Wind turbine converter - the technology and development trend

Wind turbine converter is the core component of wind power generation system, converting wind energy into stable electrical energy output. With the rapid development of the wind energy industry, converter technology is also constantly innovating and progressing.

This article will discuss in detail the technical characteristics, maintenance methods, and future development trends of wind turbine converter.

1. Technical characteristics of wind turbine converter

Differ from power inverters like 2000w inverter or 3000w inverter, there are mainly two types of wind turbine converter: doubly-fed converter and full-power converter.

Technical characteristics of doubly-fed converter:

• Bidirectional power flow: Realizes bidirectional energy transmission between wind turbines and the grid, improving system flexibility and controllability.
• Partial power conversion: Transfer part of the wind turbine power to the grid through the rotor, reducing the power demand on the converter and reducing costs.
• Smaller capacity: Compared with traditional full-power converters, doubly-fed converters have smaller capacities, reducing costs and reducing the need for rare materials.
• Improved voltage quality: By introducing a frequency converter on the rotor side, control of the rotor voltage and frequency is achieved, improving voltage quality and grid stability.

Technical characteristics of full-power converter:

• Full power conversion: Transmit the power of the entire wind turbine to the grid through the frequency converter to improve the efficiency and power generation capacity of the system.
• High efficiency: Utilize efficient power devices and advanced control strategies to maximize energy conversion efficiency and reduce energy loss.
• High stability: It has higher anti-interference ability and grid adaptability, stably injects power into the grid, and improves the reliability and controllability of the system.
• Network supporting: Provide functions such as reactive power control and voltage/frequency adjustment to enhance grid stability and reliability.

2. Maintenance of wind turbine converter

As one of the core components of wind turbines, the wind turbine converter needs to be maintained regularly as required to ensure its normal operation.

Maintenance items

• Check radiator temperature and clean every 6 to 12 months (depending on the contamination situation of the site).
• Clean or replace the filter screen every year. For example, in windy and dusty weather, or in wind fields with poor tower sealing, inspection and cleaning are required before the onset of hot weather in summer. The recommended maintenance cycle for northwest wind farms is half a year.
• Check the circuit breaker and perform necessary maintenance every year or after a certain number of operations.
• Check and clean the connections of the power section.
• Adjust the temperature and humidity controller to achieve heating conditions and see if the heater is working. Manually test each radiator through the converter software operation interface to check whether the cooling fan is working.
• Check whether the optical fiber connection is firm or damaged.
• Check whether the UPS power supply has a fault warning and replace the internal batteries every 3 years, and you can click to check how to do battery hookup. UPS power supplies that are in standby mode for a long time need to be discharged and recharged every 3-6 months to extend the service life of the power supply.

Precautions

• Before performing any installation work on the converter, the stator of the generator and the power supply to the converter must be disconnected. It is strongly recommended that the mechanical brake device locks the generator rotor.
• Before starting work, you must wait 5 minutes to allow the capacitor of the intermediate DC circuit to be completely discharged. And use a multimeter to measure the voltage between the UDC+ and UDC- terminals to confirm that the converter has been discharged.
• Do not perform any insulation tests on the wind turbine converter before disconnecting the converter cables (because applying external voltages will impact the power module).
• When the processing cabinet contains a metal cover, there is high-intensity voltage inside. 
• The brake control terminals (UDC+, UDC-, R+ and R- terminals) contain dangerous DC voltages.
• Depending on the external wiring, the converter system relay output may contain dangerous voltages (24V, 230V).
• The wind turbine converter module is heavy on the top and light on the bottom. When moving, you should hold it on a high place.
• When unplugging a fiber, be sure to hold the connector, not the fiber. Do not bend the optical fiber too much. The minimum bending radius is 35mm.

3. Testing of wind turbine converter

In-the-loop testing of wind turbine converter usually includes the following aspects:

• Grid condition simulation: By simulating grid conditions, including voltage, frequency and grid disturbance, the performance of the wind turbine converter under different grid conditions is tested. This helps verify whether the converter meets grid requirements and guarantees its stability and efficiency in actual operation.
• Wind turbine simulation and load test: By simulating the dynamic characteristics of the wind turbine and changes in wind speed and direction, the response and control capabilities of the converter are tested. At the same time, load changes are simulated to evaluate the stability and efficiency of the converter under different load conditions.
• Control system testing: Verify the control system of the converter, including tests on response time, stability, grid synchronization, etc., to ensure that the wind turbine converter can operate normally and coordinate with the grid.
• Data collection and analysis: By collecting and analyzing data during the test process, the performance indicators of the converter are evaluated, and data support is provided for subsequent optimization and fault diagnosis.
• Efficiency and power factor testing: By measuring the efficiency and power factor of the converter, evaluate its power conversion efficiency and check whether it meets performance requirements and standards.
• Protection and safety testing: Test the protection functions of the converter, including over-voltage protection, over-current protection, short-circuit protection, etc., to ensure that the converter can operate safely under fault conditions and prevent damage to the system.
• Real-time simulation platform: Based on a high-performance computing platform, a real-time simulation model of power electronic topology structures including the wind turbines and the converters is constructed. Real-time simulation technology can be used to simulate the dynamic response of wind turbines under various operating conditions, providing a real and accurate simulation environment for in-loop testing of wind turbine converter.
• Hardware-in-the-loop (HIL) testing: Realize in-the-loop testing through the connection between the real-time simulation platform and the real converter controller. In this test, the wind turbine converter controller is connected to a real-time simulation platform to form a closed-loop system. The real-time simulation platform provides a virtual wind turbine and power grid environment, while the controller performs actual control based on feedback signals from the simulation platform. In this way, the performance of the controller and the effectiveness of the control strategy can be verified.
• Fault simulation and diagnosis: In the real-time simulation platform, various fault scenarios can be simulated, such as sensor failure, actuator failure, etc. Through simulation and testing of fault scenarios, the effectiveness of fault diagnosis and fault-tolerant control strategies of the converter can be verified.
• Automated testing and data analysis: Use automated testing tools to conduct batch and repeated testing of converters to improve testing efficiency. At the same time, through the analysis and mining of test data, potential performance problems and improvement directions of the converter can be discovered.
• Scalability and openness: The real-time simulation platform should have good scalability and openness to adapt to the in-loop testing needs of different models and specifications of converters. At the same time, the platform should support the integration of third-party software and hardware for more in-depth testing and verification.

4. Development trends of wind turbine converter

 Based on doubly-fed and full-power converter technologies, the future development trends of wind turbine converter will focus on the following directions:

• High frequency: By increasing the switching frequency of the converter, it is made more compact and lightweight, with higher response speed and more precise power control. Researchers are working on new switching devices and electromagnetic interference suppression technologies to improve system efficiency and reliability.
• Modular design: The converter is designed as a modular structure to provide a flexible, scalable, easy maintenance and upgrade solution. Researchers will further explore novel module structures, inter-module communication techniques and reconfigurable module components to achieve higher levels of flexibility and configurability.
• New power device applications: Researchers are actively exploring the applications of new power devices such as silicon carbide (SiC) and gallium nitride (GaN), which have higher switching speeds, lower power consumption and higher temperature tolerance. Further research will promote its wider application in converters and improve system efficiency and reliability.
• Intelligent control and management: By introducing advanced control algorithms, intelligent monitoring technology and remote communication capabilities, the converter can achieve adaptive control, fault diagnosis and optimized operation. Researchers will further study the reliability, security and communication technology of intelligent control and management systems to achieve higher levels of autonomous operation, intelligent optimization and network integration.
• Multi-energy interconnection: With the continuous development of renewable energy, multiple energy sources such as wind energy, solar energy and off grid batteries system are integrated to achieve energy complementation and collaborative management. Researchers will further study the interoperability, energy flow scheduling and intelligent energy management of multi-energy interconnection technologies to promote the sustainable development of renewable energy systems and the reliability of energy supply.

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