Wind Turbine Components: A Comprehensive Overview

Wind turbines are complex machines that harness the power of wind to generate electricity. They consist of several key components that work together to produce clean, renewable energy. In this article, we will provide a comprehensive overview of wind turbine components, including the generator, nacelle, tower and blades. We will explore how each component works and how they are manufactured. By the end of this article, you will have a better understanding of how wind turbines work and why they are an important part of our transition to a more sustainable future.

The parts that make up a wind turbine are as follows:

1. Blades

The blades of a wind turbine are the components that directly interact with the wind, which is why they are designed with a profile that maximizes their aerodynamic efficiency. Most blades are manufactured using polyester or epoxy reinforced with fiberglass. This material consists of a matrix of synthetic resin and fiberglass fibers, providing the blades with lightness, durability, and resistance to corrosion and moisture. Carbon fiber can also be used as a reinforcement material to enhance the strength and rigidity of the blades. However, carbon fiber comes at a higher cost and poses challenges in terms of recycling.

Transporting the blades can be a major challenge. Larger wind turbines require longer blades, which can complicate their transport to the wind farm.

2. Hub

The hub of a wind turbine is the component responsible for connecting the blades to the shaft that transmits motion to the gearbox in the case of a Doubly Fed Induction Generator (DFIG) or to the generator shaft in the case of a Direct-Drive Permanent Magnet Synchronous Generator (PMSG). The hub contains mechanisms for changing the pitch angle of the blades. The hub is typically made of steel or cast iron and is aerodynamically designed to prevent the formation of turbulence and allow for maximum free airflow.

3. Blade orientation system

It consists of a series of mechanical, electrical, or hydraulic mechanisms that allow for adjusting the pitch angle of the blades. Their purpose is to maintain constant mechanical power when the wind speed exceeds the nominal value (as can be seen in the wind turbine’s power curve). This system can also be considered a protective measure to prevent the wind turbine from exceeding its nominal speed.

The blades move relative to their axis to control the mechanical power. This type of control is called “pitch angle control”.

4. Wind turbine orientation system

The nacelle rotates along the vertical axis of the tower using an active and rotating orientation control system, which consists of electric actuators. The wind direction and speed are continuously monitored by sensors located on the nacelle’s cover, called anemometers and wind vanes. The aim is to align the wind turbines in the direction of the prevailing wind to maximize wind energy capture.

5. Gearbox

The function of the gearbox is to connect the shaft that joins the blades at the hub with the generator shaft. Its purpose is to multiply the turbine’s rotational speed to an efficient speed for the electrical generator. Without a gearbox, the electrical generator would need to rotate optimally between 10 and 25 rpm, meaning a generator with many poles would be required.

Therefore, the gearbox can be thought of as a mechanical transformer. It can multiply the wind turbine’s rotation speed, for example, 1:50, 1:70, 1:80, 1:90, 1:100, 1:110. The higher the multiplication factor, the more complex the gear system and gearbox stages will be. The gearbox provides a higher rotation speed for the electrical generator but lower mechanical torque.

6. Electric generator

6.1. Squirrel Cage Induction Generator (SCIG):

This configuration corresponds to the so-called “Danish concept”, which was very popular in the 1980s. This type of electric generator consumes reactive power, which it can absorb from the grid or a bank of capacitor batteries. To connect it to the grid, a soft-start system is used, based on thyristors, in order to limit the starting current. This generator can cause power oscillations that are directly transferred to the grid. Its main advantages are its smaller size, lower cost, and the simplicity of the control system.

6.2. Doubly Fed Induction Generator (DFIG):

It has been used since the year 2000. An electronic power converter is connected in a back-to-back configuration. Through the use of the electronic power converter, the frequency and current in the rotor can be flexibly controlled, thus extending the range of variable speeds to a satisfactory level. Control is achieved by injecting variable current into the rotor winding, both in magnitude and frequency. The speed variation range is about ± 30% of the rated speed. The stator is directly connected to the grid, while the rotor is connected through power converters with a fraction of power between 20% or 30% of the rated power. Disadvantages include having slip rings, requiring a multi-stage gearbox to connect to the wind turbine, incurring higher maintenance costs, and experiencing increased losses mainly due to the mechanical transmission train.

6.3. Permanent Magnet Synchronous Generator (PMSG):

This type of generator is the most commonly used alongside the DFIG generator. Unlike the DFIG, it integrates full-scale power electronic converters to connect to the electrical grid. This generator type has a greater capacity to support the electrical grid and requires less maintenance. It utilizes rare earth magnets in the rotor, which have a high magnetic flux density. Its primary disadvantage is the cost of the magnet, as it is subject to global uncertainty and can potentially demagnetize due to electrical faults in the generator.

7. Power electronics interface

The power electronics interface plays a crucial role in wind turbines. It is responsible for the transformation, control, and optimization of energy. Power converters are used to control the flow of active and reactive power in both steady and dynamic states, from the electric generator to the power grid. The rotational speed of variable-speed wind turbines is decoupled from the electrical frequency due to the electronic interface; in other words, they do not rotate in sync with the power grid, as a conventional synchronous generator would. The Back-to-back connection is the most commonly used and consists of two voltage-source converters (VSC).

These converters are composed of semiconductor devices such as the Insulated Gate Bipolar Transistor (IGBT), which functions as a controlled switch. IGBTs are controlled using pulse-width modulation techniques. The power converters, along with their control system, act as the “brain” of the wind turbine. It is vital that their operation is appropriate and optimal to ensure the proper functioning of the entire wind energy conversion system.

8. Transformer (LV-MV)

The electrical output power of the wind turbine is generally low voltage and is converted to medium voltage through a transformer to reduce transmission losses by connecting to the medium voltage grid. The transformer is installed either in the nacelle or at the base of the tower. It is a dry-type transformer with two windings.

Conclusion

In conclusion, wind turbines are complex systems as they encompass electrical, electronic, mechanical, aerodynamic, and structural subsystems. Wind turbines are the pillars of renewable energy generation due to their increased capacity in recent years. Each component, from the blades to the electrical generators, plays a vital role in capturing and transforming wind energy into electricity. The blades are aerodynamically designed and constructed with advanced materials to maximize efficiency and durability. The orientation systems ensure optimal operation by continuously adjusting the blades and nacelle based on wind conditions. The gearbox and various types of electrical generators, such as SCIG, DFIG, and PMSG, enable effective conversion of mechanical energy to electrical energy, each with its specific advantages.

The power electronics interface is the “brain” of the wind turbine, managing the power flow and decoupling the rotational speed of the wind turbine from the electrical grid frequency. This control and optimization capability is crucial for the overall system performance. Finally, the transformer raises the generated low voltage to a medium voltage level, minimizing transmission losses and ensuring efficient integration with the electrical grid.

Overall, the engineering behind each part of the wind turbine is fundamental to its efficiency and reliability, making these machines a key element in the transition to cleaner and more sustainable energy sources.