Multi-stage energy storage wave energy hydraulic energy conversion system and control method thereof

Abstract

The invention discloses a multistage energy storage wave energy hydraulic energy conversion system and a control method thereof, and belongs to the technical field of ocean hydraulic power generation, the system comprises an overhanging frame, a hydraulic cylinder is arranged on the side, away from a shore-based platform, of the overhanging frame, a floater is arranged below the hydraulic cylinder, and a hydraulic PTO system is arranged in the overhanging frame; the hydraulic PTO system comprises an oil tank, a one-way valve set, an energy accumulator set and a generator set, the hydraulic cylinder is connected with the oil tank through the one-way valve set, and the energy accumulator set and the generator set are both connected with the oil tank in series. By adopting the multistage energy storage wave energy hydraulic energy conversion system, the energy accumulators with different volumes are combined with the mechanical energy storage flywheel, so that the pressure pulsation of hydraulic oil in the system is reduced as much as possible, the hydraulic energy conversion efficiency of a wave energy power generation device is improved, more electric energy can be output, the wave energy is subjected to graded energy storage and multistage smooth liquid flow, and the power generation efficiency is improved. The safety and sustainability of the power generation system are improved, and the working efficiency of the hydraulic wave energy conversion system can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of marine hydraulic power generation, and in particular to a wave energy hydraulic energy conversion system with multi-stage energy storage and a control method thereof. Background Art

[0002] At present, ocean wave energy is a green, environmentally friendly, abundantly available, and highly energy-dense marine renewable in-situ energy source. Exploring the use of this type of non-land-based new energy source is expected to solve the energy shortage problem of deep-sea engineering equipment.

[0003] The generation of wave energy depends on many uncontrollable factors such as the natural environment, weather conditions and geographical location. Its energy output often shows significant volatility and discontinuity, including random changes in amplitude and frequency, and possible sudden energy surges. These characteristics require the mechanical structure of the power generation equipment to have good impact resistance, stable working conditions and high reliability. The hydraulic transmission system not only has a relatively simple structural design, but also can achieve flexible energy transmission and effectively reduce impact loads. In addition, its built-in energy storage device can stabilize the output pressure and ensure the continuity of energy supply. At the same time, hydraulic transmission is also good at handling large torque conversion requirements, further improving the overall efficiency and performance of the system. Therefore, hydraulic transmission has been widely used and promoted in the field of wave energy conversion.

[0004] In view of the above-mentioned related technologies, the traditional hydraulic transmission system is installed at sea or on a shore-based platform. When dealing with wave energy fluctuations, it often relies on accumulators to mitigate the instability caused by wave speed and state changes, and strives to achieve stable energy output. However, most existing hydraulic wave energy power generation devices only use one accumulator and one generator, or two accumulators and one generator in the entire working pressure range, which will result in the inability to maintain a high conversion efficiency in the process of converting hydraulic energy into electrical energy, which is not conducive to the full utilization of hydraulic energy. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a wave energy hydraulic energy conversion system with multi-stage energy storage and a control method thereof. The wave energy hydraulic energy conversion system with multi-stage energy storage is adopted. By combining accumulators of different volumes with a mechanical energy storage flywheel and adding an auxiliary generator, the pressure pulsation of the hydraulic oil in the system is minimized, the hydraulic energy conversion efficiency of the wave energy power generation device is improved, and it is beneficial to output more electric energy. The entire power generation process does not require external electric power participation, simplifies the energy storage method of the wave energy power generation device, saves electric energy, and also has the advantages of adjustable hydraulic circuit working pressure range, etc. Wave energy is stored in stages and multi-stage smooth liquid flow is performed, which is not only beneficial to avoid excessive accumulator pressure and improve the safety and sustainability of the power generation system, but also beneficial to improve the working efficiency of the hydraulic wave energy conversion system.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: The first object of the present invention is to provide a wave energy hydraulic energy conversion system with multi-stage energy storage, comprising an outrigger, a hydraulic cylinder is provided on the side of the outrigger away from the shore-based platform, a float is provided under the hydraulic cylinder, and a hydraulic PTO system is provided in the outrigger; The hydraulic PTO system includes an oil tank, a one-way valve group, an accumulator group and a generator group. The hydraulic cylinder is connected to the oil tank through the one-way valve group, and the accumulator group and the generator group are connected to the oil tank in series. The hydraulic cylinder is placed vertically and is used to convert the wave energy in the heave direction captured by the float into hydraulic energy; The one-way valve group converts the high-pressure fluid from the hydraulic cylinder into a one-way fluid flow through the rectifier bridge circuit and enters the main circuit of the hydraulic PTO system; The accumulator group is composed of a plurality of accumulators, and the generator group is composed of an energy storage flywheel, at least two hydraulic motors and at least two generators.

[0007] By adopting the above technical scheme, a wave energy hydraulic energy conversion system with multi-stage energy storage is adopted. By combining accumulators of different volumes with mechanical energy storage flywheels and adding an auxiliary generator, the pressure pulsation of the hydraulic oil in the system is minimized, the hydraulic energy conversion efficiency of the wave energy power generation device is improved, and it is beneficial to output more electrical energy. The entire power generation process does not require external power participation, simplifies the energy storage method of the wave energy power generation device, saves electrical energy, and also has the advantages of adjustable hydraulic circuit working pressure range, etc. Wave energy is stored in stages and multi-stage smooth liquid flow is performed, which is not only beneficial to avoid excessive accumulator pressure and improve the safety and sustainability of the power generation system, but also beneficial to improve the working efficiency of the hydraulic wave energy conversion system.

[0008] Furthermore, the hydraulic PTO system also includes a speed regulating valve, which is connected in series with the accumulator group and the generator group.

[0009] By adopting the above technical solution, the accumulator stores the hydraulic oil from the hydraulic motor and releases it after it is full. The flow rate of the hydraulic oil is adjusted by the speed regulating valve, so that the flow rate of the hydraulic oil entering the accumulator and the hydraulic motor is constant. The accumulator absorbs the hydraulic pulsation in the preceding circuit to ensure stable power generation of the generator.

[0010] Furthermore, the hydraulic PTO system also includes a flow sensor and a pressure sensor, and the flow sensor, the pressure sensor, the accumulator group, and the generator group are all connected in series.

[0011] By adopting the above technical solution, the effects of the accumulator and the energy storage flywheel on the hydraulic system can be intuitively determined by comparing the flow and pressure of the hydraulic oil in each energy storage stage.

[0012] Furthermore, the hydraulic PTO system also includes a hydraulic valve, one end of which is connected in series to the one-way valve group and the oil tank, and the other end of the hydraulic valve is connected in series to the accumulator group and the generator group.

[0013] By adopting the above technical solution, the hydraulic valve uses a pilot hydraulic valve, which further improves the safety and sustainability of the power generation system and improves the working efficiency of the hydraulic wave energy conversion system.

[0014] Furthermore, the accumulator group includes a plurality of small-capacity accumulators and a plurality of large-capacity accumulators.

[0015] By adopting the above technical solution, the accumulator is a small-volume accumulator, which mainly absorbs the pressure pulsation of the hydraulic oil flowing through the rectifier bridge, and the accumulator is a large-volume accumulator, which mainly stores relatively stable high-pressure hydraulic oil.

[0016] Furthermore, each accumulator in the accumulator group is provided with a switch.

[0017] By adopting the above technical solution to control the opening and closing of the switch, different combinations of accumulators and energy storage flywheels can be used for different sea conditions in different sea areas to achieve the effect of multi-stage energy storage and absorption of pressure pulsation.

[0018] A second object of the present invention is to provide a control method for the wave energy hydraulic energy conversion system with multi-stage energy storage as described above, comprising the following steps: Step 1: During the charging stage, the hydraulic oil in the hydraulic cylinder drives the central axis of the hydraulic motor to rotate through the variable piston, and then drives the energy storage flywheel to rotate through the transmission motion of the coupling. The energy storage flywheel stores energy in the form of kinetic energy, completing the energy change process of conversion and transmission from hydraulic energy to mechanical energy, mechanical energy and then to mechanical energy; Step 2: Energy is stored in the rotating flywheel, which in turn drives the generator to rotate and generate electricity, thus realizing the energy conversion process from mechanical energy to electrical energy. Step 3: Energy release stage. When the hydraulic oil pressure and flow rate of the hydraulic motor decrease, the output speed of the hydraulic motor decreases. Due to the mechanical energy stored in the energy storage flywheel, the energy release period begins at this time. The energy storage flywheel begins to reduce its speed and releases the stored mechanical energy to ensure the slow rotation of the hydraulic motor, energy storage flywheel and generator. The energy storage flywheel can drive the generator to generate electricity in both the charging stage and the energy release stage.

[0019] Furthermore, the accumulator stores the hydraulic oil from the hydraulic motor and releases it after it is fully stored. The flow rate of the hydraulic oil is adjusted by the speed regulating valve so that the flow rate of the hydraulic oil entering the accumulator and the hydraulic motor is constant.

[0020] Furthermore, in low sea conditions, the hydraulic PTO system stores hydraulic energy. When the hydraulic oil in the accumulator is full, it is automatically released to drive the main generator to generate electricity. The energy storage flywheel plays the function of smoothing the fluid flow. When the hydraulic motor operates at the maximum displacement, due to the low speed, the generator provides little damping, and the energy storage flywheel rotates to ensure further smoothing of the fluid flow, thereby ensuring the stable operating condition of the generator set.

[0021] Furthermore, in high sea conditions, power control is achieved by adjusting the hydraulic motor, the speed of the hydraulic motor is increased, the generator converts excess energy into electrical energy, the pressure of the hydraulic PTO system is increased, and the energy is stored in the energy storage flywheel and accumulator, driving the generator to generate electricity and ensuring the power generation efficiency of the generator set.

[0022] In summary, compared with the prior art, the above technical solution has the following beneficial effects: (1) A wave energy hydraulic energy conversion system with multi-stage energy storage is adopted. By combining accumulators of different volumes with a mechanical energy storage flywheel and adding an auxiliary generator, the pressure pulsation of the hydraulic oil in the system is minimized, the hydraulic energy conversion efficiency of the wave energy power generation device is improved, and more electric energy is output. The entire power generation process does not require external power participation, which simplifies the energy storage method of the wave energy power generation device and saves electric energy. It also has the advantages of adjustable working pressure range of the hydraulic circuit, and the wave energy is stored in stages and multi-stage smooth liquid flow, which is not only conducive to avoiding excessive pressure of the accumulator and improving the safety and sustainability of the power generation system, but also conducive to improving the working efficiency of the hydraulic wave energy conversion system; (2) The accumulator stores the hydraulic oil from the hydraulic motor and releases it when it is full. The hydraulic oil flow rate is adjusted by the speed regulating valve so that the hydraulic oil flow rate into the accumulator and the hydraulic motor is constant. The accumulator absorbs the hydraulic pulsation in the previous circuit to ensure stable power generation of the generator. (3) By comparing the flow and pressure of the hydraulic oil at each energy storage stage, the effect of the accumulator and the energy storage flywheel on the hydraulic system can be intuitively determined; (4) The present invention has the advantages of high hydraulic energy conversion efficiency, simple control method, stable energy output, etc. It can smooth the hydraulic fluid and quickly release energy in low sea conditions, and store excess energy in high sea conditions, thereby improving the efficiency of wave energy utilization. The hydraulic circuit control does not require external power participation. Through the combination of multiple accumulators and energy storage flywheels, more efficient energy utilization is achieved, the power generation quality is improved, and the power generation mode can be automatically adjusted according to the sea conditions. It is suitable for energy conversion in various wave environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of a wave energy hydraulic energy conversion system according to an embodiment of the present invention; Figure 2It is a top view of the structure installation of the wave energy hydraulic energy conversion system according to an embodiment of the present invention; Figure 3 This is a front view of the wave energy hydraulic energy conversion system structure installation according to an embodiment of the present invention.

[0024] Explanation of the accompanying drawings: 1. hydraulic cylinder; 2. first non-return valve; 3. second non-return valve; 4. third non-return valve; 5. fourth non-return valve; 6. first switch; 7. first accumulator; 8. second switch; 9. second accumulator; 10. first flow sensor; 11. first pressure sensor; 12. variable hydraulic motor; 13. energy storage flywheel; 14. auxiliary generator; 15. third switch; 16. third accumulator; 17. speed control valve; 18. fourth switch; 19. fourth accumulator; 20. second flow sensor; 21. second pressure sensor; 22. fixed hydraulic motor; 23. main generator; 24. oil tank; 25. float; 26. hydraulic valve; 27. outrigger; 28. hydraulic PTO system. DETAILED DESCRIPTION

[0025] The principles and features of the present invention are described below in conjunction with all the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0026] The embodiment of the invention discloses a wave energy hydraulic energy conversion system with multi-stage energy storage and a control method thereof.

[0027] Reference Figures 1 to 3 A wave energy hydraulic energy conversion system with multi-stage energy storage includes an outrigger 27. A hydraulic cylinder 1 is provided on the side of the outrigger 27 away from the shore-based platform. A float 25 is provided under the hydraulic cylinder 1. A hydraulic PTO system 28 is provided inside the outrigger 27. The hydraulic cylinder 1 is a double-rod double-acting hydraulic cylinder. The hydraulic cylinder 1 is placed vertically to convert the wave energy in the heave direction captured by the float 25 into hydraulic energy.

[0028] The hydraulic PTO system 28 includes an oil tank 24 , a one-way valve group, an accumulator group and a generator group. The hydraulic cylinder 1 is connected to the oil tank 24 via the one-way valve group. The accumulator group and the generator group are both connected to the oil tank 24 in series.

[0029] The one-way valve group adopts a four-way valve mode. The high-pressure liquid flow from the hydraulic cylinder 1 is converted into a one-way liquid flow through the rectifier bridge circuit and enters the main circuit of the hydraulic PTO system 28. In this embodiment, the one-way valve group includes a first one-way valve 2, a second one-way valve 3, a third one-way valve 4, and a fourth one-way valve 5.

[0030] The accumulator group is composed of a plurality of accumulators, and the accumulator group includes a plurality of small-volume accumulators and a plurality of large-volume accumulators. In this embodiment, the accumulator group includes a first accumulator 7, a second accumulator 9, a third accumulator 16, and a fourth accumulator 19, wherein the first accumulator 7 and the fourth accumulator 19 are small-volume accumulators, which are mainly used to absorb the pressure pulsation of the hydraulic oil flowing through the rectifier bridge, and the second accumulator 9 and the third accumulator 16 are large-volume accumulators, which are mainly used to store relatively stable high-pressure hydraulic oil.

[0031] Each accumulator in the accumulator group is provided with a switch. In this embodiment, the switches include a first switch 6, a second switch 8, a third switch 15 and a fourth switch 18. The switches correspond to the accumulators. By controlling the opening and closing of the switches, the opening and closing of the corresponding accumulators are realized. In the face of different sea conditions in different sea areas, different combinations of accumulators and energy storage flywheels 13 can be used to achieve the effect of multi-stage energy storage and absorption of pressure pulsation.

[0032] The generator set is composed of at least two hydraulic motors, an energy storage flywheel 13 and at least two generators. In this embodiment, the hydraulic motors are divided into variable hydraulic motors 12 and fixed hydraulic motors 22, and the generators are divided into main generators 23 and auxiliary generators 14.

[0033] The wave energy hydraulic energy conversion system with multi-stage energy storage combines accumulators of different volumes with a mechanical energy storage flywheel 13, and adds an auxiliary generator 14, so as to minimize the pressure pulsation of the hydraulic oil in the system, improve the hydraulic energy conversion efficiency of the wave energy power generation device, and is conducive to outputting more electrical energy. The entire power generation process does not require external power participation, simplifies the energy storage method of the wave energy power generation device, saves electrical energy, and also has the advantages of adjustable hydraulic circuit working pressure range, etc. Wave energy is stored in stages and multi-stage smooth liquid flow is performed, which is not only conducive to avoiding excessive accumulator pressure and improving the safety and sustainability of the power generation system, but also conducive to improving the working efficiency of the hydraulic wave energy conversion system.

[0034] The hydraulic PTO system 28 also includes a speed regulating valve 17, which is connected in series with the accumulator group and the generator group. The accumulator stores the hydraulic oil from the hydraulic motor and releases it after it is full. The speed regulating valve 17 adjusts the flow rate of the hydraulic oil so that the flow rate of the hydraulic oil entering the accumulator and the hydraulic motor is constant. The accumulator absorbs the hydraulic pulsation in the preceding circuit to ensure stable power generation of the generator.

[0035] The hydraulic PTO system 28 also includes a flow sensor and a pressure sensor, and the flow sensor, the pressure sensor, the accumulator group, and the generator group are all connected in series. In this embodiment, the flow sensor includes a first flow sensor 10 and a second flow sensor 20, and the pressure sensor includes a first pressure sensor 11 and a second pressure sensor 21, wherein the first flow sensor 10 and the first pressure sensor 11 are connected to a branch line shared by the first accumulator 7 and the second accumulator 9 to detect the flow and pressure of the hydraulic oil flowing into / out of the first accumulator 7 and the second accumulator 9; the second flow sensor 20 and the second pressure sensor 21 are connected to a branch line shared by the third accumulator 16 and the fourth accumulator 19 to detect the flow and pressure of the hydraulic oil flowing into / out of the third accumulator 16 and the fourth accumulator 19; by comparing the flow and pressure of the hydraulic oil at each energy storage stage, the effect of the accumulator and the energy storage flywheel 13 on the hydraulic system can be intuitively determined.

[0036] The hydraulic PTO system 28 further includes a hydraulic valve 26, one end of which is connected to the one-way valve group and the oil tank 24, and the other end of which is connected to the accumulator group and the generator group. The hydraulic valve 26 is a pilot hydraulic valve 26, which further improves the safety and sustainability of the power generation system and improves the working efficiency of the hydraulic wave energy conversion system.

[0037] Reference Figure 1 and Figure 2 In this embodiment, the oil outlet of the oil tank 24 is connected to three branches, wherein the first branch is connected to the oil inlet of the first one-way valve 2, the second branch is connected to the oil inlet of the third one-way valve 4, the third branch is connected to the oil outlet of the hydraulic valve 26, the oil inlet of the oil tank 24 is connected to the oil outlet of the quantitative hydraulic motor 22, the float 25 is rigidly connected to the double-rod double-acting hydraulic cylinder 1, and the two oil ports of the double-rod double-acting hydraulic cylinder 1 have two branches respectively, one of which is connected to the oil outlet of the second one-way valve 3, and then connected to the oil inlet of the first one-way valve 2, and the other branch is connected to the oil outlet of the fourth one-way valve 5, and then connected to the oil inlet of the third one-way valve 4.

[0038] The oil inlet of the hydraulic valve 26 is connected to two branches, one of which is connected to the oil inlet of the variable hydraulic motor 12, and the other is connected to the second accumulator 9. The variable hydraulic motor 12 is coaxial with the energy storage flywheel 13 and the auxiliary generator 14 and is connected through a coupling. The liquid outlet of the variable hydraulic motor 12 is connected to the third accumulator 16, and the third accumulator 16 is connected to the oil inlet of the speed regulating valve 17. The speed regulating valve 17 is connected to the fourth accumulator 19, and the fourth accumulator 19 is connected to the oil inlet of the quantitative hydraulic motor 22. The output end of the quantitative hydraulic motor 22 is connected to the main generator 23 through a coupling and is placed coaxially.

[0039] The first accumulator 7, the second accumulator 9, the third accumulator 16 and the fourth accumulator 19 all have corresponding switch devices that can control opening and closing. For different sea areas and sea conditions, different combinations of accumulators and energy storage flywheels 13 can be used to achieve multi-stage energy storage and pressure pulsation absorption effects.

[0040] A first flow sensor 10, a first pressure sensor 11, a second flow sensor 20, and a second pressure sensor 21 are also provided in the power generation circuit. By comparing the flow and pressure of the hydraulic oil in each energy storage stage, the effects of the first accumulator 7, the second accumulator 9, the third accumulator 16, the fourth accumulator 19 and the energy storage flywheel 13 on the hydraulic system are determined.

[0041] The hydraulic valve 26 is a pilot-operated hydraulic valve 26. The double-rod double-acting hydraulic cylinder 1 is placed vertically. When the float 25 connected to the piston rod of the double-rod double-acting hydraulic cylinder 1 is subjected to the force in the heave direction of the wave, the float 25 moves upward, pressing the piston rod of the hydraulic cylinder 1 to move upward, the upper chamber discharges oil, and the lower chamber absorbs oil. The upper chamber discharges oil through the second one-way valve 3, and the lower chamber absorbs oil through the third one-way valve 4. When the wave is at the trough, the float 25 moves downward due to its own gravity, driving the piston rod of the hydraulic cylinder 1 downward, the lower chamber presses oil, and the upper chamber absorbs oil. The hydraulic oil enters the lower chamber along the oil outlet of the oil tank 24 through the first one-way valve 2, and the hydraulic oil pressed out of the upper chamber flows into the subsequent hydraulic circuit through the fourth one-way valve 5.

[0042] The two chambers of the double-rod double-acting hydraulic cylinder 1 are both rod chambers. The upper chamber is connected to the first one-way valve 2 and the second one-way valve 3, and the lower chamber is connected to the third one-way valve 4 and the fourth one-way valve 5. The rectifier bridge setting of the one-way valve group ensures that the high-pressure liquid flow from the hydraulic cylinders 1 on both sides of the drive module is converted into a one-way liquid flow through the rectifier bridge circuit and enters the main circuit of the system.

[0043] The first accumulator 7 is a small-volume accumulator, which is mainly used to absorb the pressure pulsation of the hydraulic oil flowing through the rectifier bridge. The first accumulator 7 is connected to the second accumulator 9, and the second accumulator 9 is a large-volume accumulator, which is mainly used to store relatively stable high-pressure hydraulic oil.

[0044] The second accumulator 9 is connected to the oil inlet of the variable hydraulic motor 12. The hydraulic oil drives the variable hydraulic motor 12, so that the distribution plate and the main shaft rotate, realizing the conversion of hydraulic energy into mechanical energy. The energy storage flywheel 13 is connected to the variable hydraulic motor 12 and the auxiliary generator 14 through a coupling. When storing energy, the high-pressure hydraulic oil drives the distribution plate to rotate and the central shaft to rotate through the variable piston, and transmits the motion through the coupling, driving the energy storage flywheel 13 to accelerate the rotation. The energy storage flywheel 13 stores energy in the form of kinetic energy, completing the conversion of hydraulic energy to mechanical energy, and the energy change process of mechanical energy to mechanical energy conversion and transmission. Energy is stored in the high-speed rotating energy storage flywheel 13, and at the same time, it drives the auxiliary generator 14 to rotate and generate electricity, realizing the energy conversion process from mechanical energy to electrical energy.

[0045] When the hydraulic oil pressure and flow rate of the driving variable hydraulic motor 12 decrease, the output speed of the variable hydraulic motor 12 decreases, but due to the mechanical energy stored in the high-speed rotating energy storage flywheel 13, it enters the energy release period at this time, and the speed of the high-speed rotating energy storage flywheel 13 decreases to release the stored mechanical energy, ensuring that the variable hydraulic motor 12, the energy storage flywheel 13 and the auxiliary generator 14 can rotate slowly. The energy storage flywheel 13 can drag the auxiliary generator 14 in both the charging stage and the energy release stage to ensure stable power generation.

[0046] The third accumulator 16 stores the hydraulic oil from the variable hydraulic motor 12 and releases it when it is full. The flow rate of the hydraulic oil is adjusted by the speed control valve 17 so that the flow rate of the hydraulic oil entering the fourth accumulator 19 and the fixed hydraulic motor 22 is constant. The fourth accumulator 19 is a small-volume accumulator that absorbs the hydraulic pulsation in the preceding circuit to ensure stable power generation of the main generator 23.

[0047] In low sea conditions, the multi-stage energy storage system mainly absorbs pressure pulsations and stores high-pressure hydraulic oil. After storage, it is released to drive the generator set to generate electricity. In high sea conditions, the system mainly absorbs pressure pulsations, smoothes the liquid flow and drives the generator set to generate electricity. The main generator 23 and the auxiliary generator 14 will automatically generate electricity independently according to changes in sea conditions without the participation of electronic control. The efficiency of converting mechanical energy into hydraulic energy and hydraulic energy into electrical energy is high, and the control method is relatively simple. By adjusting the hydraulic circuit, the main generator 23 can generate electricity at a stable constant speed within a certain range.

[0048] Most existing hydraulic wave energy power generation devices use only one accumulator and one generator, or two accumulators and one generator in the entire working pressure range, which will result in the inability to maintain a high conversion efficiency in the process of converting hydraulic energy into electrical energy, which is not conducive to the full utilization of hydraulic energy and has poor power generation quality. In response to this problem, the multi-stage energy storage wave energy hydraulic energy conversion system proposed in the present invention combines accumulators of different volumes with a mechanical energy storage flywheel 13, and adds an auxiliary generator 14, so that the pressure pulsation of the hydraulic oil in the system is minimized, the hydraulic energy conversion efficiency of the wave energy power generation device is improved, and it is conducive to outputting more electrical energy. The entire power generation process does not require external power participation, simplifies the energy storage method of the wave energy power generation device, saves electrical energy, and also has the advantages of adjustable hydraulic circuit working pressure range.

[0049] The wave energy captured by the float 25 is converted into hydraulic energy through the hydraulic cylinder 1. The four-way valve mode is adopted. The high-pressure fluid flow from the hydraulic cylinders 1 on both sides of the drive module is converted into a one-way fluid flow through the rectifier bridge circuit and enters the main circuit of the system. The energy storage part is mainly composed of four accumulators and an energy storage flywheel 13. The generator set is composed of a main generator 23 driving a fixed hydraulic motor 22, a variable hydraulic motor 12 and an auxiliary generator 14 driven by the main generator 23. The flow regulation of the speed regulating valve 17 can keep the hydraulic motor and the permanent magnet generator of the main power generation circuit running stably and at a constant speed within a certain range, thereby improving the power generation quality. In low sea conditions, the system mainly stores hydraulic energy. When the hydraulic oil in the accumulator is full, it is automatically released to drive the main generator 23 to generate electricity and ensure stable power generation. In high sea conditions, the system accumulator and the energy storage flywheel 13 mainly absorb pressure pulsation, smoothly buffer the hydraulic fluid entering the energy storage-control circuit from the power source circuit, and drive the generator to generate electricity, which is conducive to improving the power generation efficiency and operation reliability of the wave energy power generation device.

[0050] Reference Figures 1 to 3 The embodiment of the present invention also provides a control method for a wave energy hydraulic energy conversion system with multi-stage energy storage, comprising the following steps: Step 1: During the charging stage, the hydraulic oil in the hydraulic cylinder 1 drives the central axis of the hydraulic motor to rotate through the variable piston, and then drives the energy storage flywheel 13 to rotate through the transmission motion of the coupling. The energy storage flywheel 13 stores energy in the form of kinetic energy, completing the energy change process of conversion and transmission from hydraulic energy to mechanical energy, and then from mechanical energy to mechanical energy.

[0051] Step 2: Energy is stored in the wheel body of the rotating energy storage flywheel 13, and at the same time, the generator is driven to rotate and generate electricity, thereby realizing the energy conversion process from mechanical energy to electrical energy.

[0052] Step three: Energy release stage. When the hydraulic oil pressure and flow rate of the hydraulic motor decrease, the output speed of the hydraulic motor decreases. Due to the mechanical energy stored in the energy storage flywheel 13, the energy release period begins at this time. The energy storage flywheel 13 starts to reduce its speed and releases the stored mechanical energy to ensure the slow rotation of the hydraulic motor, the energy storage flywheel 13 and the generator. The energy storage flywheel 13 can drive the generator to generate electricity in both the charging stage and the energy release stage.

[0053] The accumulator stores the hydraulic oil from the hydraulic motor and releases it when it is full. The flow rate of the hydraulic oil is adjusted by the speed regulating valve 17 so that the flow rate of the hydraulic oil entering the accumulator and the hydraulic motor is constant.

[0054] In low sea conditions, the hydraulic PTO system 28 stores hydraulic energy. When the hydraulic oil in the accumulator is full, it is automatically released to drive the main generator 23 to generate electricity. The energy storage flywheel 13 plays the function of smoothing the liquid flow. When the hydraulic motor operates at the maximum displacement, due to the low speed, the generator provides little damping, and the energy storage flywheel 13 rotates to ensure further smoothing of the liquid flow, thereby ensuring the stable operating condition of the generator set.

[0055] In high sea conditions, power control is achieved by adjusting the hydraulic motor, the speed of the hydraulic motor increases, the generator converts excess energy into electrical energy, the pressure of the hydraulic PTO system 28 increases, and the energy is stored in the energy storage flywheel 13 and the accumulator, driving the generator to generate electricity and ensuring the power generation efficiency of the generator set.

[0056] The implementation principle of a wave energy hydraulic energy conversion system with multi-stage energy storage and a control method thereof in an embodiment of the present invention is as follows: The present invention has the advantages of high hydraulic energy conversion efficiency, simple control method, stable energy output, etc., and can smooth the hydraulic fluid and quickly release energy in low sea conditions, and store excess energy in high sea conditions, thereby improving the efficiency of wave energy utilization. The hydraulic circuit control does not require external power participation. Through the combination of multiple accumulators and energy storage flywheels 13, more efficient energy utilization is achieved, the power generation quality is improved, and the power generation mode can be automatically adjusted according to the sea conditions. It is suitable for energy conversion in various wave environments.

[0057] It should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any figure mark in the claims should not be regarded as limiting the claims involved.

[0058] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A wave energy hydraulic energy conversion system with multi-stage energy storage, characterized in that: It comprises an outrigger (27), wherein a hydraulic cylinder (1) is provided on a side of the outrigger (27) away from the shore-based platform, a float (25) is provided under the hydraulic cylinder (1), and a hydraulic PTO system (28) is provided inside the outrigger (27); The hydraulic PTO system (28) comprises an oil tank (24), a one-way valve group, an accumulator group and a generator group, the hydraulic cylinder (1) is connected to the oil tank (24) via the one-way valve group, and the accumulator group and the generator group are both connected in series with the oil tank (24); The hydraulic cylinder (1) is placed vertically and is used to convert the wave energy in the heave direction captured by the float (25) into hydraulic energy; The one-way valve group converts the high-pressure fluid flow from the hydraulic cylinder (1) into a one-way fluid flow through a rectifying bridge circuit and enters the main circuit of the hydraulic PTO system (28); The energy accumulator group is composed of a plurality of energy accumulators, and the generator group is composed of an energy storage flywheel (13), at least two hydraulic motors and at least two generators.

2. A wave energy hydraulic energy conversion system with multi-stage energy storage according to claim 1, characterized in that: The hydraulic PTO system (28) further comprises a speed regulating valve (17), wherein the speed regulating valve (17) is connected in series with the accumulator group and the generator group.

3. A wave energy hydraulic energy conversion system with multi-stage energy storage according to claim 1, characterized in that: The hydraulic PTO system (28) further comprises a flow sensor and a pressure sensor, wherein the flow sensor, the pressure sensor, the accumulator group and the generator group are all connected in series.

4. A wave energy hydraulic energy conversion system with multi-stage energy storage according to claim 1, characterized in that: The hydraulic PTO system (28) further comprises a hydraulic valve (26), one end of which is connected in series with a one-way valve group and an oil tank (24), and the other end of which is connected in series with an accumulator group and a generator group.

5. A wave energy hydraulic energy conversion system with multi-stage energy storage according to claim 1, characterized in that: The accumulator group includes a plurality of small-capacity accumulators and a plurality of large-capacity accumulators.

6. A wave energy hydraulic energy conversion system with multi-stage energy storage according to claim 1, characterized in that: Each accumulator in the accumulator group is provided with a switch.

7. A control method for a wave energy hydraulic energy conversion system with multi-stage energy storage as claimed in any one of claims 1 to 6, characterized in that: The steps include: Step 1: During the charging phase, the hydraulic oil in the hydraulic cylinder (1) drives the central axis of the hydraulic motor to rotate through the variable piston, and then drives the energy storage flywheel (13) to rotate through the transmission motion of the coupling. The energy storage flywheel (13) stores energy in the form of kinetic energy, completing the energy change process of converting and transmitting hydraulic energy to mechanical energy, mechanical energy and then to mechanical energy; Step 2: Energy is stored in the wheel body of the rotating energy storage flywheel (13), and at the same time, the generator is driven to rotate to generate electricity, thereby realizing the energy conversion process from mechanical energy to electrical energy; Step 3: Energy release stage, when the hydraulic oil pressure and flow rate of the hydraulic motor decrease, the output speed of the hydraulic motor decreases. Due to the mechanical energy stored in the energy storage flywheel (13), the energy release period begins at this time, and the energy storage flywheel (13) begins to reduce its speed to release the stored mechanical energy, ensuring the slow rotation of the hydraulic motor, the energy storage flywheel (13) and the generator. The energy storage flywheel (13) can drive the generator to generate electricity in both the energy charging stage and the energy release stage.

8. The control method of the wave energy hydraulic energy conversion system with multi-stage energy storage according to claim 7 is characterized by: The accumulator stores hydraulic oil from the hydraulic motor and releases it after it is fully stored. The flow rate of the hydraulic oil is adjusted by a speed regulating valve (17) so that the flow rate of the hydraulic oil entering the accumulator and the hydraulic motor is constant.

9. The control method of the wave energy hydraulic energy conversion system with multi-stage energy storage according to claim 7 is characterized by: In low sea conditions, the hydraulic PTO system (28) stores hydraulic energy. When the hydraulic oil in the accumulator is full, it is automatically released to drive the main generator (23) to generate electricity. The energy storage flywheel (13) plays the role of smoothing the liquid flow. When the hydraulic motor works at the maximum displacement, due to the low speed, the generator provides little damping, and the energy storage flywheel (13) rotates to ensure further smoothing of the liquid flow, thereby ensuring the stable working condition of the generator set.

10. The control method of the wave energy hydraulic energy conversion system with multi-stage energy storage according to claim 7 is characterized by: In high sea conditions, power control is achieved by adjusting the hydraulic motor, the speed of the hydraulic motor is increased, the generator converts excess energy into electrical energy, the pressure of the hydraulic PTO system (28) is increased, and the energy is stored in the energy storage flywheel (13) and the accumulator, driving the generator to generate electricity, thereby ensuring the power generation efficiency of the generator set.

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