Feature‡ Benefit

Built on proven technology ‡ An evolutionary design that shares many systems proven on the D8-2000 DFIG.

Established track record ‡ WinDrive® technology has proven itself in other demanding power and industrial applications of new components where it has established a MTBF of more than 39 years. The synchronous generator has a long history of use in diesel generator systems achieving a MTBF of 45 years.

synchronous generator ‡ Generates at medium voltage and capable of operating with a broad power factor range and inherent LVRT capability.

Use of Voith WinDrive® Technology ‡ Removes the need for Power Conversion Electronics and provides dampening of load transients.

Use of carbon fiber spar in rotor blade ‡ Provides a lighter and stiffer structure.

No Power Conversion Electronics ‡ Improves reliability and removes the need for extra packages for LVRT.

Datalog_071129_162000.svw Optimization Steps 1600 40,0

18,0 450 Through the first year of operation DeWind engineers 2000 1400 16,0 30,0 collected large amounts of operating data to enable further 1500 14,0 1200 400 optimization of the performance of the , 20,0 12,0 1000 1000 10,0 including: 350 10,0

500 8,0 ‡ Tuning pitch controller to optimize response to highly 800 6,0 0,0 0 turbulent wind conditions 600 6,0

102030405060708090100110 ‡ Optimizing the WinDrive® to aerodynamic performance Pitch Angle [*] Figure 2: Synchronization Process Wind Speed [m/s] WinDrive Output Speed [rpm] and drive train efficiency Active Power [kW] WinDrive Input Speed [rpm] ‡ Minimizing transients during the synchronization process thereby assuring smooth ramp-up D8.2 Certification ‡ Optimizing cut-in and ramp-up processes mitigating flicker DeWind has achieved a Statement of Compliance for Design and/or other grid phenomena assessment from DEWI-OCC to IEC 61400 for both the 50 & D8.2 Power Performance Curve 60Hz D8.2 Turbines. The Power Curve tests were performed by an accredited wind turbine performance test engineering consultant to measure and certify the power curve, in accordance with the guidelines published in IEC 61400-12. The resulting D8.2 Reactive Power Capabilities measured power curve demonstrates that the D8.2 meets One of the key D8.2 design goals was for the D8.2 to have the and/or exceeds the warranted published power curve. ability to produce significant reactive power. Figure 3 illustrates the results of the tests, which confirm the ability of the wind D8.2 Power Quality turbine to deliver 1MVAR of reactive power at rated output. Power quality measurements were performed to IEC 61400- 21 standards by a recognized power quality testing P organization, producing the following conclusions: Active Power ‡ Enhanced Voltage-Ride-Through (VRT) performance Active Power 2 MW resulting from the inherent characteristics of the Power synchronous generator Stability Curve ‡ Eliminated significant transients during the synchronization process thanks to the Smart-Control algorithm -Q +Q

‡ Reduced short-lived voltage variations resulting from the -986 Kvar 986 Kvar Reactive Power -986 Kvar 986 Kvar Reactive Power favorable Flicker coefficient. under-excited over-excited D8.2 Reactive Power Capability DFIG Reactive Power Capability D8.2 Synchronization Figure 2 shows a typical synchronization procedure ramping Figure 3: D8.2 PQ Stability capabilities measured to rated conditions. The synchronization is smooth with no significant transients. The active power (brown) trace shows the point of breaker close, with the subsequent ramp-up Summary slope controlled by the pitch control function (black) of the In summary, the Cuxhaven demonstration of the DeWind D8.2 control system. An industry-proven control unit automatically performance confirms that the D8.2 turbine meets the vision of controls the synchronization process. This behavior is typical its designers. The D8.2 produces excellent power performance, for a synchronous-generator-based power plant, and, is not power quality, reactive power and reliability. By April 2009 the typical for wind turbines of traditional design. DeWind D8.2 50 Hz Technology Demonstrator has operated for over 7600hrs and produced more than 6.4 GWh of energy.

For further info on Dewind Co. , Please contact (949) 250-9491 or [email protected]

Implementation of Utility Scale Generation on Distribution Grids

Summary Point of Common Coupling Direct-connecting utility-scale wind turbines on distribution The Point-of-Common-Coupling (PCC) is the connection point grids, as a part of the distributed power solution, continue to to the distribution grid, and is equipped with the necessary rise in popularity in the US. Although site configuration is protection to meet the anti-islanding requirements of the grid simplified, grid integration of the distributed utility-scale wind operator. At the Sweetwater site, the grid protection is turbines presents a new set of technical issues unique to a achieved by a recloser equipped with a relay that provides the distributed grid installation. This case study overview necessary over/under voltage, over/under current and summarizes some of the experience gained from direct- over/under frequency protection. The recloser is located on connecting a single DeWind D8.2 to a 12.47 kV distribution the pole to the left in Figure 2. The cabinet, at the base of the line near Sweetwater, Texas. center pole houses the transfer trip equipment, which provides the anti islanding protection required by the utility. The pole to Introduction the right is owned by the utility and provides the connection to In late 2007 DeWind began installing the first DeWind D8.2 the existing grid including the revenue meter. 60Hz wind turbine in the US, for Texas State Technical College (TSTC), completing the project in 2008. TSTC utilizes the turbine as a technology demonstrator, as a training platform for the TSTC Wind Technician Associate Degree Program, and as a revenue generator for the college. The turbine is located near the Roscoe High School on County Road 608, approximately one mile from the distribution grid, on a relatively flat site, as shown in Figure 1.

Figure 2: Point of Common Coupling Equipment

Distribution Line Details Figure 3 shows the one-line diagram of the original distribution system, including the turbine connection to the distribution feeder, located approximately 7 miles from the Roscoe substation. Four automatically-switched capacitor banks were originally installed on the feeder as the sole provision for voltage control Figure 1: The Installed DeWind D8.2 at Sweetwater, Texas on the line. Approximately 65% of the minimum load on the feeder, roughly approximately 0.5 MVA, is located near the The DeWind D8.2 2 MW turbine for this project is directly substation, with the balance of the load located at the end of connected without a step-up transformer to a 12.47 kV the feeder. The X/R ratio at the PCC is a low 0.3784, medium voltage distribution line. The DeWind D8.2 features a contributing to potential voltage rise challenges. The minimum hydrodynamic converter, which converts variable speed input load and elevated voltage issues on the feeder were particular from the wind turbine rotor to a constant synchronous-speed challenges that required solutions. A collaboration of the output, uniquely enabling the medium voltage generator to customer and site owner, the grid operator and power connect directly to the grid. engineering design specialists tackled the issues and developed the solution that included changing line impedance and applying distribution line voltage regulation at the 69 kV supply line upstream from the 12.47 kV line, resulting in the configuration that enables the turbine to operate while concurrently enabling the utility to keep the feeder within an acceptable operating voltage. To address the voltage rise phenomena resulting from the Rosco low load on the distribution feeder at Sweetwater, the 5447 Feet following actions were taken: 4/0 AAC CAP 1 1. Two sections of the feeder circuit were upgraded to a Bus 3 larger conductor. A total of 14,800 feet of conductor 277 kW 600.0 kvar 19443 feet 172 kvar from the PCC towards the sub-station were replaced 1/0 ACSR by the utility. Bus 4 2. A voltage regulator was installed at the Roscoe substation by the utility to regulate the voltage and ensure that the voltage at the PCC does not violate system limits, 11821 feet #4 ACSR 3. The DeWind D8.2 turbine provides reactive power CAP 2 DeWind8.2 WTG without de-rating.

300.0 kvar PCC The revised one-line diagram of the distribution system is 2000.0 kW 5200 feet shown in Figure 5. # 1/0 Copper U/G

CAP 3 Rosco 5447 Feet 300.0 kvar 4/0 AAC Voltage Reg. CAP 4 CAP 1 Bus 3 148 kW 92 kvar 600.0 kvar 277 kW 600.0 kvar 16457 feet 172 kvar Figure 3: One Line diagram of orginal Distribution System 1/0 ACSR Bus X

The characteristics of the DeWind D8.2 are a critical part of Bus 4 the solution, since the directly-connected synchronous generator provides excellent power quality with a much 14807 feet broader reactive power capability than other wind turbine 4/0 AAC configurations on the market today. The ability to provide CAP 2 broad reactive power support is graphically illustrated in the DeWind8.2 WTG capability curve of the synchronous generator (red dashed 200.0 kvar PCC line shows stability boundaries) in Figure 4. The Blue lines 2000.0 kW 5200 feet located well within the operating region of the synchronous 0.0 bar # 1/0 Copper U/G generator show the limits of a typical DFIG-based turbine. The DeWind D8.2 can operate with a power factor of 0.9 CAP 3 leading to 0.9 lagging at rated power, and can offer a much 200.0 kvar broader range of power factor capability when de-rated than CAP 4

148 kW the typical DFIG. This capability is very similar to 92 kvar 600.0 kvar conventional power stations and can be utilized to stabilize weak electrical grids and/or to compensate for less capable Figure 5: Revised One Line diagram of the Distribution System wind turbines. Turbine Performance P Active Power Once the local utility’s grid issues were resolved, a series of tests were completed to assure any voltage rise on the

Active Power 2 MW distribution feeder remained within operational limits when the wind turbine was operating at rated power. Since Power Stability commercial operation began the distribution grid has been Curve stable and availability has been excellent. Summary -Q +Q The DeWind D8.2 2 MW turbine at Sweetwater, Texas,

-986 Kvar 986 Kvar Reactive Power -986 Kvar 657 Kvar Reactive Power demonstrates the capability of the turbine to interconnect at under-excited over-excited D8.2 Reactive Power Capability medium voltage without the need for a transformer, while DFIG Reactive Power Capability providing significant grid support with no additional Figure 4: Reactive power support capability equipment, thereby demonstrating the value of this type of architecture in utility scale distributed wind generation.

For further info on Dewind Co. , Please contact (949) 250-9491 or [email protected]