Dual power excavator hydraulic system and control method thereof

Abstract

The application discloses a double-power excavator hydraulic system and a control method thereof, and belongs to the technical field of engineering machinery. The double-power excavator hydraulic system solves the defects of high production manufacturing cost and large occupied space of two groups of main pumps on the traditional excavator hydraulic system machine. The main structure comprises a working system, a motor, a light energy power supply system, a heat dissipation system, a variable frequency motor and an electric energy transmission system. The light energy power supply system is connected with the working system through the motor. The working system is also connected with hydraulic executing elements and an oil return system respectively. The electric energy transmission system is connected with the heat dissipation system through the variable frequency motor. The application is mainly used on excavators and other engineering machinery.

Description

Technical Field

[0001] This invention belongs to the field of engineering machinery technology, and more specifically, it relates to a hydraulic system for a dual-power excavator and its control method. Background Technology

[0002] In the field of construction machinery, especially excavators, engines typically drive hydraulic pumps to power the entire machine's hydraulic system, enabling actions such as digging and unloading. However, engines, as power sources, produce fuel exhaust emissions and noise, polluting the environment and hindering energy conservation and emission reduction. Compared to engines, electric motors, as power sources, are quieter, pollution-free, and significantly reduce operating costs; however, to ensure stable operation, they require an external power grid, limiting their operation to locations with an external power grid and making relocation inconvenient. Combining the advantages of both, the dual-power excavator was developed.

[0003] Existing hydraulic and electric dual-power excavator main pump oil supply system, such as Figure 7 As shown, the engine drives one set of main pumps, and the electric motor drives another set of main pumps. These two sets of main pumps work independently, but drive the same actuator through the same main control valve. In this hydraulic circuit, the electric motor drives the main pump, and the engine drives the main pump. The main pump outlet is connected to a check valve, and the main pump is also connected to a check valve. The oil is then combined through pipelines to the control valve and enters the actuator. The main pumps are connected in parallel, and the output oil passes through check valves. Each check valve individually passes through the control valve group to enter the load hydraulic power system, driving the excavator to operate. However, the above solution has the following shortcomings:

[0004] 1. Using a motor and an engine to drive a set of main pumps to achieve independent operation, that is, there are two sets of main pumps on the machine, which increases the production and manufacturing costs, occupies a lot of space, and requires additional check valves at the outlets of the two sets of main pumps. In addition, the pipeline connection is complicated and increases the risk of leakage.

[0005] 2. The motor obtains its electrical energy from the power grid, which generates electricity through thermal power generation using coal and fossil fuels, thus polluting the environment.

[0006] 3. Hydraulic systems often recover energy through hydraulic cylinders or swing motors. Because the movements of hydraulic cylinders and swing motors are periodic and have a large range during the operation of excavators, the recovered energy has large fluctuations and impacts, making it difficult to control. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and to provide a hydraulic system for a dual-power excavator and its control method.

[0008] To achieve the above objectives, the present invention employs the following technical solution:

[0009] A dual-power excavator hydraulic system includes a working system, an electric motor, a solar power supply system, a cooling system, a variable frequency motor, and an electric power transmission system. The solar power supply system is connected to the working system via the electric motor. The working system is also connected to a hydraulic actuator and a return oil system. The electric power transmission system is connected to the cooling system via the variable frequency motor.

[0010] Preferably, the solar power supply system includes a concentrator for focusing the light source, a solar cell array for generating direct current, a combiner device, a DC voltage regulator module, an energy storage device, and an inverter module for outputting three-phase alternating current. The concentrator is connected to the combiner device through the solar cell array. The combiner device is also electrically connected to the DC voltage regulator module through an LCL filter. One side of the DC voltage regulator module is connected to the input port of the energy storage device. The energy storage device is connected in parallel to the DC bus through a solar energy contactor. The input terminal of the inverter module is connected in parallel to the DC side of the DC bus, and the output terminal of the inverter module is connected to the motor.

[0011] Preferably, the power transmission system includes a power integration module, a step-down power conversion module, a DC contactor, a rectifier-inverter module, a boost power conversion module, and a capacitor bank. The other side of the DC voltage regulator module is connected to the power integration module. The step-down power conversion module, the boost power conversion module, and the capacitor bank are all connected in parallel to the DC side of the DC bus behind the power integration module. The rectifier side of the step-down power conversion module is connected in parallel to the rectifier side of the boost power conversion module. The rectifier side of the step-down power conversion module is connected to the rectifier-inverter module through the DC contactor, and the rectifier side of the boost power conversion module is connected to the rectifier-inverter module through the DC contactor. The rectifier-inverter module is connected to the variable frequency motor via three-phase AC power.

[0012] Preferably, the heat dissipation system includes a heat dissipation pump, a heat dissipation motor, and a compressor motor. One oil outlet of the heat dissipation pump is connected to two oil ports of the heat dissipation motor through a reversing valve and a second pressure compensation valve. The heat dissipation motor is coaxially connected to a variable frequency motor, and the output end of the variable frequency motor is connected to a fan. The other oil outlet of the heat dissipation pump is connected to the oil inlet of the compressor motor through a first pressure compensation valve. The oil outlet of the compressor motor is connected to a hydraulic oil tank, and the motor is coaxially connected to the heat dissipation pump through a motor clutch.

[0013] Preferably, a shuttle valve two is provided between the two oil ports of the cooling motor, and a shuttle valve one is provided between the output end of the shuttle valve two and the input oil port of the compressor motor. The output oil port of the shuttle valve one acts on the control oil port of the pressure compensation valve one, the pressure compensation valve two and the cooling pump.

[0014] Preferably, the working system includes a main valve, a main pump, and an engine. The engine is coaxially connected to the main pump via an engine clutch. The main pump is also coaxially connected to a cooling pump. The oil outlet of the main pump is connected to the oil inlet of the main valve, and the working oil port of the main valve is connected to a hydraulic actuator.

[0015] Preferably, the oil return system includes a hydraulic oil tank, a radiator, a bypass valve, and a back pressure valve. The oil return port of the main valve is connected to the hydraulic oil tank through the back pressure valve and the radiator. The back pressure valve and the radiator are connected in series and then connected in parallel with the bypass valve.

[0016] A control method employing a dual-power excavator hydraulic system as described in any of the above, including a fuel mode and an electric mode.

[0017] Preferably, the fuel mode control method is as follows:

[0018] When the engine clutch is energized and the electric motor clutch is de-energized, the engine is coaxially connected to the cooling pump and main pump, providing prime mover power to them. The electric motor is disconnected from the cooling pump. Hydraulic oil output from the main pump is delivered to the hydraulic actuators through the internal flow channels and logic control of the main valve. The return oil from the main valve returns to the hydraulic tank through the back pressure valve and radiator, or through the bypass valve. The hydraulic oil output from the cooling pump simultaneously drives the compressor motor and the cooling motor. The compressor motor drives the compressor to work for air conditioning cooling. The cooling motor is coaxially connected to the variable frequency motor, which in turn connects to the fan to drive the fan to rotate and cool the radiator. The controller outputs control signals through the variable frequency control cabinet based on the power capacity on the DC bus to change the torque magnitude and direction of the variable frequency motor, thereby controlling whether the variable frequency motor is in motoring or generating mode.

[0019] When the electrical energy on the DC bus does not meet the set value, the controller sends a control signal to the frequency converter control cabinet. The drive circuit inside the frequency converter control cabinet uses the DTC torque control algorithm to change the torque direction of the frequency converter motor, putting it into a generating state. The generated three-phase AC power is rectified into DC power by the rectifier-inverter module. If the generated voltage is higher than the DC bus voltage, DC contactor one closes and DC contactor two opens. The rectified DC power is then stepped down by the step-down power conversion module and sent to the DC bus. Excess energy is stored in the capacitor bank. If the generated voltage is lower than the DC bus voltage, DC contactor one opens and DC contactor two closes. The rectified DC power is then stepped up by the step-up power conversion module and sent to the DC bus. Excess energy is stored in the capacitor bank.

[0020] When the DC bus has sufficient power, the controller sends a control signal to the frequency converter control cabinet. The internal drive circuit of the frequency converter control cabinet uses the DTC torque control algorithm to change the torque direction of the frequency converter motor, putting it into motoring mode. If the voltage on the DC bus is lower than the voltage required by the frequency converter motor, DC contactor one closes and DC contactor two opens. The DC power from the DC bus is boosted by the step-down power conversion module and then inverted into AC power by the rectifier-inverter module to power the frequency converter motor. Together with the cooling motor, this provides power to drive the fan, and the capacitor bank discharges to replenish the power on the DC bus. Conversely, if the voltage on the DC bus is higher than the voltage required by the frequency converter motor, DC contactor one opens and DC contactor two closes. The DC power from the DC bus is stepped down by the step-up power conversion module and then inverted into AC power by the rectifier-inverter module to power the frequency converter motor. Together with the cooling motor, this provides power to drive the fan, and the capacitor bank discharges to replenish the power on the DC bus.

[0021] Preferably, the control method for the electric mode is as follows:

[0022] When the engine clutch is de-energized, the electric motor clutch is energized, allowing the electric motor to connect coaxially with the cooling pump and main pump, providing power to them. The engine is then disconnected from the main pump. The DC power, converted from solar energy to the DC bus, is inverted into AC power by the inverter module to supply the electric motor. The hydraulic oil output from the main pump is delivered to the hydraulic actuators through the internal flow channels and logic control of the main valve. The return oil from the main valve flows back to the hydraulic tank via the back pressure valve and radiator, or via a bypass valve. The hydraulic oil output from the cooling pump simultaneously drives the compressor motor and the cooling motor. The compressor motor drives the compressor for air conditioning cooling, while the cooling motor is coaxially connected to the variable frequency motor. Simultaneously, the variable frequency motor connects to the fan, driving it to cool the radiator. The controller, based on the electrical capacity on the DC bus, outputs control signals through the variable frequency control cabinet to change the torque magnitude and direction of the variable frequency motor, thus controlling whether the motor is in motoring or generating mode.

[0023] When the power on the DC bus does not meet the set value, the controller sends a control signal to the frequency converter control cabinet. The internal drive circuit of the frequency converter control cabinet uses the DTC torque control algorithm to change the torque direction of the frequency converter motor, putting it into a generating state. The generated three-phase AC power is rectified into DC power by the rectifier-inverter module. If the generated voltage is higher than the DC bus voltage, DC contactor one closes and DC contactor two opens. The rectified DC power is then stepped down by the step-down power conversion module and sent to the DC bus. Excess energy is stored in the capacitor bank. If the generated voltage is lower than the DC bus voltage, the DC contactor... When contactor one is disconnected and contactor two is closed, the rectified DC power is boosted by the step-up power conversion module and sent to the DC bus. Excess energy is stored through capacitor banks. The function of the power integration module is to optimize and regulate the current, voltage, and power on the DC bus. It can transfer the power from the solar power generation side to the variable frequency motor side according to the actual operating conditions, coordinate the power on both sides, improve the power utilization rate, and improve the coordination of the solar power generation system. In motor mode, the power generated by the variable frequency motor is voltage controlled and power matched by the power integration module and sent to the solar power generation side to provide energy for the motor.

[0024] When the DC bus has sufficient power, the controller sends a control signal to the frequency converter control cabinet. Then, the drive circuit inside the cabinet uses the DTC torque control algorithm to change the torque direction of the frequency converter motor, putting it into motoring mode. If the voltage on the DC bus is lower than the voltage required by the frequency converter motor, DC contactor one closes and DC contactor two opens. The DC power from the DC bus is boosted by the step-down power conversion module and then inverted into AC power by the rectifier-inverter module to provide power to the frequency converter motor. Together with the cooling motor, this provides power to drive the fan. Meanwhile, the capacitor bank discharges, contributing to the DC power output. The power supply to the bus is replenished. If the voltage on the DC bus is higher than the voltage required by the variable frequency motor, DC contactor one is disconnected and DC contactor two is closed. The DC power on the DC bus is stepped down by the boost power conversion module and then converted into AC power by the rectifier-inverter module to provide power to the variable frequency motor. Together with the cooling motor, it provides power to drive the fan to rotate. The capacitor bank discharges to replenish the power supply to the DC bus. At the same time, the power from the solar power generation side is controlled by the power integration module for voltage control and power matching, and then transferred to the variable frequency motor side to provide energy, or stored in the capacitor bank.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. By using an electric motor clutch and an engine clutch (two electromagnetic clutches), the engine clutch is connected between the main pump and the engine, and the electric motor clutch is connected between the electric motor and the cooling pump. The opening and closing states of the two electromagnetic clutches are controlled by a controller to switch between fuel mode and electric mode. Therefore, only one main pump and one set of pipelines are needed to achieve dual power output, reducing design and production costs, simplifying pipelines, and saving space.

[0027] 2. This invention uses light energy as an energy input and designs a light energy power supply system to convert light energy into electrical energy to provide power for the excavator system. Light energy is a renewable energy source that is clean, environmentally friendly, and pollution-free. It is also safe and reliable, which greatly reduces the user's operating and maintenance costs. At the same time, the light energy power supply system designed in this invention is not connected to the power grid and will not have any impact or other effects on the national power grid.

[0028] 3. The solar power supply system and electric power transmission system designed in this invention include a DC voltage regulator module, an electric power integration module, a power conversion module, an energy storage device, and a capacitor bank. It can effectively utilize the transmission of solar energy and electric energy, improve energy utilization efficiency and the coordination of energy transmission, and ensure the reliable and stable operation of the solar power supply system and the electric power transmission system.

[0029] 4. Through the combination of shuttle valve and pressure compensation valve to form a hydraulic circuit, and by reasonably designing the displacement ratio of the cooling motor and the compressor motor, a single cooling pump can drive both the cooling motor and the compressor motor to work normally, without affecting the flow distribution due to the increase or decrease of load.

[0030] 5. This invention uses a cooling motor to drive a variable frequency motor to generate electricity and transfer electrical energy. Because the cooling motor has a small speed range and small fluctuations, the generated energy is stable, which has little impact on the solar power supply system and the electric transmission system and is easy to adjust.

[0031] In summary, the two power sources of this invention provide power to the hydraulic system through only one main pump, which reduces costs, simplifies pipelines, enhances reliability, and saves space. When there is an external power source, the motor is used as the power source to complete the operation, while the engine is used for transportation and auxiliary operations. Attached Figure Description

[0032] Figure 1 This is a hydraulic schematic diagram of the present invention;

[0033] Figure 2 A schematic diagram of the four-quadrant operation of the variable frequency motor in this invention;

[0034] Figure 3 Schematic diagram of the variable frequency motor power generation operation in this invention;

[0035] Figure 4 This is a schematic diagram of the electric operating conditions of the variable frequency motor in this invention;

[0036] Figure 5 This is a schematic diagram of energy flow in this invention;

[0037] Figure 6 This is a schematic diagram of the control method in this invention;

[0038] Figure 7 This is a schematic diagram of a dual-power main pump oil supply system in the prior art.

[0039] In the diagram: 1. Concentrator; 2. Solar panel; 3. Combiner unit; 4. LCL filter; 5. DC voltage regulator module; 6. Energy storage device; 7. Photovoltaic contactor; 8. Inverter module; 9. Power integration module; 10. Variable frequency drive cabinet; 11. Buck converter module; 12. DC contactor one; 13. Rectifier-inverter module; 14. DC contactor two; 15. Boost converter module; 16. Capacitor bank; 17. Hydraulic tank; 18. Radiator; 19. Bypass valve ; 20. Back pressure valve; 21. Fan; 22. Air conditioning compressor; 23. Compressor motor; 24. Variable frequency motor; 25. Pressure compensation valve one; 261. Shuttle valve one; 262. Shuttle valve two; 27. Cooling motor; 28. Pressure compensation valve two; 29. ​​Directional control valve; 30. Hydraulic actuator; 31. Electric motor; 32. Main valve; 33. Controller; 34. Electric motor clutch; 35. Cooling pump; 36. Main pump; 37. Engine clutch; 38. Engine; 39. DC bus. Detailed Implementation

[0040] The present invention will be further described below through specific embodiments and in conjunction with the accompanying drawings.

[0041] Example 1:

[0042] like Figure 1 As shown, a dual-power excavator hydraulic system includes a working system, an electric motor 31, a solar power supply system, a cooling system, a variable frequency motor 24, and an electric power transmission system. The solar power supply system is connected to the working system via the electric motor 31. The working system is also connected to hydraulic actuators 30 and a return oil system. The electric power transmission system is connected to the cooling system via the variable frequency motor 24. The hydraulic actuators 30 include a boom cylinder, a bucket cylinder, a stick cylinder, a swing motor, and a travel motor.

[0043] Example 2:

[0044] A dual-power excavator hydraulic system differs from Embodiment 1 in that the solar power supply system includes a concentrator 1 for focusing a light source, a solar cell array 2 for generating direct current (DC), a combiner 3, a DC voltage regulator module 5, an energy storage device 6, and an inverter module 8 for outputting three-phase AC power. In this embodiment, the light emitted by the light source (sunlight or other illumination light source) is focused by the concentrator 1 and irradiates the solar cell array 2 to generate DC power, which is connected to the combiner 3 via a DC bus 39. The combiner 3 is also electrically connected to the DC voltage regulator module 5 via an LCL filter 4. One side of the DC voltage regulator module 5 is connected to the input port of the energy storage device 6, and the energy storage device 6 is connected in parallel to the DC bus 39 via a solar energy contactor 7. The input terminal of the inverter module 8 is connected in parallel to the DC side of the DC bus 39, and the output terminal of the inverter module 8 is three-phase AC power connected to the motor 31.

[0045] Furthermore, the power transmission system includes a power integration module 9, a step-down power conversion module 11, a DC contactor 12, a rectifier-inverter module 13, a boost power conversion module 15, and a capacitor bank 16. The other side of the DC voltage regulator module 5 is connected to the power integration module 9. The step-down power conversion module 11, the boost power conversion module 15, and the capacitor bank 16 are all connected in parallel to the DC side of the DC bus 39 on the rear side of the power integration module 9. The rectifier side of the step-down power conversion module 11 is connected in parallel to the rectifier side of the boost power conversion module 15. The rectifier side of the step-down power conversion module 11 is connected to the rectifier-inverter module 13 through the DC contactor 12. The rectifier side of the boost power conversion module 15 is connected to the rectifier-inverter module 13 through the DC contactor 14. The rectifier-inverter module 13 is connected to the variable frequency motor 24 through three-phase AC power.

[0046] Furthermore, the cooling system includes a cooling pump 35, a cooling motor 27, and a compressor motor 23. One oil outlet of the cooling pump 35 is connected to two oil ports of the cooling motor 27 through a reversing valve 29 and a pressure compensation valve 28. The cooling motor 27 is coaxially connected to a variable frequency motor 24, and the output end of the variable frequency motor 24 is connected to a fan 21. The other oil outlet of the cooling pump 35 is connected to the oil inlet of the compressor motor 23 through a pressure compensation valve 25. The oil outlet of the compressor motor 23 is connected to a hydraulic oil tank 17, and the motor 31 is coaxially connected to the cooling pump 35 through a motor clutch 34.

[0047] Furthermore, a shuttle valve 262 is provided between the two oil ports of the cooling motor 27, and a shuttle valve 261 is provided between the output end of the shuttle valve 262 and the input oil port of the compressor motor 23. The output oil port of the shuttle valve 261 acts on the control oil port of the pressure compensation valve 25, the pressure compensation valve 28 and the cooling pump 35.

[0048] Furthermore, the working system includes a main valve 32, a main pump 36, and an engine 38. The engine 38 is coaxially connected to the main pump 36 via an engine clutch 37. The main pump 36 is also coaxially connected to a cooling pump 35. The oil outlet of the main pump 36 is connected to the oil inlet of the main valve 32, and the working oil port of the main valve 32 is connected to a hydraulic actuator 30. Both the electric motor clutch 34 and the engine clutch 37 are electromagnetic clutches.

[0049] Furthermore, the oil return system includes a hydraulic oil tank 17, a radiator 18, a bypass valve 19, and a back pressure valve 20. The oil return port of the main valve 32 is connected to the hydraulic oil tank 17 through the back pressure valve 20 and the radiator 18. The back pressure valve 20 and the radiator 18 are connected in series and then connected in parallel with the bypass valve 19.

[0050] Example 3:

[0051] pass Figure 1 and Figure 6 As shown, the light source is focused by the concentrator 1 onto the solar cell array 2 to reduce light dispersion, increase energy density, and improve the output power of the solar cell array 2. The solar cell array 2 converts the light energy into direct current (DC), which is then combined by the combiner device 3 and connected to the DC bus 39. The LCL filter 4 eliminates high-order harmonics, maintaining the harmonic content at an extremely low level, ensuring that the voltage and current on the DC bus 39 remain stable and unaffected by fluctuations in the generated electricity. The voltage is increased by the DC voltage regulator module 5, and an energy storage system composed of a bidirectional DC / DC converter connected in parallel with energy storage elements enables the recovery and reuse of DC power, improving the stability and energy utilization of the DC power system and ensuring that the voltage on the DC bus 39 is unaffected by load changes. When there is sufficient sunlight, the photovoltaic system provides energy to the AC load, and the remaining energy is transferred to the converter. When there is insufficient sunlight, the photovoltaic array provides insufficient energy to the AC load, and the battery supplies energy to the AC load via the converter. Through the above process, the light energy is converted into stable DC power and stabilized on the DC bus 39.

[0052] A control method employs a dual-power excavator hydraulic system as described in Embodiment 1 or Embodiment 2 above. Since this system is a dual-power mode, it is divided into a fuel mode and an electric mode.

[0053] The control method for the fuel mode is as follows:

[0054] When the engine clutch 37 is energized and the electric motor clutch 34 is de-energized, the engine 38 is coaxially connected to the cooling pump 35 and the main pump 36, providing power to the main pump 36 and the cooling pump 35. The electric motor 31 is disconnected from the cooling pump 35. The hydraulic oil output from the main pump 36 is delivered to the hydraulic actuator 30 through the internal flow channel and logic control of the main valve 32. The return oil from the main valve 32 returns to the hydraulic oil tank 17 through the back pressure valve 20 and the radiator 18, or through the bypass valve 19. The hydraulic oil output from the cooling pump 35 simultaneously drives the compressor motor 23 and the cooling motor 27. The compressor motor 23 drives the compressor to work for air conditioning cooling. The cooling motor 27 is coaxially connected to the variable frequency motor 24. At the same time, the variable frequency motor 24 is connected to the fan 21 to drive the fan to rotate and cool the radiator 18. The controller 33, based on the power capacity on the DC bus 39, outputs a control signal through the variable frequency control cabinet 10 to change the torque magnitude and direction of the variable frequency motor 24, thereby controlling whether the variable frequency motor 24 is in motor mode or generator mode.

[0055] When the electrical energy on the DC bus 39 does not meet the set value, the controller 33 sends a control signal to the frequency converter control cabinet 10. The drive circuit inside the frequency converter control cabinet 10 uses the DTC torque control algorithm to change the torque direction of the frequency converter motor 24 so that it is in the generating state. The generated three-phase AC power is rectified into DC power by the rectifier-inverter module 13. If the generated voltage value is higher than the voltage value on the DC bus 39, the DC contactor 12 is closed and the DC contactor 2 is opened. The rectified DC power is stepped down by the step-down power conversion module 11 and sent to the DC bus 39. The excess energy is stored in the capacitor bank 16. If the generated voltage value is lower than the voltage value on the DC bus 39, the DC contactor 12 is opened and the DC contactor 2 is closed. The rectified DC power is stepped up by the step-up power conversion module 15 and sent to the DC bus 39. The excess energy is stored in the capacitor bank 16.

[0056] When the DC bus 39 has sufficient power, the controller 33 sends a control signal to the frequency converter control cabinet 10. The drive circuit inside the frequency converter control cabinet 10 uses a DTC torque control algorithm to change the torque direction of the frequency converter motor 24, putting it into motoring mode. If the voltage on the DC bus 39 is lower than the voltage required by the frequency converter motor 24, DC contactor 12 closes and DC contactor 24 opens. The DC power from the DC bus 39 is boosted by the step-down power conversion module 11 and then inverted into AC power by the rectifier-inverter module 13 to provide power to the frequency converter motor 24 and the heat sink. Together with the cooling motor 27, they provide power to drive the fan 21 to rotate, and the capacitor bank 16 discharges to replenish the electrical energy of the DC bus 39. At this time, if the voltage value on the DC bus 39 is higher than the voltage value required by the variable frequency motor 24, the DC contactor 12 is disconnected and the DC contactor 24 is closed. The DC power of the DC bus 39 is stepped down by the boost power conversion module 15 and then inverted into AC power by the rectifier-inverter module 13 to provide electrical energy for the variable frequency motor 24. Together with the cooling motor 27, they provide power to drive the fan 21 to rotate, and the capacitor bank 16 discharges to replenish the electrical energy of the DC bus 39.

[0057] The cooling pump 35 outputs hydraulic oil to simultaneously drive the compressor motor 23 and the cooling motor 27. By reasonably determining the displacement ratio of the two motors and the pressure compensation functions of pressure compensation valve 1 25 and pressure compensation valve 28, it is possible to ensure that the two motors can operate within the set working speed range, and that the speed of the two motors is not affected by load fluctuations. This is because both the compressor motor 23 and the cooling motor 27 have their own working speed ranges, and thus the displacements of the two motors are also correspondingly related. In this embodiment, it is assumed that the operating speed range of both the compressor motor 23 and the cooling motor 27 is 1000 r / min to 1200 r / min. Therefore, the displacement of the compressor motor 23 and the cooling motor 27 is set to be equal (the displacement relationship between the two motors can be redistributed according to actual working requirements). When the loads of the compressor motor 23 and the cooling motor 27 are the same, the hydraulic oil output by the cooling pump 35 can be evenly distributed to the compressor motor 23 and the cooling motor 27, and the two motors rotate at the same speed. If the fan 21 speed needs to be increased due to the increase in hydraulic oil temperature, that is, the load of the cooling motor 27 increases, and the loads of the compressor motor 23 and the cooling motor 27 are different, the hydraulic oil output by the cooling pump 35 will flow to the side with the lower load, and at this time, it will all flow to the compressor motor 23. In this embodiment, a pressure compensation valve and a shuttle valve are added to the front end of the compressor motor 23 and the cooling motor 27 to avoid uneven flow distribution caused by different loads. The same cooling pump 35 can supply oil to the two motors, and they can work within their respective speed ranges without flow imbalance caused by different loads of the two motors. When the electromagnet at the lower end of the reversing valve 29 is energized and operates in the lower position, the hydraulic oil output by the cooling pump 35 goes through the reversing valve 29 to port A of the cooling motor 27, and the hydraulic oil at port B of the cooling motor 27 returns to the hydraulic oil tank 17 through the reversing valve 29. At the same time, the hydraulic oil output by the cooling pump 35 goes through the pressure compensation valve 25 to the oil inlet of the compressor motor 23, and the oil outlet returns to the hydraulic oil tank 17. In this way, the cooling pump 35 drives the cooling motor 27 and the compressor motor 23 to rotate, and the two motors drive the fan 21 for cooling and the air conditioning compressor 22 for refrigeration, respectively. Assuming that the oil temperature rises during operation and the fan 21 speed needs to be increased, the cooling motor 27 needs to provide greater torque, that is, the load on the cooling motor 27 increases. To ensure that the flow distribution ratio between the cooling motor 27 and the compressor motor 23 remains unchanged, the highest system pressure, that is, the pressure at port A of the cooling motor 27, is obtained through shuttle valve 1 261 and shuttle valve 2 262, and is applied to the left oil port of pressure compensation valve 1 25 and the upper oil port of pressure compensation valve 28, respectively. The pressure oil output by the cooling pump 35 is applied to the right oil port of pressure compensation valve 1 25 and the lower oil port of pressure compensation valve 28, respectively.Due to the pressure difference across the pressure compensation valves, pressure compensation valve 25, acting as a low-pressure compensation valve, will shift its valve core to the right, reducing its opening area until the pressure at the right end of pressure compensation valve 25 balances with the system's highest pressure. Pressure compensation valve 28, acting as the maximum load compensation valve, will shift its valve core upwards, increasing its opening. Simultaneously, as the load pressure increases, the system's highest pressure will also affect the variable displacement mechanism of the cooling pump 35, increasing its displacement to compensate for the system's flow rate. The reverse rotation (oil inlet at port B) of the cooling motor 27 and the increased load on the compressor motor 23 are governed by the same principle.

[0058] The control method for the electric mode is as follows:

[0059] When the engine clutch 37 is de-energized, the electric motor clutch 34 is energized, causing the electric motor 31 to be coaxially connected to the cooling pump 35 and the main pump 36, providing prime mover power to the main pump 36 and the cooling pump 35. The engine 38 is disconnected from the main pump 36. The DC power converted from light energy to DC bus 39 is inverted into AC power by inverter module 8 and supplied to the electric motor 31. The hydraulic oil output from the main pump 36 is delivered to the hydraulic actuator 30 through the internal flow channel and logic control of the main valve 32. The return oil from the main valve 32 returns to the hydraulic oil tank 17 through the back pressure valve 20 and radiator 18, or through the bypass valve. 19 returns to the hydraulic oil tank 17; the cooling pump 35 outputs hydraulic oil to drive the compressor motor 23 and the cooling motor 27. The compressor motor 23 drives the compressor to work for air conditioning cooling. The cooling motor 27 is coaxially connected to the variable frequency motor 24. At the same time, the variable frequency motor 24 is connected to the fan 21 and drives the fan 21 to rotate to cool the radiator 18. The controller 33, based on the power capacity on the DC bus 39, outputs control signals through the variable frequency control cabinet 10 to change the torque magnitude and direction of the variable frequency motor 24, thereby controlling whether the variable frequency motor 24 is in motoring or generating mode.

[0060] When the electrical energy on the DC bus 39 does not meet the set value, the controller 33 sends a control signal to the frequency converter control cabinet 10. The drive circuit inside the frequency converter control cabinet 10 uses the DTC torque control algorithm to change the torque direction of the frequency converter motor 24, putting it into a generating state. The generated three-phase AC power is rectified into DC power by the rectifier-inverter module 13. If the generated voltage is higher than the voltage on the DC bus 39, DC contactor 12 closes and DC contactor 214 opens. The rectified DC power is then stepped down by the step-down power conversion module 11 and sent to the DC bus 39. Excess energy is stored in the capacitor bank 16. If the generated voltage is lower than the voltage on the DC bus 39, the DC contactor 12 closes and DC contactor 14 opens. When the DC contactor 12 is open and the DC contactor 14 is closed, the rectified DC power is boosted by the boost-type power conversion module 15 and sent to the DC bus 39. Excess energy is stored through the capacitor bank 16. The function of the power integration module 9 is to optimize and regulate the current, voltage and power on the DC bus 39. It can transfer the power from the solar power generation side to the power from the variable frequency motor 24 side according to the actual working conditions, coordinate the power on both sides, improve the power utilization rate and improve the coordination of the solar power generation system. In motor mode, the power generated by the variable frequency motor 24 is voltage controlled and power matched by the power integration module 9 and sent to the solar power generation side to provide energy for the motor 31.

[0061] When the DC bus 39 has sufficient power, the controller 33 sends a control signal to the frequency converter control cabinet 10. Then, the drive circuit inside the frequency converter control cabinet 10 uses the DTC torque control algorithm to change the torque direction of the frequency converter motor 24, putting it into motoring mode. At this time, if the voltage value on the DC bus 39 is lower than the voltage value required by the frequency converter motor 24, DC contactor 12 closes and DC contactor 24 opens. The DC power from the DC bus 39 is boosted by the step-down power conversion module 11 and inverted into AC power by the rectifier-inverter module 13 to provide power to the frequency converter motor 24. Together with the cooling motor 27, they provide power to drive the fan 21 to rotate, and the capacitor bank 16 discharges. The power supply to the DC bus 39 is replenished. If the voltage on the DC bus 39 is higher than the voltage required by the variable frequency motor 24, the DC contactor 12 is disconnected and the DC contactor 14 is closed. The DC power on the DC bus 39 is stepped down by the boost power conversion module 15 and then converted into AC power by the rectifier-inverter module 13 to provide power to the variable frequency motor 24. Together with the cooling motor 27, it provides power to drive the fan 21 to rotate. The capacitor bank 16 discharges to replenish the power supply to the DC bus 39. At the same time, the power from the solar power generation side is controlled by the power integration module 9 and the power is matched to the voltage. The power is then transferred to the variable frequency motor side to provide energy or stored in the capacitor bank 16.

[0062] like Figure 2The diagram shows the four-quadrant operation of a variable frequency motor. The horizontal axis represents the motor torque, and the vertical axis represents the motor speed. In the first quadrant, the motor speed and torque are in the same direction, and the motor is in motoring mode. In the second quadrant, the motor speed and torque are in opposite directions, and the motor is in generating mode. In the third quadrant, the motor speed and torque are in opposite directions, and the motor is in generating mode. In the fourth quadrant, the motor speed and torque are in the same direction, and the motor is in motoring mode.

[0063] like Figure 3 The diagram shows the operation of the variable frequency motor generating electricity. The solar power supply system generates AC power to the motor 31. The controller 33 controls the electromagnetic clutch to be energized. The motor 31 drives the cooling pump 35 to work. The cooling pump 35 outputs hydraulic oil to supply the cooling motor 27. The cooling motor 27 is coaxially connected to the variable frequency motor 24 and the fan 21. At this time, the controller 33 controls the direction of the motor torque to be opposite to the direction of the motor rotation. The variable frequency motor 24 generates electricity and feeds it back to the power transmission system.

[0064] like Figure 4 The diagram shows the electric operation of the variable frequency motor. The solar power supply system generates AC power to the motor 31. The controller 33 controls the electromagnetic clutch to be energized. The motor 31 drives the cooling pump 35 to work. The cooling pump 35 outputs hydraulic oil to supply the cooling motor 27. The cooling motor 27 is coaxially connected to the variable frequency motor 24 and the fan 21. At this time, the controller 33 controls the direction of the motor torque to be in the same direction as the direction of the motor rotation. The variable frequency motor 24 obtains electrical energy from the electric power transmission system and drives the fan 21 together with the cooling motor 27.

[0065] like Figure 5The diagram illustrates the energy flow of this invention. The system utilizes four energy forms: light energy, electrical energy, hydraulic energy, and mechanical energy. Light energy is used as input, converted into electrical energy by relevant components, and simultaneously output as electrical energy, with feedback and recycling occurring simultaneously. The light energy transfer process is as follows: the light source is focused by the concentrator 1, converted into electrical energy by the solar cell array 2, and transferred to the DC bus 39. The electrical energy transfer process is as follows: the DC bus 39 serves as the electrical energy input source, transmitting it to the motor 31 via the inverter module 8; simultaneously, the variable frequency motor 24 acts as a generator, feeding the generated electrical energy back to the DC bus 39 via the rectifier-inverter module 13, and then transmitting it to the motor 31 or storing it in the capacitor bank 16. The mechanical energy transfer process is as follows: the output torque from the drive motor is transmitted to the main pump 36 via a coupling and other transmission devices; the cooling motor 27 transmits its output torque as mechanical energy to the variable frequency motor 24 via the coupling. The hydraulic energy transfer process is as follows: when the main pump 36 is working, it outputs high-pressure oil and transfers it to the main valve 32 in the form of hydraulic energy. The cooling pump 35 then transfers the hydraulic energy to the compressor motor 23 and the cooling motor 27. Under the above four energy transfer methods, there are hydraulic energy losses caused by leakage in the hydraulic system and overflow units; mechanical energy losses caused by motor friction and transmission devices such as couplings; and electrical energy losses caused by heat generated during the power conversion process of the rectifier-inverter module 13. These energy losses are obtained from the power grid.

Claims

1. A dual power excavator hydraulic system, characterized by: The system comprises a working system, a motor (31), a light energy power supply system, a heat dissipation system, a variable frequency motor (24) and an electric energy transmission system, the light energy power supply system is connected with the working system through the motor (31), the working system is also connected with a hydraulic executing element (30) and an oil return system respectively, the electric energy transmission system is connected with the heat dissipation system through the variable frequency motor (24); The heat dissipation system comprises a heat dissipation pump (35), a heat dissipation motor (27) and a compressor motor (23), one oil outlet of the heat dissipation pump (35) is connected with two oil ports of the heat dissipation motor (27) through a reversing valve (29) and a pressure compensation valve (28), the heat dissipation motor (27) is coaxially connected with the variable frequency motor (24), and an output end of the variable frequency motor (24) is connected with a fan (21); the other oil outlet of the heat dissipation pump (35) is connected with an oil inlet of the compressor motor (23) through a pressure compensation valve (25), an oil outlet of the compressor motor (23) is connected with a hydraulic oil tank (17), and the motor (31) is coaxially connected with the heat dissipation pump (35) through a motor clutch (34); the heat dissipation motor (27) is also provided with a shuttle valve (262) between the two oil ports, a shuttle valve (261) is arranged between an output end of the shuttle valve (262) and an input oil port of the compressor motor (23), and an output oil port of the shuttle valve (261) acts on control oil ports of the pressure compensation valve (25), the pressure compensation valve (28) and the heat dissipation pump (35); the system maximum pressure is obtained through the shuttle valve (261) and the shuttle valve (262), and acts on a left end oil port of the pressure compensation valve (25) and an upper end oil port of the pressure compensation valve (28) respectively; the pressure oil output by the heat dissipation pump (35) acts on a right end oil port of the pressure compensation valve (25) and a lower end oil port of the pressure compensation valve (28) respectively, so that the flow distribution ratio of the heat dissipation motor (27) and the compressor motor (23) is unchanged.

2. The dual power excavator hydraulic system of claim 1, wherein: The light energy power supply system comprises a light collector (1) for collecting light sources, a solar cell group (2) for generating direct current, a current collecting device (3), a direct current stabilizing module (5), an energy storage device (6) and an inverter module (8) for outputting three-phase alternating current, the light collector (1) is connected with the current collecting device (3) through the solar cell group (2), the current collecting device (3) is also electrically connected with the direct current stabilizing module (5) through an LCL filter (4), one side of the direct current stabilizing module (5) is connected with an input port of the energy storage device (6), the energy storage device (6) is connected with a direct current bus (39) in parallel through a light energy contactor (7); an input end of the inverter module (8) is connected with the direct current bus (39) in parallel, and an output end of the inverter module (8) is connected with the motor (31).

3. The dual power excavator hydraulic system of claim 2, wherein: The electric power transmission system comprises an electric power integration module (9), a step-down power conversion module (11), a direct current contactor I (12), a rectifier-inverter module (13), a step-up power conversion module (15) and a capacitor group (16), the other side of the direct current voltage stabilizing module (5) is connected with the electric power integration module (9), the step-down power conversion module (11), the step-up power conversion module (15) and the capacitor group (16) are all connected in parallel with a direct current bus (39) on the rear side of the electric power integration module (9), the rectification side of the step-down power conversion module (11) is connected in parallel with the rectification side of the step-up power conversion module (15), the rectification side of the step-down power conversion module (11) is connected with the rectifier-inverter module (13) through the direct current contactor I (12), the rectification side of the step-up power conversion module (15) is connected with the rectifier-inverter module (13) through a direct current contactor (14), and the rectifier-inverter module (13) is connected with the variable frequency motor (24) through three-phase alternating current.

4. The dual power excavator hydraulic system of any of claims 1-3, wherein: The working system comprises a main valve (32), a main pump (36) and an engine (38), the engine (38) is coaxially connected with the main pump (36) through an engine clutch (37), the main pump (36) is also coaxially connected with a heat dissipation pump (35), an oil outlet of the main pump (36) is connected with an oil inlet of the main valve (32), and an oil outlet of the main valve (32) is connected with the hydraulic actuating element (30).

5. The dual power excavator hydraulic system of claim 4, wherein: The oil return system comprises a hydraulic oil tank (17), a radiator (18), a bypass valve (19) and a back pressure valve (20), an oil return port of the main valve (32) is connected with the hydraulic oil tank (17) through the back pressure valve (20) and the radiator (18), and the back pressure valve (20) and the radiator (18) are connected in series and then connected in parallel with the bypass valve (19).

6. A control method characterized by: The dual-power excavator hydraulic system comprises a fuel mode and an electric mode.

7. The control method according to claim 6, characterized in that: The control method of the fuel mode is: The engine clutch (37) is powered, the motor clutch (34) is powered off, so that the engine (38) is coaxially connected with the heat pump (35) and the main pump (36), and the main pump (36) and the heat pump (35) are provided with a motive power, the motor (31) is disconnected with the heat pump (35), the hydraulic oil output from the main pump (36) is transported to the hydraulic actuator (30) through the internal flow channel of the main valve (32) and the logic control; the back oil of the main valve (32) returns to the hydraulic oil tank (17) through the back pressure valve (20) and the radiator (18), or returns to the hydraulic oil tank (17) through the bypass valve (19); the heat pump (35) outputs the hydraulic oil and drives the compressor motor (23) and the heat motor (27) at the same time, the compressor motor (23) drives the compressor to work to carry out air conditioning refrigeration, the heat motor (27) is coaxially connected with the variable frequency motor (24), and the variable frequency motor (24) is connected with the fan (21) to drive the fan to rotate, so that the radiator (18) is cooled; the controller (33) changes the torque size and direction of the variable frequency motor (24) by outputting a control signal through the variable frequency control cabinet (10) according to the electric energy capacity on the direct current bus (39), so as to control whether the variable frequency motor (24) is in the electric state or the power generation state; When the electric energy on the direct current bus (39) does not meet the set value, the controller (33) sends a control signal to the variable frequency control cabinet (10), and the variable frequency control cabinet (10) changes the torque direction of the variable frequency motor (24) by using the DTC torque control algorithm through the drive circuit inside the variable frequency control cabinet (10), so that the variable frequency motor (24) is in the power generation state; When the electric energy on the direct current bus (39) is sufficient, the controller (33) sends a control signal to the variable frequency control cabinet (10), and the variable frequency control cabinet (10) changes the torque direction of the variable frequency motor (24) by using the DTC torque control algorithm through the drive circuit inside the variable frequency control cabinet (10), so that the variable frequency motor (24) is in the electric state.

8. The control method according to claim 6, characterized by: The control method of the electric mode is: The engine clutch (37) is de-energized, the motor clutch (34) is energized, so that the motor (31) is coaxially connected with the heat pump (35) and the main pump (36), and the main pump (36) and the heat pump (35) are provided with driving force, the engine (38) is disconnected with the main pump (36); the direct current converted from the light energy to the direct current bus (39) is inverted to alternating current by the inverter module (8) to supply the motor (31); the hydraulic oil output by the main pump (36) is delivered to the hydraulic actuator (30) through the internal flow channel of the main valve (32) and the logic control; the back oil of the main valve (32) returns to the hydraulic oil tank (17) through the back pressure valve (20) and the radiator (18), or returns to the hydraulic oil tank (17) through the bypass valve (19); the heat pump (35) outputs hydraulic oil while driving the compressor motor (23) and the heat dissipation motor (27), the compressor motor (23) drives the compressor to work to carry out air conditioning refrigeration, the heat dissipation motor (27) is coaxially connected with the variable frequency motor (24), and the variable frequency motor (24) is connected with the fan (21) to drive the fan (21) to rotate, so that the radiator (18) is cooled; the controller (33) changes the torque size and direction of the variable frequency motor (24) by outputting control signals through the variable frequency control cabinet (10) according to the electric energy capacity on the direct current bus (39), so as to control whether the variable frequency motor (24) is in the electric state or the power generation state; When the electric energy on the direct current bus (39) does not meet the set value, the controller (33) sends a control signal to the variable frequency control cabinet (10), and the variable frequency control cabinet (10) changes the torque direction of the variable frequency motor (24) to make it in the power generation state by using the DTC torque control algorithm of the drive circuit inside the variable frequency control cabinet (10); When the electric energy on the direct current bus (39) is sufficient, the controller (33) sends a control signal to the variable frequency control cabinet (10), and then changes the torque direction of the variable frequency motor (24) to make it in the electric state by using the DTC torque control algorithm of the drive circuit inside the variable frequency control cabinet (10).

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