ABB HiPerGuard MV UPS User Manual page 58

EX TE R NA L P OW E R A ND CO N T RO L CO N NE C T IO NS
Figure 6.8: HiPerGuard MV UPS Power Exchanger and Generator Interface connections
6.4.7. Generator Interface
In some installations with local generator(s) providing back-up in the event of loss of mains power
supply, an event such as a step load change can affect the frequency stability of the generator(s). Island
detection routines in the MV UPS based on phase and frequency change will need to be muted, and
angle tracking filters sped up, to prevent this from causing frequent apparently spurious transitions
from Power Conditioning mode to Independent mode and opening of S .
in
By restricting the UPS frequency excursions, the MV UPS is able to support the supply during load step
events. This helps the generator voltage and frequency regulation loops to re-stabilize more quickly.
This may cause short term battery charge or discharge until generator stability is reached again. This is
achieved by adjusting or suppressing certain filter rates and thresholds in the UPS System Controller.
This generator support is most needed with systems with small back-up generators, with capacity
comparable to the UPS (and load) capacity. It is also useful for larger generators with poor output
frequency stability. The generator interface to the MV UPS can be either via Modbus TCP
communications or over a digital input on the same hard-wired remote I/O module used for the Power
Exchanger interface as shown in Figure 6.8.
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