A parameter self-tuning constant pressure water supply control method based on pressure fluctuation rate

Abstract

The present invention discloses a parameter self-tuning constant pressure water supply control method based on pressure fluctuation rate, and belongs to the technical field of water supply control of secondary water supply equipment. The present invention is aimed at the phenomenon that the traditional PID algorithm has a slow response speed or a very unstable response speed, and the sampling period T is always a fixed value, which causes the controller to enter the next sampling period before the frequency of the frequency converter arrives after the given frequency, causing the problem of uncontrolled constant pressure of the system. The present invention adopts different control algorithms (PT algorithm and self-approximation algorithm) in stages through different pressure deviations. Through the PT algorithm, the present invention controls and automatically adjusts the proportional coefficient Kp and the sampling period T compared with the traditional algorithm, and the control is simpler and easier to control, and the fast performance is greatly improved; wherein the PT algorithm of the present invention adopts a dynamic setting proportional coefficient Kp to ensure that the system can enter the next fine-tuning stage using the self-approximation algorithm very quickly and relatively stably, thereby improving the control efficiency. The present invention can realize constant pressure more quickly and stably without overshoot through the combination of these control methods, and meet the precise constant pressure requirements under different working conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of water supply control of secondary water supply equipment, and in particular relates to a parameter self-tuning constant pressure water supply control method based on pressure fluctuation rate. Background Art

[0002] With the increasing number of high-rise and super-high-rise buildings, the number of people accommodated in residential areas is also increasing, and users' demand for stable water supply is becoming stronger and stronger. However, using PID algorithm with the same control accuracy under high head conditions will often cause large pressure fluctuations, affecting users' water use experience.

[0003] The existing secondary water supply equipment basically controls the inverter output by receiving the pressure sensor signal in real time and relying on the traditional PID algorithm built into the controller to achieve variable frequency control constant pressure water supply. The PID algorithm built into the most commonly used ordinary version controller on the market often does not have the parameter self-tuning function, and can only rely on manual experience to set the values ​​of P (proportional), I (integral), D (differential), and T (sampling period). Although the advanced version controller has the parameter self-tuning function, it can only automatically tune the PID value under a certain operating condition and keep the value fixed. The built-in PID algorithms of these two controllers can only obtain fixed PID values, and cannot meet the constant pressure requirements under different operating conditions (such as the pump head selection is too large or too small, the actual use flow is extremely unstable, etc.). At the same time, the traditional PID algorithm has the phenomenon of slow response speed or extremely unstable response speed, and the sampling period T is always a fixed value, which causes the controller to enter the next sampling period before the inverter frequency is reached after the given frequency, causing the system constant pressure to be uncontrolled.

[0004] In view of the above shortcomings of the prior art, the present invention not only designs a control algorithm that integrates the PT algorithm and the self-approximation algorithm to achieve constant pressure more quickly and stably without overshoot, but also can automatically adjust the control parameters according to the pressure fluctuations under different working conditions, so as to further achieve accurate and fast constant pressure. Summary of the invention

[0005] Traditional PID algorithms have the phenomenon that they have slow response speed or extremely unstable response speed, and the sampling period T is always a fixed value, which causes the controller to enter the next sampling period before the inverter frequency is reached after the given frequency is given, causing the system constant pressure to be uncontrolled. The present invention aims to provide a parameter self-tuning constant pressure water supply control method that can be quickly and accurately adjusted.

[0006] To this end, the present invention adopts the following technical solution: a parameter self-tuning constant pressure water supply control method based on pressure fluctuation rate, comprising the following steps:

[0007] The first step is to use different control algorithms according to the pressure deviation rate

[0008] Calculate the ratio of (constant outlet pressure Ps-inlet pressure Pi) and the rated head of the pump Pr as the adjustment coefficient k, that is, k = (Ps-Pi) / Pr, (under normal circumstances, the k value is 1, the smaller the k value is, the pump's operating capacity exceeds the actual demand, and the adjustment speed can be slowed down to avoid overshoot, and vice versa);

[0009] Calculate the absolute value of (outlet pressure Po - outlet constant pressure Ps) and the ratio of (outlet constant pressure Ps - inlet pressure Pi) as the pressure deviation rate x, that is, x = |(Po-Ps)| / (Ps-Pi);

[0010] Calculate the corrected pressure deviation rate Y=kx after implanting the adjustment coefficient;

[0011] When the correction pressure deviation rate is 30%<Y≤100%, the system directly controls the output to run at the maximum frequency;

[0012] When the correction pressure deviation rate is 10%<Y≤30%, the system uses the PT algorithm to quickly approach the target pressure;

[0013] When the correction pressure deviation rate is 0%≤Y≤10%, the system uses a self-approaching algorithm to accurately maintain constant pressure and prevent overshoot;

[0014] Step 2: PT algorithm

[0015] The PT algorithm is different from the traditional PID algorithm. It only controls and automatically adjusts the proportional coefficient Kp and the sampling period T. The control is simpler and easier to control, and the fast performance is greatly improved.

[0016] Step s1: Determine whether to use the PT algorithm by correcting the pressure deviation rate;

[0017] Step s2: If the PT algorithm is used, the current inverter frequency and the current corrected pressure deviation rate are obtained;

[0018] Step s3: Calculate the current controller output value U(t) according to the current inverter frequency (current controller output value U(t)=current inverter frequency fn / maximum frequency fmax);

[0019] Step s4: Calculate the controller output value of the next sampling period according to the current controller output value U(t) and the current corrected pressure deviation rate Y(t);

[0020] Ua=Kp*Y(t), Ua is the controller output increment of the next sampling period, Kp is the proportional coefficient (default value is 0.5, value range is 0-1);

[0021] If the outlet water pressure Po is less than the outlet water constant pressure Ps, the controller output value of the next sampling period is U(t+1)=U(t)+Ua=U(t)+Kp*Y(t);

[0022] If the outlet water pressure Po> the outlet water constant pressure Ps, the controller output value of the next sampling period is U(t+1)=U(t)-Ua=U(t)-Kp*Y(t);

[0023] Step s5: Calculate the time of the next sampling cycle each time, and perform sampling after it arrives. The sampling cycle obtained by dynamic adjustment can ensure the synchronization of the controller output value and the actual operating frequency;

[0024] Step s51: manually start the frequency converter, record the maximum acceleration time Tmax+ of the frequency converter frequency from 0 to the maximum frequency fmax, and the maximum deceleration time Tmax- of the frequency converter frequency from the maximum frequency fmax to 0;

[0025] Step s52: Calculate the next sampling cycle time according to the controller output increment Ua of the next sampling cycle and the maximum acceleration time Tmax+ or the maximum deceleration time Tmax-;

[0026] If the outlet water pressure Po is less than the outlet water constant pressure Ps, the next sampling cycle time T(n+1)=Ua*Tmax+

[0027] If the outlet water pressure Po> outlet water constant pressure Ps, the next sampling cycle time T(n+1)=Ua*Tmax-

[0028] Step s6: Dynamically adjust the proportional coefficient Kp

[0029] Record the time from entering to exiting the PT algorithm. If it exceeds the preset time limit, Kp will increase by 0.1 each time before entering the next cycle. On the contrary, if it is lower than the preset time limit, Kp will decrease by 0.1 each time before entering the next cycle, thereby ensuring that the system can enter the next fine-tuning stage using the self-approximation algorithm very quickly and relatively stably.

[0030] Step s7: The current controller output value U(t) is amplified according to the upper limit of the analog output value of the controller and then output to the frequency converter;

[0031] Step 3: Self-approaching algorithm

[0032] Step s1: Determine whether to use the self-approximation algorithm by correcting the pressure deviation rate;

[0033] Step s2: If the self-approximation algorithm is used, the current inverter frequency fo is obtained, and a fixed sampling period (the value can be set to 0-1s) is set (because the fine-tuning of the self-approximation algorithm needs to consider the water consumption fluctuation after the inverter feedback frequency is stabilized, a fixed relatively long sampling period is required);

[0034] Step s3: Determine the self-approaching frequency increase Z based on the pressure fluctuation rate S in 10 sampling periods calculated by the formula;

[0035] S 2 =[(Po1-Ps) 2 +(Po2-Ps) 2 +……+(Po10-Ps) 2 ] / 10, where s is the pressure

[0036] force fluctuation rate, Po1~Po10 are the outlet water pressures collected in 10 sampling periods of the rolling cycle, and Ps is the outlet water constant pressure;

[0037] When the pressure fluctuation rate S≤0.005, Z=0

[0038] When the pressure fluctuation rate is 0.005<S≤0.01, then Z=0.1

[0039] When the pressure fluctuation rate S>0.01, then Z=10S

[0040] Step s4: Determine the controller output frequency fn of the next sampling period according to the current inverter frequency fo and the self-approaching frequency increment Z;

[0041] If the outlet water pressure Po is less than the outlet water constant pressure Ps, the controller output frequency of the next sampling period is fn=fo+Z;

[0042] If the outlet water pressure Po> the outlet water constant pressure Ps, the controller output frequency of the next sampling period is fn=fo-Z;

[0043] If the outlet water pressure Po = the outlet water constant pressure Ps, the controller output frequency of the next sampling period is fn = fo.

[0044] The present invention can achieve the following beneficial effects: The present invention adopts a strategy of using different control algorithms (PT algorithm and self-approximation algorithm) in stages according to different pressure deviations. Through the PT algorithm, the present invention controls and automatically adjusts the proportional coefficient Kp and the sampling period T compared to the traditional algorithm, and the control is simpler and easier to control, and the rapid performance is greatly improved; wherein the PT algorithm of the present invention adopts a dynamically adjusted proportional coefficient Kp to ensure that the system can enter the next fine-adjustment stage using the self-approximation algorithm extremely quickly and relatively stably, thereby improving the control efficiency. The present invention can achieve constant pressure more quickly and stably without overshooting through the combination of these control methods, thereby meeting the precise constant pressure requirements under different working conditions. DETAILED DESCRIPTION

[0045] The specific implementation modes of the present invention are described in detail below. The described embodiments are only for illustration and explanation of the present invention and do not constitute the sole limitation of the present invention.

[0046] Embodiment 1: The parameter self-tuning constant pressure water supply control method based on pressure fluctuation rate of the present invention comprises the following steps:

[0047] The first step is to use different control algorithms according to the pressure deviation rate to ensure fast and accurate regulation.

[0048] Calculate the ratio of (constant outlet pressure Ps-inlet pressure Pi) and the rated head of the pump Pr as the adjustment coefficient k, that is, k = (Ps-Pi) / Pr, (under normal circumstances, the k value is 1, the smaller the k value is, the pump's operating capacity exceeds the actual demand, and the adjustment speed can be slowed down to avoid overshoot, and vice versa);

[0049] Calculate the absolute value of (outlet pressure Po - outlet constant pressure Ps) and the ratio of (outlet constant pressure Ps - inlet pressure Pi) as the pressure deviation rate x, that is, x = |(Po-Ps)| / (Ps-Pi);

[0050] Calculate the corrected pressure deviation rate Y=kx after implanting the adjustment coefficient;

[0051] When the correction pressure deviation rate is 30%<Y≤100%, the system directly controls the output to run at the maximum frequency;

[0052] When the correction pressure deviation rate is 10%<Y≤30%, the system uses the PT algorithm to quickly approach the target pressure;

[0053] When the correction pressure deviation rate is 0%≤Y≤10%, the system uses a self-approaching algorithm to accurately maintain constant pressure and prevent overshoot;

[0054] Step 2: PT algorithm

[0055] The PT algorithm is different from the traditional PID algorithm. It only controls and automatically adjusts the proportional coefficient Kp and the sampling period T. The control is simpler and easier to control, and the fast performance is greatly improved.

[0056] Step s1: Determine whether to use the PT algorithm by correcting the pressure deviation rate;

[0057] Step s2: If the PT algorithm is used, the current inverter frequency and the current corrected pressure deviation rate are obtained;

[0058] Step s3: Calculate the current controller output value U(t) according to the current inverter frequency (current controller output value U(t)=current inverter frequency fn / maximum frequency fmax);

[0059] Step s4: Calculate the controller output value of the next sampling period according to the current controller output value U(t) and the current corrected pressure deviation rate Y(t);

[0060] Ua=Kp*Y(t), Ua is the controller output increment of the next sampling period, Kp is the proportional coefficient (default value is 0.5, value range is 0-1);

[0061] If the outlet water pressure Po is less than the outlet water constant pressure Ps, the controller output value of the next sampling period is U(t+1)=U(t)+Ua=U(t)+Kp*Y(t);

[0062] If the outlet water pressure Po> the outlet water constant pressure Ps, the controller output value of the next sampling period is U(t+1)=U(t)-Ua=U(t)-Kp*Y(t);

[0063] Step s5: Calculate the time of the next sampling cycle each time, and perform sampling after it arrives. The sampling cycle obtained by dynamic adjustment can ensure the synchronization of the controller output value and the actual operating frequency;

[0064] Step s51: manually start the frequency converter, record the maximum acceleration time Tmax+ of the frequency converter frequency from 0 to the maximum frequency fmax, and the maximum deceleration time Tmax- of the frequency converter frequency from the maximum frequency fmax to 0;

[0065] Step s52: Calculate the next sampling cycle time according to the controller output increment Ua of the next sampling cycle and the maximum acceleration time Tmax+ or the maximum deceleration time Tmax-;

[0066] If the outlet water pressure Po is less than the outlet water constant pressure Ps, the next sampling cycle time T(n+1)=Ua*Tmax+

[0067] If the outlet water pressure Po> outlet water constant pressure Ps, the next sampling cycle time T(n+1)=Ua*Tmax-

[0068] Step s6: Dynamically adjust the proportional coefficient Kp

[0069] Record the time from entering to exiting the PT algorithm. If it exceeds the preset time limit, Kp will increase by 0.1 each time before entering the next cycle. On the contrary, if it is lower than the preset time limit, Kp will decrease by 0.1 each time before entering the next cycle, thereby ensuring that the system can enter the next fine-tuning stage using the self-approximation algorithm very quickly and relatively stably.

[0070] Step s7: The current controller output value U(t) (value range is 0-1) is amplified according to the upper limit of the analog output of the controller and then output to the frequency converter;

[0071] Step 3: Self-approaching algorithm

[0072] Step s1: Determine whether to use the self-approximation algorithm by correcting the pressure deviation rate;

[0073] Step s2: If the self-approximation algorithm is used, the current inverter frequency fo is obtained, and a fixed sampling period (the value can be set to 0-1s) is set (because the fine-tuning of the self-approximation algorithm needs to consider the water consumption fluctuation after the inverter feedback frequency is stabilized, a fixed relatively long sampling period is required);

[0074] Step s3: Determine the self-approaching frequency increase Z based on the pressure fluctuation rate S in 10 sampling periods calculated by the formula;

[0075] S 2 =[(Po1-Ps) 2 +(Po2-Ps) 2 +……+(Po10-Ps) 2 ] / 10, where s is the pressure

[0076] force fluctuation rate, Po1~Po10 are the outlet water pressures collected in 10 sampling periods of the rolling cycle, and Ps is the outlet water constant pressure;

[0077] When the pressure fluctuation rate S≤0.005, Z=0

[0078] When the pressure fluctuation rate is 0.005<S≤0.01, then Z=0.1

[0079] When the pressure fluctuation rate S>0.01, then Z=10S

[0080] Step s4: Determine the controller output frequency fn of the next sampling period according to the current inverter frequency fo and the self-approaching frequency increment Z;

[0081] If the outlet water pressure Po is less than the outlet water constant pressure Ps, the controller output frequency of the next sampling period is fn=fo+Z;

[0082] If the outlet water pressure Po> the outlet water constant pressure Ps, the controller output frequency of the next sampling period is fn=fo-Z;

[0083] If the outlet water pressure Po = the outlet water constant pressure Ps, the controller output frequency of the next sampling period is fn = fo.

[0084] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A parameter self-tuning constant pressure water supply control method based on pressure fluctuation rate, characterized in that: The parameter self-tuning constant pressure water supply control method based on pressure fluctuation rate comprises the following steps: The first step is to use different control algorithms according to the pressure deviation rate Calculate the ratio of the outlet constant pressure Ps-inlet pressure Pi and the pump rated head Pr as the adjustment coefficient k, that is, k = (Ps-Pi) / Pr; Calculate the absolute value of the outlet water pressure Po-the outlet water constant pressure Ps and the ratio of the outlet water constant pressure Ps-the inlet water pressure Pi as the pressure deviation rate x, that is, x = |(Po-Ps)| / (Ps-Pi); Calculate the corrected pressure deviation rate Y=kx after implanting the adjustment coefficient; Step 2: PT algorithm Step s1: Determine whether to use the PT algorithm by correcting the pressure deviation rate; Step s2: Using the PT algorithm, the current inverter frequency and the current corrected pressure deviation rate are obtained; Step s3: Calculate the current controller output value U(t) according to the current inverter frequency; Step s4: Calculate the controller output value of the next sampling period according to the current controller output value U(t) and the current corrected pressure deviation rate Y(t); Ua=Kp*Y(t), Ua is the controller output increment of the next sampling period, Kp is the proportional coefficient; Step s5: Calculate the time of the next sampling cycle each time, and perform sampling after it arrives. The sampling cycle obtained by dynamic adjustment can ensure the synchronization of the controller output value and the actual operating frequency; Step s51: manually start the frequency converter, record the maximum acceleration time Tmax+ of the frequency converter frequency from 0 to the maximum frequency fmax, and the maximum deceleration time Tmax- of the frequency converter frequency from the maximum frequency fmax to 0; Step s52: Calculate the next sampling cycle time according to the controller output increment Ua of the next sampling cycle and the maximum acceleration time Tmax+ or the maximum deceleration time Tmax-; Step s6: Dynamically adjust the proportional coefficient Kp Record the time from entering to exiting the PT algorithm. If it exceeds the preset time limit, Kp will increase by 0.1 each time before entering the next cycle. On the contrary, if it is lower than the preset time limit, Kp will decrease by 0.1 each time before entering the next cycle, ensuring that the system can enter the next fine-tuning stage using the self-approximation algorithm very quickly and relatively stably. Step s7: The current controller output value U(t) is amplified according to the upper limit of the analog output value of the controller and then output to the frequency converter, wherein the value range of U(t) is 0-1; Step 3: Self-approaching algorithm Step s1: Determine whether to use the self-approximation algorithm by correcting the pressure deviation rate; Step s2: If the self-approximation algorithm is used, the current inverter frequency fo is obtained and a fixed sampling period is set; Step s3: Determine the self-approaching frequency increase Z based on the pressure fluctuation rate S in 10 sampling periods calculated by the formula; S 2 =[(Po1-Ps) 2 +(Po2-Ps) 2 +……+(Po10-Ps) 2 ] / 10, where S is the pressure force fluctuation rate, Po1~Po10 are the outlet water pressures collected in 10 sampling periods of the rolling cycle, and Ps is the outlet water constant pressure; Step s4: Determine the controller output frequency fn of the next sampling period according to the current inverter frequency fo and the self-approaching frequency increment Z.

2. The method for controlling constant pressure water supply by parameter self-tuning based on pressure fluctuation rate according to claim 1 is characterized in that: In the first step, When the correction pressure deviation rate is 30%<Y≤100%, the system directly controls the output to run at the maximum frequency; When the correction pressure deviation rate is 10%<Y≤30%, the system uses the PT algorithm to quickly approach the target pressure; When the corrected pressure deviation rate is 0%≤Y≤10%, the system uses a self-approaching algorithm to accurately maintain constant pressure and prevent overshoot.

3. The method for controlling constant pressure water supply by parameter self-tuning based on pressure fluctuation rate according to claim 2 is characterized in that: In the second step, In step s4: if the outlet water pressure Po is less than the outlet water constant pressure Ps, the controller output value of the next sampling period is U(t+1)=U(t)+Ua=U(t)+Kp*Y(t); If the outlet water pressure Po> the outlet water constant pressure Ps, the controller output value of the next sampling period is U(t+1)=U(t)-Ua=U(t)-Kp*Y(t); In step s52, if the outlet water pressure Po is less than the outlet water constant pressure Ps, the next sampling cycle time T(n+1)=Ua*Tmax+ If the outlet water pressure Po>the outlet water constant pressure Ps, the next sampling cycle time T(n+1)=Ua*Tmax-.

4. The method for controlling constant pressure water supply by parameter self-tuning based on pressure fluctuation rate according to claim 3 is characterized in that: In the second step, the current controller output value U(t)=current inverter frequency fn / maximum frequency fmax.

5. The method for controlling constant pressure water supply by parameter self-tuning based on pressure fluctuation rate according to claim 4 is characterized in that: In the third step, When the pressure fluctuation rate S≤0.005, Z=0 When the pressure fluctuation rate is 0.005<S≤0.01, then Z=0.1 When the pressure fluctuation rate S>0.01, then Z=10S If the outlet water pressure Po is less than the outlet water constant pressure Ps, the controller output frequency of the next sampling period is fn=fo+Z; If the outlet water pressure Po> the outlet water constant pressure Ps, the controller output frequency of the next sampling period is fn=fo-Z; If the outlet water pressure Po = the outlet water constant pressure Ps, the controller output frequency of the next sampling period is fn = fo.

6. A parameter self-tuning constant pressure water supply control method based on pressure fluctuation rate according to claim 5, characterized in that: In the third step, the sampling period can be set to 0-1s. Since the fine-tuning of the self-approximation algorithm needs to take into account the fluctuation of water consumption after the feedback frequency of the inverter is stabilized, a fixed sampling period is required.

7. A parameter self-tuning constant pressure water supply control method based on pressure fluctuation rate according to claim 1, 5 or 6, characterized in that: In the third step, Kp is a proportional coefficient with a default value of 0.5 and a value range of 0-1.