Woodward EGCP-2 - Figure 4-3. Droop;Isochronous Load Sharing

Manual 26086 EGCP-2 Engine Generator Control Package
Woodward 73
Figure 4-3. Droop/Isochronous Load Sharing
Maximum load for this type of system is limited to the combined output of the
swing machine the total set power of the droop machines. The minimum system
load cannot be allowed to decrease below the output set for the droop machines.
If it does, the system frequency will change, and the swing machine can be
motorized.
The machine with the highest output capacity should be operated as the swing
machine, so that the system will accept the largest load changes within its
capacity.
Isochronous Load Sharing on an Isolated Bus
Isochronous Load Sharing is the most common means of paralleling multiple
generators together to a common load on an isolated bus. The EGCP-2 uses
Isochronous Load Sharing control when operating in a Multiple Unit mode with
the Load Control Mode in either Normal or Soft Transfer. Isochronous load
sharing operates all generator sets in a system in the isochronous mode. Load
sharing is accomplished by using the load sensor of the EGCP-2 to bias the
speed reference of the isochronous governor. The EGCP-2 load sensors are
connected by inter-control RS-485 network. In the case of the EGCP-2 control
Isochronous Load Sharing is done digitally via this network. Any imbalance in
load between units will cause a change to the regulating circuit in each governor.
While each unit continues to run at isochronous speed, these changes force
each machine to supply a proportional share of power to meet the total load
demand on the system.
Base Load Against the Mains
Base Load is a method of setting a base or fixed load on a machine operating in
parallel with the mains. The EGCP-2 control operates the generator set in base
load whenever the generator is in parallel with the utility, unless a process control
mode of operation is selected through the Process discrete input. This is
accomplished by using an isochronous load control and providing a reference at
which to control the load. The governor will force the generator output to increase
or decrease until the output of the load sensor is equal to the reference setting.
The base load reference is set in the Real Load Control tuning menu of the
EGCP-2. At this point, the system is in balance.