A control method of a hydraulic variable pitch system of a wind turbine generator

Abstract

A kind of control method of wind turbine hydraulic variable pitch system, comprising the following steps: S1: obtaining the relevant parameters of hydraulic cylinder;S2: according to the relevant parameters in S1, establish hydraulic cylinder piston position formula;S3: according to the relevant parameters in S1 and the hydraulic cylinder piston position formula in S2, establish piston thrust formula;S4: according to the relevant parameters in S1 and the piston thrust formula in S3, establish variable pitch torque formula, calculate variable pitch torque;S5: according to the relevant parameters in S1 and the hydraulic cylinder piston position formula in S2, establish proportional valve control signal formula, calculate to obtain proportional valve control signal;S6: according to variable pitch torque and proportional valve control signal, control hydraulic variable pitch system.The present application realizes the mature electric variable pitch control algorithm to be indirectly transplanted to the control of hydraulic variable pitch, solves the follow-up technical improvement upgrade and technical optimization problem after the manufacturer of foreign orphan unit using hydraulic variable pitch system withdraws from Chinese market.

Description

Technical Field

[0001] This invention relates to the field of wind turbine control, and in particular to a control method for a hydraulic pitch system of a wind turbine. Background Technology

[0002] Hydraulic pitch systems are characterized by high transmission torque, light weight, accurate positioning, and fast dynamic response of the actuators. Major international wind turbine manufacturers such as Vestas and Gemesa have adopted hydraulic pitch systems. The main actuators of a hydraulic pitch system are mechanical linkages and hydraulic cylinders, while the main actuators of an electric pitch system are a pitch motor and a drive. The significant differences in their structural designs make replacing existing hydraulic pitch systems with electric pitch systems virtually impossible. With the gradual withdrawal of major international wind turbine manufacturers from the Chinese market, due to their intellectual property protection policies and the significant differences in structural design and control circuitry between hydraulic and electric pitch systems, only a few turbines using hydraulic pitch systems remain in China. Their subsequent upgrades and optimizations have become a major challenge in the current wind power market. Summary of the Invention

[0003] The present invention aims to overcome the difficulties in subsequent upgrades and optimizations of existing domestic wind turbine units that use hydraulic pitch systems, and provides a control method for a hydraulic pitch system of a wind turbine unit.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A control method for a hydraulic pitch system of a wind turbine includes the following steps: S1: Obtaining relevant parameters of the hydraulic cylinder; S2: Establishing a piston position formula for the hydraulic cylinder based on the relevant parameters in S1; S3: Establishing a piston thrust formula based on the relevant parameters in S1 and the piston position formula in S2; S4: Establishing a pitch torque formula based on the relevant parameters in S1 and the piston thrust formula in S3, and calculating the pitch torque; S5: Establishing a proportional valve control signal formula based on the relevant parameters in S1 and the piston position formula in S2, and calculating the proportional valve control signal; S6: Controlling the hydraulic pitch system based on the pitch torque and the proportional valve control signal. This invention utilizes dynamic geometric analysis of the pitch hydraulic cylinder actuator to express the nonlinear relationship between the linear motion of the hydraulic cylinder piston and the circular motion of the blades using a mathematical formula based on relevant parameters. Through dynamic force analysis of the hydraulic cylinder piston during normal operation, relevant parameters are used to establish a mathematical control model with the proportional valve control signal, the hydraulic cylinder piston stroke, and the corresponding pitch angle. This allows for the indirect transfer of mature electric pitch control algorithms to hydraulic pitch control, solving the challenges of subsequent technological upgrades and optimizations faced by manufacturers of orphan turbines using hydraulic pitch systems in China after their withdrawal from the market.

[0006] As a preferred embodiment of the present invention, the relevant parameters include: the length L from the fixed fulcrum of the hydraulic cylinder to the center of rotation of the hub, the torque arm r of the hydraulic pitch actuator when the blade feathers, the included angle α0 of the line connecting the fixed fulcrum of the hydraulic cylinder to the center of rotation of the hub, the pitch angle θ, and the area parameter S. a and S b Cylinder pressure P a and P b Actual pitch angle θ 实际 and reference pitch angle θ 参考 .

[0007] As a preferred embodiment of the present invention, the hydraulic cylinder piston position formula is specifically as follows:

[0008]

[0009] Where l is the length of the hydraulic cylinder piston extension, θ is the pitch angle, α0 is the angle between the line connecting the fixed fulcrum of the hydraulic cylinder to the rotation center of the hub, L is the length from the fixed fulcrum of the hydraulic cylinder to the rotation center of the hub, and r is the torque arm of the hydraulic pitch actuator when the blade feathers.

[0010] As a preferred embodiment of the present invention, the piston thrust formula is specifically as follows:

[0011]

[0012] Where η is the viscous damping coefficient on the hydraulic cylinder piston, P a and P b S is the cylinder chamber pressure. a and S b For area parameters, Let x be the differential of the piston position x of the hydraulic cylinder.

[0013] As a preferred embodiment of the present invention, the pitch torque formula is specifically as follows:

[0014]

[0015] in, This is a function related to piston thrust.

[0016] As a preferred embodiment of the present invention, the proportional valve control signal formula is specifically as follows:

[0017]

[0018] Where k is the proportional gain, θ 实际 θ is the actual pitch angle. 参考 This is the reference pitch angle.

[0019] Therefore, the present invention has the following beneficial effects: by establishing a mathematical model, the present invention indirectly transplants the currently mature electric pitch control algorithm to the hydraulic pitch control, solving the problem of subsequent technical transformation and upgrading and technical optimization for manufacturers of orphan units using hydraulic pitch systems abroad after they withdraw from the Chinese market. Attached Figure Description

[0020] Figure 1 This is a flowchart of the method of the present invention;

[0021] Figure 2 This is a schematic diagram of the geometric structure of the hydraulic pitch actuator in an embodiment of the present invention;

[0022] Figure 3 This is a force analysis diagram of the hydraulic cylinder piston in an embodiment of the present invention;

[0023] In the diagram: 1. Chamber a of the hydraulic cylinder; 2. Chamber b of the hydraulic cylinder; 3. Hydraulic cylinder piston; 4. Check valve; 5. Proportional valve; 6. Hydraulic pump; 7. Hub rotation center. Detailed Implementation

[0024] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0025] like Figure 1 As shown, a control method for a wind turbine hydraulic pitch system includes the following steps: S1: Obtaining relevant parameters of the hydraulic cylinder; the relevant parameters include: the length L from the fixed fulcrum of the hydraulic cylinder to the center of rotation of the hub, the torque arm r of the hydraulic pitch actuator when the blades feather, the included angle α0 of the line connecting the fixed fulcrum of the hydraulic cylinder to the center of rotation of the hub, the pitch angle θ, and the area parameter S. a and S b Cylinder pressure P a and P b Actual pitch angle θ 实际 and reference pitch angle θ 参考 S2: Establish the hydraulic cylinder piston position formula based on the relevant parameters in S1; S3: Establish the piston thrust formula based on the relevant parameters in S1 and the hydraulic cylinder piston position formula in S2; S4: Establish the pitch torque formula based on the relevant parameters in S1 and the piston thrust formula in S3, and calculate the pitch torque; S5: Establish the proportional valve control signal formula based on the relevant parameters in S1 and the hydraulic cylinder piston position formula in S2, and calculate the proportional valve control signal; S6: Control the hydraulic pitch system based on the pitch torque and the proportional valve control signal.

[0026] In this embodiment, as Figure 2The diagram shows the geometric structure of the hydraulic pitch actuator. By measuring the length L from the fixed fulcrum of the hydraulic cylinder to the hub rotation center, the torque arm r of the hydraulic pitch actuator, and the angle α0 between the torque arm r of the hydraulic pitch actuator when the blade feathers and the line connecting the fixed fulcrum of the hydraulic cylinder to the hub rotation center, dynamic geometric analysis of the pitch hydraulic cylinder actuator is performed. This analysis establishes a mathematical formula related to three variables: the blade pitch angle θ, the piston extension length l, and the piston position x. The hydraulic cylinder piston position formula is as follows:

[0027]

[0028] Where l is the length of the hydraulic cylinder piston extension, and θ is the pitch angle.

[0029] like Figure 3 The diagram shows the force analysis of the hydraulic cylinder piston. It includes chamber a1, chamber b2, piston 3, check valve 4, proportional valve 5, hydraulic pump 6, and hub rotation center 7. x = 0 represents the blade opening position. Check valve 4 can only be open in the return direction to ensure the blade moves in the feathering direction. The 3-position 4-way proportional valve 5 is in its normal closed position, where the piston remains stationary. The left position opens the blade in the opening direction, and the right position opens the blade in the feathering direction. The pressure P0 of the hydraulic pump 6 is the design working pressure. The area parameters S of chamber a1 and chamber b2 of the hydraulic cylinder are obtained from the instruction manual. a S b The pressure P in chambers a1 and b2 of the hydraulic cylinder was measured. a P b By analyzing the dynamic force on the hydraulic cylinder piston during normal operation, the following equation, i.e., the piston thrust formula, is obtained:

[0030]

[0031] Where η is the viscous damping coefficient on the hydraulic cylinder piston, P a and P b S is the cylinder chamber pressure. a and S b For area parameters, Let x be the differential of the piston position x in the hydraulic cylinder, and F be the thrust on the piston.

[0032] Based on the relationship between pitch torque and lever arm, the relationship between pitch torque T, pitch angle θ, and hydraulic cylinder piston position x is obtained, i.e., the pitch torque formula is as follows:

[0033]

[0034] Where T is the pitch torque. This is a function related to piston thrust.

[0035] Based on the actual pitch angle θ 实际 and reference pitch angle θ 参考 The position error of the hydraulic cylinder piston, θ, is obtained. 参考 The formula for the proportional valve control signal, obtained from calculations in the pitch control loop, is as follows: The relationship between the proportional valve control signal, the hydraulic cylinder piston stroke, and the corresponding pitch angle is:

[0036]

[0037] Where k is the proportional gain, θ 实际 θ is the actual pitch angle. 参考 The reference pitch angle is used. The piston error is determined by the actual pitch angle θ. 实际 and reference pitch angle θ 参考 Determine, x(θ) 实际 ( ) is related to the propeller pitch angle θ 实际 The relevant actual cylinder piston position is obtained from the hydraulic cylinder piston position formula; x(θ) 参考 ( ) is relative to the reference pitch angle θ 参考 The relevant reference cylinder piston position is determined by the reference paddle pitch angle θ. 参考 The position of the hydraulic cylinder piston is calculated using the formula. y is the proportional valve control signal, typically a 4-20mA current signal or a 0-10V voltage signal. Therefore, the electric pitch control algorithm can be applied to control the hydraulic pitch. This indirectly transplants the mature electric pitch control algorithm to the hydraulic pitch control, solving the subsequent technical upgrades and optimization challenges faced by manufacturers of orphan turbines using hydraulic pitch systems abroad after they withdraw from the Chinese market.

[0038] This invention, through dynamic geometric analysis of the pitch control hydraulic cylinder actuator, uses a mathematical formula related to three variables—the blade pitch angle θ, the piston extension length l, and the position x of the hydraulic cylinder piston—to express the nonlinear relationship between the linear motion of the hydraulic cylinder piston and the circular motion of the blade. This is based on the length L from the fixed fulcrum of the hydraulic cylinder to the center of rotation of the hub, the torque arm r of the hydraulic pitch actuator, and the angle α0 between the torque arm r of the hydraulic pitch actuator during blade feathering and the line connecting the fixed fulcrum of the hydraulic cylinder to the center of rotation of the hub. Furthermore, through dynamic force analysis of the hydraulic cylinder piston during normal operation, based on the pressure P of the two cylinder chambers a and b... a P b and area parameter S a S b The relationship between pitch torque T, pitch angle θ, and hydraulic cylinder piston position x is obtained; based on the actual pitch angle θ 实际 and reference pitch angle θ 参考By obtaining the position error of the hydraulic cylinder piston, a mathematical control model is established by controlling the proportional valve control signal, the hydraulic cylinder piston stroke, and the corresponding pitch angle. This allows for the indirect transplantation of the currently mature electric pitch control algorithm to the control of hydraulic pitch, solving the subsequent technical upgrade and optimization problems faced by manufacturers of orphan turbines using hydraulic pitch systems in foreign countries after they withdraw from the Chinese market.

[0039] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions conceived without creative effort should be included within the scope of protection of the present invention.

Claims

1. A control method for a hydraulic pitch system of a wind turbine generator, characterized in that, By analyzing the dynamic force on the hydraulic cylinder piston during normal operation, a mathematical control model is established based on the piston stroke and the corresponding pitch angle; including the following steps: S1: Obtain relevant parameters of the hydraulic cylinder, including the length from the fixed fulcrum of the hydraulic cylinder to the center of rotation of the hub, the torque arm of the hydraulic pitch actuator when the blade feathers, the included angle of the line connecting the fixed fulcrum of the hydraulic cylinder to the center of rotation of the hub, the pitch angle, the area parameters, the cylinder pressure, the actual pitch angle and the reference pitch angle. S2: Based on the length from the fixed fulcrum of the hydraulic cylinder to the center of rotation of the hub, the torque arm of the hydraulic pitch actuator when the blade feathers and the angle between the line connecting the fixed fulcrum of the hydraulic cylinder to the center of rotation of the hub, construct the hydraulic cylinder piston position formula to represent the nonlinear relationship between the linear motion of the hydraulic cylinder piston and the circular motion of the blade. S3: Establish the piston thrust formula based on the cylinder chamber pressure and area parameters of the hydraulic cylinder and the hydraulic cylinder piston position formula in S2; S4: Based on the pitch torque and pitch angle, and the piston thrust formula in S3, establish the pitch torque formula and calculate the pitch torque. S5: Based on the actual pitch angle and the reference pitch angle, the hydraulic cylinder piston position formula in S2 is used to establish the proportional valve control signal formula, and the proportional valve control signal is calculated; the relationship between the proportional valve control signal and the hydraulic cylinder piston stroke and the corresponding pitch angle is the proportional valve control signal formula. S6: Control the hydraulic pitch system based on the pitch torque and proportional valve control signal.

2. The control method for a hydraulic pitch system of a wind turbine according to claim 1, characterized in that, The proportional valve control signal is a 4-20mA current signal or a 0-10V voltage signal.

3. The control method for a hydraulic pitch system of a wind turbine according to claim 1, characterized in that, The formula for the position of the hydraulic cylinder piston is as follows: Where l is the length of the hydraulic cylinder piston extension, θ is the pitch angle, α0 is the angle between the line connecting the fixed fulcrum of the hydraulic cylinder to the rotation center of the hub, L is the length from the fixed fulcrum of the hydraulic cylinder to the rotation center of the hub, and r is the torque arm of the hydraulic pitch actuator when the blade feathers.

4. The control method for a hydraulic pitch system of a wind turbine according to claim 1, characterized in that, The piston thrust formula is as follows: Where η is the viscous damping coefficient on the hydraulic cylinder piston, P a and P b S is the cylinder chamber pressure. a and S b For area parameters, Let x be the differential of the piston position x of the hydraulic cylinder.

5. The control method for a hydraulic pitch system of a wind turbine according to claim 1, characterized in that, The specific formula for the pitch torque is as follows: in, Let P be a function related to piston thrust, r be the torque arm of the hydraulic pitch actuator during blade feathering, F be the piston thrust, η be the viscous damping coefficient on the piston of the hydraulic cylinder, and P be a function related to piston thrust. a and P b S is the cylinder chamber pressure. a and S b For area parameters, Let x be the differential of the piston position x of the hydraulic cylinder.

6. A control method for a hydraulic pitch system of a wind turbine according to claim 1, 2, 3, 4, or 5, characterized in that, The formula for the proportional valve control signal is as follows: Where k is the proportional gain, θ 实际 θ is the actual pitch angle. 参考 For the reference pitch angle, x (θ) 参考 x(θ) represents the reference cylinder piston position related to the reference propeller pitch angle. 实际 () represents the actual cylinder piston position related to the actual pitch angle.

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