Closed hydraulic system of hydrogen compressor

Abstract

The invention relates to the technical field of hydrogen compression and hydraulic drive, in particular to a hydrogen compressor closed hydraulic system which comprises a hydraulic oil tank, a double-output-shaft drive motor, a closed pump, a hydraulic drive gas supercharger, a four-quadrant pump and an energy accumulator. The closed pump and the supercharger form a closed loop, and oil supplementing and flushing functions are integrated in the closed loop. And the four-quadrant pump is connected to the other end of the motor and is connected with the energy accumulator. Load is monitored in real time through a pressure sensor, in the reversing or low-load stage, a four-quadrant pump is controlled to be in a pump working condition, residual power of a motor is absorbed, and an energy accumulator is charged; and in the high-load compression stage, the four-quadrant pump is controlled to be in a motor working condition, and energy of the energy accumulator is released for auxiliary driving. Throttling loss is eliminated, constant-power operation of the motor is achieved through peak clipping and valley filling of energy, the problem of impact on a power grid is solved, meanwhile, the system structure is compact, and the energy efficiency is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of hydrogen compression and hydraulic drive technology, and particularly to a closed-loop hydraulic system for a hydrogen compressor. Background Technology

[0002] In the hydrogen energy industry chain, hydrogen compressors are key core equipment for hydrogen refueling stations and hydrogen production plants. Existing hydraulically driven reciprocating compressors typically use open hydraulic systems as power sources, that is, using fixed displacement pumps or variable displacement pumps with relief valves in conjunction with directional valves to control the actuators.

[0003] This traditional technology has the following drawbacks: 1. Regardless of the actual load of the compressor (hydrogen inlet and outlet pressure), the pump always outputs power at a constant or near-constant rate. A large amount of hydraulic energy is converted into heat energy and lost through the relief valve or throttle valve, resulting in low system efficiency and serious energy waste.

[0004] 2. Because a large amount of pressure energy is converted into heat energy, the hydraulic oil temperature rises rapidly, requiring a high-power cooling system and a large-capacity oil tank to balance the heat. This directly results in the hydraulic station occupying a large space, having a bulky appearance, and increasing transportation and installation costs.

[0005] 3. During the piston reversal of a hydraulically driven compressor, the hydraulic pump needs to change discharge at the zero point or switch valves. At this time, the motor load will drop instantly from full load to no load, and then quickly return to full load. This frequent and drastic power fluctuation will cause serious harmonic pollution and impact on the power grid, and will also shorten the service life of the motor.

[0006] To address these issues, this application presents a closed-loop hydraulic system for a hydrogen compressor. Summary of the Invention

[0007] In order to overcome the shortcomings of existing technologies such as high energy consumption, large size and large impact on the power grid, this invention proposes a closed hydraulic system for a hydrogen compressor and its control method.

[0008] A closed-loop hydraulic system for a hydrogen compressor includes a hydraulic tank, a drive motor, a closed-loop pump, and a liquid-driven gas booster driven by the closed-loop pump. The drive motor is a dual-output-shaft motor; its first output shaft is connected to the closed-loop pump, and its second output shaft is connected to a four-quadrant pump. The four-quadrant pump's oil supply port is connected to the hydraulic tank, and its inlet and outlet ports are connected to an accumulator. The system also includes a sensor assembly for monitoring the system's operating status and a controller; the controller is configured to control the four-quadrant pump to switch between pump operation and motor operation based on feedback signals from the sensor assembly. This allows the four-quadrant pump to charge the accumulator during closed-loop pump reversal or low load, and to utilize the energy released from the accumulator to assist the drive motor during high load conditions of the closed-loop pump.

[0009] Furthermore, in order to better realize the present invention, the closed pump has a first working oil port and a second working oil port, and the first working oil port and the second working oil port are directly connected to the two chambers of the liquid-driven gas booster through closed loop pipelines respectively; the closed pump has an integrated proportional directional valve for controlling the flow direction and flow rate of hydraulic oil.

[0010] Furthermore, in order to better realize the present invention, the sensor assembly includes at least a pressure sensor, a temperature sensor and a liquid level sensor; the pressure sensor is installed on the main oil line between the closed pump and the liquid-driven gas booster and on the pipeline between the four-quadrant pump and the accumulator; the temperature sensor is installed on the hydraulic oil tank or on the system return oil line; and the liquid level sensor is installed on the hydraulic oil tank.

[0011] Furthermore, in order to better realize the present invention, the closed-loop pump also integrates a replenishing pump, a safety valve assembly and a flushing valve; the oil inlet of the replenishing pump is connected to the hydraulic oil tank to replenish leakage losses to the low-pressure side of the closed-loop pump.

[0012] Furthermore, in order to better realize the present invention, the system also includes an independent heat dissipation circulation loop, which includes a circulation pump and a radiator; the input end of the circulation pump is connected to the hydraulic oil tank, the output end is connected to the radiator, and the return end of the radiator is connected back to the hydraulic oil tank.

[0013] Furthermore, in order to better realize the present invention, a safety valve group is also provided between the four-quadrant pump and the accumulator, the safety valve group including a shut-off valve and an overflow valve.

[0014] Based on the above hydraulic system, the specific control method is as follows: S1, the main oil circuit pressure P1 of the closed pump and the energy storage pressure P2 of the accumulator are collected in real time through the pressure sensor; S2, the controller determines the operating stage of the hydraulically driven gas booster based on the rate of change of the main oil circuit pressure P1; S3, when it is determined that the system is in the reversing stage or the main oil circuit pressure P1 is lower than the preset load threshold, the controller controls the four-quadrant pump to work in pump mode, and uses the residual torque of the drive motor to pump hydraulic oil into the accumulator, so that the accumulator pressure P2 rises, while maintaining the output power of the drive motor stable. S4, when it is determined that the compression work stage is in progress and the main oil circuit pressure P1 is higher than the preset load threshold, the controller controls the four-quadrant pump to work in motor mode, releases the high-pressure hydraulic oil in the accumulator to drive the four-quadrant pump to rotate, and applies auxiliary torque to the second output shaft of the drive motor.

[0015] The beneficial effects of this invention are as follows: The closed-loop pump drive eliminates throttling and overflow losses in the main oil circuit, enabling on-demand energy supply and significantly improving system efficiency. An innovative energy recovery system, consisting of a four-quadrant pump and an accumulator, stores energy during compressor reversals or low loads, and releases energy during high loads, ensuring the drive motor operates at a relatively constant power level. This completely eliminates the impact on the power grid and reduces the installed power of the motor. The highly integrated closed-loop pump (with built-in oil replenishment, flushing, and safety valves) requires only a tiny oil tank, significantly reducing equipment size and facilitating installation and transportation. Combined with intelligent control methods based on sensor feedback, this achieves automated and precise energy management, enhancing the equipment's operational stability and intelligence. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the closed-loop hydraulic system for the hydrogen compressor of the present invention. Figure 2 This is a flowchart of the control method of the present invention.

[0017] In the picture, 1. Hydraulic oil tank; 2. Level gauge; 3. Air filter; 4. Drain ball valve; 5. Heater; 6. Level sensor; 7. Return oil filter; 8. Temperature sensor; 9. Circulating pump; 10. Radiator; 11. Closed-loop pump; 12. Hydraulic-driven gas booster; 13. Four-quadrant pump; 14. Accumulator; 15. Pressure sensor; 16. Safety valve assembly; 17. Check valve; 18. Relief valve; 19. Make-up pump; 20. Pressure gauge; M1. Drive motor. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0020] Figures 1-2 In a specific embodiment of the present invention, this embodiment is a closed hydraulic system for a hydrogen compressor, the main core components of which include a hydraulic oil tank 1, a drive motor M1, a closed pump 11, a liquid-driven gas booster 12, a four-quadrant pump 13, and an accumulator 14.

[0021] The drive motor is designed with a dual-output shaft structure. One output shaft is mechanically connected to the closed-loop pump 11, and the other output shaft is mechanically connected to the four-quadrant pump 13. The closed-loop pump 11 serves as the main drive source, directly connecting to the left and right oil chambers of the hydraulically driven gas booster 12 via two main oil circuits, forming a closed-loop circulation circuit. The closed-loop pump 11 is a variable displacement piston pump with an integrated proportional directional valve. By controlling the swashplate angle and the directional valve, the output flow rate and pressure can be steplessly adjusted, thereby precisely controlling the reciprocating speed and directional change of the hydraulically driven gas booster 12 without the need for a large directional valve assembly on the external pipeline.

[0022] The closed-loop pump 11 housing also integrates a replenishing pump 19, a safety valve 16, and a flushing valve. The replenishing pump 19 draws oil from the hydraulic oil tank 1 through the return oil filter 7, replenishing the oil leaking due to volumetric efficiency loss on the low-pressure side of the closed loop and maintaining the control pressure. The flushing valve is used to draw out the hot oil in the closed loop, allowing it to flow back to the oil tank for cooling.

[0023] To achieve energy recovery and constant power control, the system is equipped with a four-quadrant pump 13. The four-quadrant pump 13 is connected to the other end of the motor, its oil supply port is connected to the hydraulic oil tank 1, and its inlet and outlet ports are connected to the accumulator 14 via the safety valve assembly 16. Pressure sensors 15 are installed on the main oil circuit of the closed-loop pump 11 and the pipeline of the accumulator 14, respectively, to monitor the load pressure and energy storage status in real time.

[0024] The control logic of this system is as follows: During system operation, the controller reads data from pressure sensor 15 and temperature sensor 8 in real time. When the hydraulically driven gas booster 12 reaches the end of its stroke and needs to reverse, the swashplate of the closed-loop pump 11 crosses zero, causing the main oil circuit pressure P1 to drop instantaneously and the motor load to decrease. The controller detects this state and immediately controls the four-quadrant pump 13 to enter pumping mode. At this time, the motor drives the four-quadrant pump 13 to rotate, pumping hydraulic oil into the accumulator 14. This process not only recovers excess kinetic and electrical energy from the motor and converts it into hydraulic potential energy, but also artificially increases the motor load, avoiding power factor fluctuations caused by motor idling.

[0025] When the liquid-driven gas booster 12 completes its reversal and enters the high-pressure compression stroke, the main oil circuit pressure P1 rises sharply, increasing the motor load. The controller commands the four-quadrant pump 13 to switch to motor operation. At this time, the high-pressure oil in the accumulator 14 is released, driving the four-quadrant pump 13 to rotate, causing it to generate torque in the same direction to assist the motor in driving the closed-loop pump 11. This is equivalent to using previously stored energy for boosting, reducing the peak current drawn by the motor from the grid, and achieving constant power operation.

[0026] In addition, the system has an independent cooling circuit. The circulating pump 9 draws oil from the hydraulic oil tank 1, cools it through the radiator 10, and then flows back. When the temperature sensor 8 detects that the oil temperature is too high, the controller starts the circulating pump 9 and can increase the opening of the flushing valve of the closed pump 11 to ensure system thermal balance. The level sensor 6 is used to monitor the oil level and prevent the pump from drawing in cavitation. Accessories such as the air filter 3 and the drain ball valve 4 ensure the breathing of the oil tank and ease of maintenance.

[0027] In summary, this embodiment, through its unique dual-pump coupling and energy storage control architecture, perfectly resolves the contradiction between the energy efficiency of hydrogen compressors and grid impact, providing a highly efficient, compact, and intelligent solution.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A closed-loop hydraulic system for a hydrogen compressor, comprising a hydraulic tank (1), a drive motor (M1), a closed-loop pump (11), and a liquid-driven gas booster (12) driven by the closed-loop pump (11), characterized in that: The drive motor is a dual-output shaft motor. The first output shaft of the drive motor is connected to the closed pump (11), and the second output shaft of the drive motor is connected to the four-quadrant pump (13). The oil replenishment port of the four-quadrant pump (13) is connected to the hydraulic oil tank (1), and the inlet and outlet ports of the four-quadrant pump (13) are connected to an accumulator (14). The system also includes a sensor assembly for monitoring the system's operating status and a controller; the controller controls the four-quadrant pump (13) to switch between pump operating conditions and motor operating conditions based on the feedback signal from the sensor assembly, so that the four-quadrant pump (13) charges the accumulator (14) when the closed pump (11) is reversed or under low load, and uses the energy released by the accumulator (14) to assist the motor in running when the closed pump (11) is under high load.

2. The closed-loop hydraulic system for a hydrogen compressor according to claim 1, characterized in that: The closed-loop pump (11) has a first working port and a second working port. The first working port and the second working port are directly connected to the two chambers of the liquid-driven gas booster (12) through closed-loop pipelines. The closed-loop pump (11) has a proportional directional valve integrated inside, which is used to control the flow direction and flow rate of hydraulic oil.

3. The closed-loop hydraulic system for a hydrogen compressor according to claim 1, characterized in that: The sensor assembly includes a pressure sensor (15), a temperature sensor (8), and a liquid level sensor (6). The pressure sensor (15) is installed on the main oil line between the closed pump (11) and the liquid-driven gas booster (12), and also on the pipeline between the four-quadrant pump (13) and the accumulator (14). The temperature sensor (8) is installed in the hydraulic oil tank (1) or on the system return oil line; The liquid level sensor (6) is mounted on the hydraulic oil tank (1).

4. The closed-loop hydraulic system for a hydrogen compressor according to claim 1, characterized in that: The closed-loop pump (11) also integrates a replenishing pump (19), a safety valve group (16), and a flushing valve; the oil inlet of the replenishing pump (19) is connected to the hydraulic oil tank (1) to replenish leakage losses to the low-pressure side of the closed-loop pump (11).

5. The closed-loop hydraulic system for a hydrogen compressor according to claim 4, characterized in that: The system also includes an independent heat dissipation circulation loop, which includes a circulation pump (9) and a radiator (10); the input end of the circulation pump (9) is connected to the hydraulic oil tank (1), the output end is connected to the radiator (10), and the return end of the radiator (10) is connected back to the hydraulic oil tank (1).

6. The closed-loop hydraulic system for a hydrogen compressor according to claim 1, characterized in that: A safety valve assembly (16) is also provided between the four-quadrant pump (13) and the accumulator (14), the safety valve assembly (16) including a shut-off valve and an overflow valve.

7. A control method for a closed-loop hydraulic system of a hydrogen compressor, based on the closed-loop hydraulic system of a hydrogen compressor according to any one of claims 1-6, characterized in that, Includes the following steps: S1, the main oil circuit pressure P1 of the closed pump (11) and the energy storage pressure P2 of the accumulator (14) are collected in real time by the pressure sensor (15); S2, the controller determines the operating stage of the liquid-driven gas booster (12) based on the rate of change of the main oil circuit pressure P1; S3, when it is determined that the system is in the reversing stage or the main oil circuit pressure P1 is lower than the preset load threshold, the controller controls the four-quadrant pump (13) to be in pump mode, and uses the remaining torque of the drive motor to pump the hydraulic oil into the accumulator (14), so that the accumulator pressure P2 rises, while maintaining the output power of the drive motor stable. S4, when it is determined that the compression work stage is in progress and the main oil circuit pressure P1 is higher than the preset load threshold, the controller controls the four-quadrant pump (13) to be in motor working condition, releases the high pressure hydraulic oil in the accumulator (14) to drive the four-quadrant pump (13) to rotate, and applies auxiliary torque to the second output shaft of the drive motor.

8. The control method for the closed-loop hydraulic system of the hydrogen compressor according to claim 7, characterized in that: The control process includes a thermal management step. The temperature of the hydraulic oil is monitored in real time by a temperature sensor (8). When the temperature exceeds the set value, the controller turns on the circulation pump (9) and radiator (10) for forced heat dissipation. At the same time, the opening of the flushing valve integrated in the closed pump (11) is adjusted to increase the hot oil replacement volume.

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