IEEE Power & Energy Magazine - November/December 2015 - 30

Field Test Results (2.5 Unit)
1,500
Turbine kVAR

Reactive
Power

Active
Power
(Zero)
0

75
Time (s)

100

figure 6. A demonstration of reactive power with no wind.

active power available from the turbine, the converter can
continue to deliver or absorb reactive power.
Test results for a single wind turbine operating with the
GE WindFREE zero power reactive control are shown in
Figure 6. Throughout the test, the real power output is zero,
while the reactive power output varies. This independent
controllability of reactive power enables voltage regulation,
regardless of wind condition. Other mainstream wind turbine manufacturers offer similar functionality.

Reactive Power Supply
as an Ancillary Service
Planners have long recognized the need for reactive power
and, in particular, the value of fast, dynamic VAR of the
type that can be delivered by wind turbines. Nevertheless,
ancillary services markets that offer incentives for independent participants to provide this service are only just
emerging (such as is the case in New York). The behavior
is similar to traditional synchronous condensers, and the
applicability parallels situations where generators (usually, gas turbine generators) are provided with a clutch
that allows operation as a synchronous condenser when
grid (and market) conditions demand it. Historically, this
capability is usually utility-owned, so transparent market
mechanisms are lacking.
The systemic operational value of being able to deliver
reactive power is very location-specific-much more so
than control of active power. The most significant benefits
are observed for systems with substantial dynamic reactive
power requirements. These include very large projects, projects that are physically remote with electrically weak connections to the grid, and projects in areas with heavy and
variable loads. Wind power plants equipped with this feature
will provide effective grid reinforcements by maintaining
continuous voltage regulation.

Conclusion
Commercially available wind power plants today are
capable of meeting the full range of grid requirements and
already provide performance similar to that of-and, in

ieee power & energy magazine

some cases, superior to-conventional generating equipment. The technology has evolved because of the growing
demand for advanced functionality in active and reactive
power control to maintain the integrity of the bulk system,
and it has been proven to work well in many operating wind
plants supplied by various manufacturers throughout the
world today. This opens the possibility for wind plants to
provide ancillary services to the power system. Wind plants
are available today with the full range of these services.
Mechanisms to enable the value of these functions and features through interconnection requirements, grid codes, and
market incentives continue to evolve as a necessary means
to maintain power system integrity, reliability, and economical operation.

For Further Reading
Florida Reliability Coordinating Council Event Analysis Team interim recommendations report. (Feb. 26,
2008). [Online]. Available: http://www.balch.com/files/upload/FRCC_Interim_Report_6_3_08.pdf >
M. E. Cardinal and N. W. Miller, "Grid friendly wind
plant controls: WindCONTROL-Field test results," in
Proc. WindPower 2006, Pittsburgh, PA, pp. 1-6.
Electric Reliability Council of Texas, Wind Operations
Task Force. [Online]. Available: www.ercot.com/committees/
board/tac/ros/wotf
California Energy Commission. (2007, July). California
Energy Commission's Intermittency Analysis Project Study.
Appendix B-Impact of intermittent generation on operation of California Power Grid. [Online]. Available: http://
www.energy.ca.gov/2007publications/CEC-500-2007-081/
CEC-500-2007-081-APB.PDF
K. Clark and N. Miller, "Advanced controls enable wind
plants to provide ancillary services," in Proc. IEEE Power
Engineering Society General Meeting, Minneapolis, MN,
2010, pp. 1-6.
N. Miller, K. Clark, and G. Jordan, "Planning and operating power systems with a high percentage of wind generation: Taking advantage of the latest wind plant controls," in
Proc. Amercian Wind Energy Assoc., June 6, 2007, pp. 1-8.

Biographies:
Jason MacDowell is with GE Energy Consulting, Schenectady, New York.
Sudipta Dutta is with GE Energy Consulting, Schenectady, New York.
Matt Richwine is with GE Energy Consulting, Schenectady, New York.
Sebastian Achilles is with GE Energy Consulting, Schenectady, New York.
Nicholas Miller is with GE Energy Consulting, Schenectady, New York.
p&e

november/december 2015

http://www.balch.com/files/up http://www.ercot.com/committees/ http://http:// http://www.energy.ca.gov/2007publications/CEC-500-2007-081/

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - November/December 2015