf) the output voltage is lowered to decrease
inductive current from the generator.
Mains Parallel
When paralleling with mains supply, the use of a generator load share controller with active kvar
sharing and voltage compensation is recommended. Such controllers include the DSE8xxx series of
load share controllers. Contact DSE Technical Support for more information.
Where such a mains controller does not exist, the droop setting is used to provide stabilisation to the
output of kvar when in parallel with the mains.
To set the droop function when paralleling with mains and no other form of kvar control exists:
1. With the generator running off load, adjust the
Voltage Setpoint
so that the generator is
providing the desired voltage.
2. Adjust the
Droop
setting as required (typically 2.5%).
3. When in parallel with the mains, adjust the
Voltage Setpoint
while monitoring the kvar output
from the alternator to set the amount of kvar desired from the alternator. Increase the
Voltage
Setpoint
to increase the kvar.
