Accommodating High Levels of Variable Generation - NERC

Characteristics of Power Systems & Variable Generation
Figure 2.1 illustrates the planning and operations processes and the associated technology issues
for the shorter timeframes mentioned above. 13 For operations closer to a day or days ahead of
the real time, the reliability of the bulk power system is secured by ensuring that there is
adequate generation supply with proper characteristics available to meet the forecast demand and
its expected variation while maintaining bulk power system reliability. As time moves closer to
a few minutes to a few hours ahead of real time, the operator requires a forecast of demand and
generation at much higher accuracy and will also more closely consider the ramp rate capability
of the resource fleet within or outside its Balancing Area to ensure that these resources are
available and can be dispatched or maneuvered to ensure supply-demand balance while
maintaining bulk power system reliability.
Planning and
Operation Process
Technology
Is s u e s
1 Year
Unit Dispatch
Faster (seconds) Time Frame Slower (Years)
Resource and
Capacity Planning
(R e lia b ility)
U n it C o m m itm e n t
and
Day-Ahead
Scheduling
Load Follow ing
(5 M inute Dispatch)
Frequency and
Tie-Line Regulation
(A G C )
Capacity Valuation
(U C A P , IC A P )
and
Long-Term Load
G row th Forecasting
Day-ahead and
M u lti-D a y
Forecasting
Hour-Ahead
Forecasting
and
P lan t A ctive P o w er
M aneuvering and
Managem ent
Real-Tim e and
Autonom ous Protection
and Control Functions
(A G C , L V R T , P S S ,
Governor, V-Reg, etc.)
NYISO Load (MW)
MW
MW
700
600
500
400
300
200
100
0
0 2000 4000 6000 8000
Hour
30,000
25,000
20,000
15,000
10,000
5,000
0
3000
2500
2000
1500
1000
500
0
1 Day
2001 Average Load vs Average W ind
1,600
1,400
1,200
1,000
800
600
400
J u ly lo a d August load Septem ber load 200
July w ind August w ind Septem ber w ind
0
1 6 11 16 21
Hour
3 Hours
1 6 1 1 2 1
M i n u te s
September Morning A u gu s t M o rn ing M ay Ev e n in g October Evening April Afternoon
10 M inutes
Wind Output (MW)
Figure 2.1 Power System Planning and Operation
13 http://www.nyserda.org/publications/wind_integration_report.pdf
Accommodating High Levels of Variable Generation 7