Parallel multi-circulating water pump cooling water flow control system and control method

Abstract

The application discloses a kind of parallel multiple circulating water pumps cooling water flow control system and control method, by economic flow calculation test loop and circulating pump current balance control loop composition.The parallel multiple circulating water pumps cooling water flow control system and control method of the application are convenient to use, the change of the water quantity of circulating water pump front water pool is converted and characterized the water output of certain circulating water pump.Through the curve comparison of circulating water pump water output and power consumption, the most economical circulating water pump operation mode combination is found, and the control matching performance of circulating water quantity is realized.

Description

Technical Field

[0001] This invention relates to the field of cooling water flow control system technology, specifically to a cooling water flow control system and control method for multiple parallel circulating water pumps. Background Technology

[0002] Circulating water pumps are one of the main auxiliary equipment in thermal power generating units, and their primary task is to provide circulating cooling water for condensers and other equipment requiring cooling. To improve the operating efficiency of circulating water pumps, many thermal power plants adopt a working mode in which multiple circulating water pumps of the same type operate in parallel, simultaneously supplying circulating cooling water to multiple thermal power units. How to rationally adjust the combined circulating water flow demand of multiple thermal power units has become an important issue in ensuring the most economical operation of the circulating water pumps.

[0003] Current domestic research on the economic performance matching of circulating water systems aims to achieve a balance between the most economical circulating water flow rate demand of the generator set at a certain load range and circulating water temperature, and the flow rate demand supplied by the circulating pump. At this dynamic equilibrium point, if the circulating water volume is too large or too small, the increased power consumption of the circulating pump will exceed the increase in the generator load.

[0004] Because the combination and matching of generator set and circulating water pump operation modes mainly varies with two key factors—grid load demand and circulating water temperature—the circulating water flow rate is assessed on an annual time axis, resulting in significant fluctuations. However, the circulating water is taken from seawater or natural freshwater, which is turbid, and flow measurement would incur additional throttling losses, leading to the lack of reliable measurement devices for circulating water flow rate in engineering applications.

[0005] Given a clear demand for circulating water flow at the unit end, the circulating water pump side needs an economical flow matching curve. This means that there are different numbers, combinations, and output accumulations of circulating water pumps operating for different flow demands. There are controllable quantities to ensure that each operating circulating water pump matches the demand end in real time, and that the output of each circulating water pump is balanced and does not compete for water.

[0006] Based on the above, this invention proposes a control system and method for cooling water flow of multiple parallel circulating water pumps, which can effectively solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to provide a control system and method for cooling water flow of multiple parallel circulating water pumps. This control system and method is easy to use. By measuring the change in the water pumping volume of the pool before the circulating water pumps, the output water volume of a particular circulating water pump is calculated and characterized. By comparing the curves of circulating water pump output water volume and power consumption, the most economical combination of circulating water pump operating modes is found, achieving controlled matching performance of the circulating water volume.

[0008] This invention is achieved through the following technical solution:

[0009] A cooling water flow control system for multiple parallel circulating water pumps consists of an economic flow calculation test loop and a circulating pump current balance control loop.

[0010] The purpose of this invention is to provide a control system and method for cooling water flow of multiple parallel circulating water pumps. This control system and method is easy to use. By measuring the change in the water pumping volume of the pool before the circulating water pumps, the output water volume of a particular circulating water pump is calculated and characterized. By comparing the curves of circulating water pump output water volume and power consumption, the most economical combination of circulating water pump operating modes is found, achieving controlled matching performance of the circulating water volume.

[0011] Preferably, the economic flow calculation test loop includes a comprehensive calculation of the circulating water tank level and the circulating pump power consumption.

[0012] A control method for a cooling water flow control system for multiple parallel circulating water pumps includes the following steps:

[0013] Step S1: Multiple circulating water pumps of the same type running in parallel can all control the output of the circulating water pumps through blade angle adjustment. The cooling water source is the same, and each is equipped with a relatively independent forepool pit with the same cross-sectional area S. The liquid level L is measured in the forepool pit without a circulating water pump.

[0014] Step S2: During normal operation of the circulating water pump A1, the liquid level L1 is measured and the liquid level drop value ΔL1 = L - L1 is calculated. (ΔL1)2*S*k1 represents the flow output of the circulating water pump A1 at this time. The value of k1 is obtained by actual measurement of the flow rate of the circulating water main pipe.

[0015] Step S3: Record the power P(A1) corresponding to the change of (△L1)2*S*k1 when the active power of circulating water pump A1 is adjusted from zero blade angle to 100% blade angle. The output curve f(A1) is obtained when (△L1)2*S*k1 changes. The ratio of circulating water flow to electricity is the circulating water flow per kilowatt-hour. k(A1)=(△L1)2*S*n / P(A1), which represents the circulating water flow generated by circulating water pump A1 for each kilowatt-hour consumed. The larger this value is, the more economical it is. Thus, the most economical circulating water pump Ag is obtained by comparison.

[0016] Step S4: Under the premise that Ag is running, start another circulating water pump A1 at the same time and measure the liquid levels Lg and L1;

[0017] Step S5: Calculate f(Ag)+f(A1)=(△Lg)2*S*k2+(△L1)2*S*k2=(L-Lg)2*S*k2+(L-L1)2*S*k2, where k2 is the gain coefficient of the two pumps running in parallel, and the value of k2 is obtained by actual measurement of the flow rate of the circulating pump's main pipe; record the corresponding output curve f(Ag, A1) and k(Ag, A1) of the power change of △L when the power of circulating water pumps A1 and Ag is adjusted from zero blade angle to 100% blade angle during parallel operation;

[0018] Step S6: By analogy, obtain the corresponding output curve f(Ag, An) and k(Ag, An) of the power change ΔL when the power is adjusted from zero blade angle to 100% blade angle when the circulating water pumps Ag and An are running in parallel. From this, obtain the circulating water pump Ag and An combination that is most energy-efficient.

[0019] Step S7: Under the premise that circulating water pumps Ag and Am are running in parallel, start the third circulating water pump at the same time to obtain the three circulating water pumps Ag, Am and Ab that operate in the most energy-efficient manner, as well as f(Ag, Am, Ab) and k(Ag, Am, Ab); and so on, to obtain combinations of different numbers of circulating water pumps running in parallel.

[0020] Step S8: Based on the output curves of the above n circulating water pumps, obtain the operating curve of the most energy-efficient circulating pump combination;

[0021] Step S9: According to the total demand value Ft of the circulating water pump flow, start the number of pumps selected in the combined economic operation output curve, and adjust the opening of the blade angle regulating valve according to △L to control the output of each circulating water pump to maintain at △L.

[0022] Step S10: Similarly, after confirming that p circulating water pumps are in maintenance status, a combination of np circulating water pump output curves other than those in maintenance status is obtained. According to the total circulating water pump flow demand value Ft, the number of pumps selected in the combined economic operation output curve is turned on, and the opening of the blade angle regulating valve is adjusted according to ΔL to control the output of each circulating water pump to be maintained at ΔL.

[0023] Preferably, in the circulating pump current balance control loop, the current deviation between the current of a certain circulating water pump and the currents of the other circulating water pumps is determined. When the current Ig of a certain circulating water pump deviates from the currents of the other circulating water pumps by more than a set value B, the current is adjusted based on Ig and the average value I of the other motor currents. 平均 The deviation value is used to adjust the opening of the blade angle regulating valve by the PID controller to achieve output balance between the circulating water pumps.

[0024] Preferably, the remaining circulating water pumps maintain the liquid level in the inlet pool by adjusting the blade angle valve opening of the PID controller to achieve a balance in the output of the circulating water pumps, while maintaining the total output of the circulating water pumps at the required value Ft.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] The purpose of this invention is to provide a control system and method for cooling water flow of multiple parallel circulating water pumps. This control system and method is easy to use. By measuring the change in the water pumping volume of the pool before the circulating water pumps, the output water volume of a particular circulating water pump is calculated and characterized. By comparing the curves of circulating water pump output water volume and power consumption, the most economical combination of circulating water pump operating modes is found, achieving controlled matching performance of the circulating water volume. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the economic flow measurement test loop described in this invention;

[0028] Figure 2 This is a schematic diagram of the current balance control circuit for the circulating water pump (a circulating water pump with current deviation) described in this invention.

[0029] Figure 3 This is a schematic diagram of the circulating pump current balance control circuit (other circulating water pumps in normal operation) described in this invention. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solutions of the present invention, preferred embodiments of the present invention are described below in conjunction with specific examples. However, it should be understood that the accompanying drawings are for illustrative purposes only and should not be construed as limiting the present patent. For better illustration of this embodiment, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable that some well-known structures and their descriptions may be omitted in the drawings for those skilled in the art. The positional relationships described in the drawings are for illustrative purposes only and should not be construed as limiting the present patent.

[0031] Example 1:

[0032] like Figures 1 to 3 As shown, a cooling water flow control system for multiple circulating water pumps in parallel consists of an economic flow calculation test loop and a circulating pump current balance control loop.

[0033] Furthermore, in another embodiment, the economic flow calculation test loop includes a comprehensive calculation of the circulating water tank level and the circulating pump power consumption.

[0034] A control method for a cooling water flow control system for multiple parallel circulating water pumps includes the following steps:

[0035] Step S1: Multiple circulating water pumps of the same type running in parallel can all control the output of the circulating water pumps through blade angle adjustment. The cooling water source is the same, and each is equipped with a relatively independent forepool pit with the same cross-sectional area S. The liquid level L is measured in the forepool pit without a circulating water pump.

[0036] Step S2: During normal operation of the circulating water pump A1, the liquid level L1 is measured and the liquid level drop value ΔL1 = L - L1 is calculated. (ΔL1)2*S*k1 represents the flow output of the circulating water pump A1 at this time. The value of k1 is obtained by actual measurement of the flow rate of the circulating water main pipe.

[0037] Step S3: Record the power P(A1) corresponding to the change of (△L1)2*S*k1 when the active power of circulating water pump A1 is adjusted from zero blade angle to 100% blade angle. The output curve f(A1) is obtained when (△L1)2*S*k1 changes. The ratio of circulating water flow to electricity is the circulating water flow per kilowatt-hour. k(A1)=(△L1)2*S*n / P(A1), which represents the circulating water flow generated by circulating water pump A1 for each kilowatt-hour consumed. The larger this value is, the more economical it is. Thus, the most economical circulating water pump Ag is obtained by comparison.

[0038] Step S4: Under the premise that Ag is running, start another circulating water pump A1 at the same time and measure the liquid levels Lg and L1;

[0039] Step S5: Calculate f(Ag)+f(A1)=(△Lg)2*S*k2+(△L1)2*S*k2=(L-Lg)2*S*k2+(L-L1)2*S*k2, where k2 is the gain coefficient of the two pumps running in parallel, and the value of k2 is obtained by actual measurement of the flow rate of the circulating pump's main pipe; record the corresponding output curve f(Ag, A1) and k(Ag, A1) of the power change of △L when the power of circulating water pumps A1 and Ag is adjusted from zero blade angle to 100% blade angle during parallel operation;

[0040] Step S6: By analogy, obtain the corresponding output curve f(Ag, An) and k(Ag, An) of the power change ΔL when the power is adjusted from zero blade angle to 100% blade angle when the circulating water pumps Ag and An are running in parallel. From this, obtain the circulating water pump Ag and An combination that is most energy-efficient.

[0041] Step S7: Under the premise that circulating water pumps Ag and Am are running in parallel, start the third circulating water pump at the same time to obtain the three circulating water pumps Ag, Am and Ab that operate in the most energy-efficient manner, as well as f(Ag, Am, Ab) and k(Ag, Am, Ab); and so on, to obtain combinations of different numbers of circulating water pumps running in parallel.

[0042] Step S8: Based on the output curves of the above n circulating water pumps, obtain the operating curve of the most energy-efficient circulating pump combination;

[0043] Step S9: According to the total demand value Ft of the circulating water pump flow, start the number of pumps selected in the combined economic operation output curve, and adjust the opening of the blade angle regulating valve according to △L to control the output of each circulating water pump to maintain at △L.

[0044] Step S10: Similarly, after confirming that p circulating water pumps are in maintenance status, a combination of np circulating water pump output curves other than those in maintenance status is obtained. According to the total circulating water pump flow demand value Ft, the number of pumps selected in the combined economic operation output curve is turned on, and the opening of the blade angle regulating valve is adjusted according to ΔL to control the output of each circulating water pump to be maintained at ΔL.

[0045] Furthermore, in another embodiment, in the circulating pump current balance control loop, the current deviation between the current of a certain circulating pump and the currents of the other circulating pumps is determined. When the current Ig of a certain circulating pump deviates from the currents of the other circulating pumps by more than a set value B, the current is adjusted based on Ig and the average value I of the remaining motor currents. 平均 The deviation value is used to adjust the opening of the blade angle regulating valve by the PID controller to achieve output balance between the circulating water pumps.

[0046] Furthermore, in another embodiment, the remaining circulating water pumps maintain the opening of the blade angle regulating valve adjusted by the PID controller of the inlet water level controller to achieve a balance of circulating water pump output, while maintaining the total output of the circulating water pump at the required value Ft.

[0047] Example 2:

[0048] A power plant's second-phase generating units have eight circulating water pumps operating in parallel via a mains pipe, named A1, A2...A8. These pumps supply circulating cooling water to a maximum of six generating units. The multiple identical circulating water pumps operating in parallel can all have their output controlled by a blade angle regulating valve. The cooling water source is consistent, and each pump is equipped with a relatively independent forebay with a uniform cross-sectional area of ​​S. The liquid level L is measured in the forebay where no circulating water pump is installed.

[0049] During normal operation, the liquid level L1 of circulating water pump A1 is measured. At this time, the liquid level drop value ΔL1 = L - L1 is calculated. (ΔL1)2*S*k1 represents the flow output of circulating water pump A1 at this time. When the active power of circulating water pump A1 is adjusted from zero blade angle to 100% blade angle, the power P(A1) corresponding to the change of (ΔL1)2*S*k1 is recorded, and the corresponding output curve f(A1) is obtained. The value of k1 is obtained by actual measurement of the flow rate of the outlet main pipe. The ratio of circulating water flow rate to electricity is the circulating water flow rate corresponding to each kilowatt-hour of electricity. k(A1) = (ΔL1)2*S*k1 / P(A1) represents the circulating water flow rate generated by circulating water pump A1 for each kilowatt-hour of electricity consumed. The larger this value is, the more economical it is. Thus, the most economical circulating water pump A3 is obtained by comparison.

[0050] With pump A3 running, another circulating water pump A1 is simultaneously started, and the liquid levels L3 and L1 are measured. The calculation is then performed as f(A3) + f(A1) = (ΔL3)² * S * k² + (ΔL1)² * S * k² = (L - L3)² * S * k² + (L - L1)² * S * k², where k² is obtained through actual flow measurement of the outlet header. Record the output curve f(A3, A1) and k(A3, A1) corresponding to the power-to-electricity change in ΔL when the power is adjusted from zero blade angle to 100% blade angle during parallel operation of circulating water pumps A1 and A3. Similarly, obtain the output curve f(A3, An) and k(A3, An) corresponding to the power-to-electricity change in ΔL when the power is adjusted from zero blade angle to 100% blade angle during parallel operation of circulating water pumps A3 and An. From this, the most energy-efficient combination of circulating water pumps A3 and A8 is determined.

[0051] With circulating water pumps A3 and A8 running in parallel, the third circulating water pump is started simultaneously to obtain the three circulating water pumps A3, A8 and A2 that operate in the most energy-efficient manner, and their output curves.

[0052] By analogy, combinations of different numbers of circulating water pumps operating in parallel are obtained, along with their output curves.

[0053] Based on the output curves of the above n circulating water pumps, the most energy-efficient pump combination operation curve is obtained, that is, different circulating water demand corresponds to different operating numbers and output combinations of circulating water pumps. At this time, according to the total circulating water pump flow demand value Ft, and according to the curve requirements, 4 circulating pumps A3, A8, A2, and A1 need to be turned on. Each circulating water pump controls the opening of the impeller angle regulating valve according to the preset flow control ΔL to control the circulating water output and ensure the most economical circulating water pump output.

[0054] Example 3:

[0055] A power plant's second-phase generating units have eight circulating water pumps operating in parallel via a mains valve, named A1, A2...A8. These pumps supply circulating cooling water to a maximum of six generating units. The parallel-operating pumps are all identical and their output can be controlled by a blade angle regulating valve. The cooling water source is consistent, and each pump has a relatively independent forebay with a uniform cross-sectional area of ​​S. At a certain moment, three pumps, A3, A8, and A2, are operating in parallel with operating currents of 292A, 293A, and 280A respectively, and the total circulating water flow rate is 100 t / h.

[0056] The currents of circulating water pumps A2, A3, and A8 all differ by more than the set value B, which is 10A. Therefore, the average current of A3 and A8 is calculated as (293A + 292A) divided by 2, which is 292.5A. The set values ​​of 292.5A and 280A are fed into the current deviation PID controller to adjust the opening of the blade angle regulating valve to reduce the current deviation value. At the same time, the flow output of circulating water pump A2 is 30t / h and the water level PID automatic control of the water tank is withdrawn. Circulating water pumps A3 and A8 are adjusted according to the total flow demand of 100t / h - 30t / h = 70t / h.

[0057] Based on the 70t / h demand of the circulating water pump and the economic operation curve of the dual pumps, the circulating water pumps use the most economical flow rate of the dual pumps, and the opening of the blade angle regulating valve is controlled by the PID control of the water tank level, thereby controlling the output of circulating water pumps A3 and A8.

[0058] At the same time, the control system issued an alarm for abnormal output of circulating water pump A2, prompting maintenance personnel to analyze and check the output of circulating water pump A2.

[0059] Based on the description and accompanying drawings of this invention, those skilled in the art can easily manufacture or use the parallel multi-circulating water pump cooling water flow control system and control method of this invention, and can produce the positive effects described in this invention.

[0060] Unless otherwise specified, in this invention, terms such as "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention 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. Therefore, the terms used to describe orientation or positional relationships in this invention are for illustrative purposes only and should not be construed as limiting this patent. For those skilled in the art, the specific meaning of the above terms can be understood in conjunction with the accompanying drawings and according to the specific circumstances.

[0061] Unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" in this invention should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for controlling the cooling water flow rate of multiple parallel circulating water pumps, characterized in that: Includes the following steps: Step S1: Multiple circulating water pumps of the same type running in parallel can all control the output of the circulating water pumps through blade angle adjustment. The cooling water source is the same, and each is equipped with a relatively independent forepool pit with the same cross-sectional area S. The liquid level L is measured in the forepool pit without a circulating water pump. Step S2: During normal operation of the circulating water pump A1, the liquid level L1 is measured. At this time, the liquid level drop ΔL1 = L - L1 is calculated. (ΔL1) 2 *S*k1 represents the flow rate and output of circulating water pump A1 at this time. The value of k1 is obtained by actual measurement of the flow rate of the circulating water main pipe. Step S3: Record the power P(A1) corresponding to the adjustment of the active power of circulating water pump A1 from zero blade angle to 100% blade angle, and obtain (△L1). 2 The output curve f(A1) corresponding to the change of *S*k1, the ratio of circulating water flow to electricity is the circulating water flow per kilowatt-hour, k(A1) = (△L1). 2 *S*k1 / P(A1) represents the circulating water flow rate generated by the circulating water pump A1 for every kilowatt-hour of electricity consumed. The larger this value is, the more economical it is. Thus, the most economical circulating water pump Ag is obtained by comparison. Step S4: Under the premise that Ag is running, start another circulating water pump A1 at the same time and measure the liquid levels Lg and L1; Step S5: Calculate f(Ag) + f(A1) = (△Lg) 2 *S*k2 +(△L1) 2 *S*k2 =(L-Lg) 2 *S*k2 +(L-L1) 2 *S*k2, where k2 is the gain coefficient of the two pumps running in parallel, and the value of k2 is obtained by actual measurement of the flow rate of the circulating pump header; record the output curve f(Ag, A1) and k(Ag, A1) corresponding to the change of power and electricity ΔL when the power is adjusted from zero blade angle to 100% blade angle when the circulating water pumps A1 and Ag are running in parallel. Step S6: By analogy, obtain the corresponding output curve f(Ag, An) and k(Ag, An) of the power change ΔL when the power is adjusted from zero blade angle to 100% blade angle when the circulating water pumps Ag and An are running in parallel. From this, obtain the most energy-efficient combination of circulating water pumps Ag and An. Step S7: Under the premise that circulating water pumps Ag and Am are running in parallel, start the third circulating water pump at the same time to obtain the three circulating water pumps Ag, Am and Ab that operate in the most energy-efficient manner, as well as f(Ag, Am, Ab) and k(Ag, Am, Ab); and so on, to obtain combinations of different numbers of circulating water pumps running in parallel. Step S8: Based on the output curves of n circulating water pumps, obtain the operating curve of the most energy-efficient circulating pump combination; Step S9: According to the total demand value Ft of the circulating water pump flow, start the number of pumps selected in the combined economic operation output curve, and adjust the opening of the blade angle regulating valve according to the preset △L to control the output of each circulating water pump to maintain at the preset △L. Step S10: Similarly, after confirming that p circulating water pumps are in maintenance status, a combination of np circulating water pump output curves other than those in maintenance status is obtained. According to the total circulating water pump flow demand value Ft, the number of pumps selected in the combined economic operation output curve is turned on, and the opening of the blade angle regulating valve is adjusted according to the preset ΔL to control the output of each circulating water pump to be maintained at the preset ΔL.

2. A control system for cooling water flow of multiple parallel circulating water pumps, using the control method for cooling water flow of multiple parallel circulating water pumps as described in claim 1, characterized in that: It consists of an economic flow measurement test circuit and a circulating pump current balance control circuit.

3. The parallel multi-circulating water pump cooling water flow control system according to claim 2, characterized in that: The economic flow calculation test loop includes a comprehensive calculation of the circulating water tank level and the circulating pump power consumption.

4. The parallel multi-circulating water pump cooling water flow control system according to claim 3, characterized in that: In the circulating water pump current balance control loop, the current deviation between a certain circulating water pump current and the currents of the other circulating water pumps is determined. When the current Ig of a certain circulating water pump deviates from the currents of the other circulating water pumps by more than a set value B, the current is adjusted based on Ig and the average value I of the other motor currents. 平均 The deviation value is used to adjust the opening of the blade angle regulating valve by the PID controller to achieve output balance between the circulating water pumps.

5. The parallel multi-circulating water pump cooling water flow control system according to claim 4, characterized in that: The remaining circulating water pumps maintain the liquid level in the inlet pool. The PID controller adjusts the blade angle valve opening to achieve a balance in the output of the circulating water pumps, while maintaining the total output of the circulating water pumps at the required value Ft.

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