Pumping-back structure and control method thereof

Abstract

The invention discloses a pumpback structure and a control method thereof. The pumpback structure comprises a liquid storage tank, a circulating pump, a pumpback pump and a controller, the circulating pump is connected between the liquid storage tank and the liquid inlet of the load; the pumpback pump is connected between the liquid storage tank and the liquid outlet of the load; a first liquid level sensor is arranged in the liquid storage tank and used for collecting first liquid level data in the liquid storage tank; the controller is in communication connection with the first liquid level sensor and the pumpback pump and used for adjusting the working frequency of the pumpback pump according to the first liquid level data so that the liquid level of the liquid storage tank can be maintained within the first preset liquid level range. According to the pumpback structure provided by the embodiment of the invention, the liquid level fluctuation caused by follow lag and performance difference between pumps is eliminated, the long-term stability of the liquid level in the motor is ensured, and liquid shortage or liquid overflow is effectively prevented; and on the other hand, the frequency of the pumpback pump can be dynamically adjusted according to actual requirements, waste caused by continuous high-energy-consumption operation of the pumpback pump under the existing non-overflow working condition is avoided, and the energy efficiency of the system is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of fluid transport technology, and in particular to a retraction structure and its control method. Background Technology

[0002] There are two operating conditions for liquid-cooled motor cooling (limited to single-inlet and single-outlet loads). One is the motor without overflow. This condition has lower requirements. It is only necessary to increase the frequency of the return pump to ensure that the liquid is pumped out faster than the liquid is injected. In order to ensure that there is no overflow, the return pump will operate at a higher frequency value in this condition. Often, the return pump has excessive return capacity, which will result in energy waste.

[0003] Another operating condition is the need for liquid level control. This condition requires the liquid level inside the motor to be maintained within a certain range. If liquid level control is required, the return pump can only follow the frequency of the liquid cooler injection pump. This results in a certain lag in the response of the return pump. Moreover, the injection pump and return pump are often of different brands and models, and the differences in their frequency following result in large fluctuations, making it difficult to maintain a stable liquid level. Long-term operation may lead to insufficient liquid or liquid overflow.

[0004] In addition, some motors have poor air permeability (similar to closed motors). When the return pump directly draws liquid from inside the motor, it will create negative pressure inside the motor and in the liquid cooler's injection pipeline, resulting in unstable liquid injection flow and pressure in the liquid cooler. The flow deviation can reach 15%-40% of the target value, and may even cause cavitation damage to components. Summary of the Invention

[0005] This invention provides a back-pull structure and its control method. By adjusting the back-pull pump frequency through the liquid level in the storage tank, the energy consumption of the back-pull system is reduced while ensuring that the motor does not overflow. This solves the problems of unstable liquid level caused by the lag in response and performance difference of the back-pull pump, and the easy occurrence of liquid shortage or overflow during long-term operation.

[0006] In a first aspect, embodiments of the present invention provide a backflow structure, including a storage tank, a circulation pump, a backflow pump, and a controller; the circulation pump is connected between the storage tank and the inlet of the load, and is used to drive liquid to flow from the storage tank to the load; the backflow pump is connected between the storage tank and the outlet of the load, and is used to drive liquid to flow from the load to the storage tank; a first liquid level sensor is provided in the storage tank, and is used to collect first liquid level data in the storage tank; the controller is communicatively connected to the first liquid level sensor and the backflow pump, and is used to adjust the operating frequency of the backflow pump according to the first liquid level data, so that the liquid level in the storage tank is maintained within a first preset liquid level range.

[0007] Optionally, the controller is also used to output an alarm signal when the liquid level in the storage tank is lower than the minimum value of a first preset liquid level range.

[0008] Optionally, the retraction structure also includes a transition liquid tank; the top of the transition liquid tank is provided with an inlet, which is connected to the outlet of the load; the outlet of the transition liquid tank is connected to the retraction pump to receive the gravity-flow liquid of the load.

[0009] Optionally, a second liquid level sensor is provided in the transition liquid tank to collect the second liquid level data in the transition liquid tank; the controller is also connected in communication with the second liquid level sensor to adjust the operating frequency of the return pump according to the second liquid level data so that the liquid level in the transition liquid tank is maintained within the second preset liquid level range.

[0010] Optionally, the controller is also used to output an alarm signal when the liquid level in the storage tank is higher than the maximum value of a first preset liquid level range.

[0011] Optionally, a three-way valve is also included, which is connected to the outlet of the transition liquid tank, the outlet of the load, and the return pump, respectively, for switching the flow direction of the liquid path; the controller is used to control the on / off state of the three-way valve to switch the liquid path connection mode; the controller includes a storage tank mode and a transition tank mode; in the storage tank mode, the controller controls the three-way valve to connect the passage between the outlet of the load and the inlet of the return pump, and to disconnect the passage between the outlet of the transition liquid tank and the inlet of the return pump; in the transition tank mode, the controller controls the three-way valve to disconnect the passage between the outlet of the load and the inlet of the return pump, and to connect the passage between the outlet of the transition liquid tank and the inlet of the return pump.

[0012] Optionally, the volume of the transition tank is 10%-15% of the system flow rate.

[0013] Optionally, the frequency adjustment range of the back pump is 22-50Hz.

[0014] In a second aspect, embodiments of the present invention also provide a pullback structure control method, which applies a pullback structure as described in any of the first aspects, the pullback structure control method comprising: Obtain the target liquid level to calculate the first preset liquid level range; The liquid level in the storage tank is maintained within the first preset range by adjusting the operating frequency of the return pump.

[0015] Optionally, the return structure also includes a transition tank and a three-way valve. The three-way valve is connected to the outlet of the transition tank, the outlet of the load, and the return pump, respectively, for switching the flow direction of the liquid path. The controller is also used to control the on / off state of the three-way valve to switch the liquid path connection mode. The controller includes a storage tank mode and a transition tank mode. In the storage tank mode, the controller controls the three-way valve to connect the passage between the outlet of the load and the inlet of the return pump, and to disconnect the passage between the outlet of the transition tank and the inlet of the return pump. In the transition tank mode, the controller controls the three-way valve to disconnect the passage between the outlet of the load and the inlet of the return pump, and to connect the passage between the outlet of the transition tank and the inlet of the return pump. Before setting the target liquid level, it also includes: Select the control mode, which includes reservoir mode and transition tank mode; Obtain the target liquid level to calculate the first preset liquid level range, including: In the liquid storage tank mode, the target liquid level of the liquid storage tank is obtained to calculate the first preset liquid level range; In the transition tank mode, the target liquid level of the transition tank is obtained to calculate the second preset liquid level range; Maintaining the liquid level in the storage tank within a first preset range by adjusting the operating frequency of the return pump includes: In the storage tank mode, the liquid level in the storage tank is maintained within the first preset liquid level range by adjusting the operating frequency of the return pump; In the transition tank mode, the liquid level in the transition tank is maintained within the second preset liquid level range by adjusting the operating frequency of the return pump.

[0016] This invention provides a retraction structure and its control method. The retraction structure includes a storage tank, a circulation pump, a retraction pump, and a controller. The circulation pump is connected between the storage tank and the inlet of the load. The retraction pump is connected between the storage tank and the outlet of the load. A first liquid level sensor is installed in the storage tank to collect first liquid level data. The controller is communicatively connected to both the first liquid level sensor and the retraction pump, and is used to adjust the operating frequency of the retraction pump according to the first liquid level data to maintain the liquid level in the storage tank within a first preset liquid level range. This invention provides a retraction structure that controls the retraction pump frequency based on the liquid level in the storage tank, thereby transforming the problem of internal motor liquid level control into liquid level control of the storage tank. This system achieves decoupled operation of the return pump and the circulation pump, fundamentally eliminating liquid level fluctuations caused by pump lag and performance differences, ensuring long-term stability of the liquid level inside the motor, and effectively preventing liquid shortage or overflow. On the other hand, the return pump can dynamically adjust its frequency according to actual needs, avoiding the waste of continuous high-energy operation of the return pump under the existing "no overflow condition", and significantly improving the system's energy efficiency. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a retraction structure provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a generator cooling system provided in an embodiment of the present invention; Figure 3 A flowchart illustrating a retraction structure control method provided in an embodiment of the present invention; Figure 4 This is a flowchart illustrating another method for controlling a pullback structure provided in an embodiment of the present invention. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0020] Figure 1 This is a schematic diagram of a retraction structure provided in an embodiment of the present invention, for reference. Figure 1 The present invention provides a back-pull structure, including a liquid storage tank 10, a circulation pump 21, a back-pull pump 22, and a controller 30.

[0021] The circulating pump 21 is connected between the liquid storage tank and the liquid inlet of the load 40, and is used to drive the liquid to flow from the liquid storage tank 10 to the load 40.

[0022] The return pump 22 is connected between the liquid storage tank 10 and the liquid outlet of the load 40, and is used to drive the liquid to flow from the load 40 to the liquid storage tank 10.

[0023] A first liquid level sensor 11 is installed inside the liquid storage tank 10 to collect the first liquid level data inside the liquid storage tank 10.

[0024] The controller 30 is communicatively connected to the first liquid level sensor 11 and the return pump 22, and is used to adjust the operating frequency of the return pump 22 according to the first liquid level data so that the liquid level of the storage tank 10 is maintained within the first preset liquid level range.

[0025] Specifically, the return pump 22 is connected between the storage tank 10 and the load 40, forming a liquid return path; the first liquid level sensor 11 continuously collects the first liquid level data in the storage tank 10 and sends it to the controller 30; the controller 30 compares the received real-time liquid level data with the preset liquid level; wherein, the first preset liquid level range is the upper and lower limits of the preset liquid level in the storage tank. When the liquid level is within the first preset liquid level range, if the liquid level is higher than the preset liquid level, the operating frequency of the return pump 22 is reduced to reduce the return flow; if the liquid level is lower than the preset liquid level, its operating frequency is increased to increase the return flow; through this closed-loop feedback control, the system automatically stabilizes the liquid level in the storage tank within the preset range, thereby maintaining the system's liquid supply balance and preventing the storage tank from overflowing or running out of liquid.

[0026] This invention provides a backflow structure, including a storage tank, a circulation pump, a backflow pump, and a controller. The circulation pump is connected between the storage tank and the inlet of the load. The backflow pump is connected between the storage tank and the outlet of the load. A first liquid level sensor is installed inside the storage tank to collect first liquid level data. The controller is communicatively connected to both the first liquid level sensor and the backflow pump, and is used to adjust the operating frequency of the backflow pump according to the first liquid level data to maintain the liquid level in the storage tank within a first preset liquid level range. This invention provides a backflow structure that controls the backflow pump frequency based on the liquid level in the storage tank, thereby transforming the problem of internal motor liquid level control into liquid level control of the storage tank. This system achieves decoupled operation of the return pump and the circulation pump, fundamentally eliminating liquid level fluctuations caused by pump lag and performance differences, ensuring long-term stability of the liquid level inside the motor, and effectively preventing liquid shortage or overflow. On the other hand, the return pump can dynamically adjust its frequency according to actual needs, avoiding the waste of continuous high-energy operation of the return pump under the existing "no overflow condition", and significantly improving the system's energy efficiency.

[0027] In one specific embodiment, the retraction structure is used in new energy vehicle motor test benches, open-loop large hydraulic stations, or high-power-density generator cooling systems. Figure 2 This is a schematic diagram of a generator cooling system provided in an embodiment of the present invention, for reference. Figure 2When the backflow structure is applied to the motor cooling system, the liquid storage tank 10 also integrates a heat exchange module 12 (such as a shell-and-tube heat exchanger or a plate heat exchanger) and is coupled to the main circulation pipeline of the cooling system. In this scenario, the liquid storage tank 10 not only serves as a buffer and recovery unit for the cooling medium, but its internal heat exchange module 12 also drives the liquid in the tank to flow through the heat exchanger 24 to exchange heat with an external cold source (such as cooling water) to cool down when the temperature of the returned coolant is too high. When the system is cold-started or the temperature is too low, the heating pipe 25 provides auxiliary heating to the coolant so that the liquid in the liquid storage tank 10 can quickly reach the optimal operating temperature.

[0028] In an optional embodiment, the controller 30 is also configured to output an alarm signal when the liquid level in the storage tank 10 is lower than the minimum value of a first preset liquid level range.

[0029] Specifically, the controller 30 continuously monitors the liquid level data collected by the first liquid level sensor 11; when it is determined that the liquid level of the storage tank 10 is lower than the minimum value of the first preset liquid level range (i.e., reaching the low level alarm threshold), the controller 30 outputs an alarm signal through its I / O interface or communication port to prompt the operator to check and handle the abnormality of the back pumping control in a timely manner, thereby preventing the load from overflowing.

[0030] Continue to refer to Figure 2 In an optional embodiment, the backflow structure further includes a transition liquid tank 50; the top of the transition liquid tank 50 is provided with a liquid inlet, which is connected to the liquid outlet of the load 40; the liquid outlet of the transition liquid tank 50 is connected to the backflow pump 22 to receive the gravity-flow liquid of the load 40.

[0031] Specifically, the transition liquid tank 50 is connected to the outlet of the load 40 through its top inlet to directly receive the liquid from the load that flows by gravity. The outlet of the transition liquid tank 50 is connected to the inlet of the return pump 20. When the liquid flowing out of the load (gravity-flowing liquid) enters the transition liquid tank, it can be temporarily stored in the tank and form a stable liquid level, so that the return pump can stably draw liquid from the bottom of the tank and pump it back to the main storage tank 10. This solves the problem of cavitation or air intake of the return pump 22 caused by fluctuations in the load's liquid output or intermittent gravity flow, and improves the reliability of the return pump system.

[0032] Continue to refer to Figure 2 In an optional embodiment, a second liquid level sensor 51 is provided in the transition liquid tank 50 to collect second liquid level data in the transition liquid tank 50; the controller 30 is also communicatively connected to the second liquid level sensor 51 to adjust the operating frequency of the return pump 22 according to the second liquid level data so that the liquid level in the transition liquid tank 50 is maintained within the second preset liquid level range.

[0033] Specifically, the second liquid level sensor 51 installed in the transition liquid tank 50 continuously collects the second liquid level data inside and sends it to the controller 30. The controller 30 compares this data with a second preset liquid level, where the second preset liquid level range is the upper and lower limits of the preset liquid level in the transition liquid tank. When the liquid level is within the second preset liquid level range, if the liquid level is higher than the second preset liquid level, the controller increases the operating frequency of the return pump 20 to accelerate the pumping speed from the transition liquid tank to prevent overflow; if the liquid level is lower than the second preset liquid level, the controller decreases the pump operating frequency to slow down the pumping speed to avoid pump cavitation, thereby ensuring the stability of the return pump inlet conditions and improving the adaptability and operational reliability of the entire return system to different load discharge conditions.

[0034] In an optional embodiment, the controller 30 is also configured to output an alarm signal when the liquid level in the storage tank 10 is higher than the maximum value of a first preset liquid level range.

[0035] Specifically, when the controller 30 continuously monitors the data of the first liquid level sensor 11, if it determines that the liquid level of the storage tank 10 is higher than the maximum value of the first preset liquid level range (i.e., reaching the high level alarm threshold), the controller 30 outputs an alarm signal through its I / O interface or communication port to indicate that the back pumping control is abnormal and timely investigation and intervention are required to prevent the transition tank from overflowing.

[0036] Continue to refer to Figure 2 In an optional embodiment, the backflow structure further includes a three-way valve 60, which is connected to the outlet of the transition liquid tank 50, the outlet of the load 40, and the backflow pump 22, respectively, for switching the flow direction of the liquid path; the controller 30 is used to control the on / off state of the three-way valve 60 to switch the liquid path connection mode; the controller 30 includes a storage tank mode and a transition tank mode.

[0037] In the storage tank mode, the controller 30 controls the three-way valve 60 to connect the passage between the outlet of the load 40 and the inlet of the return pump 22, and disconnects the passage between the outlet of the transition tank 50 and the inlet of the return pump 22.

[0038] In the transition tank mode, the controller 30 controls the three-way valve 60 to disconnect the passage between the outlet of the load 40 and the inlet of the return pump 22, and connect the passage between the outlet of the transition tank 50 and the inlet of the return pump 22.

[0039] Specifically, the three ports of the three-way valve 60 are connected to the outlet of the load 40, the outlet of the transition tank 50, and the inlet of the return pump 22, respectively. The controller 30 selects the operating mode and controls the three-way valve according to preset conditions or external commands: In the storage tank mode, the controller controls the three-way valve to switch to the first state, connecting the outlet of the load 40 with the inlet of the return pump 22, while simultaneously disconnecting the connection between the outlet of the transition tank and the pump. The liquid is directly pumped back to the storage tank by the load. That is, a cycle of load → return pump → storage tank. In the transition tank mode, the controller controls the three-way valve to switch to the second state, disconnecting the direct connection between the load and the pump, and instead connecting the outlet of the transition tank 50 with the inlet of the return pump 22. The liquid flowing out of the load first enters the transition tank for buffering, and then is stably pumped back to the storage tank by the return pump. That is, a cycle of load → transition tank → return pump → storage tank.

[0040] It should be noted that the liquid storage tank mode is suitable for traditional loads with good air permeability, while the transition tank mode is suitable for various types of open loads.

[0041] In an optional embodiment, the volume of the transition tank 50 is 10%-15% of the system flow rate.

[0042] Specifically, the volume of the transition tank 50 is designed to be 10%-15% of the system flow rate. This 10%-15% ratio effectively smooths out typical fluctuations in the load output. Simultaneously, it provides a buffer time of several seconds to tens of seconds for the return pump 22, preventing the pump from becoming unstable due to sudden changes in flow rate.

[0043] In an optional embodiment, the frequency modulation range of the back pump 22 is 22-50Hz.

[0044] Specifically, the frequency adjustment range of the back pump 22 is 22-50Hz; the controller 30 dynamically adjusts the pump speed within the frequency range of 22-50Hz based on the feedback signals from the first liquid level sensor 11 and / or the second liquid level sensor 51, thereby precisely controlling the back pump flow rate and stabilizing the liquid levels of the storage tank and / or transition tank within their respective preset ranges.

[0045] Figure 3 This is a flowchart illustrating a retraction structure control method provided in an embodiment of the present invention. The present invention also provides a retraction structure control method, see reference... Figure 3 The method includes: S110. Obtain the target liquid level to calculate the first preset liquid level range.

[0046] The target liquid level can be understood as the desired liquid level in the storage tank that needs to be maintained.

[0047] Specifically, the controller 30 obtains the target liquid level manually set by the user through the human-machine interface, or calls the default value of the target liquid level pre-stored within it; at the same time, the controller also pre-stores the deviation liquid level, which can be adjusted according to the system's flow fluctuation characteristics, control accuracy requirements, or the safety margin of the storage tank; by combining the target liquid level and the deviation liquid level, a first preset liquid level range can be generated and determined: [target liquid level - deviation liquid level, target liquid level + deviation liquid level]. This range is used as the reference interval for subsequent liquid level control.

[0048] S120. The liquid level in the storage tank is maintained within the first preset liquid level range by adjusting the operating frequency of the return pump.

[0049] Specifically, the controller 30 compares the received real-time liquid level data with the preset liquid level; if the liquid level is higher than the preset liquid level within the first preset liquid level range, the operating frequency of the return pump 22 is reduced to reduce the return flow; if the liquid level is lower than the preset liquid level, its operating frequency is increased to increase the return flow. Through this closed-loop feedback control, the system automatically stabilizes the liquid level of the storage tank within the preset range, thereby maintaining the system's liquid supply balance and preventing the storage tank from overflowing or running out of liquid.

[0050] Figure 4 This is a flowchart illustrating another method for controlling a pullback structure provided in an embodiment of the present invention.

[0051] In the above embodiment, the backflow structure further includes a transition liquid tank 50 and a three-way valve 60. The three-way valve 60 is connected to the outlet of the transition liquid tank 50, the outlet of the load 40, and the backflow pump 22, respectively, for switching the liquid flow direction. The controller 30 controls the on / off state of the three-way valve 60 to switch the liquid flow connection mode. The controller 30 includes a storage tank mode and a transition tank mode. In the storage tank mode, the controller 30 controls the three-way valve 60 to connect the passage between the outlet of the load 40 and the inlet of the backflow pump 22, and disconnects the passage between the outlet of the transition liquid tank 50 and the inlet of the backflow pump 22. In the transition tank mode, the controller 30 controls the three-way valve 60 to disconnect the passage between the outlet of the load 40 and the inlet of the backflow pump 22, and connects the passage between the outlet of the transition liquid tank 50 and the inlet of the backflow pump 22.

[0052] Before "S110, Obtain the target liquid level to calculate the first preset liquid level range", the following is also included: Select the control mode; the control modes include the reservoir mode and the transition tank mode. Furthermore, "S110. Obtain the target liquid level to calculate the first preset liquid level range" can be further refined as follows: In the storage tank mode, obtain the target liquid level of the storage tank; In the transition tank mode, obtain the target liquid level of the transition tank; Meanwhile, "S120, by adjusting the operating frequency of the return pump to maintain the liquid level in the storage tank within the first preset liquid level range" can be further specified as follows: In the storage tank mode, the liquid level in the storage tank is maintained within the first preset liquid level range by adjusting the operating frequency of the return pump; In the transition tank mode, the liquid level in the transition tank is maintained within the second preset liquid level range by adjusting the operating frequency of the return pump.

[0053] like Figure 4 As shown, the process includes the following steps: S210, Select control mode.

[0054] The control modes include a storage tank mode and a transition tank mode. The storage tank mode can be understood as the working mode in which the return pump is directly adjusted according to the liquid level in the storage tank, which is suitable for working conditions where the load discharge is stable and the pressure is sufficient. The transition tank mode can be understood as the working mode in which the return pump is adjusted according to the liquid level in the transition tank, and the load discharge first enters the transition tank for buffering, which is suitable for working conditions where the load discharge is intermittent or low-pressure gravity flow.

[0055] Specifically, the controller 30 selects between the storage tank mode and the transition tank mode based on preset conditions (such as load type and liquid output characteristic parameters) or received external mode switching instructions, and controls the three-way valve 60 to switch to the corresponding liquid circuit connection state accordingly.

[0056] S221. In the liquid storage tank mode, obtain the target liquid level of the liquid storage tank to calculate the first preset liquid level range.

[0057] Specifically, in the storage tank mode, the controller 30 obtains the target liquid level manually set by the user through the human-machine interface, or calls the default value of the target liquid level pre-stored internally; at the same time, the controller also pre-stores the deviation liquid level, which can be adjusted according to the system's flow fluctuation characteristics, control accuracy requirements, or the storage tank's safety margin; by combining the target liquid level and the deviation liquid level, the first preset liquid level range can be generated and determined as [target liquid level - deviation liquid level, target liquid level + deviation liquid level]. For example, refer to... Figure 2 The storage tank 10 is equipped with a first liquid level sensor 11, which is used to continuously collect the first liquid level data in the storage tank 10. This real-time data is the real-time liquid level of the storage tank compared with a preset target for closed-loop control.

[0058] S222. In the transition tank mode, obtain the target liquid level of the transition liquid tank to calculate the second preset liquid level range.

[0059] Specifically, in the transition tank mode, the controller 30 uses the same logic as in step S221 to acquire or set the target liquid level and corresponding deviation liquid level of the transition liquid tank, thereby calculating and generating a second preset liquid level range [target liquid level - deviation liquid level, target liquid level + deviation liquid level]. For example, refer to... Figure 2 A second liquid level sensor 51 is installed in the transition liquid tank 50 to continuously collect the second liquid level data in the transition liquid tank 50. This real-time data is the real-time liquid level of the transition liquid tank used for closed-loop control of the transition tank mode.

[0060] S231. In the liquid storage tank mode, the liquid level in the liquid storage tank is maintained within the first preset liquid level range by adjusting the operating frequency of the return pump.

[0061] Specifically, the return pump 22 is connected between the storage tank 10 and the load 40, forming a liquid return path; the first liquid level sensor 11 continuously collects the first liquid level data in the storage tank 10 and sends it to the controller 30; the controller 30 compares the received real-time liquid level data with the preset liquid level; wherein, the first preset liquid level range is the upper and lower limits of the preset liquid level in the storage tank. When the liquid level is within the first preset liquid level range, if the liquid level is higher than the preset liquid level, the operating frequency of the return pump 22 is reduced to reduce the return flow; if the liquid level is lower than the preset liquid level, its operating frequency is increased to increase the return flow; through this closed-loop feedback control, the system automatically stabilizes the liquid level in the storage tank within the preset range, thereby maintaining the system's liquid supply balance and preventing the storage tank from overflowing or running out of liquid.

[0062] S232. In the transition tank mode, the liquid level in the transition tank is maintained within the second preset liquid level range by adjusting the operating frequency of the return pump.

[0063] Specifically, the second liquid level sensor 51 installed in the transition liquid tank 50 continuously collects the second liquid level data inside and sends it to the controller 30. The controller 30 compares this data with a second preset liquid level, where the second preset liquid level range is the upper and lower limits of the preset liquid level in the transition liquid tank. When the liquid level is within the second preset liquid level range, if the liquid level is higher than the second preset liquid level, the controller increases the operating frequency of the return pump 20 to accelerate the pumping speed from the transition liquid tank to prevent overflow; if the liquid level is lower than the second preset liquid level, the controller decreases the pump operating frequency to slow down the pumping speed to avoid pump cavitation, thereby ensuring the stability of the return pump inlet conditions and improving the adaptability and operational reliability of the entire return system to different load discharge conditions.

[0064] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A retraction structure, characterized in that, Includes a storage tank, circulation pump, return pump, and controller; The circulating pump is connected between the liquid storage tank and the inlet of the load, and is used to drive the liquid to flow from the liquid storage tank to the load; The backflow pump is connected between the liquid storage tank and the liquid outlet of the load, and is used to drive the liquid to flow from the load to the liquid storage tank; The liquid storage tank is equipped with a first liquid level sensor for collecting the first liquid level data in the liquid storage tank; The controller is communicatively connected to the first liquid level sensor and the return pump, and is used to adjust the operating frequency of the return pump according to the first liquid level data so that the liquid level in the storage tank is maintained within a first preset liquid level range.

2. The retraction structure according to claim 1, characterized in that, The controller is also used to output an alarm signal when the liquid level in the storage tank is lower than the minimum value of the first preset liquid level range.

3. The retraction structure according to claim 1, characterized in that, The retraction structure also includes a transition liquid tank; The transition liquid tank is provided with an inlet at the top, which is connected to the outlet of the load; the outlet of the transition liquid tank is connected to the return pump to receive the gravity-flow liquid from the load.

4. The retraction structure according to claim 3, characterized in that, The transition liquid tank is equipped with a second liquid level sensor for collecting the second liquid level data in the transition liquid tank; The controller is also communicatively connected to the second liquid level sensor and is used to adjust the operating frequency of the return pump according to the second liquid level data so that the liquid level of the transition tank is maintained within the second preset liquid level range.

5. The retraction structure according to claim 4, characterized in that, The controller is also used to output an alarm signal when the liquid level in the storage tank is higher than the maximum value of the first preset liquid level range.

6. The retraction structure according to claim 3, characterized in that, It also includes a three-way valve, which is connected to the outlet of the transition liquid tank, the outlet of the load and the return pump respectively, for switching the liquid flow direction; The controller is also used to control the on / off state of the three-way valve to switch the liquid circuit connection mode; The controller includes a liquid storage tank mode and a transition tank mode; In the storage tank mode, the controller controls the three-way valve to connect the passage between the outlet of the load and the inlet of the return pump, and to disconnect the passage between the outlet of the transition tank and the inlet of the return pump. In the transition tank mode, the controller controls the three-way valve to disconnect the passage between the outlet of the load and the inlet of the return pump, and connect the passage between the outlet of the transition tank and the inlet of the return pump.

7. The retraction structure according to claim 3, characterized in that, The volume of the transition liquid tank is 10%-15% of the system flow rate.

8. The retraction structure according to claim 1, characterized in that, The frequency adjustment range of the back pump is 22-50Hz.

9. A method for controlling a pullback structure, characterized in that, The application executes the pullback structure as described in any one of claims 1-8, wherein the pullback structure control method comprises: Obtain the target liquid level to calculate the first preset liquid level range; The liquid level in the storage tank is maintained within the first preset range by adjusting the operating frequency of the return pump.

10. The retraction structure control method according to claim 9, characterized in that, The described backflow structure also includes a transition liquid tank and a three-way valve. The three-way valve is connected to the outlet of the transition liquid tank, the outlet of the load, and the backflow pump, respectively, for switching the liquid flow direction. The controller is also used to control the on / off state of the three-way valve to switch the liquid flow connection mode. The controller includes a storage tank mode and a transition tank mode. In the storage tank mode, the controller controls the three-way valve to connect the passage between the outlet of the load and the inlet of the backflow pump, and to disconnect the passage between the outlet of the transition liquid tank and the inlet of the backflow pump. In the transition tank mode, the controller controls the three-way valve to disconnect the passage between the outlet of the load and the inlet of the backflow pump, and to connect the passage between the outlet of the transition liquid tank and the inlet of the backflow pump. Before setting the target liquid level, the following is also included: Select a control mode, which includes a liquid storage tank mode and a transition tank mode; Obtain the target liquid level to calculate the first preset liquid level range, including: In the liquid storage tank mode, the target liquid level of the liquid storage tank is obtained to calculate the first preset liquid level range; In the transition tank mode, the target liquid level of the transition tank is obtained to calculate the second preset liquid level range; Maintaining the liquid level in the storage tank within a first preset range by adjusting the operating frequency of the return pump includes: In the storage tank mode, the liquid level in the storage tank is maintained within the first preset liquid level range by adjusting the operating frequency of the return pump; In the transition tank mode, the liquid level in the transition tank is maintained within the second preset liquid level range by adjusting the operating frequency of the return pump.

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