1. Current research status of non-destructive testing technology for wind power equipment

Wind power generation, as an important part of renewable clean energy, has been developing rapidly in recent years. China has become the world's largest producer and consumer of wind power equipment, and various parts of the country have accelerated the construction of wind power facilities. However, during the operation of wind power equipment, it is easy to encounter various equipment failures, which not only affect the normal operation of the wind power generation system, but also may form serious safety hazards. Therefore, vigorously developing non-destructive testing technology for wind power facilities in China and accelerating the research and development of core technologies with independent intellectual property rights are of great significance for promoting the sustainable development of China's wind power generation industry.

2.Reasons and research results of failure in various links of wind power generation institutions

·Failure analysis and detection of wind turbine blades

Humidity, fatigue, sudden strong winds, and lightning strikes can all cause damage to wind turbine blades. Wind turbine blades must withstand loads such as tension, compression, bending, and torsion, leading to cumulative damage and instability of the wind turbine blade structure. In wind farms, aerodynamic interference between different turbines may cause excessive loads on the blades, resulting in excessive deflection and strain on the cantilever blades, leading to failure. Therefore, the key to monitoring the health of blades lies in real-time detection of their operating conditions.

The teams of Newcastle University and Nanjing University of Aeronautics and Astronautics (hereinafter referred to as the joint team of Newcastle University and Southern Airlines) have embedded a new type of sensor into wind turbine blades in their research, in order to detect real-time performance changes and damage in the blade mechanism before blade failure. And using pulsed eddy current excitation, infrared thermal imaging technology was studied for composite materials, successfully identifying the type characteristics of defects.

·Analysis and Detection of Failure Causes of Gearboxes

The gearbox of wind turbines is mainly made of high-strength forged steel parts and ductile iron raw materials. The gearbox is mainly composed of rotating components that bear cyclic loads and are susceptible to fatigue and wear damage caused by cyclic loads. In addition, corrosive marine environments and stress caused by wind changes can also cause corrosion cracking related to them. These damages and cracks can lead to the failure of the entire transmission system.

Non destructive testing of gearboxes is a feasible method for assessing material condition and performance without affecting their performance. The joint research team of New York University and Southern Airlines has conducted extensive research on defect detection techniques for gearboxes, using various electromagnetic testing methods including eddy current testing, pulse eddy current and electromagnetic Barkhausen noise, magnetic particle testing, magnetic flux leakage testing, etc. The joint team has conducted extensive research on stress distribution and microstructure detection of gears using electromagnetic Buckhausen noise technology, and has been applied in engineering at the National Gear Measurement Laboratory (NGML) in the UK.

·Monitoring of generators and power electronic equipment

The generator includes electromagnetic components and many power electronic components. The reliability testing of these components is also an important part of wind power equipment monitoring. Mechanical vibration, humidity, temperature, and packaging form can all cause the failure of these components. In addition, wind turbines can cause significant vibrations in the motor and engine compartment in various directions during operation due to various reasons. When the frequency, amplitude, and other parameters of the vibration exceed the design requirements of the wind turbine, it can pose a threat to the normal operation of the wind turbine.

In addition to the mechanical parts, insulation withstand voltage, corrosion, and contact resistance failure of the line will also occur under wind, temperature difference, and humid conditions. At present, impedance testing is still used in China to detect motor faults. However, impedance testing is suitable for testing in the production stage and cannot monitor faults during motor operation. In the field of power electronics, the heat generated by power loss when current passes through semiconductor devices is also the main factor causing failure.
Therefore, the research on online effective monitoring methods and technologies for motors still faces severe challenges, and it is necessary to use non-destructive testing and health monitoring to monitor the status of power electronic systems.

·Wind power system operation monitoring and status evaluation

Due to the fact that wind power plants are usually located in hilly and mountainous areas, remote western regions, coastal or offshore areas, and the monitoring of power generation equipment requires the detection, monitoring, and information processing of a large number of components and systems, including rotating components such as wind blades. The characteristics of renewable energy determine the complexity of wind power generation systems in terms of interface with the grid. Online monitoring and information collection and integration technology can provide favorable technical support for the efficiency and reliability of the system.

Wireless sensor networks integrate sensor technology, embedded computing technology, modern network and wireless communication technology, distributed information processing technology, and other fields of technology. The network consists of a cluster of similar or heterogeneous sensor nodes and gateway nodes composed of randomly distributed integrated micro power supplies, sensitive components, embedded processors, memory, communication components, and software (including embedded operating systems, embedded database systems, etc.). Each sensor node can collect and perform simple calculations on surrounding environmental data, and can communicate with other nodes and the outside world. A sensor network composed of a large number of intelligent nodes has strong self-organizing ability, and its multi node characteristics enable numerous different types of sensors to work together for high-quality measurement, forming a fault-tolerant wireless data acquisition system.

3. The main research directions in the field of state monitoring of wind turbine systems

On a global scale, non-destructive testing and health monitoring technologies for wind power generation systems are still in the exploratory stage, lacking a complete inspection and intelligent status evaluation system for the entire wind power equipment. At present, as an important component of wind power technology, the research work in the field of state monitoring of wind turbine systems mainly includes the following aspects:

1. Research methods and technologies for non-destructive testing and condition monitoring of wind turbine blade materials (composite materials), combined with load analysis and failure mode analysis, to develop wireless sensor networks for health monitoring of turbine blades.

2. Research on electromagnetic non-destructive testing, transmission fault monitoring, status monitoring, and lifecycle assessment technologies for transmissions.

3. Research non-destructive testing technology for tower foundations, combined with system stability analysis, as well as system structural fault monitoring, status monitoring, and lifecycle assessment technology.

4. Research fault detection technology for the power electronics part of wind power generation equipment, create a fault prediction model, and implement a monitoring and sensor detection network prototype system for power electronics and control systems.

5. Research a hybrid sensor network system for online real-time state detection of wind power generation systems and build a system for data acquisition, as well as information fusion and real-time judgment methods.

4.Summary of non-destructive testing technology for wind power equipment

Against the backdrop of technological progress and economic development, the wind power generation industry has rapidly improved. However, the complexity and nonlinearity of wind power generation systems may lead to anomalies in their operation due to certain factors, resulting in poor power supply quality. So, using non-destructive testing technology to detect and monitor the operation of wind power generation systems, detecting the operating status of important equipment such as power electronic equipment, generators, gearboxes, and wind power systems, in order to timely detect abnormalities, eliminate faults, and ensure the safety of the entire system operation.

In the future, China's new and renewable energy represented by wind power will enter a stage of high-quality development. Non destructive testing technology can ensure the safe operation of wind power generation equipment and the orderly and stable operation of the overall equipment. It plays a crucial role in promoting energy transformation and accelerating high-quality development in the wind power field.