Method for controlling hydraulic cylinder, and hydraulic circuit

Abstract

To provide a method for controlling a hydraulic cylinder, which can reliably hold a blade pitch in a feathering position even during an emergency stop due to a power stoppage or the like.SOLUTION: There is provided a method for controlling a hydraulic cylinder for changing the blade pitch of a wind power generator. A first chamber and a second chamber of the hydraulic cylinder are connected by a bypass flow path that can be opened and closed by a bypass valve. The blade pitch is moved to a feathering position to stop power generation when the displacement of a cylinder rod becomes maximum, and is separated from the feathering position to start power generation when the displacement of the cylinder rod decreases. The cylinder rod is urged in a direction to increase the displacement by the elastic force of a spring, and is configured such that the displacement decreases / increases as hydraulic oil is pressed into the first chamber / the second chamber through a first throttle valve / a second throttle valve by the hydraulic pressure accumulated in an accumulator from a hydraulic pump. The method for controlling the hydraulic cylinder opens the bypass valve to connect the first and second chambers of the hydraulic cylinder in a power generation stopping process.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control method and hydraulic circuit for a hydraulic cylinder used to change the blade pitch of a wind turbine generator. [Background technology]

[0002] Wind turbine generators that generate electricity by rotating blades in response to wind force have been well known in the art. For example, Patent Document 1 describes a method for computer-controlled blade pitch angles.

[0003] The conventional blade pitch variable mechanism illustrated in Patent Document 1 is composed of a hydraulic unit, a servo valve, an accumulator, a rotary joint, a hydraulic cylinder, a link, a potentiometer for detecting the blade pitch position, and a slip ring, and an accumulator is provided in the hydraulic system as an emergency stop device in case an abnormality occurs during operation as a power generation device.

[0004] In Patent Document 1, the above-mentioned blade pitch variable mechanism is improved by providing an emergency stop spring in a through hole provided in the main rotating shaft connected to the generator. When hydraulic pressure is lost due to a power outage or the like, the force of the spring is used to hold the blade pitch in the feathering position, thereby preventing problems caused by the blades (rotating part) starting to rotate due to wind force during an emergency stop. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 5-149237 Summary of the Invention [Problem to be solved by the invention]

[0006] According to the blade pitch variable mechanism of Patent Document 1, in the event of an emergency stop due to a power outage or other reason, the hydraulic cylinder should extend using the force of the emergency stop spring, and the blade pitch should be maintained in the feathering position. However, if the spring's elastic coefficient is not large enough, the resistance of the throttle valve and other components in the hydraulic circuit to the hydraulic oil moving when the hydraulic cylinder extends can be large, making it difficult to fully extend the hydraulic cylinder with spring pressure. Furthermore, using a spring with elasticity strong enough to withstand this resistance could result in cavitation in the hydraulic oil.

[0007] Therefore, an object of the present invention is to provide a method for controlling a hydraulic cylinder that can reliably maintain the blade pitch in the feathering position even during an emergency stop due to a power outage or the like. [Means for solving the problem]

[0008] In order to solve the above problems, a hydraulic cylinder control method according to the present invention is a method for controlling a hydraulic cylinder that changes the blade pitch of a wind turbine generator that generates electricity by receiving wind force and rotating the blades, the method comprising: The first chamber and the second chamber of the hydraulic cylinder are connected by a bypass flow path that can be opened and closed by a bypass valve, the blade pitch is configured to move to a feathering position to stop power generation when the displacement of the cylinder rod of the hydraulic cylinder reaches a maximum, and to start power generation when the displacement of the cylinder rod decreases and moves away from the feathering position, The cylinder rod is biased in a direction to increase displacement by the elastic force of a spring, and the displacement is reduced by hydraulic oil being forced into a first chamber of the hydraulic cylinder through a first throttle valve by hydraulic oil accumulated in an accumulator from a hydraulic pump, and the displacement is increased by hydraulic oil being forced into a second chamber of the hydraulic cylinder through a second throttle valve by the hydraulic oil. In the power generation stopping step of stopping the power generation, the bypass valve is opened to allow communication between the first chamber and the second chamber of the hydraulic cylinder.

[0009] In order to solve the above problem, the hydraulic circuit according to the present invention includes a hydraulic cylinder having a cylinder rod biased in a predetermined direction by the elastic force of a spring; A hydraulic pump that generates hydraulic pressure; an accumulator that accumulates the hydraulic pressure; a first throttle valve provided in a flow path connecting the accumulator and a first chamber of the hydraulic cylinder; a second throttle valve provided in a flow path connecting the accumulator and a second chamber of the hydraulic cylinder; a bypass valve provided in a bypass flow path connecting the first chamber and the second chamber of the hydraulic cylinder, The cylinder rod is configured to change the blade pitch of a wind turbine generator that generates electricity by receiving wind force and rotating the blades, by displacement of the cylinder rod, The bypass valve is configured to open when the power generation is stopped.

[0010] According to the hydraulic cylinder control method and hydraulic circuit of the present invention as described above, the blade pitch can be reliably maintained in the feathering position not only when power generation is stopped normally, but also during an emergency stop due to a power outage or the like. [Effects of the Invention]

[0011] The hydraulic cylinder control method and hydraulic circuit of the present invention can reliably maintain the blade pitch in the feathering position even during an emergency stop due to a power outage or the like, and effectively prevent the blades from starting to rotate due to wind force when power generation is stopped. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a flow diagram showing a hydraulic circuit according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Preferred embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a schematic flow diagram of a hydraulic cylinder circuit 1 for changing the blade pitch of a wind turbine generator. A cylinder rod 3, which is the movable part of a hydraulic cylinder 2, is connected to the blades via a control rod (not shown), and the blade pitch is changed by extending and contracting the cylinder rod 3. When the cylinder rod 3 extends and the displacement reaches a maximum, the blade pitch reaches the feathering position, and when the cylinder rod 3 contracts and the displacement approaches a minimum, the blade pitch moves away from the feathering position and reaches a power generation position, and power generation begins.

[0014] The accumulator 4 accumulates hydraulic pressure generated by the hydraulic pump 5. When the accumulated hydraulic pressure pressurizes hydraulic oil into the first chamber 2a (front chamber) of the hydraulic cylinder 2 through the first throttle valve 6A, the displacement of the cylinder rod decreases. A flow path switching valve 5 is provided downstream of the accumulator 4, and it is possible to change the circuit configuration so that the flow path is switched and hydraulic oil is pressed into the second chamber 2b (rear chamber) of the hydraulic cylinder 2 through the second throttle valve 6B, thereby increasing the displacement of the cylinder rod.

[0015] A shutoff valve 7 is provided upstream of the first throttle valve 6A and the second throttle valve 6B. By closing the shutoff valve 7, the displacement of the cylinder rod is fixed, and the blade pitch position can be maintained.

[0016] The cylinder rod 3 is biased in a direction that increases its displacement by the elastic force of the emergency stop spring 8. The above-mentioned blade pitch control is performed during power generation, but when power generation is stopped, the displacement of the cylinder rod 3 is maximized to maintain the blade pitch in the feathering position. Even in the event of a power outage or other power loss, if there is sufficient hydraulic pressure stored in the accumulator 4, normal blade pitch control may be possible, but if there is insufficient hydraulic pressure remaining, the elastic force of the emergency stop spring 8 is used to extend the cylinder rod 3.

[0017] However, if the resistance of a throttle valve or the like to the hydraulic oil is large, the hydraulic oil will hinder the movement of the cylinder rod 3, making it difficult to sufficiently extend the cylinder rod 3 using only the elastic force of the emergency stop spring 8. Therefore, in the event of an emergency stop due to a loss of control power or the like, the bypass valve 9 is forcibly opened to connect the first chamber 2a (front chamber) and the second chamber 2b (rear chamber) of the hydraulic cylinder, allowing the hydraulic oil to move freely from the first chamber 2a (front chamber) to the second chamber 2b (rear chamber).This allows the cylinder rod 3 to be quickly extended to its maximum length using only the elastic force of the emergency stop spring 8, and the blade pitch to move to the feathering position.

[0018] In addition to power loss, a possible cause of an emergency shutdown may be loss of hydraulic pressure due to piping damage. However, by configuring the bypass valve 9 to be forcibly opened even in the event of hydraulic pressure loss, an emergency shutdown operation can be performed appropriately, just as in the case of power loss described above. [Industrial Applicability]

[0019] The hydraulic cylinder control method and hydraulic circuit according to the present invention can be widely used to change the blade pitch of wind turbine generators. [Explanation of symbols]

[0020] 1 Hydraulic cylinder circuit 2 hydraulic cylinders 2a First chamber (front chamber) of hydraulic cylinder 2b Second chamber (rear chamber) of hydraulic cylinder 3 Cylinder Rod 4 Accumulator 5 Flow path switching valve 6A First throttle valve 6B Second throttle valve 7 Shut-off valve 8 Emergency stop spring 9. Bypass valve

Claims

1. A method for controlling a hydraulic cylinder that changes the blade pitch of a wind turbine generator that generates electricity by rotating its blades in response to wind force, comprising: The first chamber and the second chamber of the hydraulic cylinder are connected by a bypass flow path that can be opened and closed by a bypass valve, the blade pitch is configured to move to a feathering position to stop power generation when the displacement of the cylinder rod of the hydraulic cylinder reaches a maximum, and to start power generation when the displacement of the cylinder rod decreases and moves away from the feathering position, The cylinder rod is biased in a direction to increase displacement by the elastic force of a spring, and the displacement is reduced by hydraulic oil being forced into a first chamber of the hydraulic cylinder through a first throttle valve by hydraulic oil accumulated in an accumulator from a hydraulic pump, and the displacement is increased by hydraulic oil being forced into a second chamber of the hydraulic cylinder through a second throttle valve by the hydraulic oil. a power generation stopping step of stopping the power generation, the bypass valve being opened to allow communication between the first chamber and the second chamber of the hydraulic cylinder;

2. a hydraulic cylinder having a cylinder rod biased in a predetermined direction by the elastic force of a spring; A hydraulic pump that generates hydraulic pressure; an accumulator that accumulates the hydraulic pressure; a first throttle valve provided in a flow path connecting the accumulator and a first chamber of the hydraulic cylinder; a second throttle valve provided in a flow path connecting the accumulator and a second chamber of the hydraulic cylinder; a bypass valve provided in a bypass flow path connecting the first chamber and the second chamber of the hydraulic cylinder, The cylinder rod is configured to change the blade pitch of a wind turbine generator that generates electricity by receiving wind force and rotating the blades, by displacement of the cylinder rod, A hydraulic circuit configured to open the bypass valve when the power generation is stopped.

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