Hydraulic diaphragm type hydrogen compressor based on servo control

Abstract

The hydraulic diaphragm type hydrogen compressor based on servo control comprises a hydraulic system and a diaphragm pressurization system, the hydraulic system mainly comprises a plunger pump and a rotary reversing valve, and the diaphragm pressurization system mainly comprises two vertically-arranged diaphragm heads. The plunger pump is driven by the variable frequency motor to convey high-pressure hydraulic oil to the rotary reversing valve, and the high-pressure hydraulic oil is alternately conveyed to the two membrane heads through the rotary reversing valve, so that low-pressure hydrogen in the membrane heads is circularly pressurized; the rotating speed of the rotary reversing valve is controlled through a servo motor, and the servo motor is subjected to automatic optimal speed adaptation through a whole machine control system according to load conditions. The method is good in self-adaption effect, and flow distribution can be adjusted in a self-adaption mode according to load characteristics.

Description

Technical Field

[0001] This invention relates to the field of hydrogen pressurization technology. More specifically, this invention relates to a servo-controlled hydraulic diaphragm hydrogen compressor. Background Technology

[0002] As a core power source, hydrogen compressors play a particularly prominent role in the three major areas of hydrogen transportation, filling, and refueling. However, with the increasing complexity of field application conditions and the increasingly stringent requirements for the purity of end-use hydrogen, the technological bottlenecks of the two mainstream models—liquid-driven hydrogen compressors and diaphragm hydrogen compressors—are becoming increasingly apparent. The liquid-driven diaphragm hybrid hydrogen compressor retains the advantages of diaphragm compressors, possessing significant advantages such as good sealing, high compression ratio, and low energy consumption, while also meeting the operating conditions of liquid-driven compressors, namely frequent start-stop, cold start-up, and load start-stop. Therefore, this type of compressor has become an important piece of equipment for addressing the current application needs and challenges of hydrogen compressors. Various hydrogen compressor manufacturers have successively carried out the principle design of hydraulic diaphragm hydrogen compressors, but currently, there are virtually no manufacturers that have completed the research, development, and widespread application of hydraulic diaphragm hydrogen compressors. The main technical problems currently exist as follows: one is the large vibration of hydraulic reversing; there is a dead zone in the internal flow channel of the reversing valve, which induces pressure pulsation, resulting in high vibration and noise of the whole machine; the other is the poor adaptive effect; the piston pump and the reversing valve are mechanically directly connected, and the speed ratio is strictly limited, making it impossible to adaptively adjust the flow distribution according to the load characteristics. Summary of the Invention

[0003] One objective of this invention is to provide a servo-controlled hydraulic diaphragm hydrogen compressor with good adaptive performance, capable of adaptively adjusting flow distribution according to load characteristics.

[0004] To address the aforementioned technical problems, this invention provides a servo-controlled hydraulic diaphragm hydrogen compressor. The core components include a hydraulic system and a diaphragm pressurization system. The hydraulic system mainly comprises a piston pump and a rotary directional valve. The diaphragm pressurization system mainly comprises two diaphragm heads. The piston pump, driven by a variable frequency motor, delivers high-pressure hydraulic oil to the rotary directional valve, which then alternately delivers the oil to the two diaphragm heads, thereby circulating and pressurizing the low-pressure hydrogen within the diaphragm heads. The rotary directional valve's rotation speed is controlled by a servo motor.

[0005] Preferably, the hydraulic system further includes an oil tank, which is connected to the plunger pump via a pipeline and is used for replenishing oil.

[0006] Preferably, the height of the oil tank relative to the two diaphragm heads is greater than zero, and no oil replenishment pump is installed; automatic oil replenishment is achieved by utilizing the gravity of the hydraulic oil.

[0007] Preferably, the two diaphragm heads are connected to the oil tank via pipelines, and the rotary directional valve also returns oil to the oil tank via a return oil pipeline.

[0008] Preferably, the two membrane heads are placed vertically and supported by a support mechanism.

[0009] Preferably, based on the volumetric efficiency of the diaphragm pressurization system, the optimal speed ratio between the variable frequency motor and the servo motor is established under different speeds of the servo motor and different intake and exhaust pressures of the diaphragm pressurization system, forming a speed matching table to guide the servo motor control to achieve the maximum actual displacement of the hydraulic diaphragm hydrogen compressor.

[0010] Preferably, the process of generating a speed matching table by testing the rotational speed of the rotary directional valve is as follows: 1) After the compressor starts normally, the speed of the variable frequency motor corresponding to the plunger pump remains unchanged, and the intake pressure is adjusted to A and the exhaust pressure to B; 2) Keep the intake pressure A constant, and gradually increase the exhaust pressure B within the set range, and increase it at the set increase gradient; for each gradient increase of the exhaust pressure, adjust the servo motor speed to maximize the compressor displacement, and thus determine the value as the optimal servo motor speed value that matches the intake pressure and exhaust pressure; and thus obtain a series of optimal speed values ​​corresponding to the gradual increase of the exhaust pressure within the set range when the intake pressure is A. 3) Reduce the intake pressure A by one gradient according to the set reduction gradient, and similarly adjust the exhaust pressure B to gradually increase within the set range, and increase it by the set increase gradient; repeat the operation of step 2) above to obtain a series of optimal speed values ​​corresponding to the gradual increase of exhaust pressure within the set range under the pressure of intake pressure A reduced by one gradient. 4) By analogy, the optimal servo motor speed values ​​corresponding to different intake and exhaust pressures under a fixed variable frequency motor speed are compiled into a built-in speed matching table. As part of the compressor control system, the whole machine can be operated in the optimal state by using the internal speed matching table to make adjustments and ensure the best displacement.

[0011] Preferably, for different models of compressors, if the rated operating speed of the variable frequency motor changes, the above steps are repeated for testing, and the built-in speed matching table of the compressor control system is changed synchronously.

[0012] The present invention has at least the following beneficial effects: 1. The diaphragm pressurization system of the present invention includes two membrane heads placed vertically, which increases the support area, reduces the complexity of the support design, reduces membrane head vibration, and improves working stability.

[0013] 2. In the hydraulic system of the present invention, the height of the oil tank relative to the diaphragm is greater than zero. The hydraulic system eliminates the need for a replenishing oil pump and can achieve automatic oil replenishment by utilizing the gravity of the hydraulic oil. The system design is more simplified, which not only reduces energy consumption but also significantly reduces the risk of gas explosion during frequent start-stop operations.

[0014] 3. Based on experimental results, this invention takes the volumetric efficiency of the diaphragm compressor as the optimization target, establishes the optimal speed ratio between the variable frequency motor and the servo motor under different speeds and different inlet pressures, and forms a speed matching table. By incorporating the optimal matching speed ratio between the servo motor and the variable frequency motor under different operating conditions into the whole machine control system, the volumetric efficiency of the membrane head is maximized, making it applicable to a wider range of operating conditions and having broad application prospects for future hydrogen refueling station construction and current hydrogen refueling station renovation.

[0015] 4. The hydraulic diaphragm hydrogen compressor of the present invention is a liquid-driven diaphragm composite hydrogen compressor. It retains the advantages of mechanical diaphragm hydrogen compressors, such as good sealing and high compression ratio. At the same time, unlike the passive diaphragm drive in mechanical diaphragm hydrogen compressors, this type of compressor can use the pressure difference between the gas side and the oil side to drive the diaphragm to move in a flexible and active pressure manner, which greatly improves the diaphragm life. This fully meets the operating conditions of frequent start-stop, cold start-up, and load start-stop in hydrogen refueling stations, and has excellent characteristics.

[0016] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0017] Figure 1 This invention relates to a servo-controlled hydraulic diaphragm hydrogen compressor system assembly. Figure 2 This is a 3D illustration of the servo-controlled hydraulic diaphragm hydrogen compressor system of the present invention. Figure 3 This is a three-dimensional design drawing of the servo-controlled hydraulic diaphragm hydrogen compressor system of the present invention.

[0018] Explanation of reference numerals in the attached figures: 1. Left diaphragm head, 2. Right diaphragm head, 3. Servo motor, 4. Rotary directional valve, 5. Piston pump, 6. Oil tank, 7. Support structure, 8. Variable frequency motor, 9. Buffer tank, 10. Overflow valve. Detailed Implementation

[0019] To better understand the purpose, structure, and function of this invention, the invention will be further described in detail below with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0020] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified. In the description of this invention, the terms "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] like Figures 1 to 3 As shown, this invention provides a servo-controlled hydraulic diaphragm hydrogen compressor, including a hydraulic system and a diaphragm pressurization system. The hydraulic system includes a plunger pump 5 and a rotary directional valve 4. The diaphragm pressurization system includes two diaphragm heads. The plunger pump 5 is driven by a variable frequency motor 8 to deliver high-pressure hydraulic oil to the rotary directional valve 4, which alternately delivers the oil to the two diaphragm heads, thereby circulating and pressurizing the low-pressure hydrogen in the diaphragm heads. The rotary directional valve 4 is speed-controlled by a servo motor 3.

[0022] The hydraulically driven diaphragm pressurization system of this invention mainly consists of a hydraulic system and a diaphragm pressurization system. In the hydraulic system, a three-plunger high-pressure pump driven by a variable frequency motor provides high-pressure hydraulic oil. This high-pressure hydraulic oil alternately enters or exits the two diaphragm heads via a rotary directional valve, thereby circulating and pressurizing the low-pressure hydrogen gas within the diaphragm heads. The diaphragm pressurization system mainly consists of two diaphragm heads: a left diaphragm head 1 and a right diaphragm head 2. The plunger pump is a high-pressure oil pump driven by a variable frequency motor with frequency conversion adjustment. Additionally, the servo motor's speed is also adjustable. Therefore, the compressor corresponding to this application has a large actual discharge operating range; only the speed of the variable frequency motor needs to be adjusted to change the system's discharge capacity.

[0023] In another embodiment, the hydraulic system further includes an oil tank 6, which is connected to the plunger pump via pipeline and used for oil replenishment. The height of the oil tank relative to the two diaphragm heads is greater than zero, eliminating the need for a replenishment pump; automatic oil replenishment is achieved using the gravity of the hydraulic oil. With the oil tank at a height greater than zero relative to the diaphragm heads, the hydraulic system eliminates the need for a replenishment pump, achieving automatic oil replenishment solely through gravity. This simplifies the system design, reduces energy consumption, and significantly lowers the risk of gas explosions during frequent start-stop cycles. The two diaphragm heads are connected to the oil tank via pipelines, and the rotary directional valve also returns oil to the oil tank via a return pipeline. A buffer tank 9 and an overflow valve 10 are also connected to the upstream pipeline of the rotary directional valve, both located downstream of the plunger pump 5.

[0024] In another embodiment, the two membrane heads are placed vertically and supported by support mechanism 7. The vertical placement of the two membrane heads, compared to the conventional horizontal placement, increases the support area, thereby reducing the complexity of the support design. Figure 3 As shown, stable support can be achieved simply by using a common support plate, reducing membrane head vibration and improving operational stability.

[0025] In another implementation, based on the diaphragm head volumetric efficiency of the diaphragm pressurization system, the optimal speed ratio between the variable frequency motor and the servo motor is established under different servo motor speeds, different inlet pressures and exhaust pressures of the diaphragm pressurization system, forming a speed matching table to guide the servo motor control to achieve the maximum actual displacement of the hydraulic diaphragm hydrogen compressor.

[0026] The actual displacement of a hydraulic diaphragm hydrogen compressor is mainly affected by the high-pressure oil supply of the variable frequency piston pump, the rotational directional valve speed, and external load conditions (inlet pressure and exhaust pressure). Typically, once the variable frequency piston pump speed is determined, the total external oil supply is fixed, and the diaphragm head cavity volume is known, thus the rotational valve speed can be roughly determined. However, there is a certain difference between this basic speed value and the optimal value. In reality, the diaphragm head volumetric efficiency changes with the external load conditions during the operation of the hydraulic diaphragm compressor. Therefore, under different external load conditions, in order to achieve higher diaphragm head volumetric efficiency and thus better diaphragm head exhaust performance, the rotational directional valve speed needs to be optimized based on the basic speed. This optimal value is usually determined through experimental testing. Once confirmed, a relationship table can be created between the rotational directional valve speed, piston pump speed, and external load, and embedded into the compressor control system to achieve the optimal compressor operation.

[0027] Based on the self-circulation test platform, the process of generating a speed matching table by testing the rotational speed of a rotary directional valve can be described as follows: 1) After the compressor starts normally, the speed of the variable frequency motor corresponding to the plunger pump remains unchanged, and the intake pressure is adjusted to A and the exhaust pressure to B; 2) Keep the intake pressure A constant, and gradually increase the exhaust pressure B within the set range, and increase it at the set increase gradient; for each gradient increase of the exhaust pressure, adjust the servo motor speed to maximize the compressor displacement, and thus determine the value as the optimal servo motor speed value that matches the intake pressure and exhaust pressure; and thus obtain a series of optimal speed values ​​corresponding to the gradual increase of the exhaust pressure within the set range when the intake pressure is A. 3) Reduce the intake pressure A by one gradient according to the set reduction gradient, and similarly adjust the exhaust pressure B to gradually increase within the set range, and increase it by the set increase gradient; repeat the operation of step 2) above to obtain a series of optimal speed values ​​corresponding to the gradual increase of exhaust pressure within the set range under the pressure of intake pressure A reduced by one gradient. 4) By analogy, the optimal servo motor speed values ​​corresponding to different intake and exhaust pressures under a fixed variable frequency motor speed are compiled into a built-in speed matching table. As part of the compressor control system, the whole machine can be operated in the optimal state by using the internal speed matching table to make adjustments and ensure the best displacement.

[0028] One specific test process is as follows: 1) After the compressor starts normally, the speed of the plunger pump variable frequency motor remains unchanged, and the intake pressure is adjusted to 20MPa and the exhaust pressure is adjusted to 20MPa.

[0029] 2) Keep the intake pressure constant at 20 MPa, and gradually increase the exhaust pressure from 20 MPa to 45 MPa, with a gradient of approximately 0.5 MPa. For every 0.5 MPa increase in exhaust pressure, adjust the servo motor speed to maximize the compressor displacement, thus determining the optimal servo motor speed that matches the intake and exhaust pressures. This yields a series of optimal speed values ​​corresponding to the process of increasing the exhaust pressure from 20 MPa to 45 MPa while the intake pressure is 20 MPa.

[0030] 3) Reduce the intake pressure to 19.5 MPa, and similarly adjust the exhaust pressure from 20 MPa to 45 MPa, with a gradient of 0.5 MPa being appropriate. Repeat step 2) to obtain a series of optimal speed values ​​corresponding to the process of increasing the exhaust pressure from 20 MPa to 45 MPa while the intake pressure is 19.5 MPa.

[0031] 4) By analogy, the optimal servo motor speed values ​​corresponding to different intake and exhaust pressures under a fixed variable frequency motor speed are compiled into a built-in speed matching parameter table. As part of the compressor control system, the whole machine can be operated in the optimal state by using the internal speed matching table to ensure the best displacement.

[0032] 5) In particular, for different models of compressors, if the rated operating speed of the variable frequency motor changes, repeat the above steps for testing, and the built-in speed matching table of the compressor control system should be changed accordingly.

[0033] The rotary reversing valve uses a servo motor for speed control. Based on simulation and experimental results, with the volumetric efficiency of the diaphragm compressor as the ultimate goal, the optimal speed ratio between the variable frequency motor and the servo motor under different load conditions (intake pressure and exhaust pressure) can be established, forming a speed matching table, which is then embedded into the whole machine control system, thereby maximizing the overall machine performance through servo control.

[0034] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be applied to various fields suitable for the present invention, and other modifications can be easily implemented by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and examples shown and described herein.

Claims

1. A servo-controlled hydraulic diaphragm hydrogen compressor, characterized in that, The core components include a hydraulic system and a diaphragm pressurization system. The hydraulic system includes a piston pump and a rotary directional valve. The diaphragm pressurization system includes two diaphragm heads. The piston pump, driven by a variable frequency motor, delivers high-pressure hydraulic oil to the rotary directional valve, which then alternately delivers the oil to the two diaphragm heads, thereby circulating and pressurizing the low-pressure hydrogen gas within the diaphragm heads. The rotary directional valve is speed-controlled by a servo motor.

2. The servo-controlled hydraulic diaphragm hydrogen compressor as described in claim 1, characterized in that, The hydraulic system also includes an oil tank, which is connected to the plunger pump via a pipeline and is used for replenishing oil.

3. The servo-controlled hydraulic diaphragm hydrogen compressor as described in claim 2, characterized in that, The height of the oil tank relative to the two diaphragm heads is greater than zero, and no oil replenishment pump is installed. Automatic oil replenishment is achieved by utilizing the gravity of the hydraulic oil.

4. The servo-controlled hydraulic diaphragm hydrogen compressor as described in claim 2, characterized in that, The two diaphragm heads are connected to the oil tank via pipelines, and the rotary directional valve also returns oil to the oil tank via a return oil pipeline.

5. The servo-controlled hydraulic diaphragm hydrogen compressor as described in claim 1, characterized in that, The two membrane heads are placed vertically and supported by a support mechanism.

6. The servo-controlled hydraulic diaphragm hydrogen compressor as described in claim 1, characterized in that, Based on the volumetric efficiency of the diaphragm pressurization system, the optimal speed ratio between the variable frequency motor and the servo motor is established under different servo motor speeds, different inlet pressures and exhaust pressures of the diaphragm pressurization system, forming a speed matching table to guide the servo motor control to achieve the maximum actual displacement of the hydraulic diaphragm hydrogen compressor.

7. The servo-controlled hydraulic diaphragm hydrogen compressor as described in claim 6, characterized in that, The process of generating a speed matching table by testing the rotational speed of a rotary directional valve is as follows: 1) After the compressor starts normally, the speed of the variable frequency motor corresponding to the plunger pump remains unchanged, and the intake pressure is adjusted to A and the exhaust pressure to B; 2) Keep the intake pressure A constant, and gradually increase the exhaust pressure B within the set range, and increase it at the set increase gradient; for each increase in exhaust pressure, adjust the servo motor speed to maximize the compressor displacement, and thus determine the value as the optimal servo motor speed value that matches the intake and exhaust pressures. This leads to a series of optimal engine speeds as the intake pressure is A and the exhaust pressure gradually increases within a set range. 3) Reduce the intake pressure A by one gradient according to the set reduction gradient, and similarly adjust the exhaust pressure B to gradually increase within the set range, and increase it by the set increase gradient; repeat the operation of step 2) above to obtain a series of optimal speed values ​​corresponding to the gradual increase of exhaust pressure within the set range under the pressure of intake pressure A reduced by one gradient. 4) By analogy, the optimal servo motor speed values ​​corresponding to different intake and exhaust pressures under a fixed variable frequency motor speed are compiled into a built-in speed matching table. As part of the compressor control system, the whole machine can be operated in the optimal state by using the internal speed matching table to make adjustments and ensure the best displacement.

8. The servo-controlled hydraulic diaphragm hydrogen compressor as described in claim 7, characterized in that, For different compressor models, if the rated operating speed of the variable frequency motor changes, repeat the above steps for testing, and the built-in speed matching table of the compressor control system will be changed synchronously.

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