Power Semiconductors -Wind Power Generation
Renewable energy refers to energy sources that are inexhaustible and continuously replenished. These include wind energy, solar energy, hydro energy, tidal energy, ocean energy, and geothermal energy, as well as biofuels derived from plants. All of these are renewable and come from nature, making them theoretically unlimited.
Wind energy, as a key pillar of renewable energy, has evolved from its historical use in mechanical applications like windmills and wind pumps to modern electricity production, primarily through wind turbines. These turbines are typically concentrated in wind farms connected to the power grid.
There are two common types of wind farms: offshore wind farms and onshore wind farms：
Offshore Wind Power: The construction and operation costs of offshore wind farms are higher than those of onshore wind farms. However, offshore wind farms are typically located in areas with stronger and more stable winds, where wind speeds are higher and fluctuations are smaller. This allows wind turbines to operate closer to their maximum capacity for longer periods, improving both electricity generation efficiency and the reliability of power output. As a result, offshore wind farms have a higher capacity factor (the ratio of actual power generation to the theoretical maximum power generation) compared to onshore wind farms.
Onshore Wind Power: Onshore wind power technology is well-developed, with significantly lower infrastructure and operational costs compared to offshore wind. Additionally, onshore wind farms are typically easier to connect to the power grid, which further reduces system integration complexity and costs. This makes onshore wind energy a preferred form of wind power development in many regions.
Wind power generation is typically stronger at night and during the winter, while solar power generation peaks during the day and in the summer. By combining these two energy sources, fluctuations in power generation caused by weather, seasons, or time of day can be reduced, improving the overall stability and reliability of the electricity supply. In 2023, global wind power generation reached approximately 2,304 TWh, accounting for 7.8% of global electricity production. This marks an important milestone in the development of renewable energy, as renewable sources for the first time accounted for 30% of global electricity supply throughout the year.
Wind and solar energy have played a crucial role in achieving the goals of the Paris Climate Agreement,highlighting that the development of wind energy is in line with the agreement’s decarbonization objectives. However, a faster rate of expansion is still needed to fully meet climate targets. Due to its low operational costs, scalability, and environmental friendliness, wind energy has become a key resource for achieving climate goals.
Wind Turbine
Modern wind turbines come in various sizes, but all types generally consist of three main components: rotor blades, nacelle, and tower.
Schematic Diagram of a Wind Turbine Nacelle
Wind turbines come in various topologies, architectures, and design characteristics, which directly affect the efficiency and stability of power generation. The industry is increasingly adopting system designs that integrate drivetrain components. By incorporating integrated control systems, devices such as wind generators, converters, inverters, and grid connectors can be interconnected. This enables comprehensive system monitoring and management, while optimizing control strategies to achieve more efficient and stable wind power generation.
Hardware Systems of a Wind Turbine Nacelle
Wind Generators
One of the limiting factors of wind turbines lies in the generator technology used. Currently, there are three main types of wind generators:
- DC Generators (Direct Current)
- AC Synchronous Generators (Alternating Current)
- AC Asynchronous Generators (Alternating Current)
The output power from wind generators is converted to direct current (DC) in an AC/DC converter and then further converted into alternating current (AC) at a commercial frequency through an inverter. These generators can operate at either fixed speeds or variable speeds.
Variable-speed operation is generally preferred because it can adapt to fluctuations in wind speed, reducing physical stress on the blades and drivetrain, while improving wind energy utilization and ensuring more stable power generation.
Wind Generator Topologies
Applications of Power Semiconductors
Power semiconductors play a critical role in renewable energy generation. In wind turbines, power semiconductors convert electrical energy and connect generators to the grid. Beyond power transmission, wind turbine converters also manage several key functions, necessitating the use of the highest quality power semiconductors. Power semiconductors are essential components in the hardware systems of wind power generators.
- Rectification and Inversion: In wind power systems, the AC electricity generated by the turbine needs to be converted into DC by a rectifier and then back into AC that meets grid requirements via an inverter. Power semiconductor devices such as IGBTs (Insulated Gate Bipolar Transistors) play a key role in the rectification and inversion processes, ensuring efficient energy conversion and transmission.
- Variable Frequency Control: Wind turbines often operate at variable speeds to adapt to different wind conditions. Power semiconductor devices are used in frequency converters to control the generator’s speed and output frequency. This enables Maximum Power Point Tracking (MPPT), improving power generation efficiency.
- Energy Conversion and Transmission: Wind turbines convert wind energy into electricity, which is then efficiently transmitted to the grid through power electronics systems. Power semiconductors play a central role in this process.
Power semiconductors are indispensable in rectification, inversion, variable frequency control, and energy transmission, ensuring the efficient, reliable, and cost-effective operation of wind power systems.
IGBT, IGCT, and Silicon Carbide Devices
According to wind turbine systems and designs, we commonly see the use of IGBT modules, Press-Pack IGBTs, thyristors, and IGCTs in wind power applications.
1700V IGBT modules are widely used in wind turbine converters to convert the AC power generated by the generator into grid-compatible electricity. These modules' high efficiency and reliability ensure the stable operation of wind turbines. 3300V IGBT modules are suitable for higher voltage wind turbine systems, especially in applications requiring higher DC bus voltage. These modules can handle higher voltages and power levels, meeting the demands of large-scale wind power equipment. The emergence of 4500V and 6500V IGCT and IGBT technologies has significantly improved medium-voltage converters in many aspects. Press-Pack IGBT semiconductor devices offer high efficiency, while IGCTs have a lower cost factor.
IGCT Press-Pack: MV (medium voltage) IGCT press-pack devices are primarily used in high-power industrial applications due to several advantages of press-pack packaging over modules. These advantages include higher thermal cycling and power cycling capabilities, as well as a failure mode without explosion risk.
IGBT Module and IGBT Press-Pack: The switching current capacity of 6.5kV IGBT modules on the market has reached approximately 1500A. Recently developed press-pack IGBT devices combine the advantages of IGBT technology with the benefits of press-pack packaging. As a result, press-pack IGBTs have become competitors to IGCTs in medium- and high-power industrial applications, such as medium-voltage drives in wind turbines.
Hitachi Energy's StakPak modules feature a typical press-pack packaging design and are optimized for high-voltage and high-power applications, making them suitable for wind power generation, high-voltage direct current (HVDC) transmission, and flexible alternating current transmission systems (FACTS).
Silicon Carbide (SiC) Devices
Silicon Carbide (SiC) MOSFETs, as a new generation of power semiconductor devices, are driving the upgrade and development of wind power technology with their unique advantages.
SiC devices offer high voltage tolerance, low losses, and high-frequency operation. In wind power systems, SiC devices are used to improve the efficiency and power density of converters, while reducing the system’s size and weight. Furthermore, with the advancement of high-voltage direct current (HVDC) transmission technology, SiC MOSFETs have demonstrated great potential in long-distance power transmission, providing strong support for the broader application of wind power generation.
Wind Turbine Solution Providers and Trends
As the output power of wind turbines continues to increase (often exceeding 2MW), IGBT modules commonly adopt water-cooling technology to meet thermal management requirements. In power semiconductor applications, one significant challenge is ensuring the system can continue operating for a specified period during grid faults, a critical requirement from grid operators for wind turbines. This is particularly important in wind power systems using doubly-fed induction generators, where IGBTs and freewheeling diodes must be capable of withstanding high-current and high-voltage transient surges.
Currently, leading power semiconductor manufacturers have introduced customized solutions for wind power applications, including:
- Infineon
- Fuji Electric
- Mitsubishi Electric
- Hitachi ABB Power Grids
Hitachi Energy
Hitachi Energy has achieved multiple technological advancements in the field of power semiconductors, particularly in applications for wind power generation.
1.Application of 300mm Wafer Technology
Hitachi Energy has successfully introduced 300mm wafers for IGBT (Insulated Gate Bipolar Transistor) production. This innovation enhances chip manufacturing capacity and enables the development of more advanced 1200V IGBT structures, facilitating faster power switching in high-power applications. Compared to traditional 200mm wafers, 300mm wafers increase the number of integrated circuits per wafer by 2.4 times, significantly reducing costs. Additionally, the latest generation of precision trench IGBT designs improves power conversion efficiency and reduces power losses during operation.
2. OceaniQ™ Offshore Energy Portfolio
In response to the trend of large-capacity and deep-sea offshore wind power systems, Hitachi Energy has launched the OceaniQ™ offshore energy portfolio. This includes the 66 kV HiDry dry-type transformer, WindSTAR™ transformer, and PASS M00-Wind high-power switchgear for wind turbines, supporting larger-scale integration of renewable energy into the grid. These products are designed to meet the demand for efficient and reliable power transmission in offshore wind farms, contributing to the growth of offshore wind energy.
3. Pre-Assembled Modular Offshore Substation
Hitachi Energy has developed a pre-assembled modular offshore substation to optimize power transmission solutions for offshore wind energy. This compact, pre-assembled grid access solution reduces the footprint of offshore substation topsides by 30% and decreases their weight by 20%, significantly lowering the costs and operational expenses of offshore wind power generation.
Hitachi Energy has made significant advancements in the digital domain, introducing the Lumada Asset Performance Management (APM) solution and the TXpert™ ecosystem. These systems collect and analyze operational data, enabling users to perform predictive management of critical assets, thereby improving the efficiency of wind power production and management.
Future Trends in Wind Power System Development
Application of Silicon Carbide (SiC) Technology: SiC power devices offer higher switching speeds and efficiency, reducing system losses and improving the overall performance of wind power systems.
Modular Design: Modular design allows wind turbine power conversion systems to adapt more flexibly to different power level requirements, simplifying production and maintenance processes.
Digitalization and Intelligence: The integration of digital control and monitoring technologies enables real-time monitoring and optimized control, enhancing system reliability and efficiency.
Conclusion
Power semiconductors play a critical role in wind power systems, particularly in the processes of energy conversion and transmission. With continuous advancements in wind power technology, the performance and reliability of power semiconductors are also improving, providing a solid technical foundation for achieving sustainable energy goals.
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