Generator Walk-In - ABB PCS100 UPS-I User Manual

74 PCS100 UPS-I User Manual
Initial charging time of the Ultracapacitor Energy Storage, from 0 V to 650 V, is up to 120 minutes.

9.5 Generator Walk-In

The PCS100 UPS-I with Battery Energy Storage with 30 seconds autonomy is typically used to bridge start-up
time for stand-by generator backup systems where critical applications may be subject to longer supply outages.
If a stand-by generator is included in the installation it is connected to the Automatic Transfer Switch (ATS).
Generally, stand-by generator is started automatically in the event of a utility supply failure.
The Automatic Transfer Switch transfers to the generator when it detects that the generator voltage is stable.
When the utility supply is restored, the ATS disconnects stand-by generator and reconnects utility supply.
Automatic
Transfer
Switch
G
PCS100 UPS-I
3-Phase
Protected
Load
3-Phase
Utility
Supply
Figure 9-2: PCS100 UPS-I combined with stand-by generator
The PCS100 UPS-I needs to support the need to transfer load back to a generator supply from the energy storage
mode of operation. However, a step transfer of load to generator (or weak utility supply networks) will result in
the voltage and/or frequency disturbance on the generator terminals exceeding the transfer threshold. The result
would be a transfer back to the stored mode.
The Generator Walk-in function of the PCS100 UPS-I supports controlled transfer of the load to stand-by
generators.
The transfer to the generator will be made when the generator voltage has been stable and within the acceptable
bounds as defined by the voltage event criteria. Then the inverter will synchronize to the generator supply and
continue to support the load. A linear ramp is imposed on the set-points, ramping the support to generator to
zero over a defined time. Once the ramp down is complete the walk-in process is complete and the PCS100 UPS-I
reverts to charging mode.
The transfer sequences utility supply – energy storage – generator and generator – energy storage - utility supply
are fully automatic and the load is not affected during automatic switch transfers.
The generator walk-in time can be set through parameter 521 Walk in Time in range from 0 seconds to maximum
8 seconds.
The following image shows the timing diagram of the PCS100 UPS-I Generator Walk-in functionality in the
common stand-by generator back-up system with an automatic transfer switch. It can be seen that the load
supply is not affected in any case.
Note that the duration of individual events is not in scale.