Variable-frequency water pump control method for dual-combined heat supply pump unit and heat pump system

Abstract

The invention relates to a variable-frequency water pump control method for a dual-combined heat supply pump unit and a heat pump system. Comprising the steps that S1-S2, a lift-flow performance curve and a flow-power performance curve corresponding to each rotating speed of the variable frequency water pump are obtained; s3, according to the number of the started user end devices, the water flow needed by the two-combined heat supply pump unit is determined; s4, the rotating speed of the variable frequency water pump is adjusted, the current power is calculated, and the real-time flow at the current rotating speed is obtained according to the flow-power characteristic curve; s5, the rotating speed of the variable-frequency water pump is adjusted to enable the real-time flow to meet the required water flow, and the real-time lift of the variable-frequency water pump is detected in real time; s6, the real-time flow, the rotating speed of the variable frequency water pump and the real-time lift are substituted into the lift-flow performance curve, and whether the real-time lift meets the theoretical lift or not is checked; s7, if yes, executing according to the current rotating speed; and if not, the steps S4 to S6 are executed, and the rotating speed of the variable-frequency water pump is adjusted again until the real-time flow and the real-time lift both meet the requirements. The stability and the energy efficiency of the heat pump unit are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pump systems, and more specifically, to a variable frequency water pump control method for a dual-energy heat pump unit and a heat pump system. Background Art

[0002] The traditional integrated two-way heat pump system has cooling and heating functions, and its main equipment includes compressors, finned heat exchangers, shell-and-tube heat exchangers, water pumps, etc. Most manufacturers of existing domestic integrated two-way heat pump systems use fixed-frequency water pumps. In the early stage of design, they calculate the rated flow rate based on the rated capacity of the system and configure a relatively load-adapted fixed-frequency water pump. However, the current service and development targets of the water pump industry tend to be user water supply, large equipment water supply, chemical water supply, etc., and models specifically designed for heat pumps are in the minority. Therefore, in the design of heat pumps, it is inevitable that the load is large and the energy efficiency is poor; the load is small and the head and flow are insufficient, and the optimal solution cannot be achieved.

[0003] During the operation of the unit, the fixed-frequency water pump has been running at the rated / fixed frequency, and the energy efficiency is also very poor. In the actual user scenario, the flow rate of the pipeline often changes greatly due to the start and stop of the fixed-frequency water pump, resulting in water hammer sound in the water system, affecting the user experience. Among the few manufacturers that use variable-frequency water pumps, the required flow rate is generally determined by real-time monitoring of the cooling / heat required by the system, thereby controlling the speed of the water pump. There is a lack of calculation and matching for the flow rate and head required by the system at this time. In addition, there is a general lack of judgment on the minimum head and minimum flow rate, and the reliability, stability and energy efficiency of the unit need to be improved. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art, such as the lack of judgment on the minimum head and the minimum flow rate, and the low reliability, stability and energy efficiency of the unit, and to provide a variable frequency water pump control method and a heat pump system for a dual-energy heat pump unit, which effectively improves the stability and energy efficiency of the heat pump unit.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: A variable frequency water pump control method for a combined heat pump unit is provided, comprising the following steps: S1. Obtain the head-flow performance curve corresponding to each speed of the variable frequency water pump; S2. Obtain the flow-power performance curve corresponding to each speed of the variable frequency water pump; S3. Determine the required water flow rate of the dual heat pump unit according to the number of user terminal devices turned on; S4. Adjust the speed of the variable frequency water pump, detect the current and voltage values, calculate the current power, and obtain the real-time flow rate at the current speed based on the flow-power characteristic curve; S5. Adjust the speed of the variable frequency water pump so that the real-time flow rate meets the required water flow rate, and detect the real-time head of the variable frequency water pump in real time; S6. Substitute the real-time flow rate, speed of the variable frequency water pump and real-time head when the water flow rate required by the dual-generation heat pump unit is met into the head-flow performance curve to check whether the real-time head meets the theoretical head; S7. If satisfied, execute according to the current speed; if not satisfied, execute steps S4 to S6, readjust the speed of the variable frequency water pump until the real-time flow and real-time head meet the requirements.

[0006] A variable frequency water pump control method for a dual-energy heat pump unit of the present invention can accurately control the current working state of the variable frequency water pump through the power-flow characteristic curve and the head-flow characteristic curve of the variable frequency water pump without adding redundant detection equipment. The system water flow rate is obtained by using the current, voltage, and power-flow curve relationship. The system water flow rate demand is based on the actual end-use situation of the user, and supply is fundamentally achieved on demand, so as to maximize energy efficiency and improve the stability of the entire system. Preferably, in step S3, the required water flow is greater than or equal to the minimum water flow of the combined heat pump unit. Based on the frequency conversion range of the variable frequency water pump, the present invention makes a mandatory protection measure for the minimum flow of the unit.

[0007] Preferably, the rated water flow is calculated according to the rated capacity of the dual heat pump unit, and the minimum water flow is set according to the rated water flow. Preferably, 60% of the rated water flow is set as the minimum water flow Q min The frequency corresponding to the minimum water flow is the minimum flow speed of the unit.

[0008] Preferably, when the number of user terminal devices turned on is n=1, the terminal rated water flow Q is compared. 末 And the minimum water flow Q of the unit min The size of Q 末 ≥Q min , then maintain the current speed; if Q 末 <Q min , then increase the speed of the variable frequency water pump and obtain the real-time flow rate Q of the variable frequency water pump in real time 实 , until the real-time flow Q 实 Equal to the rated water flow Q at the end 末 When the current speed is maintained, the real-time head q is compared. 时 and the size of the theoretical head H1, if q 时 ≥H1, then maintain the current speed; if q 时 时 ≥H1.

[0009] ​Preferably, when the number of user terminal devices turned on is n=2, the terminal rated water flow Q is compared. 末 And the minimum water flow Q of the unit min The size of 末 ≥Q min , then maintain the current speed; if 2Q 末 <Q min , then increase the speed of the variable frequency water pump and obtain the real-time flow rate Q of the variable frequency water pump in real time 实 , until the real-time flow Q 实 =2Q 末 When the current speed is maintained, the real-time head q is compared. 时 and the size of the theoretical head H2, if q 时 ≥H2, then maintain the current speed; if q 时 <H2, then increase the speed of the variable frequency water pump until q 时 ≥H2.

[0010] Preferably, when the number of user terminal devices turned on is n=3, the terminal rated water flow Q is compared. 末 And the minimum water flow Q of the unit min size; if 3Q 末 ≥Q min , then maintain the current speed; if 3Q 末 <Q min , then increase the speed of the variable frequency water pump and obtain the real-time flow rate Q of the variable frequency water pump in real time 实 , until the real-time flow Q 实 =3Q 末 When the current speed is maintained, the real-time head q is compared. 时 and the size of the theoretical head H3, if q 时 ≥H3, then maintain the current speed; if q 时 <H3, then increase the speed of the variable frequency water pump until q 时 ≥H3.

[0011] Preferably, in step S1, the head-flow characteristic curve corresponding to each speed is obtained according to the data provided by the variable frequency water pump manufacturer or by testing; in step S2, the flow-power characteristic curve corresponding to each speed is obtained according to the data provided by the variable frequency water pump manufacturer or by testing.

[0012] Preferably, the current operating power of the variable frequency water pump is calculated by detecting the current and voltage of the variable frequency water pump, and then the current real-time water flow rate of the variable frequency water pump is obtained based on the real-time speed of the variable frequency water pump and the flow-power characteristic curve at the current speed; a pressure gauge is set at the water outlet of the unit to obtain the real-time head of the water pump.

[0013] The present invention also provides a combined heat pump system, comprising a heat pump unit, a variable frequency water pump connected to the water inlet end of the heat pump unit, a plurality of terminal devices connected to the water outlet end of the heat pump unit and arranged in parallel, a water tank connecting the variable frequency water pump and the terminal devices, a detection unit arranged in the water path for detecting water flow or pipeline pressure, and a controller communicatively connected to the variable frequency water pump and the detection unit, wherein the controller executes the variable frequency water pump control method of the combined heat pump unit described above.

[0014] Compared with the prior art, the present invention has the following beneficial effects: A variable frequency water pump control method for a dual-generation heat pump unit of the present invention can accurately control the current working state of the variable frequency water pump through the power-flow characteristic curve and the head-flow characteristic curve of the variable frequency water pump, without adding redundant detection equipment, and obtain the system water flow by using the current, voltage, and power-flow curve relationship; the system water flow demand is fundamentally based on the user's actual end-use situation, so as to maximize energy efficiency and improve the stability of the entire system; with respect to the frequency conversion range of the variable frequency water pump and the minimum flow of the unit, emphasized protection measures are particularly made, and through the flow feedback / flow meter real-time monitoring of the variable frequency water pump, the effect of removing the water flow switch can be achieved, thereby reducing costs and improving quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The present invention is a flow chart of a variable frequency water pump control method for a combined heat pump unit.

[0016] Figure 2 This is a schematic diagram of the system structure of Example 3.

[0017] In the attached drawings: 10, heat pump unit; 20, variable frequency water pump; 30, terminal equipment; 40, water tank; 50, detection unit. DETAILED DESCRIPTION

[0018] The present invention is further described below in conjunction with specific implementation methods. The accompanying drawings are only used for exemplary descriptions and are only schematic diagrams, not actual drawings, and cannot be understood as limiting this patent; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the accompanying drawings may be omitted.

[0019] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limitations on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0020] Embodiment 1 This embodiment is a first embodiment of a variable frequency water pump control method for a dual heat pump unit. Figure 1 As shown, the following steps are included: S1. Obtain the head-flow performance curve corresponding to each speed of the variable frequency water pump; S2. Obtain the flow-power performance curve corresponding to each speed of the variable frequency water pump; S3. Determine the required water flow rate of the dual heat pump unit according to the number of user terminal devices turned on; S4. Adjust the speed of the variable frequency water pump, detect the current and voltage values, calculate the current power, and obtain the real-time flow rate at the current speed based on the flow-power characteristic curve; S5. Adjust the speed of the variable frequency water pump so that the real-time flow rate meets the required water flow rate, and detect the real-time head of the variable frequency water pump in real time; S6. Substitute the real-time flow rate, speed of the variable frequency water pump and real-time head when the water flow rate required by the dual-generation heat pump unit is met into the head-flow performance curve to check whether the real-time head meets the theoretical head; S7. If satisfied, execute according to the current speed; if not satisfied, execute steps S4 to S6, readjust the speed of the variable frequency water pump until the real-time flow and real-time head meet the requirements.

[0021] In step S1, the head-flow characteristic curve corresponding to each speed is obtained according to the data provided by the variable frequency water pump manufacturer or by testing; in step S2, the flow-power characteristic curve corresponding to each speed is obtained according to the data provided by the variable frequency water pump manufacturer or by testing. The performance curve of the variable frequency water pump is generally the performance curve of the maximum speed specified in the specification, and the speed is automatically adjusted according to the system requirements. At this time, the characteristic curve moves up (preferably not more than 6%) and down (preferably not more than 40%) in parallel. The head-flow performance curve and flow-power characteristic curve corresponding to each speed can be obtained according to the manufacturer's data or tests.

[0022] In step S3, the required water flow rate is greater than or equal to the minimum water flow rate of the combined heat pump unit. Based on the frequency conversion range of the variable frequency water pump, the present invention has made mandatory protection measures for the minimum flow rate of the unit. According to the rated capacity of the combined heat pump unit, the rated water flow rate is calculated, and the minimum water flow rate is set according to the rated water flow rate. In this embodiment, 60% of the rated water flow rate is set as the minimum water flow rate Q min The frequency corresponding to the minimum water flow is the minimum flow speed of the unit.

[0023] In this embodiment, when the number of user terminal devices turned on is n=1, the terminal rated water flow Q is compared. 末 And the minimum water flow Q of the unit min The size of Q 末 ≥Q min , then maintain the current speed; if Q 末 <Q min , then increase the speed of the variable frequency water pump and obtain the real-time flow rate Q of the variable frequency water pump in real time 实 , until the real-time flow Q 实 Equal to the rated water flow Q at the end 末 When the current speed is maintained, the real-time head q is compared. 时 and the size of the theoretical head H1, if q 时 ≥H1, then maintain the current speed; if q 时 时 ≥H1.

[0024] When the number of user terminal devices turned on is n=2, compare the rated water flow Q at the terminal 末 And the minimum water flow Q of the unit min The size of 末 ≥Q min , then maintain the current speed; if 2Q 末 <Q min , then increase the speed of the variable frequency water pump and obtain the real-time flow rate Q of the variable frequency water pump in real time 实 , until the real-time flow Q 实 =2Q 末 When the current speed is maintained, the real-time head q is compared. 时 and the size of the theoretical head H2, if q 时 ≥H2, then maintain the current speed; if q 时 <H2, then increase the speed of the variable frequency water pump until q 时 ≥H2.

[0025] When the number of user terminal devices turned on is n=3, compare the rated water flow Q at the terminal 末 And the minimum water flow Q of the unit min size; if 3Q 末 ​≥Q min , then maintain the current speed; if 3Q 末 <Q min , then increase the speed of the variable frequency water pump and obtain the real-time flow rate Q of the variable frequency water pump in real time 实 , until the real-time flow Q 实 =3Q 末 When the current speed is maintained, the real-time head q is compared. 时 and the size of the theoretical head H3, if q 时 ≥H3, then maintain the current speed; if q 时 <H3, then increase the speed of the variable frequency water pump until q 时 ≥H3.

[0026] In this embodiment, the current and voltage of the variable frequency water pump are detected to calculate the current operating power of the variable frequency water pump, and then the current real-time water flow rate of the variable frequency water pump is obtained based on the real-time speed of the variable frequency water pump and the flow-power characteristic curve at the current speed; a pressure gauge is set at the water outlet of the unit to obtain the real-time head of the water pump.

[0027] A variable frequency water pump control method for a dual-energy heat pump unit in this embodiment can accurately control the current working state of the variable frequency water pump through the power-flow characteristic curve and the head-flow characteristic curve of the variable frequency water pump without adding redundant detection equipment. The system water flow rate is obtained by using the current, voltage, and power-flow curve relationship. The system water flow rate demand is based on the actual end-use situation of the user, and supply is fundamentally achieved on demand, so as to maximize energy efficiency and improve the stability of the entire system. Embodiment 2 This embodiment is a second embodiment of a variable frequency water pump control method for a dual heat pump unit. This embodiment is similar to the first embodiment and includes the following steps: Step 1: The unit is running and the variable frequency water pump is started.

[0028] Step 2: Start the water pump, slowly increase the frequency for 1 minute, and detect the real-time power p of the variable frequency water pump 时 , when the real-time speed is r, the real-time flow rate Q is obtained 时 , after 1 minute, the real-time flow of the unit reaches the minimum flow of the unit Q min , at this time the speed is the minimum flow speed r of the unit min : If the real-time flow rate of the unit Q = Q min (±0.1m 3 / h), and run stably at the minimum flow platform of the unit for 15s If the real-time flow rate of the unit Q> or <Q min (±0.1m 3 / h), and test again after 15s; if the conditions are not met three times, a water flow switch fault will be reported, and the machine will be shut down for troubleshooting.

[0029] Step 3: The unit runs stably at minimum flow for 15 seconds.

[0030] Step 4: Check the number of user terminal devices turned on: When the number of user terminal devices turned on is n=1, compare the rated water flow Q at the terminal 末 And the minimum water flow Q of the unit min size; If Q 末 ≥Q min , then keep the current speed; If Q 末 <Q min , then increase the speed of the variable frequency water pump and obtain the real-time flow rate Q of the variable frequency water pump in real time 实 , until the real-time flow Q 实 Equal to the rated water flow Q at the end 末 When the current speed is maintained; Then compare the real-time head q 时 The size of the theoretical head H1: If q 时 ≥H1, then maintain the current speed; If q 时 时 ≥H1.

[0031] When the number of user terminal devices turned on is n=2, compare the rated water flow Q at the terminal 末 And the minimum water flow Q of the unit min size; If 2Q 末 ≥Q min , then keep the current speed; If 2Q 末 <Q min , then increase the speed of the variable frequency water pump and obtain the real-time flow rate Q of the variable frequency water pump in real time 实 , until the real-time flow Q 实 =2Q 末 When the current speed is maintained; Then compare the real-time head q 时 The size of the theoretical head H2: If q 时 ≥H2, then maintain the current speed; If q 时 <H2, then increase the speed of the variable frequency water pump until q 时 ≥H2.

[0032] ​When the number of user terminal devices turned on is n=3, compare the rated water flow Q at the terminal 末 And the minimum water flow Q of the unit min size; If 3Q 末 ≥Q min , then keep the current speed; If 3Q 末 <Q min , then increase the speed of the variable frequency water pump and obtain the real-time flow rate Q of the variable frequency water pump in real time 实 , until the real-time flow Q 实 =3Q 末 When the current speed is maintained; Then compare the real-time head q 时 The size of the theoretical head H3: If q 时 ≥H3, the current speed is maintained; If q 时 <H3, then increase the speed of the variable frequency water pump until q 时 ≥H3.

[0033] Based on the first embodiment, this embodiment adds a starting platform to perform unit fault diagnosis at the early stage of the variable frequency water pump start-up to avoid inaccurate subsequent control due to unit equipment failure, thereby further improving system stability.

[0034] Embodiment 3 This embodiment is an embodiment of a dual heat pump system. Figure 2 As shown, it includes a heat pump unit 10, a variable frequency water pump 20 connected to the water inlet end of the heat pump unit 10, a plurality of terminal devices 30 connected to the water outlet end of the heat pump unit 10 and arranged in parallel, a water tank 40 connecting the variable frequency water pump 20 and the terminal device 30, a detection unit 50 arranged in the water path for detecting water flow or pipeline pressure, and a controller communicatively connected to the variable frequency water pump 20 and the detection unit 50, wherein the controller executes the control method of the variable frequency water pump 20 of the dual-energy heat pump unit 10 described in Example 1 or Example 2.

[0035] In this embodiment, the detection unit 50 includes a pressure gauge and a flow meter.

[0036] In the specific contents of the above-mentioned specific implementation methods, the various technical features can be combined in any non-contradictory manner. In order to make the description concise, not all possible combinations of the above-mentioned technical features are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0037] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A variable frequency water pump control method for a dual heat pump unit, characterized in that: The following steps are involved: S1. Obtain the head-flow performance curve corresponding to each speed of the variable frequency water pump; S2. Obtain the flow-power performance curve corresponding to each speed of the variable frequency water pump; S3. Determine the required water flow rate of the dual heat pump unit according to the number of user terminal devices turned on; S4. Adjust the speed of the variable frequency water pump, detect the current and voltage values, calculate the current power, and obtain the real-time flow rate at the current speed based on the flow-power characteristic curve; S5. Adjust the speed of the variable frequency water pump so that the real-time flow rate meets the required water flow rate, and detect the real-time head of the variable frequency water pump in real time; S6. Substitute the real-time flow rate, speed of the variable frequency water pump and real-time head when the water flow rate required by the dual-generation heat pump unit is met into the head-flow performance curve to check whether the real-time head meets the theoretical head; S7. If satisfied, execute according to the current speed; if not satisfied, execute steps S4 to S6, readjust the speed of the variable frequency water pump until the real-time flow and real-time head meet the requirements.

2. The variable frequency water pump control method for a dual heat pump unit according to claim 1, characterized in that: In step S3, the required water flow rate is greater than or equal to the minimum water flow rate of the combined heat pump unit.

3. The variable frequency water pump control method for a dual heat pump unit according to claim 2, characterized in that: According to the rated capacity of the combined heat pump unit, the rated water flow is calculated, and the minimum water flow is set according to the rated water flow.

4. The variable frequency water pump control method for a dual heat pump unit according to claim 3, characterized in that: When the number of user terminal devices turned on is n=1, compare the rated water flow Q at the terminal 末 And the minimum water flow Q of the unit min The size of Q 末 ≥Q min , then maintain the current speed; if Q 末 <Q min , then increase the speed of the variable frequency water pump and obtain the real-time flow rate Q of the variable frequency water pump in real time 实 , until the real-time flow Q 实 Equal to the rated water flow Q at the end 末 When the current speed is maintained, the real-time head q is compared. 时 and the size of the theoretical head H1, if q 时 ≥H1, then maintain the current speed; if q 时 时 ≥H1.​ 5. The variable frequency water pump control method for a dual heat pump unit according to claim 3, characterized in that: When the number of user terminal devices turned on is n=2, compare the rated water flow Q at the terminal 末 And the minimum water flow Q of the unit min The size of 末 ≥Q min , then maintain the current speed; if 2Q 末 <Q min , then increase the speed of the variable frequency water pump and obtain the real-time flow rate Q of the variable frequency water pump in real time 实 , until the real-time flow Q 实 =2Q 末 When the current speed is maintained, the real-time head q is compared. 时 and the size of the theoretical head H2, if q 时 ≥H2, then maintain the current speed; if q 时 <H2, then increase the speed of the variable frequency water pump until q 时 ≥H2.

6. The variable frequency water pump control method for a dual heat pump unit according to claim 3, characterized in that: When the number of user terminal devices turned on is n=3, compare the rated water flow Q at the terminal 末 And the minimum water flow Q of the unit min size; if 3Q 末 ≥Q min , then maintain the current speed; if 3Q 末 <Q min , then increase the speed of the variable frequency water pump and obtain the real-time flow rate Q of the variable frequency water pump in real time 实 , until the real-time flow Q 实 =3Q 末 When the current speed is maintained, the real-time head q is compared. 时 and the size of the theoretical head H3, if q 时 ≥H3, then maintain the current speed; if q 时 <H3, then increase the speed of the variable frequency water pump until q 时 ≥H3.

7. The variable frequency water pump control method for a dual heat pump unit according to any one of claims 3 to 6, characterized in that: Set 60% of the rated water flow as the minimum water flow Q min .

8. The variable frequency water pump control method for a dual heat pump unit according to any one of claims 3 to 6, characterized in that: In step S1, the head-flow characteristic curve corresponding to each speed is obtained according to the data provided by the variable frequency water pump manufacturer or by testing; in step S2, the flow-power characteristic curve corresponding to each speed is obtained according to the data provided by the variable frequency water pump manufacturer or by testing.

9. The variable frequency water pump control method of the dual heat pump unit according to claim 8, characterized in that: By detecting the current and voltage of the variable frequency water pump, the current operating power of the variable frequency water pump is calculated, and then according to the real-time speed of the variable frequency water pump and the flow-power characteristic curve at the current speed, the current real-time water flow of the variable frequency water pump is obtained; A pressure gauge is installed at the water outlet of the unit to obtain the real-time head of the variable frequency water pump.

10. A dual heat pump system, comprising a heat pump unit, a variable frequency water pump connected to the water inlet of the heat pump unit, a plurality of terminal devices connected to the water outlet of the heat pump unit and arranged in parallel, a water tank connecting the variable frequency water pump and the terminal devices, a detection unit arranged in a water channel for detecting water flow or pipeline pressure, and a controller connected to the variable frequency water pump and the detection unit, characterized in that: The controller executes the variable frequency water pump control method for a combined heat pump unit according to any one of claims 1 to 9.

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