Wind power generation is a promising new energy industry in China in recent ten years. At the end of 2010, China has become the largest wind power country in the world with installed capacity. In large-scale wind turbine, the realization of yaw system, main shaft braking and wind wheel locking depends on the hydraulic system with small volume and large function. Hydraulic technology has been widely used in the field of wind power generation.

1、 Yaw brake hydraulic system

Yaw system is one of the indispensable components of horizontal axis wind turbine, which is composed of wind vane sensor, yaw bearing, yaw drive motor, yaw brake, twist cable protection device, etc. it cooperates with the control system of wind turbine to make the impeller of the turbine always in windward state, make full use of wind energy and improve the power generation efficiency of the turbine. The yaw brake is provided with braking force by the hydraulic station. When the impeller is working in the windward state, the hydraulic station provides a larger pressure to the brake to anchor the yaw system, so as to prevent the engine room from deflection and violent vibration under the action of wind force; when the yaw action is triggered by the change of wind direction, the pressure provided by the hydraulic station to the brake is switched to a smaller value to absorb the yaw The free deflection oscillation caused by the wind in the process can prevent the yaw gear from premature damage due to the alternating stress caused by the oscillation. In addition, the output power cables of most wind turbines will rotate together during yaw. When the twist of the cables reaches the degree of threatening the safe operation of the unit, the cable release condition will be triggered. At this time, the unit will stop, and the hydraulic station will control the pressure oil in the yaw brake to completely relieve pressure. The system will perform the cable release action. When it returns to the central position, the cable release will stop automatically and the unit will restart .

2、 Spindle brake hydraulic system

The main shaft braking system is an important device in the fan safety chain, which generally has two ways of active hydraulic braking and passive hydraulic braking. Like the yaw brake, the hydraulic station provides the braking force, with one normally closed solenoid valve and one normally open solenoid valve. The accumulator keeps the pressure, and the pressure switch detects the brake pressure to control the start and stop of the motor.

Take the active hydraulic braking as an example, when the fan stops, the main shaft brake is required to brake, at this time, the normally closed and normally open solenoid valves are powered on, the return oil circuit is disconnected, the pressure oil enters the brake chamber, and the brake is braked; when the fan starts, the main shaft brake is required to release, at this time, the normally closed and normally open solenoid valves are powered off, the brake is released under the action of the return spring, and the oil returns to the oil tank.

3、 Lock pin hydraulic system

When the wind speed exceeds the maximum allowable value for generating operation of the unit, or when the unit is maintained or overhauled, the unit needs to be shut down. At this time, the locking pin is needed to realize the mechanical locking of the wind turbine impeller. The telescopic action of the lock pin is usually driven by the hydraulic station, and its control principle is usually the typical two-way cylinder control principle, which is controlled by the electromagnetic directional valve and the hydraulic control check valve (hydraulic lock).

4、 Design of hydraulic system

The space of wind turbine engine room is relatively compact, and due to the limitation of lifting requirements for maintenance or replacement of accessories, the design shape and weight of hydraulic station are required to be as small as possible. In the limited space, not only the function of the product should be satisfied, but also the reliability and convenience of installation and maintenance should be considered. In the design, the three circuits are concentrated on one hydraulic station.

Considering that the hydraulic system has a high requirement for long-term pressure maintenance of the brake, a large capacity diaphragm accumulator is set in the main system to store energy, and when the hydraulic valve leaks, it provides pressure oil supplement to reduce the working time of the pump; at the same time, the cleanliness of the system oil is not lower than nas7 level, and a filter with pollution transmitter is set in the main oil circuit to ensure the cleanliness of the system oil When polluted, the filter element can be replaced in time according to the monitoring signal.

There is an accumulator in the yaw circuit, which can absorb the impact and store energy, and prolong the pressure holding time of the yaw brake. In the main shaft braking circuit, the pressure reducing valve is used to adjust the braking pressure, which can ensure the stability of the braking pressure without affecting the main pressure of the system.

5、 Concluding remarks

The yaw, main shaft and lock pin hydraulic system of wind turbine, with the characteristics of light weight, small volume and wide function, is especially suitable for the wind turbine cabin with narrow space, and has been widely used. In recent years, with the rapid development of wind power industry, the company's wind power products have also been highly recognized by customers, and the orders of supporting hydraulic stations have also increased year by year. The company's design and manufacturing experience has been improved It has also reached a higher level year by year.