Handbook of Energy Storage for Transmission or ... - W2agz.com

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Reference peak shaving profiles for both PS and PQ Modules are shown in Figure 1-5. These
profiles show a gradual increase in power at the beginning of the discharge interval to minimize
grid transients, a constant power plateau, and a gradual decrease in power at the end. These
profiles illustrate a thermal management strategy that allows 100% depth of discharge within
temperature limits over the minimum time interval. Since the majority of applications that only
involve peak shaving do not require a rapid transition of power, these profiles are deemed to be
an acceptable basis for defining basic performance parameters for NAS products. As shown on
the figure, the Rated PS Capacities for the PQ and PS Modules are 360 and 430 kWh ac
,
respectively; and the Rated PS Power for both modules is 50 kW ac
.
Power, kW ac
70
60
50
40
30
20
10
0
PQ Module, 360 kWhac Rated PS Capacity
PS Module, 430 kWhac Rated PS Capacity
Rated PS Pow er, 50 kWac (both modules)
0 1 2 3 4 5 6 7 8 9 10 11
Time, hr
Figure 1-5. Reference Peak Shaving Profiles (both modules)
While gradual load changes yield the most energy efficient duty cycle, mitigation of power
disturbances such as sags and momentary outages requires step load changes within a few
milliseconds. Both NAS modules can reach full power within one millisecond, and the PQ
Module has been specifically developed for PQ applications and combined PQ and PS
applications. Figure 1-6 illustrates the capability of the PQ Module to deliver step load pulses of
power for durations ranging from 30 seconds to 3 hours. (Thermal management of longer
duration discharges requires discharge profiles similar to those shown in Figure 1-5.) As noted
in Table 1-1, NGK defines the term “Pulse Factor” as the ratio of the maximum power for the
stated duration to the Rated PS Power. For example, the PQ Module can deliver 400% Rated PS
Power (i.e., 4 times 50 kW equals 200 kW) for 15 minutes as indicated Figure 1-6.
The PS Module can also deliver step load pulses of power. It is capable of supplying 60 kW
(120% of rated power) for up to 3 hours.
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