Parallel pump group system for realizing flow disturbance-free switching

Abstract

The utility model relates to a kind of parallel pump group systems of realizing flow undisturbed switching, including water tank, at least two parallelly arranged variable frequency pumps and controller.The technical scheme of it is in at:the outlet pipeline of each variable frequency pump is all parallel to a independent minimum flow bypass circuit, minimum flow regulating valve is installed on the minimum flow bypass circuit and returns water tank;Pump outlet pipeline is also provided with outlet on-off valve.System is provided with pump outlet pressure sensor, main pipeline pressure sensor and other detection elements.Communication connection is established between controller and all sensors, the frequency converter of variable frequency pump, minimum flow regulating valve and outlet on-off valve, these actuators are controlled by cooperation, when executing pump group start-stop or switching process, first utilize minimum flow bypass circuit to realize pressure balance, then carry out flow undisturbed transfer, to effectively eliminate water hammer effect and cavitation phenomenon.

Description

Technical Field

[0001] This utility model relates to the field of industrial fluid transportation technology, and in particular to a parallel pump system that achieves seamless flow switching. Background Technology

[0002] In industrial fluid transport systems, parallel operation of multiple pumps is a common solution to meet variable flow rate requirements. However, when pump sets are started, stopped, switched, or subjected to pressure increases or decreases, traditional control methods often directly operate valves or pumps, leading to drastic fluctuations in system flow and pressure, and generating destructive "water hammer" phenomena. This not only impacts pumps, valves, and pipelines, shortening equipment lifespan, but also seriously threatens the continuity and stability of the production process.

[0003] To address these issues, existing technologies have attempted to adjust the speed of variable frequency pumps to balance the outlet pressure of the standby or standby pump with the main pipeline pressure before switching, aiming for a smooth flow transition. For example, some solutions propose using control algorithms in conjunction with the precise operation of the outlet switching valve to regulate flow. However, the success rate and reliability of these solutions are difficult to guarantee. The fundamental reason is that they primarily rely on optimizing the control algorithm based on the main pipeline structure, lacking a physical loop to provide a stable pressure environment for the switching process. The switching process is highly susceptible to real-time changes in pipeline characteristics (such as resistance variations), leading to decreased control accuracy and stability.

[0004] Currently, the minimum flow bypass loop in the system is functionally treated only as a passive, isolated safety redundancy. Its main design purpose is to prevent cavitation and excessive temperature rise of the medium inside the pump when it is running at low flow rates, thereby protecting the pump body. Unfortunately, in the existing control strategy, this bypass loop has not been actively and fully integrated into the flow-free switching process. Utility Model Content

[0005] The purpose of this invention is to provide a parallel pump system that enables seamless flow switching. Through innovative design of the system structure, the minimum flow bypass loop, which was originally only used for unit protection, is integrated with the pump and valve by the controller, providing a stable environment for seamless flow switching and thus overcoming the valve cavitation problem that cannot be avoided by traditional control methods.

[0006] To achieve the above objectives, this utility model provides a parallel pump system for seamless flow switching, comprising a water tank, at least two variable frequency pumps connected in parallel, and a main pipeline. The inlet of the variable frequency pump is connected to the bottom of the water tank via a suction pipe, and the outlet is connected to the inlet of the main pipeline via an outlet pipe. The return end of the main pipeline is connected to the top of the water tank.

[0007] Each of the variable frequency pumps has an independent minimum flow bypass circuit connected in parallel on its outlet pipe. Each minimum flow bypass circuit is equipped with a minimum flow regulating valve, and the end of the minimum flow bypass circuit is connected to the top of the water tank.

[0008] An outlet switch valve is also provided on the outlet pipeline, and the outlet switch valve is located after the connection point between the minimum flow bypass circuit and the outlet pipeline.

[0009] The parallel pump system also includes:

[0010] A pump outlet pressure sensor is used to detect the outlet pressure of each of the aforementioned variable frequency pumps;

[0011] A main pipeline pressure sensor is used to detect the pressure of the main pipeline; and,

[0012] The controller has its signal input terminal connected to the pump outlet pressure sensor and the main pipeline pressure sensor, and its control output terminal connected to the frequency converter of each variable frequency pump, the minimum flow regulating valve, and the outlet switch valve.

[0013] Optionally, the minimum flow regulating valve is an electrically operated regulating valve.

[0014] Optionally, the outlet switching valve is an electrically operated switching valve.

[0015] Optionally, a check valve is installed on the outlet pipeline of the variable frequency pump.

[0016] Optionally, a pump outlet flow sensor is installed on the outlet pipeline of the variable frequency pump.

[0017] Optionally, the pump outlet pressure sensor is located between the outlet of the strain frequency pump and the connection point of the minimum flow bypass circuit.

[0018] Optionally, the parallel pump system further includes a main pipeline flow sensor for detecting the flow rate of the main pipeline, the main pipeline flow sensor being communicatively connected to the signal input terminal of the controller.

[0019] Optionally, the controller is a PLC.

[0020] Optionally, the controller integrates a pressure proportional-integral-derivative (PID) control module and a total flow proportional-integral-derivative (PID) control module.

[0021] Optionally, it may also include a human-computer interaction interface, which is communicatively connected to the controller.

[0022] The parallel pump system for achieving seamless flow switching provided by this utility model has at least one of the following beneficial effects:

[0023] 1) The system structure has been innovated: by transforming the minimum flow bypass circuit from a passive protection unit into an active control channel, it can not only eliminate the cavitation damage of hydraulic impact on the electric valve plate, but also provide a controllable load for the pump during the start-up phase, so that the pump outlet pressure can rise steadily and smoothly, creating favorable conditions for the system's flow-free switching. It has achieved a deep integration of equipment protection and system control, and provided a brand-new solution for parallel pump group flow regulation to solve the problem of flow-free switching.

[0024] 2) Preventing water hammer and protecting equipment safety: When the target flow rate changes and pump sets need to be switched, the controller can intelligently execute a seamless flow rate switching process. This shortens the flow rate switching time, improves adjustment accuracy, effectively prevents fluid impact caused by pressure difference, significantly reduces mechanical stress on pumps, valves, and pipelines, and extends equipment service life.

[0025] 3) Improve the level of system automation and intelligence: The system can respond to changes in flow demand, intelligently select and execute seamless switching processes such as "single to single" and "single to double (multiple)", reducing the dependence on the experience of operators and laying a solid foundation for realizing unmanned operation and intelligent maintenance of pumping stations.

[0026] 4) Improved system energy efficiency and reliability: The seamless flow switching process avoids drastic fluctuations in flow and pressure, reducing system operating energy consumption. Simultaneously, the independent bypass circuit design provides precise, individualized protection for each pump, preventing cavitation and temperature rise, thus improving the overall system reliability and stability. Attached Figure Description

[0027] Those skilled in the art will understand that the accompanying drawings are provided to better understand the present invention and do not constitute any limitation on the scope of the present invention. Wherein:

[0028] Figure 1 A schematic diagram of a parallel pump group system for achieving seamless flow switching according to an embodiment of the present invention;

[0029] Figure 2 A control flowchart for single-pump switching is provided in one embodiment of this utility model;

[0030] Figure 3 A control flowchart for reducing pump size is provided in one embodiment of this utility model;

[0031] Figure 4 The control flowchart of the booster pump provided in one embodiment of this utility model is shown.

[0032] The attached figures are labeled as follows:

[0033] 1-Water tank; 2-Original variable frequency pump; 3-Target variable frequency pump; 4-Outlet pipe of original variable frequency pump; 5-Outlet pipe of target variable frequency pump; 6-PLC; 7-Main pipe; 8-Minimum flow bypass circuit of original variable frequency pump; 9-Minimum flow regulating valve of original variable frequency pump; 10-Minimum flow bypass circuit of target variable frequency pump; 11-Minimum flow regulating valve of target variable frequency pump; 12-Pressure sensor of original variable frequency pump; 13-Pressure sensor of target variable frequency pump; 14-Load; 15 16 - Inlet valve of the original variable frequency pump; 17 - Inlet valve of the target variable frequency pump; 18 - Pump outlet flow sensor of the original variable frequency pump; 19 - Pump outlet flow sensor of the target variable frequency pump; 20 - Outlet switch valve of the original variable frequency pump; 21 - Outlet switch valve of the target variable frequency pump; 22 - Main pipeline pressure sensor; 23 - Main pipeline flow sensor; 24 - Check valve of the original variable frequency pump; 25 - Check valve of the target variable frequency pump; 26 - Inverter of the original variable frequency pump; 27 - Inverter of the target variable frequency pump. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this utility model. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0036] In the description of this utility model, it should be understood that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this utility model and to simplify the description, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0037] Furthermore, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or apparatus that includes said element. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] This utility model embodiment provides a parallel pump group system for achieving seamless flow switching, including a water tank, at least two variable frequency pumps connected in parallel, and a main pipeline. The inlet of the variable frequency pump is connected to the bottom of the water tank through a suction pipe, and the outlet is connected to the inlet of the main pipeline through an outlet pipe. The return end of the main pipeline is connected to the top of the water tank.

[0039] Each variable frequency pump has an independent minimum flow bypass circuit connected in parallel on its outlet pipe. Each minimum flow bypass circuit is equipped with a minimum flow regulating valve, and the end of the minimum flow bypass circuit is connected to the top of the water tank.

[0040] An outlet switch valve is also installed on the outlet pipeline, which is located after the connection point between the minimum flow bypass circuit and the outlet pipeline.

[0041] The parallel pump system also includes:

[0042] Pump outlet pressure sensor, used to detect the outlet pressure of each variable frequency pump;

[0043] A main pipeline pressure sensor is used to detect the pressure in the main pipeline; and,

[0044] The controller's signal input terminal is connected to the pump outlet pressure sensor and the main pipeline pressure sensor, and its control output terminal is connected to the frequency converter, minimum flow regulating valve, and outlet switch valve of each variable frequency pump.

[0045] This embodiment, through innovative hardware design, upgrades the minimum flow bypass circuit from a passive protection unit to an active control channel, providing a stable pressure environment and a controllable flow path for seamless flow switching, thereby effectively eliminating the risks of fluid impact and cavitation during valve opening and closing.

[0046] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Figure 1 As shown, the inlet of the variable frequency pump (including variable frequency pump 2 and target variable frequency pump 3) is connected to the bottom of water tank 1 through a suction pipe, and the outlet is connected to the inlet of main pipeline 7 through an outlet pipe (including outlet pipe 4 of the original variable frequency pump 2 and outlet pipe 5 of the target variable frequency pump). The return end of main pipeline 7 is connected to the top of water tank 1, forming the main circulation loop. The suction pipe of the variable frequency pump is equipped with a pump inlet valve (including inlet valve 15 of the original variable frequency pump 2 and inlet valve 16 of the target variable frequency pump 3).

[0047] To achieve independent protection and control channels, each variable frequency pump has an independent minimum flow bypass circuit connected in parallel on its outlet pipeline (including the minimum flow bypass circuit 8 of the original variable frequency pump 2 and the minimum flow bypass circuit 10 of the target variable frequency pump 3). Each minimum flow bypass circuit is equipped with a minimum flow regulating valve (including the minimum flow regulating valve 9 of the original variable frequency pump 2 and the minimum flow regulating valve 11 of the target variable frequency pump 3), and the end of the minimum flow bypass circuit is connected to the top of the water tank 1.

[0048] To provide control basis, the system is equipped with pump outlet pressure sensors (including pump outlet pressure sensor 12 of the original variable frequency pump 2 and pump outlet pressure sensor 13 of the target variable frequency pump 3) and main pipeline pressure sensor 21, which are used to detect the outlet pressure of each variable frequency pump and the pressure of the main pipeline 7. The main pipeline 7 is equipped with a load 14.

[0049] Preferably, the controller 6 is a PLC, whose signal input terminal is communicatively connected to the pump outlet pressure sensor and the main pipeline pressure sensor 21, and its control output terminal is communicatively connected to the frequency converters of each variable frequency pump (including the frequency converter 25 of the original variable frequency pump 2 and the frequency converter 26 of the target variable frequency pump 3), the minimum flow regulating valve, and the outlet switching valve). The PLC stores a control program for achieving bumpless flow switching and integrates a pressure proportional-integral-derivative (PID) control module and a total flow proportional-integral-derivative (PID) control module. The pressure PID control module is used for precise pressure regulation of a single pump, and the total flow PID control module is used for stable control of the total flow when multiple pumps are operating in coordination.

[0050] Preferably, the outlet switch valve (including the outlet switch valve 19 of the original variable frequency pump 2 and the outlet switch valve 20 of the target variable frequency pump 3) is an electric switch valve, which accepts the switch command of the PLC to realize the remote automatic control of the valve.

[0051] Preferably, the minimum flow regulating valve is an electric regulating valve so that the PLC can accurately and continuously control its opening degree to achieve fine regulation of the flow rate.

[0052] Preferably, a check valve (including the check valve 23 of the original variable frequency pump 2 and the check valve 24 of the target variable frequency pump 3) is installed on the outlet pipeline of the variable frequency pump. The check valve is located before the outlet switch valve and is used to prevent fluid backflow from impacting the pump body.

[0053] Preferably, an outlet flow sensor (including the outlet flow sensor 17 of the original variable frequency pump 2 and the outlet flow sensor 18 of the target variable frequency pump 3) is installed on the outlet pipeline of the variable frequency pump. This is used to detect the real-time flow of a single pump. In this embodiment, the outlet pressure sensor is located between the outlet of the corresponding variable frequency pump and the connection point of the minimum flow bypass circuit to accurately measure the actual outlet pressure of the pump.

[0054] The parallel pump system also includes a main pipeline flow sensor 22 for detecting the flow rate of the main pipeline. The main pipeline flow sensor 22 is communicatively connected to the signal input terminal of the controller 6 and is used to provide feedback signals for the total flow control mode.

[0055] Preferably, the parallel pump system also includes a human-machine interface (HMI), which is communicatively connected to the controller 6. The HMI is used to receive user-inputted set values ​​such as flow rate and pressure, and to display the status of various system parameters in real time.

[0056] The working principle and control process of this utility model are as follows:

[0057] The PLC stores a control program for achieving seamless flow switching, which corresponds to... Figure 2 , Figure 3 and Figure 4 The flow-free switching process is shown.

[0058] First, combined Figure 2 The single-pump switching process from the original variable frequency pump 2 to the target variable frequency pump 3 is explained below:

[0059] S101: Command Acceptance and System Preset. Based on the flow rate value input by the user on the HMI, the PLC program determines that it has entered the single-pump switching working mode and issues the command "Start target variable frequency pump 3, stop the original variable frequency pump 2". It controls the outlet switch valve 20 of the target variable frequency pump 3 to remain closed and opens the minimum flow regulating valve 11 of the target variable frequency pump 3.

[0060] S102: Pressure equalization control. Start the target variable frequency pump 3. The PLC collects the values ​​of the outlet pressure sensor 13 and the main pipeline pressure sensor 21 of the target variable frequency pump 3, and adjusts the speed of the target variable frequency pump 3 through the pressure PID control module so that its outlet pressure rises steadily to equalize with the pressure of the main pipeline.

[0061] S103: Seamless Grid Connection and Control Transfer. When the pressure equalization condition is met (e.g., pressure difference < 0.05 MPa for 1 second), the PLC opens the outlet switch valve 20 of the target variable frequency pump 3 (while keeping its minimum flow regulating valve 11 open). Subsequently, the PLC exits the pressure PID control mode of the target variable frequency pump 3 and switches to the total flow PID control mode with feedback from the main pipeline flow sensor 22. This module calculates the total frequency requirement, and the PLC decomposes this requirement according to preset logic, simultaneously reducing the speed of the original variable frequency pump 2 and increasing the speed of the target variable frequency pump 3 to achieve a smooth flow transfer.

[0062] S104: Original pump shutdown and circuit closure. When the flow rate of the original variable frequency pump 2 falls below its minimum safe flow threshold, its outlet switch valve 19 is closed, and the original variable frequency pump 2 is stopped. The PLC exits the total flow PID mode and switches back to the pressure PID mode of the target variable frequency pump 3. After the speed of the target variable frequency pump 3 stabilizes, its minimum flow regulating valve is closed. Switching complete.

[0063] Combination Figure 3 When the flow demand decreases, the control process for switching from dual-pump operation to single-pump (i.e., pump reduction) operation is as follows:

[0064] S201: Instruction Received: Based on the flow rate value input by the user on the HMI, the PLC program determines that it is entering the dual-pump to single-pump working mode, and the PLC issues the instruction "Stop the original variable frequency pump 2, retain the target variable frequency pump 3".

[0065] S202: Seamless flow switching. The PLC enters the total flow PID control mode, which ensures the stability of the total system flow. This PID module calculates the total frequency requirement based on the flow demand. According to the preset allocation logic, the PLC synchronously reduces the speed of the target variable frequency pump 3 while increasing the speed of the original variable frequency pump 2, ensuring that the sum of the output flow of the two pumps always meets the user's needs.

[0066] S203: Low flow rate judgment. When the flow rate of the original variable frequency pump 2 is lower than its set minimum safe flow rate threshold (e.g., the original flow rate is less than 5%), the PLC closes the outlet switch valve 19 of the original variable frequency pump 2 and stops the original variable frequency pump 2.

[0067] S204: Control mode switching. After the PLC exits the total flow PID control mode and switches to the pressure PID control mode of the target variable frequency pump 3, the system switches to variable frequency operation by the target variable frequency pump 3 according to the flow demand. The switching is now complete.

[0068] Combination Figure 4 When the system flow increases, the control process for switching from single-pump operation to dual-pump operation is as follows:

[0069] S301: Command Acceptance and System Preset. Based on the flow rate value input by the user on the HMI, the PLC program determines that it needs to enter the single-pump to dual-pump working mode. The PLC issues the command "Start the target variable frequency pump 3 to run in parallel with the original variable frequency pump 2". The PLC ensures that the outlet switch valve 20 of the target variable frequency pump 3 is in the closed state and opens its minimum flow regulating valve 11.

[0070] S302: Pressure Equalization Control. The target variable frequency pump 3 is started. The PLC collects and compares its outlet pressure with the main pipeline pressure in real time, and adjusts the speed of the target variable frequency pump 3 through the pressure PID control module to ensure that the outlet pressure of the target variable frequency pump 3 rises smoothly to equalize with the main pipeline pressure. When the pressure equalization condition is met (e.g., pressure difference < 0.05 MPa for 1 second), the PLC opens the outlet switch valve 20 of the target variable frequency pump 3, while keeping the minimum flow regulating valve 11 of the target variable frequency pump 3 closed.

[0071] S303: Flow Distribution and Coordinated Operation. The PLC switches the control mode from the pressure PID control mode of the target variable frequency pump 3 to the system total flow PID control mode. The total flow PID module uses the user's flow demand as the set value and the measured value of the main pipeline flow sensor 22 (22) as feedback. Based on the flow error, it calculates the total frequency demand of the system. The PLC closes the minimum flow regulating valve 11 of the target variable frequency pump 3. At the same time, according to the preset distribution logic, the total frequency demand is decomposed into independent speed commands, and the speeds of the original variable frequency pump 2 and the target variable frequency pump 3 are adjusted synchronously. At this time, the outlet pipelines of the target variable frequency pump 3 and the original variable frequency pump 2 share the total flow demand. Thus, the two pumps operate synchronously according to the flow demand under the coordination of the total flow PID.

[0072] It should be noted that although the above embodiments illustrate the specific implementation of this utility model using two pumps as an example, the flow rate seamless switching method of this utility model has universal applicability. The system and control method of this utility model are also applicable to systems containing more than two parallel variable frequency pump sets. The original variable frequency pump 2 and the target variable frequency pump 3 are broadly interpreted as any one or more pumps in the currently operating pump set and any one or more pumps in the pump set to be put into or taken out. The PLC can manage the input and output processes of any number of pumps in the system according to the aforementioned same flow rate seamless switching process. For example, in a three-pump parallel system, the process of adding a variable frequency pump to seamlessly switch from two-pump operation to three-pump operation involves using the third pump as the target variable frequency pump 3 and completely following the... Figure 4 The control flow shown is as follows; conversely, the same applies to reducing the operation of the variable frequency pump.

[0073] Furthermore, it should be specifically noted that the scope of protection of this utility model is strictly limited to the hardware shape, structure, and combination of the parallel pump system. Although the accompanying drawings show the programmable logic controller (PLC) and its connection with sensors and actuators, and the existence of this controller is the basis for realizing intelligent control of the system, the technical innovation of this utility model lies in:

[0074] 1) Innovative layout of physical structure: In particular, the system structure that integrates the originally isolated minimum flow bypass loop into an active control channel through specific pipeline connections and valve configurations;

[0075] 2) Specific connection relationships in hardware structure: that is, the specific physical connection architecture established between hardware components such as sensors, controllers, frequency converters, and valves through circuits and signal lines.

[0076] The inventive point of this utility model lies in the physical structure of the aforementioned static, physical product. The "multiple PID control function blocks" shown in the figures are merely illustrative of existing hardware modules or firmware within the programmable logic controller capable of implementing corresponding control functions, and are themselves prior art. This utility model does not claim protection for any improvements to the control program, software algorithm, or method itself. Any method for implementing fluid transport control based on the hardware system structure disclosed in this utility model, using different program logic, may fall within the protection scope of this utility model.

[0077] In summary, the parallel pump system for achieving seamless flow switching provided by this utility model innovates the minimum flow bypass circuit from a passive protection unit to an active control channel. This not only eliminates the cavitation damage to the electric valve plate caused by hydraulic impact, but also provides a controllable load for the pump during the start-up phase, enabling the pump outlet pressure to rise steadily and smoothly, thus creating favorable conditions for seamless flow switching of the system.

[0078] The above description is merely a description of a preferred embodiment of the present utility model and is not intended to limit the scope of the present utility model in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the present utility model. Obviously, those skilled in the art can make various modifications and variations to the present utility model without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the present utility model and its equivalents, the present utility model also intends to include these modifications and variations.

Claims

1. A parallel pump system for achieving seamless flow switching, comprising a water tank, at least two variable frequency pumps connected in parallel, and a main pipeline, wherein the inlet of the variable frequency pump is connected to the bottom of the water tank via a suction pipe, the outlet of the pump is connected to the inlet of the main pipeline via an outlet pipe, and the return end of the main pipeline is connected to the top of the water tank, characterized in that: Each of the variable frequency pumps has an independent minimum flow bypass circuit connected in parallel on its outlet pipe. Each minimum flow bypass circuit is equipped with a minimum flow regulating valve, and the end of the minimum flow bypass circuit is connected to the top of the water tank. An outlet switch valve is also provided on the outlet pipeline, and the outlet switch valve is located after the connection point between the minimum flow bypass circuit and the outlet pipeline. The parallel pump system also includes: A pump outlet pressure sensor is used to detect the outlet pressure of each of the aforementioned variable frequency pumps; A main pipeline pressure sensor is used to detect the pressure in the main pipeline; and, The controller has its signal input terminal connected to the pump outlet pressure sensor and the main pipeline pressure sensor, and its control output terminal connected to the frequency converter of each variable frequency pump, the minimum flow regulating valve, and the outlet switch valve.

2. The parallel pump group system for achieving seamless flow switching according to claim 1, characterized in that, The minimum flow regulating valve is an electric regulating valve.

3. The parallel pump group system for achieving seamless flow switching according to claim 1, characterized in that, The outlet switch valve is an electric switch valve.

4. The parallel pump group system for achieving seamless flow switching according to claim 1, characterized in that, A check valve is installed on the outlet pipeline of the variable frequency pump.

5. The parallel pump group system for achieving seamless flow switching according to claim 1, characterized in that, The outlet flow sensor of the variable frequency pump is installed on the outlet pipeline.

6. The parallel pump group system for achieving seamless flow switching according to claim 5, characterized in that, The pump outlet pressure sensor is located between the outlet of the strain frequency pump and the connection point of the minimum flow bypass circuit.

7. The parallel pump group system for achieving seamless flow switching according to claim 1, characterized in that, The parallel pump system also includes a main pipeline flow sensor for detecting the flow rate of the main pipeline, which is communicatively connected to the signal input terminal of the controller.

8. The parallel pump group system for achieving seamless flow switching according to claim 1, characterized in that, The controller is a PLC.

9. The parallel pump group system for achieving seamless flow switching according to claim 8, characterized in that, The controller integrates a pressure proportional-integral-derivative (PID) control module and a total flow proportional-integral-derivative (PID) control module.

10. The parallel pump group system for achieving seamless flow switching according to claim 1, characterized in that, It also includes a human-computer interaction interface, which is communicatively connected to the controller.

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