IEEE Power & Energy Magazine - March/April 2017 - 64

charging, can play a similar role.
Another technology that can aid
in the efficient utilization of flexCurtailment
ible resources is advanced renew600
Wind
able energy and load forecasting.
Characterizing or reducing the
PV
500
uncertainty associated with VRE
Gas CT
output or load enables a more effiGas CC
400
cient utilization of the entire powHydropower
er system, including conventional
CSP
300
generators, storage devices, and
Coal
transmission infrastructure.
Biopower
200
As we add more VRE into power
Geothermal
systems, the grid of the future will
Nuclear
100
have many more inverter-based genShifted Load
erators and be much more distribLoad
0
uted than the current power system,
which is dominated by central-station
synchronous generators. In general, VRE resources often use inverters to connect to the grid instead
figure 2. The off-peak national production charts for an 80% VRE transmissionof
synchronous generators, and
constrained scenario show massive curtailment at high renewable energy penetrations.
if the instantaneous penetration
system at many timescales, the most important of which is in of VRE were more than 50%, the system would be operating
shifting wind and solar power from times when it might oth- as an inverter-dominated grid. The challenges with high levels
erwise be curtailed to times when the power output of VRE of inverter-based generation in power systems are discussed
is lower than current demand. This intra- and interdaily in detail later in this article, but studies such as the "Renewshifting of power can be performed by several different stor- able Electricity Futures Study" show that, at higher levels of
age technologies, such as the existing pumped hydropower VRE penetration, there is an increasing number of hours durfleet, compressed air energy storage systems, or various bat- ing the year with more inverter-based generation than synchrotery technologies. Demand-response technologies can play nous generation. Figure 3 shows the VRE penetration curves
a similar role by shifting load demand so that it coincides for each interconnect and the total in the United States for an
with VRE generation or lowers the ramping requirements 80% renewable scenario that is transmission constrained. This
of the remaining generation fleet. Similarly, new loads that figure also illustrates that the Electric Reliability Council of
have flexibility in their use patterns, such as electric vehicle Texas (ERCOT) would be an inverter-dominated system more
than 59% of the time. Figure 4 is a scatter plot of VRE compared to load in ERCOT for the same scenario. The solid lines
125
show a large number of hours when the system operates with
East
ERCOT
more than 50% VRE, and in some cases with more than 100%
Exported to
100
West
Total
Other Regions
VRE, due to exporting energy to the other interconnections.
At these high renewable energy scenarios, the power system
ERCOT System Is
75
Inverter Dominated
not only has a large number of inverter-dominated operational
59% of Hours
hours, but it also fluctuates between being synchronous gen50
erator dominated and inverter dominated on a daily basis.
30 April
12:00

30 April
00:00

29 April
12:00

29 April
00:00

28 April
12:00

28 April
00:00

27 April
12:00

VRE (%)

27 April
00:00

Power (GW)

700

25

Inverter-Dominated Grids
8,000

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0

0

Hours

figure 3. The cumulative hours in a year compared to the
instantaneous VRE penetration for three interconnections
and the total in the United States for the scenario when
total annual VRE penetration is 80%.
64

ieee power & energy magazine

So what is an inverter-dominated grid? If we examine existing
large-scale ac power systems, we note that they are predominately powered by conventional synchronous generators [Figure 5(a)]. Nuclear, coal, gas, and hydropower systems all utilize
synchronous generators to connect to the rest of the electric
grid. These generators are interconnected through an extensive transmission and distribution system providing reliable
and affordable electricity to customers; however, one of the
main distinguishing aspects of VRE integration is that, aside
march/april 2017



Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - March/April 2017

IEEE Power & Energy Magazine - March/April 2017 - Cover1
IEEE Power & Energy Magazine - March/April 2017 - Cover2
IEEE Power & Energy Magazine - March/April 2017 - 1
IEEE Power & Energy Magazine - March/April 2017 - 2
IEEE Power & Energy Magazine - March/April 2017 - 3
IEEE Power & Energy Magazine - March/April 2017 - 4
IEEE Power & Energy Magazine - March/April 2017 - 5
IEEE Power & Energy Magazine - March/April 2017 - 6
IEEE Power & Energy Magazine - March/April 2017 - 7
IEEE Power & Energy Magazine - March/April 2017 - 8
IEEE Power & Energy Magazine - March/April 2017 - 9
IEEE Power & Energy Magazine - March/April 2017 - 10
IEEE Power & Energy Magazine - March/April 2017 - 11
IEEE Power & Energy Magazine - March/April 2017 - 12
IEEE Power & Energy Magazine - March/April 2017 - 13
IEEE Power & Energy Magazine - March/April 2017 - 14
IEEE Power & Energy Magazine - March/April 2017 - 15
IEEE Power & Energy Magazine - March/April 2017 - 16
IEEE Power & Energy Magazine - March/April 2017 - 17
IEEE Power & Energy Magazine - March/April 2017 - 18
IEEE Power & Energy Magazine - March/April 2017 - 19
IEEE Power & Energy Magazine - March/April 2017 - 20
IEEE Power & Energy Magazine - March/April 2017 - 21
IEEE Power & Energy Magazine - March/April 2017 - 22
IEEE Power & Energy Magazine - March/April 2017 - 23
IEEE Power & Energy Magazine - March/April 2017 - 24
IEEE Power & Energy Magazine - March/April 2017 - 25
IEEE Power & Energy Magazine - March/April 2017 - 26
IEEE Power & Energy Magazine - March/April 2017 - 27
IEEE Power & Energy Magazine - March/April 2017 - 28
IEEE Power & Energy Magazine - March/April 2017 - 29
IEEE Power & Energy Magazine - March/April 2017 - 30
IEEE Power & Energy Magazine - March/April 2017 - 31
IEEE Power & Energy Magazine - March/April 2017 - 32
IEEE Power & Energy Magazine - March/April 2017 - 33
IEEE Power & Energy Magazine - March/April 2017 - 34
IEEE Power & Energy Magazine - March/April 2017 - 35
IEEE Power & Energy Magazine - March/April 2017 - 36
IEEE Power & Energy Magazine - March/April 2017 - 37
IEEE Power & Energy Magazine - March/April 2017 - 38
IEEE Power & Energy Magazine - March/April 2017 - 39
IEEE Power & Energy Magazine - March/April 2017 - 40
IEEE Power & Energy Magazine - March/April 2017 - 41
IEEE Power & Energy Magazine - March/April 2017 - 42
IEEE Power & Energy Magazine - March/April 2017 - 43
IEEE Power & Energy Magazine - March/April 2017 - 44
IEEE Power & Energy Magazine - March/April 2017 - 45
IEEE Power & Energy Magazine - March/April 2017 - 46
IEEE Power & Energy Magazine - March/April 2017 - 47
IEEE Power & Energy Magazine - March/April 2017 - 48
IEEE Power & Energy Magazine - March/April 2017 - 49
IEEE Power & Energy Magazine - March/April 2017 - 50
IEEE Power & Energy Magazine - March/April 2017 - 51
IEEE Power & Energy Magazine - March/April 2017 - 52
IEEE Power & Energy Magazine - March/April 2017 - 53
IEEE Power & Energy Magazine - March/April 2017 - 54
IEEE Power & Energy Magazine - March/April 2017 - 55
IEEE Power & Energy Magazine - March/April 2017 - 56
IEEE Power & Energy Magazine - March/April 2017 - 57
IEEE Power & Energy Magazine - March/April 2017 - 58
IEEE Power & Energy Magazine - March/April 2017 - 59
IEEE Power & Energy Magazine - March/April 2017 - 60
IEEE Power & Energy Magazine - March/April 2017 - 61
IEEE Power & Energy Magazine - March/April 2017 - 62
IEEE Power & Energy Magazine - March/April 2017 - 63
IEEE Power & Energy Magazine - March/April 2017 - 64
IEEE Power & Energy Magazine - March/April 2017 - 65
IEEE Power & Energy Magazine - March/April 2017 - 66
IEEE Power & Energy Magazine - March/April 2017 - 67
IEEE Power & Energy Magazine - March/April 2017 - 68
IEEE Power & Energy Magazine - March/April 2017 - 69
IEEE Power & Energy Magazine - March/April 2017 - 70
IEEE Power & Energy Magazine - March/April 2017 - 71
IEEE Power & Energy Magazine - March/April 2017 - 72
IEEE Power & Energy Magazine - March/April 2017 - 73
IEEE Power & Energy Magazine - March/April 2017 - 74
IEEE Power & Energy Magazine - March/April 2017 - 75
IEEE Power & Energy Magazine - March/April 2017 - 76
IEEE Power & Energy Magazine - March/April 2017 - 77
IEEE Power & Energy Magazine - March/April 2017 - 78
IEEE Power & Energy Magazine - March/April 2017 - 79
IEEE Power & Energy Magazine - March/April 2017 - 80
IEEE Power & Energy Magazine - March/April 2017 - 81
IEEE Power & Energy Magazine - March/April 2017 - 82
IEEE Power & Energy Magazine - March/April 2017 - 83
IEEE Power & Energy Magazine - March/April 2017 - 84
IEEE Power & Energy Magazine - March/April 2017 - 85
IEEE Power & Energy Magazine - March/April 2017 - 86
IEEE Power & Energy Magazine - March/April 2017 - 87
IEEE Power & Energy Magazine - March/April 2017 - 88
IEEE Power & Energy Magazine - March/April 2017 - 89
IEEE Power & Energy Magazine - March/April 2017 - 90
IEEE Power & Energy Magazine - March/April 2017 - 91
IEEE Power & Energy Magazine - March/April 2017 - 92
IEEE Power & Energy Magazine - March/April 2017 - 93
IEEE Power & Energy Magazine - March/April 2017 - 94
IEEE Power & Energy Magazine - March/April 2017 - 95
IEEE Power & Energy Magazine - March/April 2017 - 96
IEEE Power & Energy Magazine - March/April 2017 - Cover3
IEEE Power & Energy Magazine - March/April 2017 - Cover4
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091020
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070820
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050620
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030420
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010220
https://www.nxtbook.com/nxtbooks/pes/powerenergy_111219
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091019
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070819
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050619
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030419
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010219
https://www.nxtbook.com/nxtbooks/pes/powerenergy_111218
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091018
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070818
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050618
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030418
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010218
https://www.nxtbook.com/nxtbooks/pes/powerenergy_111217
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091017
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070817
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050617
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030417
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010217
https://www.nxtbook.com/nxtbooks/pes/powerenergy_111216
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091016
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070816
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050616
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030416
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010216
https://www.nxtbook.com/nxtbooks/ieee/powerenergy_010216
https://www.nxtbook.com/nxtbooks/pes/powerenergy_111215
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091015
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070815
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050615
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030415
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010215
https://www.nxtbook.com/nxtbooks/pes/powerenergy_111214
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091014
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070814
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050614
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030414
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010214
https://www.nxtbookmedia.com