Method and device for suppressing performance dispersion of multi-pump parallel system based on current difference

Abstract

A method and device for suppressing the dispersion of performance of a multi-pump parallel system based on current difference relates to the field of multi-pump parallel system control technology, wherein the method comprises: determining whether the speed difference between any two pumps among a plurality of running pumps is less than or equal to a preset speed difference; if not, maintaining the speed of the running pump at a given speed calculated by a speed balancing operation module; if so, obtaining the motor currents of a plurality of running pumps, and calculating the current difference between the minimum motor current and the second smallest motor current; when the current difference is greater than or equal to a first preset current difference, increasing the given speed of the running pump with the minimum motor current; or when the current difference is less than the first preset current difference, maintaining the speed of the running pump at a given speed calculated by a speed balancing operation module. The suppression method can avoid the problem of rising water temperature at the pump outlet and cavitation of the impeller, thereby maintaining a suitable temperature of the pump group, improving the reliability and service life of the equipment, and the method is low in cost and effective.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-pump parallel system control, and in particular to a method and device for suppressing the performance dispersion of a multi-pump parallel system based on current difference. Background Art

[0002] Steam-powered ships must monitor the water level in the boiler in real time when in use. Too low or too high a water level will cause a dry boiler or full water, which will have a serious impact on the ship's power system and even endanger the safety of the ship. The marine boiler feedwater system consists of a feedwater pump, a check valve and a control system. The feedwater pump is divided into a fixed-speed pump and a variable-speed pump. The variable-speed pump can be an electric feedwater pump or a steam turbine feedwater pump. In a multi-feedwater pump parallel system, multiple fixed-speed pumps, multiple electric feedwater pumps, multiple steam turbine pumps or mixed-type feedwater pumps are used in the ship boiler system. Usually, a stop check valve is set at the outlet of the feedwater pump to prevent feedwater backflow. When the water pressure at the outlet of the feedwater pump reaches a certain value, the check valve opens and the feedwater pump supplies water to the boiler normally.

[0003] In a boiler feedwater system with multiple feedwater pumps in parallel, it is difficult to ensure the performance consistency of components such as feedwater pumps and check valves. Differences in equipment processing technology, material properties, equipment installation location, power grid / steam fluctuations, control system signals, etc. all lead to a certain dispersion in the working performance of the feedwater branch. The performance dispersion of related equipment in a system with multiple feedwater pumps in parallel will result in low outlet pressure of one or more feedwater pumps during parallel operation, making it impossible for the check valve to open normally, which in turn causes a sharp rise in the outlet water temperature of the feedwater pump, causing cavitation of the feedwater pump impeller and damage to the feedwater pump. To solve this problem, common solutions are as follows:

[0004] 1. Adjust equipment performance parameters. In order to reduce the dispersion of the working performance of each branch, it is necessary to adjust the performance parameters of each related equipment, such as strengthening the performance consistency between water pumps and processing and modifying the impeller; or strengthening the performance consistency of the check valve and adjusting the parameters of the valve core and spring. Strengthening the consistency of equipment performance parameters involves processing and modification of the device. The modified equipment needs to be re-tested and verified, and the cycle of parameter calculation-processing-testing-processing-testing... etc. is continuously carried out. The whole cycle is relatively long. In addition, there may be excessive processing and modification of the equipment, which will cause irreversible damage to the equipment and endanger the safety of the equipment.

[0005] 2. Configure a return pipe. By setting a return pipe between the outlet and inlet of the feedwater pump, when the check valve is abnormally closed, part of the outlet water of the feedwater pump will flow back to the inlet of the feedwater pump, thereby reducing the outlet water temperature and pressure of the feedwater pump, avoiding damage to the feedwater pump and endangering the safety of the boiler feedwater system. However, the setting of the return pipe requires a certain amount of physical space. The location of the ship boiler system is usually small, and the pipeline layout is difficult. In addition, the additional feedwater return pipe will reduce the water supply and affect the water supply efficiency.

[0006] 3. Add a return pipe control system. Add a controllable return valve in the return pipe. When the feed pump is running, if the check valve at the feed pump outlet is detected to be abnormally closed, open the return valve; if the check valve is normally open, close the return valve. Configure a return pipe or add a controllable return valve to the return pipe. When the check valve at the feed pump outlet cannot be opened, the feed pump will run idle and cannot provide effective water supply to the system, increasing system power consumption. At the same time, the overall water supply cannot reach the target value, affecting boiler safety.

[0007] In summary, in the existing solutions for the decentralized performance of branches in the multi-water pump parallel system, there are problems such as complex equipment processing and the need for on-site construction. There are also disadvantages such as poor economy and long system transformation cycle. Summary of the invention

[0008] The present invention provides a method and device for suppressing the performance dispersion of a multi-pump parallel system based on current difference, which is used to make up for the early design defects of the multi-pump parallel system in the prior art, and at the same time solve the problems of complex equipment processing, poor economy, and long system transformation cycle in the performance dispersion suppression measures of each branch.

[0009] The present invention provides a method for suppressing the performance dispersion of a multi-pump parallel system based on current difference, comprising:

[0010] Step S100, determining whether the speed difference between any two pumps among a plurality of running pumps is less than or equal to a preset speed difference;

[0011] Step S200: If not, keep the speed of the running pump at the given speed calculated by the speed balancing calculation module; if yes, obtain the motor currents of the plurality of running pumps, and calculate the current difference between the minimum motor current and the second minimum motor current;

[0012] Step S300: when the current difference is greater than or equal to a first preset current difference, increase the given speed of the running pump of the minimum motor current; or

[0013] When the current difference is less than a first preset current difference value, the rotation speed of the running pump is maintained at the given rotation speed calculated by the rotation speed balancing calculation module.

[0014] According to a method for suppressing the performance dispersion of a multi-pump parallel system based on current difference provided by the present invention, the given speed of the running pump with increasing the minimum motor current further includes:

[0015] Based on the preset speed increase rule, the speed is gradually increased on the basis of the given speed calculated by the speed balancing calculation module until the current difference is less than or equal to the second preset current difference value, and the current speed is maintained.

[0016] According to a method for suppressing the performance dispersion of a multi-pump parallel system based on current difference provided by the present invention, after increasing the given speed of the running pump with the minimum motor current, the method further includes:

[0017] Determining whether two or more pumps among the plurality of operating pumps increase a given speed;

[0018] If so, the speed of the running pump is restored to the given speed calculated by the speed balancing operation module, and the motor currents of the multiple running pumps are reacquired after a delay of a first preset time, and the current difference between the minimum motor current and the second smallest motor current is calculated, and the execution of step S300 is jumped.

[0019] According to a method for suppressing the performance dispersion of a multi-pump parallel system based on current difference provided by the present invention, before step S100, the method further includes:

[0020] Determining whether the control mode of the multi-pump parallel system is switched from manual control to automatic control;

[0021] If yes, the speed of the running pump is maintained at the given speed calculated by the speed balancing calculation module, and the process jumps to step S100 after a delay of a second preset time;

[0022] If not, the process jumps to step S100.

[0023] According to a method for suppressing the performance dispersion of a multi-pump parallel system based on current difference provided by the present invention, before step S100, the method further includes:

[0024] Determining whether the combination of the operating pumps has changed;

[0025] If yes, the speed of the running pump is maintained at the given speed calculated by the speed balancing calculation module, and the process jumps to step S100 after a delay of a third preset time;

[0026] If not, the process jumps to step S100.

[0027] According to a method for suppressing the performance dispersion of a multi-pump parallel system based on current difference provided by the present invention, the motor currents of the plurality of running pumps are obtained, and the current difference between the minimum motor current and the second smallest motor current is calculated, further comprising:

[0028] Continuously and in real time, collecting the motor current signal of each running pump, and caching the collected motor current signal of the running pump into a corresponding buffer;

[0029] Filtering the n groups of motor current signals most recently collected in each buffer, and calculating the motor current of the corresponding running pump;

[0030] Determine the smallest motor current and the next smallest motor current and calculate the difference between the two currents.

[0031] According to a method for suppressing the performance dispersion of a multi-pump parallel system based on current difference provided by the present invention, filtering the motor current signal data of the n groups of running pumps collected most recently in the buffer zone to calculate the motor current of the running pumps further comprises:

[0032] In the buffer of the pump of the jth branch, the latest n sets of motor current signal data collected are {I j0 , I j1 , I j2 , ..., I jn-1}, where I j0 Indicates the current value of the motor collected, I jn-1 Represents the motor current value collected for the previous n-1 times, where n is a positive integer greater than 1;

[0033] Determine the maximum current value I among n sets of motor current signal data jmax and minimum current value I jmin ;

[0034] Based on the smoothing filter method, the motor current of the pump in the jth branch is calculated as follows:

[0035]

[0036] Among them, I jmean is the motor current of the pump in the jth branch, I ji is the motor current value collected for the i-th time, I jmax is the maximum current value, I jmin is the minimum current value.

[0037] According to a method for suppressing the performance dispersion of a multi-pump parallel system based on current difference provided by the present invention, before step S100, the method further includes:

[0038] Determining a pump with the highest rotation speed and a pump with the lowest rotation speed among the plurality of operating pumps;

[0039] If the speed difference between the pump with the largest speed and the pump with the smallest speed is greater than the preset speed difference, then based on the preset adjustment parameter, the given speed of the pump with the largest speed is reduced, and the given speed of the pump with the smallest speed is increased;

[0040] Repeat the above steps until the speed difference between any two pumps in the plurality of running pumps is less than or equal to the preset speed difference.

[0041] The present invention also provides a device for suppressing the dispersion of performance of a multi-pump parallel system based on current difference, comprising:

[0042] A speed difference determination module, for determining whether a speed difference between any two pumps among a plurality of running pumps is less than or equal to a preset speed difference value;

[0043] The speed difference judgment module, if not, keeps the speed of the running pump at the given speed calculated by the speed balancing calculation module; if yes, obtains the motor currents of the plurality of running pumps, and calculates the current difference between the minimum motor current and the second minimum motor current;

[0044] The speed regulating module increases the given speed of the running pump when the current difference is greater than or equal to the first preset current difference; or maintains the speed of the running pump at the given speed calculated by the speed balancing calculation module when the current difference is less than the first preset current difference.

[0045] According to the present invention, a device for suppressing the dispersion of performance of a multi-pump parallel system based on current difference also includes:

[0046] The data storage module is used to store the speed control signal of the running pump, the speed feedback signal, the motor current signal, the running pump automatic control signal and the main pipe regulating valve pressure difference signal.

[0047] The present invention provides a method and device for suppressing the performance dispersion of a multi-pump parallel system based on current difference, wherein the method detects the motor currents of multiple running pumps after the rotation speeds of multiple running pumps reach equilibrium, and calculates the current difference between the minimum motor current and the second minimum motor current. If the current difference is greater than or equal to a first preset current difference, the check valve is in a closed state. At this time, the outlet head of the pump can be increased by increasing the rotation speed of the pump, thereby increasing the inlet and outlet pressure difference of the check valve. When it is higher than the static resistance of the check valve, the check valve can be opened; if the current difference is less than the first preset current difference, the check valve is in an open state, the branch circuit operates normally, and the current rotation speed can be maintained at this time. The method for suppressing the performance dispersion of a multi-pump parallel system based on current difference can avoid the problem of the pump outlet water temperature rising and the impeller being cavitated due to the long-term idling of the running pump, thereby maintaining the appropriate temperature of the pump group and improving the reliability and service life of the equipment. In addition, the method does not require changes to the equipment or pipelines, can be put into use in a timely manner, has low cost and good effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0049] Figure 1 It is a flow chart of a method for suppressing the dispersion of performance of a multi-pump parallel system based on current difference provided by the present invention;

[0050] Figure 2 It is a process principle diagram of the boiler water supply system provided by the present invention;

[0051] Figure 3 It is a schematic diagram of a hysteresis curve of a rotation speed increase provided by the present invention;

[0052] Figure 4 It is a schematic diagram of a water feed pump speed control system provided by the present invention;

[0053] Figure 5 is a schematic diagram of the structure of an electronic device provided by the present invention;

[0054] Reference numerals:

[0055] 1: water supply pump; 2: speed measuring instrument; 3: check valve; 4: motor current measuring instrument; 5: water supply regulating valve; 6: boiler; 7: pressure difference measuring instrument; 810: processor; 820: communication interface; 830: memory; 840: communication bus. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] The terms "first" and "second" in the embodiments of the present application are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first" and "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a system, product or device comprising a series of parts or units is not limited to the listed parts or units, but optionally also includes parts or units that are not listed, or optionally also includes other parts or units inherent to these products or devices. In the description of the present application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0058] Figure 2 The process principle diagram of the boiler water supply system is shown. The boiler water supply system is a typical multi-pump parallel system, which includes multiple parallel water supply branches, each of which is respectively provided with a water supply pump 1 and a check valve 3, and the outlets of the multiple check valves 3 are connected through a bridge pipe. The specific process flow is as follows: the water supply in the water supply main is first distributed to each water supply branch, and after being pressurized by the water supply pump, it is aggregated and enters the water supply regulating valve 5. After the water supply amount is adjusted by the water supply regulating valve 5, it finally enters the boiler 6 and is converted into steam to provide power. This embodiment is mainly explained by taking a multi-water supply pump parallel system as an example, and other multi-pump parallel systems are similar and will not be described in detail.

[0059] The existing water supply control process is specifically as follows: the speed of the water supply pump 1 in each water supply branch tracks the inlet and outlet pressure difference of the water supply regulating valve 5. When the inlet and outlet pressure difference of the water supply regulating valve 5 is lower than the first set threshold, the speed of the water supply pump 1 in each water supply branch will increase; when the inlet and outlet pressure difference of the water supply regulating valve 5 is higher than the second set threshold, the speed of the water supply pump 1 in each water supply branch will decrease; when the inlet and outlet pressure difference of the water supply regulating valve 5 is maintained between the first set threshold and the second set threshold, the speed of the water supply pump 1 remains unchanged. At the same time, the speed difference of each running water supply pump 1 is controlled to be maintained within a small range, so that the running speed of each water supply pump 1 is balanced. Here, a speed balancing calculation module (belonging to the existing control module of the system) can be used to calculate the given speed signal of each water supply pump based on the PID control algorithm, and then converted into a (4-20) mA current signal for each water supply pump 1 through the water supply pump speed given signal AO conversion module. The rotation speed of the water supply pump 1 can be measured by a rotation speed measuring instrument 2 , and the inlet and outlet pressure difference of the water supply regulating valve 5 can be measured by a pressure difference measuring instrument 7 .

[0060] In actual use, especially when multiple pumps are operated in parallel, due to the performance dispersion of related equipment, the outlet pressure of one or more water supply pumps 1 will be low, that is, the inlet pressure of the check valve 3 will be low. If the outlet pressures of each check valve 3 are the same, the inlet and outlet pressure difference of the check valve 3 will become smaller, which may cause the check valve 3 to be abnormally closed.

[0061] In a water supply system using a centrifugal pump, after the check valve 3 at the outlet of the centrifugal pump is closed, the head remains unchanged and the flow rate decreases, so the current of the pump decreases. If the check valve 3 is fully closed, the current is minimum, but slightly greater than idling. The flow rate of the water supply branch can directly reflect the state of the check valve 3. When the flow rate is very small or close to 0, it means that the check valve 3 is in a closed state, otherwise it means that the check valve 3 is in an open state. If a flow detection device is used directly to detect the outlet flow of the water supply pump 1, a straight pipe section of a certain length is usually required to install the throttling device. Due to the limited space in a marine environment, the length of the pipeline from the outlet of the water supply pump 1 to the parallel bridge pipe is short, and it is difficult to install a flow meter. Therefore, it is difficult to directly detect the flow. If the pressure difference before and after the water supply pump 1 is detected, the opening and closing state of the check valve 3 can be partially characterized. However, when the check valve 3 is opened, the pressure difference value cannot be simply judged. In the process of tracking the pressure difference control of the check valve 3, the pressure difference threshold when the check valve 3 is opened cannot be accurately set. At the same time, after passing through the check valve 3, the water supply in the pipeline is in a turbulent state. Although the pressure difference measuring point is far away from the check valve 3, the fluctuation of the measurement result is still large, which affects the judgment of the state of the water supply check valve 3.

[0062] In the water supply system, the motor power P of water supply pump 1 1 The calculation is as follows:

[0063]

[0064] Among them, P 0 The shaft power of the pump, also called input power, is the power transmitted from the motor to the shaft of the water pump;

[0065] P e The effective power of the pump, also called output power, is the effective energy obtained from the pump per unit time by the output medium;

[0066] ρ is the density of the medium delivered by the water pump (kg / m 3 ), to simplify the process, the water density delivered by the water pump can be 1000kg / m 3 calculate;

[0067] Q is the flow rate of the pump (m 3 / s);

[0068] H is the pump head (m), which generally does not include the loss head caused by friction resistance of pipeline water flow;

[0069] g is the neutral acceleration (m / s 2 ), under normal conditions it can be calculated as 9.8m / s 2 ;

[0070] k is the safety factor of the motor, generally 1.1 to 1.3;

[0071] η is the efficiency of the pump, which is the ratio of the effective power of the pump to the shaft power.

[0072] According to the above formula, the outlet flow rate Q of the water pump 1 is proportional to the motor power P of the water pump 1. 1 The relationship between them is positively correlated, that is:

[0073] P 1 ~Q

[0074] For a three-phase asynchronous motor, the active power P is calculated as follows:

[0075]

[0076] Where Φ is the phase difference between voltage and current, and cosΦ is called the power factor.

[0077] Based on the above formula, the motor power and current of the water pump 1 are in direct proportion, and it is known that the motor current of the water pump 1 and the outlet flow rate Q of the water pump 1 are positively correlated, that is:

[0078] I~Q

[0079] Therefore, the decrease in the outlet flow of the water supply pump 1 will lead to a decrease in the motor current. It is worth noting that since the motor will also consume some current when it is unloaded, the current is not 0 when the flow is 0. The variable frequency water supply pump is usually driven by a frequency converter and the motor drives the pump body. Therefore, when the frequency converter current of a branch in the parallel water supply branch decreases, it can be judged that the water supply flow rate has decreased, and the check valve 3 on the branch may be abnormally closed.

[0080] In the boiler feed water system, the outlet head of feed water pump 1 and the speed of feed water pump 1 are in a quadratic relationship:

[0081]

[0082] It can be seen from the above formula that the outlet head of the water supply pump 1 can be increased by increasing the speed of the water supply pump 1, and a small speed increment can greatly increase the outlet head of the water supply pump 1 with a quadratic increment. Therefore, by increasing the outlet pressure of the water supply pump 1, the inlet and outlet pressure difference of the check valve 3 can be increased. When the inlet and outlet pressure difference of the check valve 3 is higher than the static resistance of the check valve 3, the check valve 3 can be opened, thereby maintaining the normal operation of each water supply branch and suppressing the dispersion of branch performance.

[0083] like Figure 1 As shown, a method for suppressing the performance dispersion of a multi-pump parallel system based on current difference provided by an embodiment of the present invention includes:

[0084] Step S100: Determine whether the speed difference between any two pumps in a plurality of running pumps is less than or equal to a preset speed difference.

[0085] Specifically, the rotation speeds of all pumps currently in operation are obtained, and then the pumps with the highest and lowest rotation speeds are determined by comparison, and the rotation speed difference between the two is obtained, which is the maximum rotation speed difference between all running pumps at the current moment, and then the maximum rotation speed difference is compared with the preset rotation speed difference value to determine whether it is less than or equal to the preset rotation speed difference value. The preset rotation speed difference value can be set according to user needs.

[0086] Step S200, if not, keep the speed of the running pump at the given speed calculated by the speed balancing calculation module; if yes, obtain the motor currents of multiple running pumps, and calculate the current difference between the minimum motor current and the second minimum motor current.

[0087] Specifically, if the maximum speed difference is greater than the preset speed difference, it indicates that the speeds of the running pumps have not yet reached a balanced state at the current moment. At this time, it is necessary to give priority to meeting the speed balance requirement. Therefore, the speed signal received by the running pump is the given speed signal output by the speed balance operation module. At this time, the given speed will be dynamically adjusted according to the overall operating status of all current running pumps. The pump with a larger speed will be controlled to reduce the speed, and the pump with a smaller speed will be controlled to increase the speed, until the speeds of all running pumps reach a balanced state, that is, the speed difference between any two running pumps is less than or equal to the preset speed difference.

[0088] If the maximum speed difference is less than or equal to the preset speed difference, it indicates that the speed of each running pump has reached a balanced state at the current moment. However, due to the inconsistency and dispersion of the performance of each branch, when the speed is equivalent, the outlet pressure of one or more pumps may be low, which may cause the check valve 3 to be abnormally closed, causing the pump to run idle. In order to avoid the above situation, it is necessary to appropriately increase the speed of the pump with low outlet pressure to suppress the dispersion of branch performance. In this embodiment, the motor current of the running pump is mainly detected by the motor current measuring instrument 4 installed on the pump motor, the minimum motor current and the second minimum motor current are determined, and the current difference between the two is obtained, and then the outlet pressure of the running pump with the minimum motor current is judged according to the size of the current difference. Whether it is low. Usually, when the rotation speeds of the running pumps have reached a balanced state, if the check valves 3 of each branch are opened normally, the motor currents of the running pumps should not differ much; if the check valve 3 of a branch is abnormally closed, the motor current of the running pump on this branch will be reduced, so the motor current of this running pump should be the smallest, and there will be a large current difference with the motor currents of other running pumps.

[0089] Step S300: when the current difference is greater than or equal to a first preset current difference, increase the given speed of the running pump; or when the current difference is less than the first preset current difference, maintain the speed of the running pump at the given speed calculated by the speed balancing calculation module.

[0090] Specifically, if the current difference is greater than or equal to the first preset current difference, it indicates that the check valve 3 corresponding to the running pump of the minimum motor current may be abnormally closed, and therefore the given speed of the running pump needs to be increased, that is, the speed signal received by the running pump of the minimum motor current increases a certain speed increment on the basis of the given speed signal output by the speed balancing operation module. The speed increment can be comprehensively set according to user needs and system characteristics, and it can be a fixed increment or a variable increment, which is not specifically limited here. The first preset current difference can also be defined according to user needs.

[0091] If the current difference is less than the first preset current difference, it indicates that the check valve 3 is in a normally open state, and the branch circuit operates normally. At this time, the current given speed of the running pump can be maintained.

[0092] The method for suppressing the performance dispersion of a multi-pump parallel system based on current difference provided in this embodiment detects the motor currents of multiple running pumps after the speeds of multiple running pumps reach equilibrium, and calculates the current difference between the minimum motor current and the second minimum motor current. If the current difference is greater than or equal to the first preset current difference, the check valve 3 is in a closed state. At this time, the outlet head of the pump can be increased by increasing the speed of the pump, thereby increasing the inlet and outlet pressure difference of the check valve 3. When it is higher than the static resistance of the check valve 3, the check valve 3 can be opened; if the current difference is less than the first preset current difference, the check valve 3 is in an open state, and the branch operates normally. At this time, the current speed can be maintained. The method for suppressing the performance dispersion of a multi-pump parallel system based on current difference can avoid the problem of the pump outlet water temperature rising and the impeller being cavitated due to the long-term idling of the running pump, thereby maintaining the temperature of the pump group and improving the reliability and service life of the equipment. In addition, the method does not require changes to the equipment or pipelines, can be put into use in a timely manner, has low cost and good effect.

[0093] Further, in step S300, increasing the given speed of the running pump with the minimum motor current specifically includes:

[0094] Based on the preset speed increase rule, the speed is gradually increased on the basis of the given speed calculated by the speed balancing calculation module until the current difference is less than or equal to the second preset current difference value, and the current speed is maintained.

[0095] Specifically, the preset speed increase rule can be set by the user, and a PID control algorithm or a linear increasing method can be used to gradually adjust the speed of the running pump so that the current difference gradually decreases until it is less than or equal to the second preset current difference. The second preset current difference is less than the first preset current difference, forming a hysteresis control interval.

[0096] like Figure 3 As shown, I x Represents the first preset current difference, I y represents the second preset current difference, and the specific change range is: (1) A→C: the running pump maintains a given speed, and the current of the running pump with the minimum motor current gradually decreases, so the current difference becomes larger, and the check valve 3 corresponding to the running pump with the minimum motor current may be abnormally closed; (2) C→D: the current difference is equal to the first preset current difference I x, the running pump with the minimum motor current starts to increase the speed; (3) D→E is the inertia section, the current difference will become smaller due to inertia and response delay; (4) E→F, the running pump with the minimum motor current continues to increase the speed, and the current difference gradually becomes smaller; (5) F→B: the current difference is equal to the second preset current difference value I y , the running pump with minimum motor current stops increasing the speed and maintains running at the current speed.

[0097] By setting the hysteresis interval, the speed increase regulation process will not cause frequent switching of the output (increase speed) due to slight fluctuations in the input (current difference), and the response hysteresis is used to accommodate environmental fluctuations.

[0098] Furthermore, after increasing the given speed of the running pump with the minimum motor current, the method further comprises:

[0099] Determine whether two or more pumps among the multiple running pumps increase the given speed;

[0100] If so, the speed of the running pump with the minimum motor current is restored to the given speed calculated by the speed balancing operation module, and the motor currents of multiple running pumps are reacquired after a delay of the first preset time, and the current difference between the minimum motor current and the second smallest motor current is calculated, and the execution of step S300 is jumped.

[0101] Specifically, when a running pump in a multi-pump parallel system increases its speed, it may cause the outlet pressure of other running pumps to be low, thereby triggering two or more pumps to execute the step of increasing the speed, and finally forming a situation where multiple pumps alternately increase or decrease the speed, that is, the unfavorable situation of taking turns to grab the load. This situation is more likely to occur when two pumps are running in parallel, usually the two running pumps with the smallest and second smallest motor currents. In order to avoid the above situation, when two or more pumps need to increase the given speed, that is, after the speed is increased in the first branch, the motor current of the second branch is detected to be low, which may trigger the step of increasing the speed. At this time, the speed of the running pump of the first branch is restored to the given speed calculated by the speed balancing operation module. Therefore, the speeds of the running pumps in the first branch and the second branch are equivalent, and both maintain the given speed (that is, the given speed signal output by the speed balancing operation module).

[0102] By restoring the running pump in the first branch to a given speed, the running pumps in the two branches return to a balanced state, and then after waiting for a first preset time, the motor currents of all the running pumps at the inlet and outlet of the check valve located at the outlet of the running pump are obtained, and then the current difference is calculated, and the execution of step S300 is jumped to avoid entering an unfavorable cycle of alternating increase and decrease of speeds of multiple pumps.

[0103] Based on the above embodiment, before step S100, the method further includes:

[0104] Determine whether the control mode of the multi-pump parallel system is switched from manual control to automatic control;

[0105] If so, the speed of the running pump is maintained at the given speed calculated by the speed balancing calculation module, and the process jumps to step S100 after a delay of a second preset time; if not, the process jumps to step S100.

[0106] Specifically, when the control mode of the multi-pump parallel system is switched from manual control to automatic control, each running pump may not have reached a balanced state, so the given speed is maintained without increasing the speed additionally, and step S100 is executed after the second preset time to prevent system misjudgment.

[0107] Based on the above embodiment, before step S100, the method further includes:

[0108] Determine if the combination of operating pumps has changed;

[0109] If so, the speed of the running pump is maintained at the given speed calculated by the speed balancing calculation module, and the process jumps to step S100 after a delay of a third preset time; if not, the process jumps to step S100.

[0110] Specifically, when the combination of the running pumps changes, for example, when the operation of the 1# pump and the 2# pump changes to the 1# pump and the 3# pump, the 3# pump is started, and during the start-up process of the 3# pump, its corresponding check valve 3 is in a closed state, which is a normal closure at this time. In order to prevent the system from misjudging, the speed is not increased during the start-up process of the pump, and the given speed is maintained first, and step S100 is executed after the third preset time. In addition, the combination of the running pumps can also undergo changes such as chain start, increase of running pumps, or reduction of running pumps. When the above changes occur, the running pumps all maintain the given speed calculated by the speed balance calculation module, and the speed is not increased, and step S100 is executed after the third preset time.

[0111] Based on the above embodiment, in step S200, the motor currents of multiple running pumps are obtained, and the current difference between the minimum motor current and the second minimum motor current is calculated, further comprising:

[0112] Step S210: continuously and in real time collect the motor current signal of each running pump, and cache the collected motor current signal in a corresponding buffer.

[0113] Step S220: Filter the n groups of motor current signals collected most recently in each buffer to calculate the motor current of the corresponding running pump. Specifically, the filtering process can adopt median filtering, arithmetic average filtering, recursive average filtering, median average filtering, etc. This embodiment is described by taking median average filtering as an example.

[0114] Specifically, step S220 further includes:

[0115] Step S221: In the buffer of the pump of the jth branch, the n groups of motor current signal data collected the most recently are {I j0 , I j1 , I j2 , ..., I jn-1}, where I j0 Indicates the current value of the motor collected, I jn-1 Represents the motor current value collected for the previous n-1 times, where n is a positive integer greater than 1;

[0116] Step S222: Determine the maximum current value I among the n groups of motor current signal data jmax and minimum current value I jmin ;

[0117] Step S223: Based on the smoothing filter method, the motor current of the pump of the j-th branch is calculated as follows:

[0118]

[0119] Among them, I jmean is the motor current of the pump in the jth branch, I ji is the motor current value collected for the i-th time, I jmax is the maximum current value, I jmin is the minimum current value.

[0120] By using the median average filter, the minimum and maximum values ​​in the current difference are removed, and then the arithmetic mean of n-2 data is calculated. This combines the advantages of the median filter and the arithmetic mean filter, and can eliminate the interference deviation that occurs accidentally. In addition, the second largest value, the second largest value, and the second smallest value can also be removed from the current difference. This is only an example and is not limited.

[0121] Step S230: Determine the minimum motor current and the second minimum motor current, and calculate the current difference between the two. The current difference is calculated as follows:

[0122] ΔI mean =|I jmean1 -I jmean2 ∣

[0123] Among them, Ijmean1 is the minimum motor current, I jmean2 is the second smallest motor current.

[0124] On the basis of the above embodiment, before step S100, a rotation speed balancing operation is further included:

[0125] Step S010: Determine the pump with the highest speed and the pump with the lowest speed among the multiple running pumps. Specifically, it can be determined by enumeration or one-by-one comparison. It can also be digitally encoded by various operating information of the pumps, and then the comprehensive information encoding of all running pumps is combined to solve the maximum or minimum value of the comprehensive information data, so that the pump with the highest speed and the pump with the lowest speed can be directly determined. When the number of pumps is large, the calculation amount of this method is relatively small, which is more conducive to program writing and is not easy to miss items. This method is a prior art and will not be described here.

[0126] Step S020: If the speed difference between the pump with the highest speed and the pump with the lowest speed is greater than the preset speed difference, the given speed of the pump with the highest speed is reduced based on the preset adjustment parameter, and the given speed of the pump with the lowest speed is increased. Specifically, the preset adjustment parameter can be set by the user, for example, it can be linearly increased / decreased, or based on a PID algorithm, etc., which is not limited here.

[0127] Step S030: Repeat the above steps until the speed difference between any two pumps in the plurality of running pumps is less than or equal to a preset speed difference.

[0128] The present invention also provides a device for suppressing the dispersion of performance of a multi-pump parallel system based on current difference, comprising:

[0129] A speed difference determination module, for determining whether the speed difference between any two pumps in a plurality of running pumps is less than or equal to a preset speed difference value;

[0130] The speed difference judgment module, if not, maintains the given speed of the running pump; if so, obtains the motor currents of multiple running pumps and calculates the current difference between the minimum motor current and the second minimum motor current;

[0131] The speed regulating module increases the given speed of the running pump when the current difference is greater than or equal to the first preset current difference; or maintains the speed of the running pump at the given speed calculated by the speed balancing calculation module when the current difference is less than the first preset current difference.

[0132] The device for suppressing the performance dispersion of a multi-pump parallel system based on current difference may also include:

[0133] The data storage module is used to store important parameters such as the speed control signal of the running pump, the speed feedback signal, the motor current signal, the running pump automatic control signal (switch signal) and the pressure difference signal of the main pipe regulating valve (such as the water supply regulating valve 5). Through the process control device running data storage method, the important parameters of the water supply control system are stored in a limited storage space, the data can be downloaded and the operating status of the running pump can be further analyzed. The process control device running data storage method belongs to the prior art and will not be repeated here.

[0134] like Figure 4 As shown, on the basis of the above-mentioned embodiment, as another preferred implementation mode, the present invention also provides a water supply pump speed control system including a multi-pump parallel system performance dispersion suppression device based on current difference, wherein the speed increase control module is the branch performance dispersion suppression device of the multi-pump parallel system. The water supply pump speed control system is composed of a speed balancing operation module, n speed increase control modules and n water supply pump given signal AO conversion modules, wherein the value of n is the same as the number of water supply pumps 1. First, before each water supply pump 1 has reached a balanced state, the speed balancing operation module calculates the given speed signal of each water supply pump 1 based on the PID control algorithm, and the speed increment signal output by the speed increase control module is 0, which is converted into a (4-20) mA current signal to each water supply pump 1 through the water supply pump speed given signal AO conversion module. At this time, the water supply pump 1 directly runs at a given speed. Then, when each water supply pump 1 reaches a balanced state, if the current difference between the minimum motor current and the second smallest motor current is greater than or equal to the first preset current difference, the speed increase control module corresponding to the water supply pump 1 branch with the minimum motor current outputs an appropriate speed increment signal, and accordingly increases the speed of the water supply pump 1 on the branch based on the given speed, while the water supply pumps 1 on the other branches continue to operate at the given speed.

[0135] Figure 5 An example of a physical structure diagram of an electronic device is shown in FIG. Figure 5 As shown, the electronic device may include: a processor 810, a communication interface 820, a memory 830 and a communication bus 840, wherein the processor 810, the communication interface 820 and the memory 830 communicate with each other through the communication bus 840. The processor 810 may call the logic instructions in the memory 830 to execute the method for suppressing the performance dispersion of the multi-pump parallel system based on the current difference provided in the above embodiments, and the method includes:

[0136] Determine whether a speed difference between any two pumps of the plurality of running pumps is less than or equal to a preset speed difference value;

[0137] If not, the given speed of the running pump is maintained; if yes, the motor currents of the plurality of running pumps are obtained, and the current difference between the minimum motor current and the second minimum motor current is calculated;

[0138] When the current difference is greater than or equal to the first preset current difference, the given speed of the running pump of the minimum motor current is increased; or when the current difference is less than the first preset current difference, the speed of the running pump is maintained at the given speed calculated by the speed balancing calculation module.

[0139] In addition, the logic instructions in the above-mentioned memory 830 can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when it is sold or used as an independent product. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0140] On the other hand, the present invention further provides a computer program product, which includes a computer program. The computer program can be stored in a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the method for suppressing the performance dispersion of a multi-pump parallel system based on current difference provided in the above embodiments, and the method includes:

[0141] Determine whether a speed difference between any two pumps of the plurality of running pumps is less than or equal to a preset speed difference value;

[0142] If not, the given speed of the running pump is maintained; if yes, the motor currents of the plurality of running pumps are obtained, and the current difference between the minimum motor current and the second minimum motor current is calculated;

[0143] When the current difference is greater than or equal to the first preset current difference, the given speed of the running pump of the minimum motor current is increased; or when the current difference is less than the first preset current difference, the speed of the running pump is maintained at the given speed calculated by the speed balancing calculation module.

[0144] In another aspect, the present invention further provides a non-transitory computer-readable storage medium having a computer program stored thereon, which is implemented when the computer program is executed by a processor to execute the method for suppressing the performance dispersion of a multi-pump parallel system based on current difference provided by the above methods, the method comprising:

[0145] Determine whether a speed difference between any two pumps of the plurality of running pumps is less than or equal to a preset speed difference value;

[0146] If not, the given speed of the running pump is maintained; if yes, the motor currents of the plurality of running pumps are obtained, and the current difference between the minimum motor current and the second minimum motor current is calculated;

[0147] When the current difference is greater than or equal to the first preset current difference, the given speed of the running pump of the minimum motor current is increased; or when the current difference is less than the first preset current difference, the speed of the running pump is maintained at the given speed calculated by the speed balancing calculation module.

[0148] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for suppressing the performance dispersion of a multi-pump parallel system based on current difference, characterized in that: include: Step S100, determining whether the speed difference between any two pumps among a plurality of running pumps is less than or equal to a preset speed difference; Step S200: If not, keep the speed of the running pump at the given speed calculated by the speed balancing calculation module; if yes, obtain the motor currents of the plurality of running pumps, and calculate the current difference between the minimum motor current and the second minimum motor current; The step of obtaining the motor currents of the plurality of running pumps and calculating the current difference between the minimum motor current and the second minimum motor current further comprises: Continuously and in real time, collecting the motor current signal of each running pump, and caching the collected motor current signal of the running pump into a corresponding buffer; Filtering the n groups of motor current signals most recently collected in each buffer, and calculating the motor current of the corresponding running pump; Determine the minimum motor current and the second minimum motor current, and calculate the current difference between the two; Step S300: when the current difference is greater than or equal to a first preset current difference, increase the given speed of the running pump of the minimum motor current; or When the current difference is less than a first preset current difference value, the rotation speed of the running pump is maintained at the given rotation speed calculated by the rotation speed balancing calculation module.

2. The method for suppressing the performance dispersion of a multi-pump parallel system based on current difference according to claim 1, characterized in that: The step of increasing the given speed of the running pump with the minimum motor current further comprises: Based on the preset speed increase rule, the speed is gradually increased on the basis of the given speed calculated by the speed balancing calculation module until the current difference is less than or equal to the second preset current difference value, and the current speed is maintained.

3. The method for suppressing the performance dispersion of a multi-pump parallel system based on current difference according to claim 1, characterized in that: After the step of increasing the minimum motor current to operate the pump at a given speed, the step further includes: Determining whether two or more pumps among the plurality of operating pumps increase a given speed; If so, the speed of the running pump is restored to the given speed calculated by the speed balancing operation module, and the motor currents of the multiple running pumps are reacquired after a delay of a first preset time, and the current difference between the minimum motor current and the second smallest motor current is calculated, and the execution of step S300 is jumped.

4. The method for suppressing the performance dispersion of a multi-pump parallel system based on current difference according to claim 1, characterized in that: Before step S100, the method further includes: Determining whether the control mode of the multi-pump parallel system is switched from manual control to automatic control; If yes, the speed of the running pump is maintained at the given speed calculated by the speed balancing calculation module, and the process jumps to step S100 after a delay of a second preset time; If not, the process jumps to step S100.

5. The method for suppressing the performance dispersion of a multi-pump parallel system based on current difference according to claim 1, characterized in that: Before step S100, the method further includes: Determining whether the combination of the operating pumps has changed; If yes, the speed of the running pump is maintained at the given speed calculated by the speed balancing calculation module, and the process jumps to step S100 after a delay of a third preset time; If not, the process jumps to step S100.

6. The method for suppressing the performance dispersion of a multi-pump parallel system based on current difference according to claim 1, characterized in that: The filtering process of the n groups of motor current signal data of the running pumps collected most recently in the buffer to calculate the motor current of the running pumps further includes: In the buffer of the pump of the jth branch, the latest n sets of motor current signal data collected are {I j0 , I j1 , I j2 , ..., I jn-1 }, where I j0 Indicates the current value of the motor collected, I jn-1 Represents the motor current value collected for the previous n-1 times, where n is a positive integer greater than 1; Determine the maximum current value I among n sets of motor current signal data jmax and minimum current value I jmin ; Based on the smoothing filter method, the motor current of the pump in the jth branch is calculated as follows: Among them, I jmean is the motor current of the pump in the jth branch, I ji is the motor current value collected for the i-th time, I jmax is the maximum current value, I jmin is the minimum current value.

7. The method for suppressing the performance dispersion of a multi-pump parallel system based on current difference according to any one of claims 1 to 6, characterized in that: Before step S100, the method further includes: Determining a pump with the highest rotation speed and a pump with the lowest rotation speed among the plurality of operating pumps; If the speed difference between the pump with the largest speed and the pump with the smallest speed is greater than the preset speed difference, then based on the preset adjustment parameter, the given speed of the pump with the largest speed is reduced, and the given speed of the pump with the smallest speed is increased; Repeat the above steps until the speed difference between any two pumps in the plurality of running pumps is less than or equal to the preset speed difference.

8. A device for suppressing the performance dispersion of a multi-pump parallel system based on current difference, characterized in that: include: A speed difference determination module, for determining whether the speed difference between any two pumps in a plurality of running pumps is less than or equal to a preset speed difference value; The speed difference judgment module, if not, keeps the speed of the running pump at the given speed calculated by the speed balancing calculation module; if yes, obtains the motor currents of the plurality of running pumps, and calculates the current difference between the minimum motor current and the second minimum motor current; The step of obtaining the motor currents of the plurality of running pumps and calculating the current difference between the minimum motor current and the second minimum motor current further comprises: Continuously and in real time, collecting the motor current signal of each running pump, and caching the collected motor current signal of the running pump into a corresponding buffer; Filtering the n groups of motor current signals most recently collected in each buffer, and calculating the motor current of the corresponding running pump; Determine the minimum motor current and the second minimum motor current, and calculate the current difference between the two; The speed regulating module increases the given speed of the running pump when the current difference is greater than or equal to the first preset current difference; or maintains the speed of the running pump at the given speed calculated by the speed balancing calculation module when the current difference is less than the first preset current difference.

9. The device for suppressing the performance dispersion of a multi-pump parallel system based on current difference according to claim 8, characterized in that: Also includes: The data storage module is used to store the speed control signal of the running pump, the speed feedback signal, the motor current signal, the running pump automatic control signal and the main pipe regulating valve pressure difference signal.

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