**5. Structure of wind turbines**

Some of the structures and installation configurations of wind turbines are presented in **Figure 7**. In **Figure 7a**, the complete layout of a typical wind turbine connection is shown. The major components of the wind turbine are the rotor blade, gearbox, nacelle, generator, power cables and tower. The output power of the wind turbine is distributed to the network grid via transformer and switchyard. The wind turbine generator is housed in the nacelle and **Figure 7b** and **c** shows the detailed structure of the nacelle containing the low speed shaft, gearbox, controller, anemometer, wind vane, high speed shaft, yaw motor tower and others. In **Figure 7d**, the details of the wind turbine blades and other ancillary components are described. The wind turbine rotor blade is basically made of glass reinforced plastic, while the Yaw shaft with the slip ring ensures 360° rotation. The tail pole and wind connects the body of the wind turbine through a sensitive bearing, while the tower of the wind turbine is of high quality spray painting and galvanized to be salt and acid proof. The wind turbine generator in the nacelle is extremely light and small, low in sound, swift in startup, quick in heat dissipation and of high efficiency. The nose cone of the wind turbine is made up of reinforced aluminum alloy and antisepsis casting.

**6. Onshore and offshore wind farms**

**Figure 7.** Structures and configuration of a typical wind turbine [30].

A wind farm is a collection of wind turbines of the same type of technology or different type of technology. Although, in most wind farms, the technology of the wind turbines are same, however, it has been proposed in the literature to developed modern wind farms to compose of both fixed speed and variable speed wind turbine technology. This is because the variable

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(FRT) or Low Voltage Ride Through (LVRT) capability. Wind farms connected to high voltage transmission system must stay connected when a voltage dip or frequency disturbance occurs in the grid, otherwise, the sudden disconnection of great amount of wind power may contribute to the voltage dip and drop of frequency, with terrible consequences in the utility grid. Therefore, the transient and dynamic analysis of wind generators in wind farms are necessary. Several solutions could be used in the stability analysis and improvement of wind turbines during grid disturbances, so that they can contribute to voltage and frequency control. Some of these solutions are the use of power electronic devices and reactive power compensation units like static synchronous compensator (STATCOM), superconducting magnetic energy storage (SMES), energy capacitor system (ECS), crowbar, static series compensator (SSC), a dynamic voltage restorer (DVR), series dynamic braking resistor (SDBR), superconducting fault current limiter (SFCL), passive resistance network, series antiparellel thyristors

The big challenges that wind farms must face is voltage and frequency dip in the grid during grid disturbances [28]. The magnitude of the voltage is controlled by the reactive power exchange, while the frequency is controlled by the active power. **Figure 4** displays the typical requirement for fault ride through grid code regarding terminal voltage of the wind farm. The wind farm must remain connected to the grid if the voltage drop is within the defined r.m.s. value and its duration is also within the defined period as shown in the curve. **Figure 5** shows the required reactive current support from the generating plants during voltage dip, while

Some of the structures and installation configurations of wind turbines are presented in **Figure 7**. In **Figure 7a**, the complete layout of a typical wind turbine connection is shown. The major components of the wind turbine are the rotor blade, gearbox, nacelle, generator, power cables and tower. The output power of the wind turbine is distributed to the network grid via transformer and switchyard. The wind turbine generator is housed in the nacelle and **Figure 7b** and **c** shows the detailed structure of the nacelle containing the low speed shaft, gearbox, controller, anemometer, wind vane, high speed shaft, yaw motor tower and others. In **Figure 7d**, the details of the wind turbine blades and other ancillary components are described. The wind turbine rotor blade is basically made of glass reinforced plastic, while the Yaw shaft with the slip ring ensures 360° rotation. The tail pole and wind connects the body of the wind turbine through a sensitive bearing, while the tower of the wind turbine is of high quality spray painting and galvanized to be salt and acid proof. The wind turbine generator in the nacelle is extremely light and small, low in sound, swift in startup, quick in heat dissipation and of high efficiency. The nose cone of the wind turbine is made up of reinforced

and among others discussed in the literature.

10 Stability Control and Reliable Performance of Wind Turbines

**Figure 6** shows the permissible grid frequency requirement [29].

**4.1. Operational grid requirements**

**5. Structure of wind turbines**

aluminum alloy and antisepsis casting.

**Figure 7.** Structures and configuration of a typical wind turbine [30].

## **6. Onshore and offshore wind farms**

A wind farm is a collection of wind turbines of the same type of technology or different type of technology. Although, in most wind farms, the technology of the wind turbines are same, however, it has been proposed in the literature to developed modern wind farms to compose of both fixed speed and variable speed wind turbine technology. This is because the variable speed wind turbine technology can be used to stabilize the fixed speed type, while at the same time generating power to the grid system. **Figure 8** shows typical onshore and offshore wind farms. More winds are achieved in offshore or coastal wind farms than onshore wind farms, however, the cost of installation and maintenance is high for this type of wind farm.

**6.1. Global wind turbine installation capacity**

wind capacity excepted by 2020.

trend.

**7. Wind turbine manufacturers and market trend**

**Figure 9a** shows the cumulative capacity, annual capacity installations, first, second, third and fourth quarter capacity installations of wind turbines globally from the year 2001 to 2016. This is tremendous increase in the number of wind turbine installations over the years from the figure. As at 2016, the wind power capacity is already 82,183 MW as against 4147 MW in the year 2001. The cumulative installed capacity over these years by countries is shown in **Figure 9b**, with China taking the lead, then the United States and Germany behind China. The wind turbine installation by regions of the world is shown in **Figure 9c**, from 2008 to 2016. Asia is leading with about 35,000 MW annual installed capacity in 2015. This value, however, dropped in 2016 to about 28,000 MW. There was considerably decrease in the annual installed capacity of wind turbines in Asia during 2012 from the figure, however, between 2013 and 2016, the annual installed capacity increased. In Europe, the annual installed capacities in 2015 and 2016 are same with a rough estimate of 14,000 MW. In North America, the highest annual installed capacity of 15,000 MW wind turbine was achieved in the year 2012, and in 2013, the value dropped drastically to 2500 MW. In 2015, the annual installed capacity rose to about 12,000 MW, thereafter, in 2016, the value dropped below 10,000 MW. The distribution of wind turbine installation in North America is irregular over the years due to less interest in renewable energy. The Pacific region, Africa and the Middle East are the least in annual installed capacity of wind turbine, respectively. The future forecast of the installed onshore and offshore wind turbines from 1990 to 2020 is shown in **Figure 9d**, with a value of 230 GW

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Some of the manufacturers of wind turbines are shown **Figure 10a**. The top major wind turbine manufacturers are Vestas, GE energy, Goldwind, Gamesa, Enercon, Siemens, Nordex, Envision, Ming Yang and United Power, respectively. The designs and control strategy employed in the wind turbine system is slightly different for each manufacturer. The wind turbine market trend is shown in **Figure 10b** from 2012 to 2017. There is cumulative increase

**Figure 10.** Wind turbine manufacturers and market trend [30] (a) Wind turbine manufacturers; (b) Wind turbine market

**Figure 8.** Onshore and offshore wind farms.

**Figure 9.** Global wind turbine installations [30]. (a) Cummulative; (b) Top countries; (c) By regions; (d) Future Forecast.

#### **6.1. Global wind turbine installation capacity**

speed wind turbine technology can be used to stabilize the fixed speed type, while at the same time generating power to the grid system. **Figure 8** shows typical onshore and offshore wind farms. More winds are achieved in offshore or coastal wind farms than onshore wind farms,

**Figure 9.** Global wind turbine installations [30]. (a) Cummulative; (b) Top countries; (c) By regions; (d) Future Forecast.

however, the cost of installation and maintenance is high for this type of wind farm.

**Figure 8.** Onshore and offshore wind farms.

12 Stability Control and Reliable Performance of Wind Turbines

**Figure 9a** shows the cumulative capacity, annual capacity installations, first, second, third and fourth quarter capacity installations of wind turbines globally from the year 2001 to 2016. This is tremendous increase in the number of wind turbine installations over the years from the figure. As at 2016, the wind power capacity is already 82,183 MW as against 4147 MW in the year 2001. The cumulative installed capacity over these years by countries is shown in **Figure 9b**, with China taking the lead, then the United States and Germany behind China. The wind turbine installation by regions of the world is shown in **Figure 9c**, from 2008 to 2016. Asia is leading with about 35,000 MW annual installed capacity in 2015. This value, however, dropped in 2016 to about 28,000 MW. There was considerably decrease in the annual installed capacity of wind turbines in Asia during 2012 from the figure, however, between 2013 and 2016, the annual installed capacity increased. In Europe, the annual installed capacities in 2015 and 2016 are same with a rough estimate of 14,000 MW. In North America, the highest annual installed capacity of 15,000 MW wind turbine was achieved in the year 2012, and in 2013, the value dropped drastically to 2500 MW. In 2015, the annual installed capacity rose to about 12,000 MW, thereafter, in 2016, the value dropped below 10,000 MW. The distribution of wind turbine installation in North America is irregular over the years due to less interest in renewable energy. The Pacific region, Africa and the Middle East are the least in annual installed capacity of wind turbine, respectively. The future forecast of the installed onshore and offshore wind turbines from 1990 to 2020 is shown in **Figure 9d**, with a value of 230 GW wind capacity excepted by 2020.

## **7. Wind turbine manufacturers and market trend**

Some of the manufacturers of wind turbines are shown **Figure 10a**. The top major wind turbine manufacturers are Vestas, GE energy, Goldwind, Gamesa, Enercon, Siemens, Nordex, Envision, Ming Yang and United Power, respectively. The designs and control strategy employed in the wind turbine system is slightly different for each manufacturer. The wind turbine market trend is shown in **Figure 10b** from 2012 to 2017. There is cumulative increase

**Figure 10.** Wind turbine manufacturers and market trend [30] (a) Wind turbine manufacturers; (b) Wind turbine market trend.

in power (GW) from 2012 to 2017, the cumulative capacity growth rate and annual installed capacity growth rate decreased over the considered years. There is little or no difference in the annual installed capacity (GW) over the considered years.

[12] Jamil M, Parsa S, Majidi M. Wind power statistics and an evaluation of wind energy

Introductory Chapter: Stability Control and Reliable Performance of Wind Turbines

http://dx.doi.org/10.5772/intechopen.80237

15

[13] Sen Z, Sahin AD. Regional assessment of wind power in Western Turkey by the cumula-

[14] Fung KT, Scheffler RL, Stolpe J. Wind energy-a utility perspective. IEEE Transactions on

[15] Okedu KE. Wind turbine driven by permanent magnetic synchronous generator. Pacific

[16] Okedu KE, Muyeen SM, Takahashi R, Tamura J. Protection schemes for DFIG considering rotor current and DC-link voltage. In: Proceedings of the 24th IEEE-ICEMS (International

[17] Bozhko S, Asher G, Li R, Clare J, Yao L. Large offshore DFIG-based wind farm with linecommutated HVDC connection to the main grid: Engineering studies. IEEE Transactions

[18] Santos S, Le HT. Fundamental time-domain wind turbine models for wind power stud-

[19] Haberberger M, Fuchs FW. Novel Protection Strategy for Current Interruptions in IGBT

[20] Okedu KE, Muyeen SM, Takahashi R, Tamura J. Wind farms fault ride through using DFIG with new protection scheme. IEEE Transactions on Sustainable Energy. 2012;**3**(2):

[21] El-Sattar AA, Saad NH, Shams El-Dein MZ. Dynamic response of doubly fed induction generator variable speed wind turbine under fault. Electric Power Systems Research.

[22] Takahashi T. IGBT Protection in AC or BLDC Motor Drives. El Segundo, CA: Technical

[23] Xie H. Voltage source converters with energy storage capability [Ph.D thesis]. Stockholm, Sweden: Royal Institute of Technology, School of Electrical Engineering, Division of

[24] Chowdhury BH, Chellapilia S. Doubly-fed induction generator control for variable speed wind power generation. Electric Power Systems Research. 2006;**76**:786-800

[25] Karim-Davijani H, Sheikjoleslami A, Livani H, Karimi-Davijani M. Fuzzy logic control of doubly fed induction generator wind turbine. World Applied Science Journal. 2009;

[26] Okedu KE, Muyeen SM, Takahashi R, Tamura J. Wind farm stabilization by using DFIG with current controlled voltage source converters taking grid codes into consideration.

IEEJ Transactions on Power and Energy. 2012;**132**(3):251-259

Current Source Inverters. Oslo, Norway: Proceedings EPE-PEMC; 2004

Conference on Electrical Machines and System). Beijing, China; 2011. pp. 1-6

tive semivarigram method. Renewable Energy. 1997;**12**:169-177

density. Renewable Energy. 1995;**6**:623-638

Power Apparatus and Systems. 1981;**100**:1176-1182

Journal of Science and Technology. 2011;**12**(2):168-175

on Energy Conversion. 2008;**23**(1):1119-1127

ies. Renewable Energy. 2007;**32**:2436-2452

242-254

2008;**78**:1240-1246

**6**(4):499-508

Paper, International Rectifier; 2004

Electrical Machines and Power Electronic; 2006
