ABB HiPerGuard MV UPS User Manual page 25

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In this configuration, typically one generator first livens the generator bus and the other generators synchronize
and connect to this bus. Generators are in isochronous frequency-control mode, also known as Island Forming
mode. In this mode, for multiple parallel generators to share load equally they typically employ frequency droop
and have an overriding controller which adjusts the generators' frequency reference to regulate the frequency to
nominal.
The MV UPS adaptive walk-in is designed to work with this configuration. As soon as the first generator livens the
generator bus once the voltage and frequency are within specification the UPS(s) will connect to the bus. Once the
MV UPSs are connected their adaptive walk-in algorithm will support the generator bus by not letting the fre-
quency drop below 98% of the nominal frequency. As individual generators continue to connect to the bus, they
will ramp in load to regulate the frequency back to the nominal frequency Once enough generators are supplying
load then the bus will eventually regulate to the nominal frequency.
3.2.6 Automatic bypass operation
In case of an expected or unexpected HiPerGuard MV UPS shutdown, the load current is transferred to the au-
to-bypass breaker. The MV switchgear acts as the primary system bypass, and its operation is fully controlled by
the MV UPS, while the MV UPS control switch located on the switchgear is in "UPS Control" mode.
The rated current for the automatic bypass breaker will be the same as the rated current of the MV switchgear
(rating is project dependent, please refer to specific project switchgear documentation for more information).
During the bypass operation, the MV UPS synchronizes the load output voltage to the MV UPS input voltage and
then closes the automatic bypass breaker. After confirming that the automatic bypass breaker is closed, the MV
UPS opens the input and output breakers.
In the very unlikely event where the UPS is not capable of synchronizing the output voltage to the input voltage,
the bypass will be still automatically close, as the closing logic is embedded in the switchgear. When this occurs, a
slight phase shift between the input and output voltages is expected during the operation. This phase shift is not
likely to have an impact on the load.
3.2.7 Demand response interface
This section defines the MV UPS main controller interface towards a third-party Demand Response Controller
(DRC). The DRC is an optional feature, identified by a number on the order code. Please refer to Chapter 4 for more
information. Always refer to the local grid standards/regulations before implementing Demand Response con-
trols.
The next sub-chapters will also provide a guideline to what a third-party DRC must consider and how the system
will operate in different scenarios. The Demand Response (DR) is only available when the MV UPS is operating in
Power Conditioning Mode.
—
Figure 3.07: DRC
interface.