Wind turbine electric control system:

The electrical control system of wind turbines is mainly divided into five parts: power supply system, variable speed constant frequency control system, yaw control system, pitch control system, and main control system.

Wind turbine power supply:

The generator and converter are AC 690V power sources, which are boosted and connected to the wind farm grid through a box transformer.

Variable speed constant frequency control system

1. Generator:

A fan converts rotating mechanical energy into electrical energy. There are two types of wind turbines: doubly fed asynchronous generators and permanent magnet generators.

A doubly fed asynchronous generator refers to a converter (frequency converter) that connects the stator and rotor three-phase windings to an independent three-phase symmetrical power source, directly connects the stator winding to the power grid, and adjusts the frequency, amplitude, and phase of the rotor winding according to requirements. The inverter is connected to the power grid through a DC link and inverter, controlling the motor to maintain power generation status at both sub synchronous and super synchronous speeds, and adjusting the generator speed with changes in wind speed for energy exchange.

Permanent magnet generator technology has only recently become a new darling in the wind power industry. In the past, the world’s top wind turbine manufacturers only used doubly fed asynchronous generator technology, but now they have started to use permanent magnet generators. In addition, multiple independent studies by industry experts have proven that permanent magnet generators are the preferred technology for the future.

2. Converter:

The inverter is an important component of wind turbines, which converts constantly changing wind energy into AC power with constant frequency and voltage and feeds it into the power grid, ensuring stable and reliable grid connection operation of wind turbines.

Converters are divided into doubly fed converters and full power converters based on the form of generators. The doubly fed converter is applied to doubly fed asynchronous generators, while the full power converter is used for permanent magnet generators.

Driven by the rapid development of the wind power equipment market, wind power converters have grown rapidly. In 2009, it reached around 3.45 billion yuan, and in 2010, it exceeded 4 billion yuan. At present, the converter companies that supply major domestic wind turbine manufacturers are mainly international enterprises, and domestic wind turbine converters are still in the small-scale application stage in wind farms. Huarui’s converters are mainly purchased from American superconductors, and in recent years, they have also independently developed and produced supporting converters; Jinfeng has multiple suppliers including the switch, ABB, and Converteam, and is currently independently developed and supported by Jinfeng Science and Technology Innovation; Dongfang Electric applies ABB and Converteam converters, and Chengdu Fute also supports them. Dongfang Electric Automation and Dongfang Hitachi also develop and produce converter support systems; Other companies often use ABB and Converteam wind power converters. Emerson is expected to have an annual application scale of around 100 million due to its relatively late entry into the wind power industry.

Yaw control system:

The yaw control system is controlled by a wind vane to align the wind turbine with the wind direction. The cabin rotates relative to the tower through electrical drive, which is fixed to the main frame and operates on a large gear ring connected to the tower through a spur gear. The control method adopts a frequency converter to drive four variable frequency motors, with open loop control. The cabin position detection device is an incremental encoder that can detect the current position of the cabin. By comparing the wind direction signal with the wind direction detection device, accurate wind direction control of the yaw system is achieved.

Grouting system:

After the wind turbine is connected to the grid, the control system adjusts the output power by adjusting the blade angle through the pitch adjustment mechanism based on the changes in wind speed, and more effectively utilizes wind energy. Below the rated wind speed, when the blade attack angle is near zero degrees, it can be considered equivalent to a fixed pitch wind turbine, and the output power of the generator changes with the wind speed. When the wind speed reaches above the rated wind speed, the variable pitch mechanism plays a role in adjusting the attack angle of the blades to ensure that the output power of the generator is within the allowable range.

The pitch control system is an important component of wind turbines, and its main function is to achieve maximum wind energy capture and constant speed operation by controlling the blade pitch angle. The pitch control system is also the main brake system of wind turbines, and the electric pitch control system allows each blade to adjust its angle independently. Usually, a complete AC or DC pitch system mainly consists of three electric motors (including brakes, encoders, temperature sensors, cooling fans, etc.), three shaft control cabinets with drivers, and three backup power cabinets, as well as related cables and plugs. All these components are installed inside the wheel hub.

SSB pitch driver

Helishi variable pitch driver

The integrated design of Hollysys LK820 pitch driver not only drives servo motors for blade adjustment, but also integrates PLC control functions, which can complete temperature control, sensor signal reading, safety chain operation, etc. in the pitch shaft cabinet.

Main control system:

The main control system is the brain of the fan, controlling all components of the fan to work in coordination. The main control system is divided into tower base control cabinet and engine room control cabinet, which communicate with each other through field bus.

The main control system is the central nervous system of modern wind turbine. The wind power main control system can control the system based on wind speed and direction, operate at stable voltage and frequency, automatically connect to and disconnect from the grid, and monitor the operating temperature of the gearbox and generator, the oil pressure of the hydraulic system, alarm for any abnormalities, and automatically shut down if necessary. Ensure the safe and reliable operation of wind turbines, achieve the maximum utilization rate and energy conversion rate of natural wind, and provide good electrical energy to the power grid.

Generally, PAC and PLC are used as the main controllers of this control system. By detecting grid parameters, wind conditions, and on-site temperature parameters, the wind turbine is connected and disconnected from the grid. At the same time, yaw, pitch, and other actions are carried out according to wind conditions to optimize control and improve the operational efficiency and power generation quality of the wind turbine. The controllers mainly include products from companies such as Bachmann, Beckhoff, ABB, Mita, etc. The main control systems are mostly designed by wind turbine factories in complete sets, while small-scale wind turbine factories are integrated by domestic professional companies, such as Konowei, Chengdu Fute, Tianjin Ruineng, Dongfang Electric Automation, Shanghai Haide, etc.

Cabinets:

Realize monitoring of various parameters: wind speed, direction, tower vibration frequency, spindle speed, gearbox temperature, generator temperature, lubricating oil temperature, and cabin temperature;

Implement instructions for various control functions. Specifically, it includes the following functions: controlling the heater in the cabin for heating, moistening the gearbox, and providing lighting;

Establish a communication between the tower bottom cabinet and the pitch system; Provide power to the pitch system