Accommodating High Levels of Variable Generation - NERC

Power System Operations
responsive reserves during light load conditions or explore the use of batteries, flywheels, loads,
etc. to provide this capability. Greater visualization provided by state-of-the-art system
monitoring technology, like PMUs, may assist operators and planners in managing these new
resources.
In summary, with high levels of variable generation, existing operating practices in unit
commitment and/or dispatch along with reserve management will need to change in order to
maintain bulk power system reliability. Timely forecasting of large variable generation ramping
events is particularly important. Therefore, the task force recommends:
NERC Action: NERC’s Operating Committee should identify the additional or enhanced
operational criteria, practices and procedures required to accommodate large levels of
variable generation integration. For example, probabilistic methods may be needed to
forecast uncertainty in wind plant output and included in the operations planning process.
The Committee should, further, increase the awareness of these needs through established
NERC programs and/or initiatives.
4.3. Ancillary Services and Reduced Scheduling Intervals
Ancillary services are a vital part of balancing supply and demand and maintaining bulk power
system reliability. Organizations have taken advantage of demand aggregation, provision of
ancillary services from other jurisdictions and interconnected system operation, for decades.
Since each balancing area must compensate for the variability of its own demand and random
load variations in individual demands, larger balancing areas with sufficient transmission
proportionally require relatively less system balancing through “regulation” and ramping
capability than smaller balancing areas. Smaller balancing areas can participate in wider-area
arrangements for ancillary services to meet NERC’s Control Performance Standards (CPS1 and
CPS2).
As mentioned in earlier chapters, with sufficient bulk power transmission, larger balancing areas
or participating in wide-area arrangements, can offer reliability and economic benefits when
integrating large amounts of variable generation. 92 In addition, they can lead to increased
diversity of variable generation resources and provide greater access to more dispatchable
resources, increasing the power systems ability to accommodate larger amounts of variable
generation without the addition of new sources of system flexibility. Balancing areas should
evaluate the reliability and economic issues and opportunities resulting from consolidation or
92 Report for the International Energy Agency by Holttinen et al in 2007
Accommodating High Levels of Variable Generation 60