Basler Electric DECS-250N - Manual (Page 45)

9440500990 Rev D 29
DECS-250N Regulation
Operation with Paralleled Generators
BESTCOMSPlus Navigation Path: Settings Explorer, Operating Settings, Parallel/LineDrop
Compensation
HMI Navigation Path: Settings, Operating Settings, Parallel/LineDrop Compensation
The DECS-250N can be used to control the excitation level of two or more generators operating in
parallel so that the generators share the reactive load. The DECS-250N can employ either droop
compensation or cross-current compensation (reactive differential) schemes for reactive load sharing. A
separate load sharing function enables each machine to share the load proportionally without incurring a
voltage and frequency droop.
Paralleled generator settings are illustrated in Figure 19 and described in the following paragraphs.
Reactive Droop Compensation
Droop compensation serves as a method of controlling reactive current when the generator is connected
in parallel with another energy source. Droop compensation utilizes the B-phase CT in single-phase
applications. When droop compensation is enabled
A , the generator voltage is adjusted in proportion to the
measured generator reactive power. The reactive droop compensation setting B is expressed as a
percentage of the generator rated terminal voltage.
Note
For droop compensation to operate, the PARALLEL_EN_LM logic
block must be set true in BESTlogic™Plus programmable logic.
Cross-Current Compensation
Cross-current compensation (reactive differential) mode serves as a method of connecting multiple
generators in parallel to share reactive load. When reactive load is shared properly, no current is fed into
the DECS-250N cross-current compensation input (which is connected to the B-phase transformer).
Improper sharing of reactive load causes a differential current to be fed into the cross-current
compensation input. When cross-current compensation is enabled
C , this input causes the DECS-250N to
respond with the proper level of regulation. The response of the DECS-250N is controlled by the cross-
current compensation gain setting
D which is expressed as a percentage of the system nominal CT setting.
Application information about cross-current compensation is available in the Voltage and Current chapter
of this manual.
Network Load Sharing
In a multiple-generator application, the load sharing function ensures equal generator reactive-power
sharing. It operates in a similar manner to cross-current compensation but without the external hardware
requirements and distance limitations. Instead of sharing load based on the CT ratio, load is shared on a
per-unit basis calculated from the generator rated data. Sharing of load information between DECS-250N
controllers is accomplished through the Ethernet port of each DECS-250N communicating over a peer-to-
peer network dedicated for the load sharing function. Each DECS-250N measures the reactive current of
its associated generator and broadcasts its measurement to all other DECS-250N controllers on the
network. Each DECS-250N compares its level of reactive current to the sum of all measured currents and
adjusts its excitation level accordingly.
Network load sharing implements a fading droop function based on the droop setting, washout filter gain,
and washout filter time constant. During transients, load sharing will droop according to the droop
percentage and washout filter gain settings. The droop characteristic will fade with a time constant
according to the washout filter time constant.
A Load Share ID setting identifies the DECS-250N as a load sharing unit in the network. Checking a Load
Sharing Unit number box allows any DECS-250N load sharing units on the network with that Load Share