Oahu Wind Integration Study - Hawaii Natural Energy Institute ...

challenging events when the system performance could be assessed. Figure 1-10 shows a
histogram of hourly wind power changes (modeled wind data obtained from AWS Truepower),
across the sum of the wind plants in Scenario 5 (200 MW Lanai, 200 MW Molokai, 100 MW
Oahu) for the years 2007 and 2008. The largest 60-minute wind power change was observed to
be 311 MW over one hour in Scenario 5. As a reference, in 99.9% of the events, the wind power
dropped in Scenario 5 by less than 145 MW over one hour; and in 99.9% of the cases, wind
power increased in Scenario 5 by less than 167 MW over one hour.
On a smaller time scale of 10 minutes, the largest total wind power reduction was 90 MW in
Scenario 5 (and 127 MW in Scenario 3). A 5% loss of wind energy was assumed in the transport
of power from Molokai and Lanai wind plants to Oahu through the HVDC cable system.
Frequency (%)
25
20
15
10
5
0
0.1% percentile = -145
Negative most = -311
99.9% percentile = 167
Positive most = 244
-100 -50 0 50 100
Total Wind Power Change (MW per hour)
Figure 1-10. Histogram of total wind power changes over 60-minute for Scenario 5 for the wind
energy delivered to the Oahu system (two years of simulated wind power data from AWS
Truepower).
During the event of the largest drop in wind power (311 MW over a 60-minute interval, or 27%
loss of generation), the system up-reserves were challenged. The system load was 1160 MW. At
the completion of this one-hour event, only 5 MW of up-reserve capacity remained on the system
if no additional units were committed. In the following hour, all fast-start units must be
committed to restore system up-reserve.
Figure 1-11 shows the wind and solar power change over the one-hour period and shows the
simulated system frequency during this event.
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