Water pump operation control method under low-flow working condition, water pump control device and water pump

Abstract

The water pump operation control method under the low-flow working condition comprises the steps that water pump flow data are obtained in real time, when the water pump flow is smaller than a flow reference value, low-flow control is triggered, and in the low-flow control process, the motor rotating speed RPM1 of a water pump in a low-flow using interval is obtained; after running for first set time T1 in the low-flow use interval, controlling the rotating speed of the motor to be reduced to RPM2; during the running period of the motor rotating speed RPM2, if the flow change rate Qst of the water pump is larger than the flow change rate threshold value Qm, it is judged that the use requirement of a user under the low-flow working condition exists, the motor rotating speed is controlled to return to RPM1, and a low-flow use state S1 is started; otherwise, after the motor rotating speed RPM2 is maintained to run for a second set time T2, the motor rotating speed is controlled to be reduced to RPM3, and a low-flow energy-saving state S2 is entered. The low-flow working condition use requirement of the user can be effectively judged, and energy consumption is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor control, and particularly relates to a water pump operation control technology under low-flow conditions. Background Art

[0002] The head-flow characteristic curve of a water pump refers to the mutual relationship curve between two key parameters, namely, the head (H) and the flow rate (Q), during the operation of the water pump, which can intuitively reflect the performance of the water pump under different working conditions. The flow rate Q and the head H may have a linear relationship of the first order, a quadratic parabola relationship, or a more complex relationship. During the operation of the water pump, by adjusting the relevant electrical parameters or valve openings of the water pump, the head changes according to a pre-set head-flow characteristic curve (referred to as the "characteristic curve" for short).

[0003] The low-flow reference value is a value pre-set by the user according to actual needs. When the flow rate is lower than the reference value, the motor speed of the water pump can be considered to be reduced to reduce the operating power of the motor in order to achieve the purpose of energy conservation. In the prior art, when the flow rate reaches the set critical value, the head is usually set to decrease at a constant speed according to the characteristic curve. However, in practice, the situation of the water pump operating at a low flow rate (the flow rate is lower than the critical value) often occurs, and there may be various reasons. For example, bad usage habits such as the user completely closing the valve but not cutting off the power supply of the water pump may cause the water pump to operate at a low flow rate for a long time, which may lead to damage to the water pump components; it is also possible that the user actually has the need to use the water pump in the low-flow section. For example, when using a small flow rate or closing the valve very small, the pump keeps running so that hot water can be used at any time. The prior art does not take into account the low-flow usage needs of users in the actual application process and cannot make a judgment on these reasons, which greatly reduces the user experience. Summary of the Invention

[0004] In view of this, the present invention provides a water pump operation control method under low-flow conditions, which can effectively judge the low-flow condition usage needs of users and reduce energy consumption. Further, the present invention also discloses a corresponding water pump control device and a water pump.

[0005] The technical solution of the present invention includes:

[0006] The first aspect of the present invention discloses a water pump operation control method under low-flow conditions, including:

[0007] Obtain the water pump flow rate data in real time. When the water pump flow rate is less than the flow rate reference value, trigger low-flow control;

[0008] During the low-flow control process:

[0009] Obtain the motor speed RPM1 of the water pump in the low-flow usage interval;

[0010] After operating for a first set time T1 in the low-flow usage interval, control the motor speed to drop to RPM2;

[0011] During the operation of the motor speed RPM2, if the flow rate change rate Q of the water pump st is greater than the flow rate change rate threshold Q m , it is determined that there is a user demand for low-flow working conditions, and the motor speed is controlled to return to RPM1, entering the low-flow usage state S1; otherwise, after maintaining the motor speed RPM2 for the second set time T2, the motor speed is controlled to decrease to RPM3, entering the low-flow energy-saving state S2;

[0012] The low-flow usage range is kQ ref ≤Q<Q ref , where k < 1, Q is the real-time water pump flow rate, and Q ref is the flow rate reference value.

[0013] As an optional solution, when the operation time T3 in the low-flow usage state S1 exceeds the first time threshold T m1 , the motor speed is controlled to decrease to RPM3, entering the low-flow energy-saving state S2. Among them, the first time threshold T m1 is associated with the motor operating power P of the water pump.

[0014] As an optional solution, in the low-flow usage state S1, when 50W ≤ P < 100W, the first time threshold T m1 is 70min; when 100W ≤ P < 150W, the first time threshold T m1 is 40min; when the motor operating power in the S2 state is 150W ≤ P < 200W, the value of the first time threshold T m1 is set to 20min.

[0015] As an optional solution, in the low-flow energy-saving state S2, it is judged whether the water pump can return to the low-flow usage state S1 to ensure the user's low-flow usage demand. An optional solution is to obtain the temperature of the fluid medium in the pipeline where the water pump is located in real time. If the real-time temperature W is less than the temperature threshold W m , the motor speed of the water pump is controlled to return to RPM1, and it re-enters the low-flow usage state S1.

[0016] As an optional solution, if the operation time T4 in the low-flow energy-saving state S2 exceeds the second time threshold T m2 and the flow rate change rate Q st is greater than the flow rate change rate threshold Q m , the motor speed of the water pump is controlled to return to RPM1, and it re-enters the low-flow usage state S1.

[0017] As an optional solution, when setting the low-flow usage range, the the RPM3 is the minimum operating speed of the motor; Q refThe flow reference value is one fifth or one tenth of the maximum volume flow rate Q max of the maximum volume flow rate Q

[0018] As an alternative, the first set time T1 is 30 minutes and the second set time T2 is 10 minutes

[0019] A second aspect of the present invention discloses a water pump control device, including a processor and a memory; a program is stored in the memory, and the program is loaded and executed by the processor to implement the water pump operation control method under low flow conditions described in the first aspect and any alternative of the present invention

[0020] A third aspect of the present invention discloses a water pump, including a water pump body and the water pump control device described in the second aspect of the present invention; the water pump body includes a motor and a pump body; the water pump control device is used to control the operation of the motor

[0021] The present invention has the following beneficial effects

[0022] (1) After the water pump enters the low flow usage range, by adopting a stepped reduction in rotational speed scheme, the present invention effectively discriminates the low flow condition usage requirements of users and reduces the power consumption of the water pump during low flow operation

[0023] (2) By restricting the operation time in the low flow usage state, the present invention can avoid damage to the water pump caused by long-term operation under the condition of low flow and high power

[0024] (3) The present invention can, while ensuring the safety of water pump use, detect parameters such as the temperature or flow rate change rate of the fluid medium in the pipeline, and as much as possible meet the low flow condition usage requirements of users Description of the Drawings

[0025] Figure 1 It is a flow chart of the water pump operation control method under low flow conditions described in Embodiment 1 of the present invention

[0026] Figure 2 It is a flow chart of the water pump operation control method under low flow conditions described in Embodiment 2 of the present invention

[0027] Figure 3 It is a schematic diagram of the head-flow characteristic curve of the water pump

[0028] Figure 4 It is a flow chart of the water pump operation control method under low flow conditions described in Embodiment 3 of the present invention

[0029] Figure 5 It is a schematic diagram of the water pump circuit connection

[0030] Figure 6Flow chart of the pump operation control method under low flow conditions described in Embodiment 4 of the present invention;

[0031] Figure 7 Time-temperature fitting curve under low flow conditions;

[0032] Figure 8 Flow chart of the pump operation control method under low flow conditions described in Embodiment 5 of the present invention. Detailed implementation manners

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below. The following embodiments are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0034] The present invention adopts a stepped-down scheme for the rotational speed to linearly decrease the head. During this process, it can judge whether the user has a demand for using the pump under low flow conditions, and comprehensively consider factors such as the demand for using the pump under low flow conditions, energy consumption savings, and the safety of the pump performance, and flexibly switch between the low flow usage state and the low flow energy-saving state.

[0035] As Figure 1 shown, Embodiment 1 of the present invention discloses a pump operation control method under low flow conditions, which mainly includes the following steps: obtaining the pump flow rate data in real time, and when the pump flow rate is less than the flow rate reference value, triggering the entry into low flow control.

[0036] When the real-time pump flow rate Q obtained is less than the reference value Q ref , the low flow control program can be started. The present invention defines as the low flow usage interval. Among them, Q ref is one-fifth or one-tenth of the maximum volume flow rate Q max of the pump, and can be specifically set according to the actual usage situation and application scenario. Generally, for large-diameter and large-flow pumps, Q ref is set to one-tenth of Q max ; for small-diameter and small-flow pumps, Q ref is set to one-fifth of Q max . RPM2 is set according to different characteristic curves, and RPM2 < RPM1.

[0037] Among them, the pump flow rate Q can be directly obtained through a flow sensor. Or it can also be calculated based on the pre-stored relationship between the valve opening K and the pump flow rate, and the relationship is as follows:

[0038]

[0039] In the formula, C VHere, \(C\) is the valve flow coefficient (related to the valve structure and opening degree), \(\Delta P\) is the pressure difference before and after the valve, which can be obtained by a differential pressure gauge, and \(\rho\) is the fluid density.

[0040] (In another alternative, the flow rate \(Q\) can also be calculated through the motor operating power \(P\) and the motor speed RPM. For specific details, reference can be made to the related solution described in the patent with the publication number CN117662450A and the patent title "A Method and System for Determining the Fluid Flow Rate of a Water Pump", which will not be elaborated here.

[0041] It can be understood that the above-mentioned method for obtaining or calculating the water pump flow rate data can be specifically selected and set according to actual requirements, and the present invention does not limit this.

[0042] Furthermore, as Figure 2 shown, Embodiment 2 of the present invention provides a low-flow control method, which mainly includes the following sub-steps:

[0043] Step S1: Obtain the motor speed RPM1 of the water pump in the low-flow usage interval;

[0044] Step S2: After operating for the first set time T1 in the low-flow usage interval, control the motor speed to drop to RPM2;

[0045] During the operation of the motor speed RPM2, if the water pump flow rate change rate \(Q\) st is greater than the flow rate change rate threshold \(Q\) m , it is determined that there is a user usage demand for the low-flow working condition, control the motor speed to return to RPM1, and enter the low-flow usage state S1; otherwise, maintain the motor speed RPM2 for operation for the second set time T2 and then control the motor speed to drop to RPM3, and enter the low-flow energy-saving state S2.

[0046] Specifically, when the flow rate \(Q\) of the water pump is within this low-flow usage interval, obtain the motor speed RPM1. In order to determine whether the current is in the user's target usage demand stage (i.e., the low-flow control stage), first maintain the normal operation of this flow rate for the first set time T1, and then control the motor speed to decrease to RPM2 and maintain the operation for the second set time T2. For example, RPM1 is 3000 rpm, RPM2 is 2000 rpm; T1 can be designed as 30 min. T2 can be designed as 10 min.

[0047] As Figure 3 shown, there are three types of preset head-flow characteristic curves (abbreviated as "preset curves"). Among them, preset curve a1 is the constant speed mode; preset curve b1 is the constant pressure mode, and the head remains constant with the change of the flow rate; preset curve c1 is the proportional mode, and the head increases linearly with the change of the flow rate. It can be understood that Figure 3It is just a schematic curve and can be specifically divided according to the actual operating conditions. The three modes do not necessarily decrease according to the slopes shown in the figure. Taking the preset curve c1 as an example, the low-flow usage range The corresponding black line segment is the low-flow usage state S1, and the motor speed is RPM1; the red line segment c2 is the operating state of the motor speed RPM2; the red line segment c3 is its corresponding low-flow energy-saving state S2, and the motor speed is RPM3.

[0048] During the period when the motor speed is at RPM2, calculate the flow rate change rate Q based on the collected flow rate Q st . It can be understood that the flow rate change rate reflects the flow rate change between two adjacent samplings, and the calculation formula is as follows:

[0049]

[0050] In the formula, Q st is the flow rate change rate, Q t is the real-time flow rate of the current sampling, and Q t-1 is the flow rate of the previous sampling.

[0051] Among them, the flow rate change rate threshold Q m can be set according to requirements. For example, 10%. During this period, if the flow rate change rate Q st is greater than 10%, it means that the valve opening increases. For example, if the valve opening is adjusted manually, it is defaulted that the user needs to use it normally in the low-flow usage range. Therefore, control the motor speed to callback to RPM1 and enter the low-flow usage state S1 (also known as the "S1 state"). If the flow rate change rate is less than 10%, it is judged that there is no user using this low-flow working condition, and the motor speed drops to RPM3 and enters the low-flow energy-saving state S2 (also known as the "S2 state").

[0052] Among them, RPM3 < RPM2 < RPM1. RPM3 is usually set to a relatively low value, generally the minimum speed at which the motor can run and start. For example, 1000 rpm, which is specifically set according to the motor type and requirements. In the S2 state, the pump operation deviates from the characteristic curve, but the pump can still operate normally and the energy consumption is lower. It can be understood that the low-flow area is actually a specific working condition of the conventional usage state. Therefore, RPM1 is usually the motor speed on the preset curve, and it still operates according to the preset curve within the T1 time. However, during the operation of the motor speeds RPM3 and RPM2, it has deviated from the preset curve. Among them, RPM2 is just an intermediate process quantity used to judge whether there is a usage demand for the low-flow working condition.

[0053] Among them, the motor speed, i.e., the operating speed of the motor of the water pump, can be directly detected by installing detection devices such as magnetic encoders or Hall sensors. Different detection methods usually mainly affect the cost, and the detection accuracy has little difference. For example, the cost of installing a magnetic encoder to obtain the motor speed V is usually higher than that of the sensorless estimation method of calculating the motor speed based on the back electromotive force. The method of obtaining the motor speed can be specifically selected and set according to actual needs, and the present invention does not limit this.

[0054] Furthermore, considering that the water pump is in the low-flow usage state S1 for a long time, the heat dissipated by the motor enters the limited medium in the pipeline, which will cause the medium temperature to be too high, thereby damaging the water pump. As Figure 4 shown, on the basis of Embodiment 2, Embodiment 3 of the present invention further adds the following steps, that is: when the running time T3 in the low-flow usage state S1 exceeds the first time threshold T m1 , control the motor speed to drop to RPM3 and enter the low-flow energy-saving state S2.

[0055] If the running time T3 in the S1 state exceeds the first time threshold T m1 , control the motor to reduce the speed to RPM3 and enter the low-flow energy-saving state S2 to reduce the energy consumption of the water pump and protect the water pump at the same time. Among them, the first time threshold T m1 is a value preset according to different motor operating power intervals. The basic rule is that the T m1 value in the high-power interval is smaller, and the T m1 value in the low-power interval is larger. According to experience, the motor operating power P in the low-flow usage state S1 usually does not exceed 200W. It can be set that when 50W ≤ P < 100W in the S1 state, the T m1 value is set to 70min; when 100W ≤ P < 150W, the T m1 value is set to 40min; when 150W ≤ P < 200W for the motor operating power in the S2 state, the T m1 value is set to 20min.

[0056] It is understandable that the operating power of the water pump motor can be selected and set according to actual needs, and the present invention does not limit this. For example, in the motor control system of the water pump, the power supply provides stable alternating current for the inverter, and the inverter converts the alternating current into direct current. The MCU controls the opening and closing of the switching device to achieve electronic commutation to drive and control the operation of the water pump motor. The bus voltage can be directly sampled by the ADC module built in the MCU based on the voltage dividing resistors. The bus current refers to the current on the DC bus output by the inverter. The three-phase current refers to the current in the three-phase windings of the motor, and the three-phase current can be obtained based on the three-phase voltage and Ohm's law, where the three-phase voltage can be directly obtained through three-phase sampling resistors. There is a known specific relationship between the bus current and the three-phase current, so the bus current can be obtained by acquiring the three-phase current. Combining Figure 5 As shown, in an alternative solution, the bus voltage can be directly sampled by the ADC module built in the MCU for the bus voltage dividing resistors (R1, R2). The magnitudes of the three-phase currents of the motor can also be obtained in real time by measuring the voltages of the three sampling resistors (R3, R4, R5) integrated on the driver in the water pump. One end of each of the three sampling resistors is connected to one of the three-phase lines in the motor UVW, and the other end is grounded. Thus, the three-phase voltages of the motor can be collected, and then the magnitudes of the three-phase currents can be calculated through Ohm's law (I = U / R). The bus current can be calculated based on the three-phase currents. Therefore, in an alternative solution, the operating power P of the water pump motor (abbreviated as "power P") can be calculated based on the DC bus voltage and the three-phase currents of the motor, and the calculation formula is as follows:

[0057] P = V dc *I dc (1)

[0058] In the formula, V dc is the DC bus voltage collected through the sampling resistor R2, and I dc is the DC bus current converted from the three-phase currents collected through the sampling resistors R3, R4, and R5.

[0059] It is understandable that after the operating power of the motor decreases, the heat generated by the motor decreases, and the heat dissipated by the liquid medium in the pipeline is greater than the heat generated by the motor, so the temperature of the liquid in the pipeline decreases significantly. Therefore, it can return to the low-flow usage state S1 again to meet the user's low-flow usage requirements. Based on this, as Figure 6 shown, in Embodiment 4 of the present invention, based on Embodiment 3, the following steps can be added: that is, in the low-flow energy-saving state S2, the temperature of the fluid medium in the pipeline where the water pump is located is obtained in real time. If the real-time temperature W is less than the temperature threshold W m , control the rotational speed of the water pump motor to return to RPM1 and re-enter the low-flow usage state S1.

[0060] Among them, the temperature of the medium in the pipeline can be obtained in various ways. For example, a temperature sensor can be directly installed on the water pump, and the temperature sensor is used to read the temperature data. This method is simple, accurate and effective. Or it can also be directly judged according to the empirical relationship between the actual running time of different motor operating powers and the temperature of the medium in the water pump (as Figure 7 shown), this method judges the temperature of the medium in the pipeline according to the obtained motor operating power and the corresponding running time. If the obtained real-time temperature W is less than the temperature threshold W m , it is judged that it can re-enter the low-flow usage state S1, that is, control the rotational speed of the water pump motor to return to RPM1.

[0061] As an alternative to Embodiment 4, it can be judged whether it can re-enter the S1 state according to the running time and the flow rate change rate of the low-flow energy-saving state S2. As Figure 8 shown, on the basis of Embodiment 3, Embodiment 5 of the present invention can add the following steps: If the running time T4 of the low-flow energy-saving state S2 exceeds the second time threshold T m2 (for example, 20 minutes) and the flow rate change rate Q st is greater than the flow rate change rate threshold Q m , control the rotational speed of the water pump motor to return to RPM1 and re-enter the low-flow usage state S1.

[0062] For example, when the running time T4 of the water pump in the low-flow energy-saving state S2 exceeds 20 minutes and the flow rate change rate is greater than 10%, control the rotational speed of the water pump motor to return to RPM1 and enter the low-flow usage state S1.

[0063] Furthermore, Embodiment 6 of the present invention discloses a water pump control device. The water pump control device mainly includes an MCU for collecting data and realizing the operation control of the water pump, as well as related resistors, inductors, IPMs and other devices. Among them, the MCU includes a processor and a memory. When the program stored in the memory is loaded and executed by the processor, it can realize the water pump operation control method under the low-flow working condition described in any one of Embodiments 1 to 5. The MCU may also have an ADC function, or the MCU is externally connected to an ADC module. The MCU further includes a communication module electrically connected to the processor for communicating with the upper computer, which can specifically be a Bluetooth module or the like.

[0064] Furthermore, Embodiment 7 of the present invention discloses a water pump. The water pump mainly includes a water pump body and a water pump control device. Among them, the water pump body includes a motor and a pump body, and the water pump control device can be selected from the water pump control devices described in any one of Embodiments 1 to 5.

[0065] By adopting a stepped-down rotation speed scheme, the present invention can effectively identify the user's low-flow operating condition requirements and reduce the power consumption of the water pump during low-flow operation. By restricting the running time in the low-flow usage state, the present invention can avoid damage to the water pump caused by long-term operation in the low-flow and high-power condition. While ensuring the safe use of the water pump, by detecting parameters such as the temperature or flow rate change rate of the fluid medium in the pipeline, the user's low-flow operating condition requirements are satisfied as much as possible.

[0066] Finally, it should be noted that although the embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields. The above specific embodiments are merely illustrative and guiding, rather than restrictive. Under the inspiration of this specification, those of ordinary skill in the art can also make many forms without departing from the scope protected by the claims of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A method for controlling the operation of a water pump under low flow conditions, characterized in that: include: Acquire water pump flow data in real time, and trigger low flow control when the water pump flow is less than a flow reference value; During the low flow control process: Get the motor speed RPM1 of the water pump in the low flow usage interval; After running for the first set time T1 in the low flow usage interval, the motor speed is controlled to drop to RPM2; During the operation of the motor speed RPM2, if the flow rate change rate of the pump is Q st Greater than the flow rate change threshold Q m , it is determined that there is a user demand for low flow conditions, and the motor speed is controlled to return to RPM1, entering the low flow usage state S1; otherwise, the motor speed is maintained at RPM2 and then the motor speed is controlled to drop to RPM3 after the second set time T2, entering the low flow energy-saving state S2; The low flow usage interval is kQ ref ≤Q ref , where k<1, Q is the real-time pump flow, Q ref is the flow reference value.​ 2. The water pump operation control method under low flow conditions according to claim 1, characterized in that: Also includes: In the low flow usage state S1, the running time T3 exceeds the first time threshold T m1 When the motor speed is controlled to drop to RPM3, it enters the low flow energy-saving state S2.

3. The water pump operation control method under low flow conditions as claimed in claim 2, characterized in that: The first time threshold T m1 Related to the motor operating power P of the water pump.

4. The water pump operation control method under low flow conditions as claimed in claim 3, characterized in that: In the low flow usage state S1, when 50W≤P<100W, the first time threshold T m1 is 70min; when 100W≤P<150W, the first time threshold T m1 40min; when the motor operating power is 150W≤P<200W in S2 state, the first time threshold T m1 The value is set to 20min.

5. The water pump operation control method under low flow conditions as claimed in claim 2, characterized in that: Also includes: In the low flow energy-saving state S2, the temperature of the fluid medium in the pipeline where the water pump is located is obtained in real time. If the real-time temperature W is less than the temperature threshold W m , control the water pump motor speed back to RPM1 and re-enter the low flow usage state S1.

6. The water pump operation control method under low flow conditions as claimed in claim 2, characterized in that: Also includes: If the low flow energy-saving state S2 operation time T4 exceeds the second time threshold T m2 And the flow rate change rate Q st Greater than the flow rate change threshold Q m , control the water pump motor speed back to RPM1 and re-enter the low flow usage state S1.

7. The method for controlling the operation of a water pump under low flow conditions according to any one of claims 1 to 6, characterized in that: Said RPM3 is the minimum operating speed of the motor; Q ref The flow reference value is the maximum volume flow rate Q max One fifth or one tenth of.

8. The method for controlling the operation of a water pump under low flow conditions according to any one of claims 1 to 6, characterized in that: The first set time T1 is 30 minutes, and the second set time T2 is 10 minutes.

9. A water pump control device, characterized in that: It comprises a processor and a memory; the memory stores a program, and the program is loaded and executed by the processor to implement the water pump operation control method under low flow conditions as described in any one of claims 1 to 8.

10. A water pump, characterized in that: It comprises a water pump body and the water pump control device as claimed in claim 9; the water pump body comprises a motor and a pump body; the water pump control device is used to control the operation of the motor.

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