A pump set and a control method for efficient energy-saving operation thereof

Abstract

The application discloses a pump set, which comprises a pump set system inlet pressure gauge, a pump set system outlet pressure gauge, a flow gauge, and a power frequency pump and a variable frequency pump arranged in parallel; the outlet of each power frequency pump and variable frequency pump is provided with a pressure gauge and an electric energy meter; the outlet of each power frequency pump is further provided with an electric valve; the real-time power, cumulative electric energy, pump set system pressure PIT and pump set system flow FIT parameters of each pump are displayed on the background control system interface through the pressure gauges, the flow gauge and the electric energy meters; whether each power frequency pump runs in the high efficiency area is determined through real-time calculation of the flow / electricity ratio flow; and the electric valve of each power frequency pump and / or the frequency of the variable frequency pump is adjusted according to the ratio flow display value to realize the control of the pump set system pressure PIT. The ratio flow display value can be used to directly determine whether the pump set works in the high efficiency area; if not, the valve of each power frequency pump and the frequency of the variable frequency pump are adjusted, so that each pump works at the highest efficiency working point.

Description

Technical Field

[0001] This invention relates to the technical field of pumps and pumping stations, and specifically to a control method for a multi-pump unit and its efficient and energy-saving operation. Background Technology

[0002] Pump sets are a commonly used type of liquid power transmission and distribution device, and are used extensively in industrial and mining enterprises, consuming a large amount of electrical energy. Their operating efficiency is directly related to the energy consumption of enterprises. Therefore, energy-saving operation of pumps and pump sets has become an important part of energy conservation and emission reduction.

[0003] In existing pump and pump set operation and management, pump sets mostly consist of multiple fixed-frequency pumps plus one or two variable-frequency pumps, employing constant pressure control. The fixed-frequency pumps are adjusted by changing the number of pumps in operation to coarsely adjust the water pressure; the outlet valves are generally not adjusted. The variable-frequency pumps are adjusted by changing their operating frequency to achieve fine-tuning of the system water pressure. Its advantages are simple control methods, requiring only the control of pressure. When water consumption is low and pressure rises, one pump is stopped or the frequency of the variable-frequency pump is reduced; conversely, when water consumption increases and pressure drops, one pump is started or the frequency of the variable-frequency pump is increased. The disadvantages are that it cannot identify the pump's operating point, is susceptible to individual factors, has high arbitrariness, and cannot ensure that all pumps in the pump set operate in their high-efficiency range and work in coordination.

[0004] Because the high-efficiency operating range of each pump is very small and it is impossible to determine where the high-efficiency range is, when the load changes, the operating range of each pump in the pump set often changes constantly, making it impossible to operate stably in the high-efficiency range, or even to determine whether it is operating in the high-efficiency range at all.

[0005] In existing pump and pump set control systems, the system flow rate and system head (pressure) are included in the control parameters, but the flow rate, head, power, and pump efficiency of each pump in the pump set are not included. This makes it difficult for each pump in the pump set to operate in the high-efficiency range, and it is difficult for the pumps to work simultaneously and efficiently. The opening of the outlet valve of each pump is often manually adjusted based on the on-site outlet pressure gauge. Since manual adjustment is intermittent, the operating status of the pump is greatly affected by human factors. When the load changes, it is difficult for the operator to adjust the valve opening in time, making it difficult for each pump to operate in the high-efficiency range, and the entire pump set cannot operate stably in the high-efficiency range. Summary of the Invention

[0006] In order to solve one or more technical problems existing in the prior art, one of the objectives of this application is to provide a pump set that uses a specific flow rate display value to directly determine whether the pump set is working in the high-efficiency range. If it is not in the high-efficiency range, by adjusting the valves of each power frequency pump and the frequency of the variable frequency pump, each pump can be made to work at the highest efficiency operating point.

[0007] The second objective of this application is to provide a control method for the efficient and energy-saving operation of a pump set. By using the relationship between shaft power and flow rate, the operating point position of each pump in the pump set can be seen intuitively, thereby determining whether each pump is operating in the high-efficiency zone.

[0008] To address the aforementioned technical problems, one of the objectives of this application is achieved through the following technical solution: A pump set includes a pump set system inlet pressure gauge, a pump set system outlet pressure gauge, a flow meter, and at least one fixed-frequency pump and one variable-frequency pump connected in parallel. The pump set system outlet pressure gauge displays the pump set system pressure PIT, and the flow meter displays the pump set system flow rate FIT. Each of the fixed-frequency pumps and the variable-frequency pumps has a pressure gauge and an energy meter at its outlet. Each of the fixed-frequency pumps also has an electric valve at its outlet. The real-time power, cumulative energy, pump set system pressure PIT, and pump set system flow rate FIT parameters of each pump are displayed in real time on the background control system interface through the pressure gauge, flow meter, and energy meter. The pump set system pressure PIT is controlled by calculating the flow rate / energy ratio in real time to determine whether each fixed-frequency pump is operating in the high-efficiency zone. The pump set system pressure PIT is controlled by adjusting the electric valve of each fixed-frequency pump and / or the frequency of the variable-frequency pump through the specific flow rate display value.

[0009] A method for high-efficiency and energy-saving operation control of a pump set, the control method comprising: S1. Data Acquisition: The real-time power, cumulative energy, pump system pressure (PIT), and pump system flow rate (FIT) of each pump are displayed in real time on the background control system interface through various pressure gauges, flow meters, and energy meters. S2. Calculate the specific flow rate: Calculate the head value of each pump by subtracting the system inlet pressure from the outlet pressure of each fixed frequency pump and variable frequency pump. S3. Energy Efficiency Curve: By calculating the flow rate / electricity ratio in real time, an energy efficiency curve is plotted to show the water production capacity per kilowatt-hour.

[0010] S4. High-efficiency zone determination: Taking the pump system pressure PIT as the control object, establish a power-flow NQ characteristic curve database for each industrial frequency pump. Adjust the electric valve at the outlet of each industrial frequency pump through the NQ characteristic curve to control the outlet pressure of each pump. Determine whether the pump set is currently operating in the high-efficiency zone by whether the outlet pressure of each industrial frequency pump is kept within the set range. S5. Dynamic adjustment: When the specific flow rate displayed in the NQ characteristic curve is lower than the preset lower limit of the high efficiency zone, it is determined to be inefficient operation, and its outlet pressure is adjusted by adjusting the frequency of the variable frequency pump; when the specific flow rate displayed is higher than the preset upper limit of the high efficiency zone, it is determined to be inefficient operation, and its outlet pressure is adjusted by adjusting the electric valve of each power frequency pump and the frequency of the variable frequency pump, thereby realizing the control of the pump group system pressure PIT.

[0011] Preferably, the high-efficiency zone specific flow rate of the pump set is 5.54~6.78. The high-efficiency zone range is determined according to the design efficiency curve of the power frequency pump, and is usually the specific flow rate range corresponding to the area where the efficiency drops by no more than 10% on both sides of the highest efficiency point.

[0012] Preferably, the energy efficiency curves in step S3 include HQ curves, NQ curves, and η-Q curves that exhibit a monotonic function curve distribution, where H is the head, Q is the pump system flow rate FIT, and N is the power of each power frequency pump.

[0013] Preferably, the NQ curve equation of the power frequency pump is: N = aQ² + bQ + c; where a, b, and c are constants corresponding to the sum of the three power values ​​of the power frequency pump and the power at 0 flow rate.

[0014] Preferably, the method further includes a variable pressure control mode: the system calculates the current pipeline pressure drop ΔP based on the real-time flow rate FIT using the formula ΔP=aQ²+bQ+c, and dynamically adjusts the pump system pressure setpoint PIT accordingly, so that it remains at the lowest level while meeting the pressure demand at the most unfavorable point, thereby achieving the purpose of energy saving.

[0015] To meet the terminal pressure requirements at the most unfavorable point (maximum pressure drop load), the pump set outlet pressure PIT (i.e., PIT = required terminal pressure + ΔP) can be dynamically and minimally set based on the pipeline pressure drop ΔP calculated from the real-time flow rate Q, thereby achieving energy savings.

[0016] The terminal pressure of the maximum pressure drop load is indirectly obtained by correcting the pump system pressure PIT using the pump system flow rate FIT. The formula for calculating the pump system flow rate FIT correction is: ΔP = aQ 2 +bQ+c, where △P is the pipeline pressure drop, Q is the system flow rate of the pump group FIT, and a, b, and c are constants representing the sum of the three terminal pressures of the power frequency pump and the pressure at 0 flow.

[0017] Preferably, the flow rate Q / N output per unit shaft power of the pump set is: η=ρg / 1000×H×Q / N=ρg / 1000×H×Q / (N1+N2+N3+N4), where ρ is the density of the medium (kg / m³). 3 g is the acceleration due to gravity in m / s² 2 .

[0018] Preferably, the formula for calculating the specific flow rate of the pump unit per unit time is: q=∑Q / ∑(N1+N2+N3+N4).

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By using the energy efficiency curve diagram corresponding to shaft power and flow rate, the operating point position of each pump in the pump set can be seen intuitively, thereby determining whether each pump is working in the high-efficiency zone; 2. By observing the specific flow rate displayed in the relationship diagram, it can be directly determined whether the pump set is operating in the high-efficiency zone. If it is not in the high-efficiency zone, by adjusting the valves of each fixed-frequency pump and / or the frequency of the variable-frequency pump, each pump can be made to operate at its highest efficiency point. 3. When the pump set load is low, energy saving can be achieved by lowering the system pressure without reducing the pressure of the terminal load, i.e., reducing the valve frequency of each fixed frequency pump and the frequency of the variable frequency pump. Attached Figure Description

[0020] Figure 1 This is a structural diagram of the pump unit of the present invention; Figure 2 This refers to the high-efficiency zone of the power frequency pump and the operating point range of the variable frequency pump in this invention; where lines 1234 represent the rated operating points of the four pumps. Figure 3 This is an energy efficiency curve of the power frequency pump in this invention, where the X-axis represents the percentage of the rated flow rate and the Y-axis represents the power. Detailed Implementation

[0021] The present application will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0022] In the description of this application, it should be understood that the terms "upper", "lower", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0023] The terms "first," "second," etc., used in this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class, without limiting the number of objects; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0024] Example 1: As Figure 1The pump set includes a pump set system inlet pressure gauge, a pump set system outlet pressure gauge, a flow meter, and at least one fixed-frequency pump and one variable-frequency pump connected in parallel. The pump set system outlet pressure gauge displays the pump set system pressure PIT, and the flow meter displays the pump set system flow rate FIT. Each of the fixed-frequency pumps and the variable-frequency pumps has a pressure gauge and an energy meter at its outlet. Each of the fixed-frequency pumps also has an electric valve at its outlet. The real-time power, cumulative energy, pump set system pressure PIT, and pump set system flow rate FIT parameters of each pump are displayed in real time on the background control system interface through the pressure gauge, flow meter, and energy meter. The pump set system pressure PIT is controlled by calculating the flow rate / energy ratio in real time to determine whether each fixed-frequency pump is operating in the high-efficiency zone. The pump set system pressure PIT is controlled by adjusting the electric valve of each fixed-frequency pump and / or the frequency of the variable-frequency pump through the specific flow rate display value.

[0025] like Figure 1 As shown, the pump set of this application consists of three parallel-connected industrial frequency pumps and one variable frequency pump. Each industrial frequency pump and variable frequency pump has a pressure gauge (PI1~PI4) installed at its outlet, electrically connected to the backend control system. Each industrial frequency pump and variable frequency pump also has its own energy meter (W1~W4) electrically connected to the backend control system. Each industrial frequency pump's outlet pipe is also equipped with an electric valve (M1-M3) electrically connected to the backend control system. The pump set's inlet / outlet manifold is equipped with a system inlet pressure gauge (PI0) and a system outlet pressure gauge (PIT), both electrically connected to the backend control system. The pump set's outlet manifold is also equipped with a flow meter (FIT). The flow is controlled by the pressure gauges, flow meters, and electric valves. The energy meter can transmit and display the real-time power, cumulative electrical energy, system pressure (PIT), and system flow rate (FIT) of each component pump in the pump set on the background control system interface. The background control system calculates the specific flow rate of each pump by converting the flow rate to the energy consumption ratio, and compares this to the pump's design maximum efficiency point at 100% flow. By calculating the specific flow rate / energy consumption ratio in real time, it determines whether each pump is operating in its high-efficiency zone. When the displayed specific flow rate / energy consumption ratio exceeds the design maximum efficiency range, the system adjusts the electric valves of each pump and / or the frequency of the variable frequency pump in real time to control the system pressure (PIT), thus ensuring that each pump remains in its high-efficiency zone. This solves the problem of existing pump sets where component pumps cannot accurately identify their operating points, and the entire control is unaffected by individual factors.

[0026] The improved pump set incorporates the flow rate, head, power, and pump efficiency of each pump into its control parameters. By comparing the displayed flow rate with the theoretical value, the high-efficiency operating range of the fixed-frequency pump is determined. The system automatically controls the electric valves and variable-frequency pumps, ensuring that each pump in the set operates within its high-efficiency zone. Automatic control precisely and simultaneously coordinates the high-efficiency operating points, accurately calculating the high-efficiency range of each fixed-frequency pump. This solves the problem of pumps failing to maintain stable high-efficiency operation due to constantly changing loads. By adjusting the fixed-frequency pumps within each pump set, the consumed electrical energy is maximized for value conversion, thereby reducing operating efficiency and energy costs, and achieving energy conservation and emission reduction goals for the pumps and pump set.

[0027] Example 2: Figures 1-3 As shown, a high-efficiency and energy-saving operation control method for a pump set is provided, the control method comprising: S1. Data Acquisition: The real-time power, cumulative energy, pump system pressure (PIT), and pump system flow rate (FIT) of each pump are displayed in real time on the background control system interface through various pressure gauges, flow meters, and energy meters. S2. Calculate the specific flow rate: Calculate the head value of each pump by subtracting the system inlet pressure from the outlet pressure of each fixed frequency pump and variable frequency pump. S3. Energy Efficiency Curve: By calculating the flow rate / electricity ratio in real time, an energy efficiency curve is plotted to show the water production capacity per kilowatt-hour.

[0028] S4. High-efficiency zone determination: Taking the pump system pressure PIT as the control object, establish a power-flow (NQ) characteristic curve database for each industrial frequency pump. Adjust the electric valve at the outlet of each industrial frequency pump through the NQ characteristic curve to control the outlet pressure of each pump. Determine whether the pump set is currently operating in the high-efficiency zone by whether the outlet pressure of each industrial frequency pump is kept within the set range. S5. Dynamic adjustment: When the specific flow rate displayed in the NQ characteristic curve is lower than the preset lower limit of the high efficiency zone, it is determined to be inefficient operation, and its outlet pressure is adjusted by adjusting the frequency of the variable frequency pump; when the specific flow rate displayed is higher than the preset upper limit of the high efficiency zone, it is determined to be inefficient operation, and its outlet pressure is adjusted by adjusting the electric valve of each power frequency pump and the frequency of the variable frequency pump, thereby realizing the control of the pump group system pressure PIT.

[0029] Taking a pump set consisting of three industrial frequency pumps and one variable frequency pump as an example, as follows: Figure 1As shown: To ensure each pump in the pump set operates within its high-efficiency zone, the high-efficiency zone must first be determined. This requires collecting data on the pump's head, flow rate, and power consumption. Therefore, pressure gauges electrically connected to the system are installed at the pump set system inlet, outlet, and the outlets of each fixed-frequency and variable-frequency pump. Simultaneously, an energy meter connected to the control system's electrical signal is installed at the outlet of each fixed-frequency and variable-frequency pump. A flow meter is also installed at the pump set system outlet. By collecting data from the pressure gauges, flow meters, and energy meters, the control system can calculate the flow-to-power ratio in real time and plot the flow-to-power energy efficiency curve, as shown below. Figure 2 As shown, Figure 2 In this diagram, H represents the head, Q represents the flow rate, N represents the actual power of the pump, and η represents the theoretical power of the pump. This indicates the pump's ability to produce water per kilowatt-hour of electricity. A higher value indicates higher energy efficiency. Figure 2 The shaded area is shown. By increasing or decreasing the opening of the electric valve at the outlet of each fixed-frequency pump and observing the slope of the operating curve, it can be clearly seen that when the slope increases, it indicates that the pump's operating point is on the low-flow side, and the pump's potential can be increased. Conversely, when the slope decreases, it indicates that the pump's operating point is on the high-flow side, and further increasing the flow rate may cause it to exit the high-efficiency zone, and the pump's drive motor may be overloaded. Finally, the variable-frequency pump automatically fine-tunes according to the system pressure PIT to maintain the system pressure at a constant value. Theoretically, by adjusting the electric valve M and the frequency of the variable-frequency pump, the operating points of each fixed-frequency pump can be made to operate within the high-efficiency zone. Other flow ranges can be achieved using the variable-frequency pump, as follows. Figure 2 Curves 5, 6, 7, and 8 are shown in the figure.

[0030] This solves the problems in existing pump and pump set control where it is difficult to keep all pumps in the pump set working in the high-efficiency range and where it is difficult for the pumps to work in coordination and efficiency at the same time. It also solves the problem that the operation of the pump is easily affected by human factors when the outlet pressure is adjusted on site. When the load changes, it can achieve precise adjustment of the valve opening, so that the entire pump set always works stably in the high-efficiency range.

[0031] For pump sets, the more pumps there are, the easier it is to control them within the high-efficiency range. However, this also means more frequent pump switching. Therefore, at least one variable frequency (VFD) pump should be included in the pump set. The presence of a VFD allows switching between the high-efficiency ranges of two pumps. Since the VFD pump outlet does not require valve adjustment for head, there is no valve pressure loss, resulting in a very wide high-efficiency range. This allows the pump set to operate within its high-efficiency range across the entire flow rate range by adjusting the frequency of the VFD. This type of equipment can adjust the pump's operating parameters, especially flow rate and frequency, according to changes in system requirements. Based on the pump's technical parameters, its high-efficiency operating range can be roughly determined. Generally, it's the rated head and rated flow point. However, within a pump set, each pump is affected by adjacent pumps, causing their high-efficiency operating points to shift. By introducing electrical parameters, this VFD technology allows the pump set to dynamically adjust its operating status under different conditions to achieve energy savings.

[0032] Further improvements include, for example Figure 3 As shown, the energy efficiency curves in step S3 include the HQ curve, NQ curve, and η-Q curve, which are monotonic function curves, where H is the head, Q is the pump system flow rate FIT, and N is the power of each power frequency pump.

[0033] In the diagram, H0 represents the rated system pressure of the pump set, the HQ curve represents the head-flow rate curve of the power frequency pump, the NQ curve represents the power-flow rate curve displayed after actual calculation, and η-Q is the efficiency-flow rate line. From these characteristic curves HQ, NQ, and η-Q of the power frequency pump, it can be seen that they are all monotonic functions. This means that the head H, flow rate Q, and pump power N are in one-to-one correspondence. Therefore, even if the flow rate Q of a single pump is unknown, as long as the power N is known, the operating point of the power frequency pump can be represented using the pump power. Figure 3 As can be seen from the HQ curves, the power frequency pump is in its high-efficiency range between curves A and B, with the η-Q curve showing the highest efficiency and the NQ curve exhibiting the steepest slope (specific flow rate q). Because the outlet electric valve openings of each power frequency pump are different, the outlet pressures of each pump are also different. If the characteristic curves of each power frequency pump are different, even if the outlet pressures are the same, it does not necessarily mean that they are at their operating point, and therefore, it cannot be guaranteed that their operating point is in the high-efficiency range. Figure 3 As shown, when the EF segment in the NQ curve replaces the AB segment in the HQ curve, the operating point of the HQ curve corresponding to the power point E on the NQ curve is point A, and the operating point of the HQ curve corresponding to the power point F is point B. When the actual power is in N... E ~N FWhen the flow rate Q is close to 100%, the operating point will also be between points A and B, indicating that the power frequency pump is in the high-efficiency zone. When it exceeds the AB segment, that is, when the operating power of the power frequency pump is less than point E or greater than point F, it means that the operating point of the power frequency pump exceeds the AB segment of the HQ curve, that is, the pump's operating point is not in the high-efficiency zone. Therefore, by determining whether the NQ curve operates in the EF segment, it is equivalent to determining whether the HQ curve operates in the AB segment, thus determining whether it is operating in the high-efficiency zone.

[0034] A further improvement is made to the NQ curve equation of the power frequency pump as: N = aQ² + bQ + c; where a, b, and c are constants corresponding to the sum of the three power values ​​of the power frequency pump and the power at 0 flow rate.

[0035] To obtain the NQ curve, three points can be taken at 90%, 100%, and 110% of the flow rate. Using three-point interpolation, the NQ curve can be obtained. Since the NQ curve is nearly linear, it can be solved using a quadratic equation: the NQ curve equation for a power frequency pump is N = aQ. 2 +bQ+c; where a, b, and c are constants corresponding to the sum of the three powers of the power pump and the power at 0 flow rate. That is, with the power of other pumps fixed, take three values ​​of the system flow rate Q: Q1=90%, Q2=100%, Q3=110%, and measure the three powers corresponding to the current power pump: N1, N2, N3. Add the power at 0 flow rate to obtain the constants a, b, and c, thus obtaining the NQ curve. Extend this curve downwards to the power N when Q=0 to obtain the complete NQ curve.

[0036] A further improvement is that the method also includes a variable pressure control mode: the system calculates the current pipeline pressure drop ΔP based on the real-time flow rate FIT using the formula ΔP=aQ²+bQ+c, and dynamically adjusts the pump set pressure PIT of the pump group system accordingly, so that it remains at the lowest level while meeting the pressure demand at the most unfavorable end point, thereby achieving the purpose of energy saving.

[0037] To meet the terminal pressure requirements at the most unfavorable point (maximum pressure drop load), the pump set outlet pressure PIT (i.e., PIT = required terminal pressure + ΔP) can be dynamically and minimally set based on the pipeline pressure drop ΔP calculated from the real-time flow rate Q, thereby achieving energy savings.

[0038] The terminal pressure of the maximum pressure drop load is indirectly obtained by correcting the pump system pressure PIT using the pump system flow rate FIT. The formula for calculating the pump system flow rate FIT correction is: ΔP = aQ 2 +bQ+c, where △P is the pipeline pressure drop, Q is the system flow rate of the pump group FIT, and a, b, and c are constants representing the sum of the three terminal pressures of the power frequency pump and the pressure at 0 flow.

[0039] The formula for calculating the FIT correction amount of the pump system flow rate is: △P=aQ 2 +bQ+c, where △P is the pipeline pressure drop, Q is the pump system flow rate FIT, and a, b, and c are constants representing the sum of the three terminal pressures of the power frequency pump and the pressure at 0 flow rate; the flow rate Q / N output per unit shaft power of the pump set is: η=ρg / 1000×H×Q / N=ρg / 1000×H×Q / (N1+N2+N3+N4) where ρ is the density of the medium (kg / m³). 3 g is the acceleration due to gravity in m / s² 2 .

[0040] The efficiency η of a pump set is directly proportional to the specific flow rate q. The formula for calculating the specific flow rate q is q = Q / N = Q / (N1+N2+N3+N4). Therefore, the complete formula for efficiency is η = (ρg*H*Q) / (1000 * N_total). For a pump set, the more pumps there are, the easier it is to control the pumps within the high-efficiency range. However, this also leads to more frequent pump switching. Therefore, at least one variable frequency (VFD) pump should be configured in the pump set. The presence of a VFD allows operation between the high-efficiency ranges of two pumps. Since the outlet of a VFD pump does not require valve adjustment of the head, there is no valve pressure loss. Therefore, the high-efficiency range of a VFD pump is very wide. This allows the pump set to always operate within the high-efficiency range across the entire flow range by adjusting the frequency of the VFD. This type of equipment can adjust the pump's operating parameters, especially flow rate and frequency, according to changes in system requirements. Based on the pump's technical parameters, the pump's high-efficiency operating range can be basically determined, generally at the rated head and rated flow rate point. However, within a pump set, each pump is affected by adjacent pumps, and its high-efficiency operating point may shift. By incorporating electrical parameters, this variable frequency technology allows the pump unit to dynamically adjust its operating status under different working conditions, thereby achieving energy-saving effects.

[0041] For pumps and pump sets, the process requirement parameter is flow rate. Therefore, under the premise of meeting the required flow rate, the lower the pump outlet pressure, the smaller the pump power, or in other words, the larger the flow rate per unit shaft power (specific flow rate q = Q / N), resulting in greater energy savings. Thus, when the flow rate is low, the pipeline pressure drop loss is also low, the terminal pressure is higher, and the required system pressure is lower. Therefore, the pressure in constant pressure control should not be the system pressure, but rather the terminal pressure of the load with the largest pressure drop. Although the terminal pressure data is not sampled into the back-end control system, it can be indirectly obtained by correcting the system pressure using the system flow rate. The correction amount can be obtained based on actual measurements. Since the pipeline pressure drop ΔP is proportional to the square of the flow rate Q, let: ΔP = aQ 2Given the system flow rate Q, we take three values: Q1=90%, Q2=100%, and Q3=110%. We then measure the three terminal pressures corresponding to the current power frequency pump: P1, P2, and P3. Adding these to the pressure P0 at zero flow rate, we can obtain the constants a, b, and c, thus obtaining the ΔPQ curve. Extending this curve downwards to the static pressure P0 at Q=0 gives us the complete ΔPQ curve. We can then determine the system pressure as the pump's rated pressure H0 - ΔP based on the load. Specific implementation methods

[0042] Taking the 14SA-10 pump as an example, the head is 40m, the flow rate is 900m³ / h, the rated power of the motor is 160kW, the rated operating point motor input power N=146kW, and the structure is as follows. Figure 1 As shown.

[0043] Since there is a total flow rate Q in the background, and the power of each pump N1, N2, N3, and N4, the efficiency η of the pump set is proportional to the specific flow rate (flow rate Q / N per unit shaft power): η = ρg / 1000×H×Q / N=ρg / 1000×H×Q / (N1+N2+N3+N4), where ρ is the density of the medium (kg / m3) and g is the gravitational acceleration (m / s2).

[0044] Therefore, the efficiency of a pump set can be expressed by its specific flow rate q. Obviously, the larger the specific flow rate q, the higher the efficiency of the pump set. Since the rated specific flow rate of each pump is q = Q / N = 900 / 146 = 6.16 m³ / h / kW, the high-efficiency zone of the pump set should be 6.16 ± 10% = 5.54~6.78. When the specific flow rate q < 5.54, the pump set is obviously not operating in the high-efficiency zone.

[0045] A further improvement is made to the formula for calculating the specific flow rate of the pump unit per unit time: q=∑Q / ∑(N1+N2+N3+N4).

[0046] Meanwhile, the efficiency of the pump set can also be used as a report to determine whether the pump set is operating in the high-efficiency zone. When the time is one day, the flow rate Q is the cumulative value of one day, and the power is the sum of the cumulative values ​​of N1, N2, N3, and N4. The specific flow rate for each day is obtained as: q = ∑Q / ∑(N1+N2+N3+N4). The above calculation formula can also be used as a basis for determining whether the pump set is operating in the high-efficiency zone in the form of a report. For example, if the flow rate Q is the cumulative value of one day, and the power is the sum of the cumulative values ​​of N1, N2, N3, and N4, and the specific flow rate is recorded for two days under different loads, the pump set energy efficiency value in the report can indicate whether the pump set is operating in the high-efficiency zone. As can be seen from the table above, at low flow rates, the specific flow rate is less than the lower limit of the high-efficiency zone, indicating that the system pressure is too high at low flow rates, and the frequency of the power frequency pump and the high frequency pump should be reduced.

[0047] The table above also shows that at low flow rates, the power of pump 1 is 3096 / 24=129kW, which is less than 90% of the rated operating point of 146kW. In other words, it exceeds the high-efficiency zone of pump 1, so the specific flow rate is too low.

[0048] The above embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of protection of this application. Any non-substantial changes and substitutions made by those skilled in the art based on this application shall fall within the scope of protection claimed by this application.

Claims

1. A pump set, characterized in that: The system includes an inlet pressure gauge, an outlet pressure gauge, a flow meter, and at least one fixed-frequency pump and one variable-frequency pump connected in parallel. The outlet pressure gauge displays the system pressure (PIT), and the flow meter displays the system flow rate (FIT). Each fixed-frequency pump and variable-frequency pump has a pressure gauge and an energy meter at its outlet. Each fixed-frequency pump also has an electric valve at its outlet. The real-time power, cumulative energy, system pressure (PIT), and system flow rate (FIT) of each pump are displayed in real-time on the background control system interface through the pressure gauge, flow meter, and energy meter. The system determines whether each fixed-frequency pump is operating in the high-efficiency zone by calculating the flow rate / energy ratio in real time, and controls the system pressure (PIT) by adjusting the electric valve of each fixed-frequency pump and / or the frequency of the variable-frequency pump based on the displayed flow rate value.

2. A high-efficiency and energy-saving operation control method for a pump set as described in claim 1, characterized in that: The control method includes: S1. Data Acquisition: The real-time power, cumulative energy, pump system pressure (PIT), and pump system flow rate (FIT) of each pump are displayed in real time on the background control system interface through various pressure gauges, flow meters, and energy meters. S2. Calculate the specific flow rate: Calculate the head value of each pump by subtracting the system inlet pressure from the outlet pressure of each fixed frequency pump and variable frequency pump. S3. Energy Efficiency Curve: By calculating the flow rate / electricity ratio in real time, an energy efficiency curve is plotted to show the water production capacity per kilowatt-hour. 3.S4, High-efficiency zone determination: Taking the pump system pressure PIT as the control object, establish a power-flow (NQ) characteristic curve database for each industrial frequency pump. Adjust the electric valve at the outlet of each industrial frequency pump through the NQ characteristic curve to control the outlet pressure of each pump. Determine whether the pump set is currently operating in the high-efficiency zone by whether the outlet pressure of each industrial frequency pump is kept within the set range. S5. Dynamic adjustment: When the specific flow rate displayed in the NQ characteristic curve is lower than the preset lower limit of the high efficiency zone, it is determined to be inefficient operation, and its outlet pressure is adjusted by adjusting the frequency of the variable frequency pump; when the specific flow rate displayed is higher than the preset upper limit of the high efficiency zone, it is determined to be inefficient operation, and its outlet pressure is adjusted by adjusting the electric valve of each power frequency pump and the frequency of the variable frequency pump, thereby realizing the control of the pump group system pressure PIT.

4. The method for high-efficiency and energy-saving operation control of a pump set according to claim 2, characterized in that: The energy efficiency curves in step S3 include the HQ curve, NQ curve, and η-Q curve, which are monotonic function curves, where H is the head, Q is the pump system flow rate FIT, and N is the power of each power frequency pump.

5. The method for high-efficiency and energy-saving operation control of a pump set according to claim 3, characterized in that: The NQ curve equation for the power frequency pump is: N = aQ 2 +bQ+c, where a, b, and c are constants corresponding to the sum of the three power values ​​of the power pump and the power at 0 flow rate.

6. The method for high-efficiency and energy-saving operation control of a pump set according to claim 3, characterized in that: The system pressure PIT is adjusted by the flow rate FIT of the pump group system to indirectly obtain the terminal pressure of the maximum pressure drop.

7. The method for high-efficiency and energy-saving operation control of a pump set according to claim 3, characterized in that: The method also includes a variable pressure control mode: the system calculates the current pipeline pressure drop ΔP based on the real-time flow rate FIT using the formula ΔP=aQ²+bQ+c, and dynamically adjusts the pump set pressure PIT to keep it at the lowest level while meeting the pressure demand at the most unfavorable point, thereby achieving energy saving.

8. The method for high-efficiency and energy-saving operation control of a pump set according to claim 1, characterized in that: The flow rate Q / N output per unit shaft power of the pump set is: η=ρg / 1000×H×Q / N=ρg / 1000×H×Q / (N1+N2+N3+N4), where ρ is the density of the medium (kg / m³). 3 g is the acceleration due to gravity in m / s² 2 .

9. The method for high-efficiency and energy-saving operation control of a pump set according to claim 7, characterized in that: The formula for calculating the specific flow rate per unit time of the pump set is: q=∑Q / ∑(N1+N2+N3+N4).

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