A hydraulic power generation constant-speed constant-pressure control system and method for a wind turbine generator

Abstract

The application discloses a kind of wind turbine hydraulic power generation constant speed constant pressure control system and method, and the system is converted into rotating mechanical energy by wind turbine, and the rotating mechanical energy is rotated by variable hydraulic pump after adjusting rotating speed by speed change gear box, so that rotating mechanical energy is converted into hydraulic energy, to drive variable hydraulic motor rotation and drive generator to generate electricity, so that hydraulic energy is converted into electric energy, and the rotating speed of generator is measured in real time by system oil pressure, and the oil storage state of accumulator and the displacement of variable hydraulic pump are comprehensively adjusted by system oil pressure, to realize constant pressure control, and the opening size of flow valve and the displacement of variable hydraulic motor are comprehensively adjusted by the rotating speed of generator, to realize constant speed control, and the system is operated to steady state by using constant speed constant pressure control, to improve the power generation efficiency of wind turbine, and to realize smooth and continuous power generation of system without using power electronic device, to improve system adaptability.

Description

Technical Field

[0001] This invention relates to the field of wind power generation technology, and in particular to a constant speed and constant pressure control system and method for hydraulic power generation of wind turbine units. Background Technology

[0002] Currently, wind power has become one of the important development directions in the field of new energy. Wind power technology in many countries is entering a stage of rapid development, with the single-unit capacity of wind turbines increasing, and the risks associated with grid connection also constantly growing. The impact of wind turbines on the power grid during grid connection can cause a drop in power system voltage and may damage the generators and mechanical components of the turbines. Therefore, regulating grid-connected wind turbines and controlling the safe and stable operation of their generators is a necessary condition for ensuring the safe integration of wind turbines into the power grid.

[0003] Due to the inherent randomness, intermittency, and instability of wind energy, the output power of wind turbines is easily affected by changes in wind speed and can fluctuate. Current control methods for wind turbines mainly include adjusting the turbine blade orientation and pitch angle based on wind speed and direction, and using power electronic devices such as converters and frequency converters to maintain a constant generator speed, thereby stabilizing the wind turbine's output power.

[0004] However, the adjustment response speed of wind turbine blades is slow and difficult to control precisely. When the wind force changes irregularly, the wind turbine unit is difficult to operate in the optimal state, resulting in low power generation efficiency. Furthermore, the harmonics and resonances generated by power electronic devices affect the stable operation of the power grid, increasing the difficulty of peak shaving and frequency regulation, and making it less adaptable. Summary of the Invention

[0005] This invention provides a constant speed and constant pressure control system and method for hydraulic power generation of wind turbines, which solves the technical problems of low power generation efficiency and poor adaptability of wind turbines.

[0006] In view of the above, the first aspect of the present invention provides a constant speed and constant pressure control system for hydraulic power generation of wind turbine generators, comprising: a wind turbine generator, a variable speed gearbox, a variable hydraulic pump, a working circuit, an oil tank, a controller, a variable hydraulic motor, a generator, an accumulator, a flow valve, a pressure measuring module, and a first speed measuring module;

[0007] The wind turbine is connected to the gearbox, and the gearbox is connected to the variable hydraulic pump via a coupling;

[0008] The variable hydraulic pump is connected to the variable hydraulic motor through the working circuit, and the generator is connected to the variable hydraulic motor through a coupling;

[0009] The accumulator and the flow valve are both located on the working circuit. The accumulator is used to limit the oil output flow of the variable hydraulic pump, and the flow valve is used to limit the oil inlet flow of the variable hydraulic motor.

[0010] Both the pressure measuring module and the first speed measuring module are connected to the controller. The pressure measuring module is used to measure the system oil pressure, and the first speed measuring module is used to measure the speed of the generator and also to send the system oil pressure and the speed of the generator to the controller.

[0011] The controller is electrically connected to the accumulator, the variable hydraulic pump, the flow valve, and the variable hydraulic motor. The controller is used to compare the system oil pressure with a preset constant pressure range threshold, and control the oil storage state of the accumulator and the displacement of the variable hydraulic pump according to the pressure comparison result, so that the system oil pressure is maintained within the preset constant pressure range threshold. The controller is also used to compare the generator speed with a preset speed range threshold, and control the opening of the flow valve and the displacement of the variable hydraulic motor according to the speed comparison result, so that the generator speed is maintained within the preset speed range threshold.

[0012] Preferably, the generator is a permanent magnet synchronous generator.

[0013] Preferably, the pressure measurement module uses a pressure sensor.

[0014] Preferably, the first speed measuring module uses a rotational speed sensor.

[0015] Preferably, the system further includes: an unloading relief valve; the unloading relief valve is connected in parallel with the variable hydraulic pump, the unloading relief valve is connected to the pipeline between the oil outlet and the oil inlet of the variable hydraulic pump, and the oil outlet of the unloading relief valve is connected to the oil tank.

[0016] Preferably, the working circuit includes a low-pressure pipeline and a high-pressure pipeline. The oil tank is connected to the inlet of the variable hydraulic pump through the low-pressure pipeline. The outlet of the variable hydraulic pump is connected to the inlet of the variable hydraulic motor through the high-pressure pipeline. The outlet of the variable hydraulic motor is connected to the inlet of the variable hydraulic pump through the low-pressure pipeline. The pressure measuring module is connected to the high-pressure pipeline. The first speed measuring module is located on the output shaft of the variable hydraulic motor.

[0017] Preferably, the system further includes a second flow sensor and a second speed measuring module. Both the second flow sensor and the second speed measuring module are connected to the controller. The second flow sensor is located on the high-pressure pipeline between the variable hydraulic pump and the accumulator and is used to collect the flow rate of the variable hydraulic pump. The second speed measuring module is located on the input shaft of the variable hydraulic pump and is used to collect the rotational speed of the variable hydraulic pump.

[0018] The controller is further configured to: when the system oil pressure is less than the preset constant pressure range threshold, control the accumulator to release the stored hydraulic oil until the system oil pressure is within the preset constant pressure range threshold and then stop releasing the stored hydraulic oil; when the system oil pressure is within the preset constant pressure range threshold, adaptively adjust the displacement of the variable hydraulic pump according to the rotational speed of the variable hydraulic pump to keep the system oil pressure within the preset constant pressure range threshold; and when the system oil pressure is greater than the preset constant pressure range threshold, control the accumulator to store the hydraulic oil output by the variable hydraulic pump until the system oil pressure is within the preset constant pressure range threshold and then stop storing the hydraulic oil.

[0019] Preferably, the system further includes: a first flow sensor, which is used to collect the oil inlet flow of the variable hydraulic motor and send the oil inlet flow of the variable hydraulic motor to the controller;

[0020] The controller is used to adjust the displacement of the variable hydraulic motor according to the oil inlet flow rate of the variable hydraulic motor, so that the speed of the generator is maintained within the preset speed range threshold.

[0021] Preferably, the controller is further configured to, when the speed of the generator is less than the preset speed range threshold, increase the opening of the flow valve until the speed of the generator reaches the preset speed range threshold and then stop increasing the opening of the flow valve; and to, when the speed of the generator is greater than the preset speed range threshold, decrease the opening of the flow valve until the speed of the generator reaches the preset speed range threshold and then stop decreasing the opening of the flow valve.

[0022] Secondly, the present invention also provides a constant speed and constant pressure control method for hydraulic power generation of wind turbine generators, which, using the above-mentioned constant speed and constant pressure control system for hydraulic power generation of wind turbine generators, includes the following steps:

[0023] The system oil pressure and generator speed are measured.

[0024] The system oil pressure is compared with a preset constant pressure range threshold. Based on the pressure comparison result, the oil storage state of the accumulator and the displacement of the variable hydraulic pump are controlled to keep the system oil pressure within the preset constant pressure range threshold.

[0025] The generator speed is compared with a preset speed range threshold. Based on the speed comparison result, the opening of the flow valve and the displacement of the variable hydraulic motor are controlled to keep the generator speed within the preset speed range threshold.

[0026] As can be seen from the above technical solutions, the present invention has the following advantages:

[0027] This invention converts wind energy into rotational mechanical energy using a wind turbine. This rotational mechanical energy, after its speed is adjusted by a gearbox, drives a variable displacement hydraulic pump, converting the rotational mechanical energy into hydraulic energy. This hydraulic energy then drives a variable displacement hydraulic motor, which in turn drives a generator to produce electricity. The hydraulic energy is then converted into electrical energy. By real-time measurement of system oil pressure and generator speed, the system's oil pressure is used to comprehensively adjust the accumulator's oil storage state and the variable displacement hydraulic pump's displacement to achieve constant pressure control. Furthermore, the generator's speed is used to comprehensively adjust the flow valve's opening and the variable displacement hydraulic motor's displacement to achieve constant speed control. Through constant speed and constant pressure control, the system reaches a steady state, improving the wind turbine's power generation efficiency. Simultaneously, without using power electronic devices, the system achieves stable and continuous power generation, improving its adaptability. Attached Figure Description

[0028] Figure 1 A schematic diagram of a constant speed and constant pressure control system for hydraulic power generation of a wind turbine provided in an embodiment of the present invention;

[0029] Figure 2 A flowchart of a constant speed and constant pressure control method for hydraulic power generation of a wind turbine provided in an embodiment of the present invention. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] For easier understanding, please refer to Figure 1 The present invention provides a constant speed and constant pressure control system for hydraulic power generation of wind turbine, comprising: wind turbine 11, transmission gearbox 12, variable hydraulic pump 13, working circuit, oil tank 16, controller 17, variable hydraulic motor 18, generator 19, accumulator 21, flow valve 22, pressure measuring module 23 and first speed measuring module 24.

[0032] The wind turbine 11 is connected to the gearbox 12, and the gearbox 12 is connected to the variable hydraulic pump 13 via a coupling.

[0033] The wind turbine 11 includes blades. The blades of the wind turbine 11 convert wind energy into rotational mechanical energy. The rotational mechanical energy is adjusted by the speed change gearbox 12 and drives the variable hydraulic pump 13 to rotate, so that the rotational mechanical energy is converted into hydraulic energy.

[0034] It should be noted that, since the blade rotation speed of the wind turbine 11 is relatively low, the gearbox 12 can accelerate the rotation of the blade main shaft, so that the rotation speed of the wind turbine 11 is adapted to the working speed of the variable hydraulic pump 13. At the same time, wind energy is transmitted from the main shaft to the gearbox 12 through the blade, and then to the variable hydraulic pump 13 through the coupling, realizing the conversion of wind energy into rotational mechanical energy into hydraulic energy.

[0035] The variable hydraulic pump 13 is connected to the variable hydraulic motor 18 through a working circuit, and the generator 19 is connected to the variable hydraulic motor 18 through a coupling.

[0036] Hydraulic energy drives the variable hydraulic motor 18 to rotate, and the variable hydraulic motor 18 drives the generator 19 to generate electricity, thus converting hydraulic energy into electrical energy.

[0037] Among them, generator 19 can be a permanent magnet synchronous generator. Permanent magnet synchronous generators do not require excitation devices, have high efficiency, and have good power generation performance in medium and low speed situations, which is more in line with new energy power generation systems with unstable energy sources such as wind power.

[0038] In one feasible embodiment, the working circuit includes a low-pressure line 14 and a high-pressure line 15. The oil tank 16 is connected to the inlet of the variable hydraulic pump 13 via the low-pressure line 14. The outlet of the variable hydraulic pump 13 is connected to the inlet of the variable hydraulic motor 18 via the high-pressure line 15. The outlet of the variable hydraulic motor 18 is connected to the inlet of the variable hydraulic pump 13 via the low-pressure line 14. The pressure measuring module 23 is connected to the high-pressure line 15. The first speed measuring module 24 is located on the output shaft of the variable hydraulic motor 18.

[0039] Both the accumulator 21 and the flow valve 22 are located on the working circuit. The accumulator 21 is used to limit the oil output flow of the variable hydraulic pump 13, and the flow valve 22 is used to limit the oil inlet flow of the variable hydraulic motor 18.

[0040] Both the pressure measuring module 23 and the first speed measuring module 24 are connected to the controller 17. The pressure measuring module 23 is used to measure the system oil pressure, and the first speed measuring module 24 is used to measure the speed of the generator 19 and also to send the system oil pressure and the speed of the generator 19 to the controller 17.

[0041] The pressure measuring module 23 can be a pressure sensor, and the first speed measuring module 24 can be a speed sensor.

[0042] The controller 17 is electrically connected to the accumulator 21, the variable hydraulic pump 13, the flow valve 22, and the variable hydraulic motor 18. The controller 17 is used to compare the system oil pressure with a preset constant pressure range threshold, and control the oil storage state of the accumulator 21 and the displacement of the variable hydraulic pump 13 according to the pressure comparison result, so that the system oil pressure is maintained within the preset constant pressure range threshold. It is also used to compare the speed of the generator 19 with a preset speed range threshold, and control the opening of the flow valve 22 and the displacement of the variable hydraulic motor 18 according to the speed comparison result, so that the speed of the generator 19 is maintained within the preset speed range threshold.

[0043] In one specific embodiment, the system further includes a second flow sensor 27 and a second speed measuring module 28. Both the second flow sensor 27 and the second speed measuring module 28 are connected to the controller 17. The second flow sensor 27 is located on the high-pressure pipeline 15 between the variable hydraulic pump 13 and the accumulator 21 and is used to collect the flow rate of the variable hydraulic pump 13. The second speed measuring module 28 is located on the input shaft of the variable hydraulic pump 13 and is used to collect the rotational speed of the variable hydraulic pump 13.

[0044] Specifically, for constant pressure control, the controller 17 is also used to control the accumulator 21 to release the stored hydraulic oil when the system oil pressure is less than the preset constant pressure range threshold, until the system oil pressure is within the preset constant pressure range threshold and then stop releasing the stored hydraulic oil; it is also used to adaptively adjust the displacement of the variable hydraulic pump 13 according to the speed of the variable hydraulic pump 13 when the system oil pressure is within the preset constant pressure range threshold, so that the system oil pressure is maintained within the preset constant pressure range threshold; it is also used to control the accumulator 21 to store the hydraulic oil output by the variable hydraulic pump 13 when the system oil pressure is greater than the preset constant pressure range threshold, until the system oil pressure is within the preset constant pressure range threshold and then stop storing the hydraulic oil.

[0045] In one example, the constant pressure range threshold is set to [P1, P2]. The constant pressure range threshold can be set as a boundary value based on "rated working pressure ± allowable error value". The pressure measuring module 23 monitors the system oil pressure P in real time. The controller 17 compares the system oil pressure P with P1 and P2 respectively. Based on the comparison results, the oil storage state of the accumulator 21 and the displacement of the variable hydraulic pump 13 are determined. The specific comparison is as follows:

[0046] When the system oil pressure P is less than P1, the accumulator 21 releases hydraulic oil to compensate for the flow rate output by the variable hydraulic pump 13, causing the system oil pressure to rise until the system oil pressure P is P1≤P≤P2, at which point the accumulator 21 stops releasing hydraulic oil. When the system oil pressure P is P1≤P≤P2, the displacement of the variable hydraulic pump 13 is controlled. Based on the relationship "flow rate = speed * displacement", the displacement of the variable hydraulic pump 13 is adaptively adjusted according to the speed of the variable hydraulic pump 13, providing more precise and smaller-amplitude control over the output flow rate. This keeps the system oil pressure stable and maintains it within the preset pressure range for as long as possible, thereby reducing system oil pressure fluctuations and ensuring that the variable hydraulic pump 13 can continuously output a stable flow rate. When the system oil pressure P is greater than P2, the accumulator 21 stores hydraulic oil to buffer the flow rate output by the variable hydraulic pump 13, causing the system oil pressure to drop until the system oil pressure P is P1≤P≤P2, at which point the accumulator 21 stops storing hydraulic oil.

[0047] For constant speed control, the controller 17 is also used to increase the opening of the flow valve 22 until the speed of the generator 19 reaches the preset speed range threshold when the speed of the generator 19 is less than the preset speed range threshold, and then stop increasing the opening of the flow valve 22; it is also used to decrease the opening of the flow valve 22 until the speed of the generator 19 reaches the preset speed range threshold when the speed of the generator 19 is greater than the preset speed range threshold, and then stop decreasing the opening of the flow valve 22.

[0048] Meanwhile, the system also includes a first flow sensor 25, which is used to collect the oil inlet flow of the variable hydraulic motor 18 and send the oil inlet flow of the variable hydraulic motor 18 to the controller 17.

[0049] The controller 17 is used to adjust the displacement of the variable hydraulic motor 18 according to the oil inlet flow of the variable hydraulic motor 18, so that the speed of the generator 19 is kept within a preset speed range threshold.

[0050] In one example, the speed range threshold of generator 19 is set to [n1, n2]. The speed range threshold of generator 19 can be set as a boundary value based on "rated speed ± allowable error value". The first speed measurement module 24 monitors the speed n of generator 19 in real time. The controller 17 compares the speed n of generator 19 with the magnitudes of n1 and n2 respectively. Based on the speed comparison results, the opening degree of flow valve 22 and the displacement of variable hydraulic motor 18 are controlled to keep the speed of generator 19 within the preset speed range threshold. The specific comparison is as follows:

[0051] When the speed n of generator 19 is less than n1, the opening of flow valve 22 is increased to increase the flow rate into variable hydraulic motor 18, causing the speed to rise until the speed n of generator 19 is n1≤n≤n2, at which point the opening of flow valve 22 is stopped. When the speed n of generator 19 is n1≤n≤n2, according to the relationship "flow rate = speed * displacement", controller 17 collects flow data in real time through the first flow sensor 25 and synchronously adjusts the displacement of variable hydraulic motor 18 to perform smaller and more precise control of the speed, keeping the speed stable and maintaining it within the preset speed range for as long as possible, so that generator 19 can continuously output stable electrical energy. When the speed n of generator 19 is greater than n2, the opening of flow valve 22 is decreased to reduce the flow rate into variable hydraulic motor 18, causing the speed to drop until the speed n of generator 19 is n1≤n≤n2, at which point the opening of flow valve 22 is stopped.

[0052] In one specific embodiment, the system further includes: an unloading relief valve 26; the unloading relief valve 26 is connected in parallel with the variable hydraulic pump 13, the unloading relief valve 26 is connected to the pipeline between the oil outlet and the oil inlet of the variable hydraulic pump 13, and the oil outlet of the unloading relief valve 26 is connected to the oil tank 16.

[0053] During system operation, the unloading relief valve 26 is normally closed. When the system oil pressure is too high or the generator 19 generates too much power, the unloading relief valve 26 opens, allowing the hydraulic oil to flow back to the oil tank 16.

[0054] It should be noted that this invention converts wind energy into rotational mechanical energy through a wind turbine. This rotational mechanical energy, after its speed is adjusted by a gearbox, drives a variable hydraulic pump to rotate, thus converting the rotational mechanical energy into hydraulic energy. This hydraulic energy then drives a variable hydraulic motor to rotate, which in turn drives a generator to generate electricity, converting the hydraulic energy into electrical energy. By measuring the system oil pressure and the generator speed in real time, the system oil pressure is used to comprehensively adjust the oil storage state of the accumulator and the displacement of the variable hydraulic pump to achieve constant pressure control. Furthermore, the generator speed is used to comprehensively adjust the opening of the flow valve and the displacement of the variable hydraulic motor to achieve constant speed control. By utilizing constant speed and constant pressure control, the system reaches a steady state, improving the power generation efficiency of the wind turbine. At the same time, without using power electronic devices, the system achieves stable and continuous power generation, improving its adaptability.

[0055] The above is a detailed description of an embodiment of a constant speed and constant pressure control system for hydraulic power generation of a wind turbine provided by the present invention. The following is a detailed description of an embodiment of a constant speed and constant pressure control method for hydraulic power generation of a wind turbine provided by the present invention.

[0056] For easier understanding, please refer to Figure 2The present invention provides a constant speed and constant pressure control method for hydraulic power generation of wind turbine units, which applies the above-mentioned constant speed and constant pressure control system for hydraulic power generation of wind turbine units, and includes the following steps:

[0057] Step 1: Measure the system oil pressure and generator speed;

[0058] Step 2: Compare the system oil pressure with the preset constant pressure range threshold, and control the oil storage state of the accumulator and the displacement of the variable hydraulic pump according to the pressure comparison result, so that the system oil pressure is maintained within the preset constant pressure range threshold.

[0059] Step 3: Compare the generator speed with the preset speed range threshold, and control the opening of the flow valve and the displacement of the variable hydraulic motor according to the speed comparison result, so that the generator speed is kept within the preset speed range threshold.

[0060] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific process of the method described above can be referred to the corresponding process in the aforementioned system embodiments, and will not be repeated here.

[0061] In the several embodiments provided by this invention, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, indirect coupling or communication connection between devices or units, and may be electrical, mechanical, or other forms.

[0062] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A constant speed and constant pressure control system for hydraulic power generation of wind turbine generators, characterized in that, include: Wind turbine generator set, gearbox, variable hydraulic pump, working circuit, oil tank, controller, variable hydraulic motor, generator, accumulator, flow valve, pressure measuring module and first speed measuring module; The wind turbine is connected to the gearbox, and the gearbox is connected to the variable hydraulic pump via a coupling; The variable hydraulic pump is connected to the variable hydraulic motor through the working circuit, and the generator is connected to the variable hydraulic motor through a coupling; The accumulator and the flow valve are both located on the working circuit. The accumulator is used to limit the oil output flow of the variable hydraulic pump, and the flow valve is used to limit the oil inlet flow of the variable hydraulic motor. Both the pressure measuring module and the first speed measuring module are connected to the controller. The pressure measuring module is used to measure the system oil pressure, and the first speed measuring module is used to measure the speed of the generator and also to send the system oil pressure and the speed of the generator to the controller. The controller is electrically connected to the accumulator, the variable hydraulic pump, the flow valve, and the variable hydraulic motor. The controller is used to compare the system oil pressure with a preset constant pressure range threshold, and control the oil storage state of the accumulator and the displacement of the variable hydraulic pump according to the pressure comparison result, so that the system oil pressure is maintained within the preset constant pressure range threshold. The controller is also used to compare the generator speed with a preset speed range threshold, and control the opening of the flow valve and the displacement of the variable hydraulic motor according to the speed comparison result, so that the generator speed is maintained within the preset speed range threshold.

2. The constant speed and constant pressure control system for wind turbine hydraulic power generation according to claim 1, characterized in that, The generator is a permanent magnet synchronous generator.

3. The constant speed and constant pressure control system for wind turbine hydraulic power generation according to claim 1, characterized in that, The pressure measurement module uses a pressure sensor.

4. The constant speed and constant pressure control system for wind turbine hydraulic power generation according to claim 1, characterized in that, The first speed measurement module uses a rotation speed sensor.

5. The constant speed and constant pressure control system for wind turbine hydraulic power generation according to claim 1, characterized in that, Also includes: Unloading relief valve; The unloading relief valve is connected in parallel with the variable hydraulic pump. The unloading relief valve is connected to the pipeline between the oil outlet and the oil inlet of the variable hydraulic pump. The oil outlet of the unloading relief valve is connected to the oil tank.

6. The constant speed and constant pressure control system for wind turbine hydraulic power generation according to claim 1, characterized in that, The working circuit includes a low-pressure pipeline and a high-pressure pipeline. The oil tank is connected to the inlet of the variable hydraulic pump through the low-pressure pipeline. The outlet of the variable hydraulic pump is connected to the inlet of the variable hydraulic motor through the high-pressure pipeline. The outlet of the variable hydraulic motor is connected to the inlet of the variable hydraulic pump through the low-pressure pipeline. The pressure measuring module is connected to the high-pressure pipeline. The first speed measuring module is located on the output shaft of the variable hydraulic motor.

7. The constant speed and constant pressure control system for wind turbine hydraulic power generation according to claim 6, characterized in that, It also includes a second flow sensor and a second speed measuring module. Both the second flow sensor and the second speed measuring module are connected to the controller. The second flow sensor is located on the high-pressure pipeline between the variable hydraulic pump and the accumulator and is used to collect the flow rate of the variable hydraulic pump. The second speed measuring module is located on the input shaft of the variable hydraulic pump and is used to collect the rotational speed of the variable hydraulic pump. The controller is further configured to: when the system oil pressure is less than the preset constant pressure range threshold, control the accumulator to release the stored hydraulic oil until the system oil pressure is within the preset constant pressure range threshold and then stop releasing the stored hydraulic oil; when the system oil pressure is within the preset constant pressure range threshold, adaptively adjust the displacement of the variable hydraulic pump according to the rotational speed of the variable hydraulic pump to keep the system oil pressure within the preset constant pressure range threshold; and when the system oil pressure is greater than the preset constant pressure range threshold, control the accumulator to store the hydraulic oil output by the variable hydraulic pump until the system oil pressure is within the preset constant pressure range threshold and then stop storing the hydraulic oil.

8. The constant speed and constant pressure control system for wind turbine hydraulic power generation according to claim 1, characterized in that, Also includes: A first flow sensor is used to collect the oil inlet flow of the variable hydraulic motor and send the oil inlet flow of the variable hydraulic motor to the controller; The controller is used to adjust the displacement of the variable hydraulic motor according to the oil inlet flow rate of the variable hydraulic motor, so that the speed of the generator is maintained within the preset speed range threshold.

9. The constant speed and constant pressure control system for wind turbine hydraulic power generation according to claim 8, characterized in that, The controller is also configured to increase the opening of the flow valve until the generator speed reaches the preset speed range threshold when the generator speed is less than the preset speed range threshold, and then stop increasing the opening of the flow valve. It is also used to reduce the opening of the flow valve when the speed of the generator is greater than the preset speed range threshold, until the speed of the generator is equal to the preset speed range threshold, and then stop reducing the opening of the flow valve.

10. A constant speed and constant pressure control method for hydraulic power generation of a wind turbine, using the constant speed and constant pressure control system for hydraulic power generation of a wind turbine as described in any one of claims 1 to 9, characterized in that, Includes the following steps: The system oil pressure and generator speed are measured. The system oil pressure is compared with a preset constant pressure range threshold. Based on the pressure comparison result, the oil storage state of the accumulator and the displacement of the variable hydraulic pump are controlled to keep the system oil pressure within the preset constant pressure range threshold. The generator speed is compared with a preset speed range threshold. Based on the speed comparison result, the opening of the flow valve and the displacement of the variable hydraulic motor are controlled to keep the generator speed within the preset speed range threshold.

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