WIND ENERGY SYSTEMS - Cd3wd

Chapter 5—Electrical Network 5–57
TABLE 5.3 Communication and Control
between a Large Wind Turbine Generator
and a Dispatch Center
Under Local Control
(a) Start Capability
(b) Synchronization
(c) Stand-Alone Capability
(d) Protection
Information to Dispatch Center
(a) Operating Mode (on/off)
(b) Power Flow
(c) Voltage Magnitude
(d) Revenue Metering
Control from Dispatch Center
(a) Change Operating Mode
(b) Change Power Level
If there were 75 wind turbines being monitored and controlled by the dispatch center,
and all the dispatch center costs were to be allocated to them, each wind turbine would be
responsible for $10,000 of equipment at the dispatch center and another $10,000 of equipment
at the turbine. This $20,000 would present a major obstacle to the purchase of a 5 kW wind
generator priced at $8000, but not nearly as much of an obstacle to a 2.5 MW wind generator
priced at $2,000,000. In one case the monitoring and control equipment cost 2.5 times as
much as the wind generator itself, and only 1 percent of the wind generator cost in the second
case. This is another economy of scale for wind generators. In addition to turbine cost per
unit area decreasing with size, and power output per unit area increasing with size because of
greater height and therefore better wind speeds, the cost of monitoring and control per unit
area also decreases with turbine size.
The probable result of these economic factors is that small wind generators, less than
perhaps 20 kW maximum power rating, will not be monitored and controlled by a dispatch
center. Each small wind generator will have its own start, stop, and protective systems. The
utility will somehow assure itself that voltage magnitudes are within acceptable limits and
that electrical islands cannot operate on wind power alone and continue to operate the system
in a manner much like the past. This should be satisfactory as long as the total installed wind
generator capacity is significantly less than the minimum load on a feeder line.
On the other hand, large wind turbines will almost certainly be monitored and controlled
by the appropriate dispatch center. This control can result in significant benefits to both the
utility and the wind turbine, with acceptable costs.
Wind Energy Systems by Dr. Gary L. Johnson November 21, 2001