VAR Control Technology

Until recently, most wind power plant operators and utilities have employed capacitors to correct power factor to near unity during operation. Because these devices are slow and not able to provide fine, continuous control, they are unable to react to sudden momentary dips in voltage commonly seen in weak grid or gusty wind conditions; this, in turn, can add stress to the utility grid. To make up for these performance limitations, some wind projects have added static VAR compensators or other similar equipment. Unfortunately, these methods are expensive and complex and unable to provide an optimal solution.

More Power to You

Today, through GE's unique WindVAR electronics, voltage is controlled and regulated in real-time. Similar to conventional utility generators, the WindVAR system supplies reactive power to the grid at the time it is needed, in a fraction of a second, regulating system voltage and stabilizing weak grids. With the ability to supply reactive power to the grid, this technology opens the door to new opportunities in areas where weak rural distribution systems had discouraged new wind power applications. The addition of a wind project equipped with WindVAR electronics can actually strengthen a weak grid. This system also has the potential to provide emergency backup support and support to weak grids in need of transmission and distribution capital improvements. The turbine's power electronics also reduce the inrush current to about 75 percent of full load current during the wind turbine's start-up and provide ride-thru capability.

How It Works

GE's WindVAR system is provided through the same power electronics employed in achieving variable speed operation. Our full line of wind turbines employ the variable speed technology to reduce torque transients and increase the blades' ability to capture more of the kinetic energy available in the wind. A voltage controller placed at the point of interconnect measures utility line voltage, compares it to the desired level and computes the amount of reactive power needed to bring the line voltage back to the specified range. To reach the desired voltage level at the substation, the VAR controller communicates the reactive power requirement to each of the project's wind turbines via a distributed control network. Individually, each wind turbine's power processor excites the generator to produce the commanded power factor. As the power factor changes, the measured line voltage moves toward the desired voltage level, forming a closed-loop voltage control system.

The Proving Ground

We first demonstrated the capabilities of our WindVAR selectable power factor system in cooperation with the Department of Energy and the Electric Power Research Institute's Turbine Verification Program at a wind project at Algona in North Central Iowa. Three wind turbines, installed 6.5 miles from a 69/13.8 kV 10 MVA substation, today successfully operate without voltage rise or flicker issues. The TVP specified the placement of this amount of generation in conjunction with the relatively long distance from the substation, as a demonstration of the flexibility of the WindVAR control technology.

Today, more than 2,000 WindVAR equipped wind turbines operate around the globe. With the ability to supply reactive power to the grid at the time it's needed, our WindVAR electronics are fast becoming a standard feature requested by both developers and utilities and a requirement of many interconnect agreements.

Download More Information

• "WindVAR:" Unique VAR Control Technology (379KB PDF)