CN101892688A - Method for controlling pipe network pressure-superposed water supply system based on efficiency optimization of asynchronous motor - Google Patents

Abstract

The invention relates to a method for controlling a pipe network pressure-superposed water supply system, in particular to a method for controlling a pipe network pressure-superposed water supply system based on efficiency optimization of an asynchronous motor. The method identifies the rotating speed of the asynchronous motor based on a pump model, and takes the identified rotating speed as an input of a minimum loss efficiency optimizing control algorithm of the asynchronous motor, the operation is finished in a digital control unit and is output to the frequency given end of a transducer through D/A conversion, the set pressure value is subtracted from the water pump pressure value collected by a pressure sensor to obtain the error signal delta H of the water pressure, PI operation is carried out on delta H, and then delta H is output to the voltage given end of the transducer by D/A conversion. The invention has the beneficial effects that the operation efficiency of the asynchronous motor is increased, the operation efficiency of the system can be improved, the problem that the rotating speed of the water pump machine set is difficult to be detected directly is solved, and the load characteristics of the water pump in the pressure-superposed water supply system is analyzed, therefore, the attention on energy-saving potential of optimization control of the water pump machine set can be enhanced in engineering fields.

Description

Method for controlling pipe network pressure-superposed water supply system based on efficiency optimization of asynchronous motor

Technical field

The present invention relates to a kind of method for controlling pipe network pressure-superposed water supply system, particularly relate to a kind of method for controlling pipe network pressure-superposed water supply system based on efficiency optimization of asynchronous motor.

Background technology

At present, the asynchronous machine control mode that generally adopts in the variable-frequency speed-regulating water supply system is constant voltage and frequency ratio control, since the characteristics of water system and the load characteristic characteristics of water pump, the frequent light running of asynchronous machine, and its operational efficiency is lower.Water pump is that dynamic property is responded less demanding load, and when the asynchronous machine light running, permanent flux regulator mode is dispensable, can have bigger energy-saving potential in the water system by the optimization of weak magnetic control system implementation efficiency.

Because the characteristics of water system and the load characteristic of water pump in order to improve the operational efficiency of asynchronous machine, are necessary to seek asynchronous machine control method efficiently.Traditional efficiency optimization of asynchronous motor control method is according to the torque of motor and rotating speed requirement, calculates required frequency converter output voltage and the frequency of motor optimized operation.But when carrying water pump, can't directly detect the torque and the rotating speed requirement of asynchronous machine, so this algorithm can not directly apply in the water system owing to the asynchronous machine band.According to the Mathematical Modeling of water pump as can be known, if the water pump parameter determines that then the relation between the rotating speed of the lift of water pump, flow and water pump is determined, therefore, can draw the method for indirect calculation rotating speed thus.In existing network pressure superposition water supply system, the flow of water pump and lift can detect by flow meter and pressure sensor, and then according to the water pump model, obtain the rotating speed of water pump, also are the rotating speed of asynchronous machine.The present invention will integrate based on the rotating speed identification of water pump model with based on the minimal losses efficiency optimization control algolithm of asynchronous machine equivalent circuit, be applied to the control of asynchronous machine in the network pressure superposition water supply system.

Summary of the invention

Purpose of the present invention is to solve above-mentioned deficiency of the prior art exactly, and a kind of method for controlling pipe network pressure-superposed water supply system based on efficiency optimization of asynchronous motor is provided, and further reduces the energy consumption level of laminating water supply equipment.

In order to achieve the above object, technical scheme of the present invention is: a kind of method for controlling pipe network pressure-superposed water supply system based on efficiency optimization of asynchronous motor, it is characterized in that: based on the rotating speed of water pump Model Distinguish asynchronous machine, and with the input of the rotating speed that picks out as asynchronous machine minimal losses efficiency optimization control algolithm, above computing is finished in digital control unit, and through D A transform the frequency given side output to frequency converter, it is poor that the water-aspirator pressure value of pressure sensor collection and pressure design value are done, obtain the error signal Δ H of hydraulic pressure, Δ H is carried out the PI computing, through D A transform the voltage given end output to frequency converter.

Above-mentioned identification based on water pump model asynchronous machine rotating speed, the foundation of water pump model is to come by fitting of a polynomial according to the test data of water pump, and the match number of times gets 2, i.e. match also is shown below according to the pump head-rating curve after the proportionality law conversion

$H=a_2{Q}^2+a_1\left(\frac{n}{n_0}\right)Q+a_0{\left(\frac{n}{n_0}\right)}^2;$

Above-mentioned asynchronous machine minimal losses efficiency optimization control algolithm, equivalent circuit based on asynchronous machine, according to the relation of operational efficiency, asynchronous machine rotating speed and the supply frequency of asynchronous machine, determine under the given rotating speed pairing supply frequency when asynchronous machine runs on maximal efficiency;

Above-mentioned asynchronous machine minimal losses efficiency optimization control algolithm, realize that this algorithm is not to adopt the method for directly solving an equation, but adopt a kind of searching algorithm, the i.e. supply frequency of correspondence during the asynchronous machine optimized operation during method search given rotating speed by increment progressively, thus make operand obtain reducing greatly;

The voltage of above-mentioned frequency converter and frequency are separately control, the operational efficiency maximum of asynchronous machine in the independent regulation and control assurance system of frequency, and exit of pump pressure is kept constant in the independent regulation and control assurance system of voltage;

Above-mentioned network pressure superposition water supply system based on efficiency optimization of asynchronous motor control, the structure of this system comprises: frequency converter, water pump assembly, pressure sensor, flow meter and based on the digital control unit of efficiency optimization of asynchronous motor control algolithm;

Above-mentioned digital control unit based on the efficiency optimization of asynchronous motor control algolithm is with the force value of the pressure sensor input that receives and the flow value of flow meter input, after A/D conversion and internal efficiency optimal control routine processes, output to frequency converter with the form of analog voltage signal and analog frequency signal; The input of inverter output terminal water pump unit, water pump assembly carries out speed governing according to frequency converter given voltage and frequency signal, and exit of pump pressure is regulated, and realizes asynchronous machine operational efficiency optimum in the water pump assembly simultaneously;

Above-mentioned efficiency optimization of asynchronous motor control algolithm, the concrete steps of enforcement are as follows:

1. based on water pump Model Distinguish asynchronous machine rotating speed

Describing between the lift H of water pump, flow Q and the rotation speed n by following formula

$H=a_2{Q}^1+a_1\left(\frac{n}{n_0}\right)Q+a_0{\left(\frac{n}{n_0}\right)}^2---\left(1\right)$

In the formula, n₀Be the rated speed of water pump, a_0-2Be coefficient, performance parameter match by water pump obtains, in laminating water supply equipment, gather the flow of water pump and outlet pressure, inlet pressure signal by flow meter and pressure sensor, the lift of water pump is the poor of outlet pressure and inlet pressure, with detected every value input digit control system calculation process, obtains the rotating speed of asynchronous machine, according to formula (1), the expression formula of rotating speed is:

$n=\frac{-a_{1}Q+\sqrt{{a_1}^2{Q}^2-4a_0(a_2{Q}^2-H)}}{2a_0}\·n_0---\left(2\right)$

$=k_n\&CenterDot;{\mathrm{<figure-callout\; label="n"\; filenames="HSA00000094072400021.png"\; state="\{\{state\}\}">n</figure-callout>}}_0$

2. the supply frequency when running on maximal efficiency according to asynchronous machine equivalent circuit calculating asynchronous machine,

According to the simplification equivalent circuit of asynchronous machine, the expression formula of asynchronous machine operational efficiency is

$\mathrm{\&eta;}=\frac{R_2^{\&prime;}(\left(60f\right)/(60f-\mathrm{pn})-1)}{R_1+\left(60f{R}_2^{\&prime;}\right)/(60f-\mathrm{pn})/+K_2(R_1+R_m)}---\left(3\right)$

In theformula$K_{}$${}_2=\frac{{(R_1+\left(60\mathrm{<figure-callout\; label="f\; R"\; filenames="HSA00000094072400021.png"\; state="\{\{state\}\}">f</figure-callout>}{R}_{}^{}{}_2^{\&prime;}\right)/(60f-\mathrm{pn}))}^2+{\left(\left(2\mathrm{\&pi;f}\right)({\mathrm{<figure-callout\; label="L"\; filenames="HSA00000094072400021.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+{\mathrm{<figure-callout\; label="L"\; filenames="HSA00000094072400021.png"\; state="\{\{state\}\}">L</figure-callout>}}_2^{\&prime;})\right)}^2}{{(R_1+R_m)}^2+{\left(\left(2\mathrm{\&pi;f}\right)({\mathrm{<figure-callout\; label="L"\; filenames="HSA00000094072400021.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_m^{\&prime;})\right)}^2}$

R₁, L₁, R₂, L₂, R_mAnd L_m: asynchronous machine equivalent circuit parameter,

P, n, f: asynchronous machine number of pole-pairs, rotating speed and stator power frequency,

On the principle, formula (3) is asked partial derivative, promptly

Then when the asynchronous machine rotation speed n is known, can determine the asynchronous machine supply frequency f when asynchronous machine runs on maximal efficiency, but because the calculating formula more complicated of efficient, if directly solve an equation again after the partial differential computing, then operand will be very huge, arithmetic speed and performance to numerical control system have higher requirement, be unfavorable for actual application, in the present invention, adopted a kind of searching algorithm, utilize the supply frequency when progressively the method for increment is searched for given rotating speed, thereby avoided solving an equation, ask loaded down with trivial details computings such as partial differential, operand has obtained reducing greatly, the flow chart of this algorithm with the input as this algorithm of the asynchronous machine rotating speed that picks out in thestep 1, obtains the required supply frequency of asynchronous machine optimized operation through the numerical control system calculation process as shown in Figure 2, with the given signal of operation result as frequency converter frequency, more than two steps guarantee that the operational efficiency of asynchronous machines is optimum.

3. set the pressure set points of network pressure superposition water supply system, and do difference with the detected water-aspirator pressure of pressure sensor and obtain the error signal Δ H of hydraulic pressure, Δ H is carried out the PI computing, after the numerical control system calculation process as the given signal of frequency converter voltage, the exit of pump pressure of this step assurance laminating water service system is kept constant, to satisfy user's water requirement.

Beneficial effect of the present invention:

1. the optimum efficiency control algolithm of asynchronous machine has effectively realized the bigger raising of operational efficiency of asynchronous machine, especially under the little operating mode of water supply flow, avoided the bad running status of asynchronous machine " low load with strong power ", the operational efficiency of system obtains bigger improvement.

2. propose rotating speed, effectively solved the water pump assembly rotating speed and be difficult to the directly problem of measurement based on water pump Model Distinguish asynchronous machine.

3. analyzed the load characteristic of water pump in the laminating water service system, point out that it is not the quadratic power torque load(ing), but along with the reduction of rotating speed, the load characteristic of water pump significantly is lower than the quadratic power load characteristic in the water system, and this will improve the attention of engineering field to the energy-saving potential of water pump assembly optimal control.

Description of drawings

Efficiency optimization of asynchronous motor control block diagram in Fig. 1 laminating water service system

Fig. 2 efficiency optimization adjustment module program flow diagram

Fig. 3 efficiency optimization control dynamic response process

The operational efficiency of asynchronous machine contrast under Fig. 4 different control modes

Fig. 5 laminating water service system schematic diagram

The specific embodiment

Specific embodiment: a kind of method for controlling pipe network pressure-superposed water supply system of the present invention based on efficiency optimization of asynchronous motor, rotating speed based on water pump Model Distinguish asynchronous machine, and with the input of the rotating speed that picks out as asynchronous machine minimal losses efficiency optimization control algolithm, above computing is finished in digital control unit, and through D A transform the frequency given side output to frequency converter, it is poor that the water-aspirator pressure value of pressure sensor collection and pressure design value are done, obtain the error signal Δ H of hydraulic pressure, Δ H is carried out the PI computing, through D A transform the voltage given end output to frequency converter.

This network pressure superposition water supply system is mainly by frequency converter, water pump assembly, pressure sensor, flow meter and form based on the digital control unit of efficiency optimization of asynchronous motor control algolithm.Pressure sensor and flow meter are used to survey the force value and the flow of pipe network Pressure-superposed water supply equipment various piece; Input based on the digital control unit of efficiency optimization of asynchronous motor control algolithm connects pressure sensor, flow meter signal terminal, and its output is received the input of frequency converter; Said inverter output terminal connects the input of water pump assembly; Water pump assembly is regulated the outlet pressure of water pump according to the voltage and the frequency signal of frequency converter input, makes it consistent with the reference value of setting, and makes the operational efficiency optimum of asynchronous machine simultaneously.

As shown in Figure 1, efficiency optimization of asynchronous motor control in the laminating water service system, the control method that proposes according to the present invention, concrete implementation step has following a few step:

1. at first water pump, asynchronous machine in the water system are carried out parameter model, the result is stored among the RAM of digital control unit.According to the test data of water pump, the method for utilization least square method fitting of a polynomial is set up the model of water pump, and for water pump, the match number of times is got 2 requirements that can satisfy control accuracy.This step is promptly determined a in the formula (1)₀, a₁And a₂Measure the equivalent circuit parameter of asynchronous machine, R₁, L₁, R₂, L₂, R_mAnd L_m, these parameter values are stored.

2. write the rotating speed recognition module according to formula (2).The measured value of pressure sensor and flow meter is after the A/D conversion, as the input of rotating speed recognition module.

3. set the set-point H of pump head₀, do difference with the measurement result of pressure sensor and obtain lift deviation delta H, Δ H is carried out PI regulate, transform through saturation block and D/A, as the given signal of frequency converter voltage.

4. write the efficiency optimization adjustment module according to formula (3), it is input as the output of rotating speed recognition module on the principle, but in order to quicken frequency response speed, adopts the input of the proportional of rotating speed and pump head deviation delta H as this module.Its output transforms through saturation block and D/A, as the given signal of frequency converter frequency.

So go round and begin again, when whole laminating water service system can be realized satisfying water supply requirement, the optimized operation of implementation efficiency.The dynamic response characteristic of system as shown in Figure 3.Under the stable situation, the contrast that the operational efficiency that adopts the network pressure superposition water supply system of control method among the present invention and traditional constant voltage and frequency ratio are controlled as shown in Figure 4.As can be seen from Figure 4, at the metered flow place, asynchronous machine is fully loaded, and asynchronous machine all can run on greater efficiency under two kinds of control modes.Along with flow reduces, the operational efficiency of asynchronous machine descends gradually under the constant voltage and frequency ratio control mode; The operational efficiency of asynchronous machine descends very little under the minimal losses control mode.When the water pump low discharge, the minimal losses control algolithm has effectively improved the operational efficiency of asynchronous machine.

As shown in Figure 2, be the flow chart of asynchronous machine minimal losses efficiency optimization control algolithm, the concrete steps of enforcement are as follows:

(1), based on water pump Model Distinguish asynchronous machine rotating speed

Describing between the lift H of water pump, flow Q and the rotation speed n by following formula

$H=a_2{Q}^2+a_1\left(\frac{n}{n_0}\right)Q+a_0{\left(\frac{n}{n_0}\right)}^2---\left(1\right)$

In the formula, n₀Be the rated speed of water pump, a_0-2Be coefficient, performance parameter match by water pump obtains, in laminating water supply equipment, gather the flow of water pump and outlet pressure, inlet pressure signal by flow meter and pressure sensor, the lift of water pump is the poor of outlet pressure and inlet pressure, with detected every value input digit control system calculation process, obtains the rotating speed of asynchronous machine, according to formula (1), the expression formula of rotating speed is:

$n=\frac{-a_{1}Q+\sqrt{{a_1}^2{Q}^2-4a_0(a_2{Q}^2-H)}}{2a_0}\&CenterDot;n_0---\left(2\right)$

$=k_n\&CenterDot;{\mathrm{<figure-callout\; label="n"\; filenames="HSA00000094072400021.png"\; state="\{\{state\}\}">n</figure-callout>}}_0$

(2), the supply frequency when calculating asynchronous machine and run on maximal efficiency according to the asynchronous machine equivalent circuit,

According to the simplification equivalent circuit of asynchronous machine, the expression formula of asynchronous machine operational efficiency is

$\mathrm{\&eta;}=\frac{{\mathrm{<figure-callout\; label="R"\; filenames="HSA00000094072400021.png"\; state="\{\{state\}\}">R</figure-callout>}}_2^{\&prime;}(\left(60f\right)/(60f-\mathrm{pn})-1)}{{\mathrm{<figure-callout\; label="R"\; filenames="HSA00000094072400021.png"\; state="\{\{state\}\}">R</figure-callout>}}_1+\left(60\mathrm{<figure-callout\; label="f\; R"\; filenames="HSA00000094072400021.png"\; state="\{\{state\}\}">f</figure-callout>}{R}_{}^{}{}_2^{\&prime;}\right)/(60f-\mathrm{pn})/+K_2({\mathrm{<figure-callout\; label="R"\; filenames="HSA00000094072400021.png"\; state="\{\{state\}\}">R</figure-callout>}}_1+R_m)}---\left(3\right)$

In theformula$K_{}$${}_2=\frac{{({\mathrm{<figure-callout\; label="R"\; filenames="HSA00000094072400021.png"\; state="\{\{state\}\}">R</figure-callout>}}_1+\left(60\mathrm{<figure-callout\; label="f\; R"\; filenames="HSA00000094072400021.png"\; state="\{\{state\}\}">f</figure-callout>}{R}_{}^{}{}_2^{\&prime;}\right)/(60f-\mathrm{pn}))}^2+{\left(\left(2\mathrm{\&pi;f}\right)({\mathrm{<figure-callout\; label="L"\; filenames="HSA00000094072400021.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+{\mathrm{<figure-callout\; label="L"\; filenames="HSA00000094072400021.png"\; state="\{\{state\}\}">L</figure-callout>}}_2^{\&prime;})\right)}^2}{{({\mathrm{<figure-callout\; label="R"\; filenames="HSA00000094072400021.png"\; state="\{\{state\}\}">R</figure-callout>}}_1+R_m)}^2+{\left(\left(2\mathrm{\&pi;f}\right)({\mathrm{<figure-callout\; label="L"\; filenames="HSA00000094072400021.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_m^{\&prime;})\right)}^2}$

R₁, L₁, R₂, L₂, R_mAnd L_m: asynchronous machine equivalent circuit parameter,

P, n, f: asynchronous machine number of pole-pairs, rotating speed and stator power frequency,

On the principle, formula (3) is asked partial derivative, promptly

Then when the asynchronous machine rotation speed n is known, can determine the asynchronous machine supply frequency f when asynchronous machine runs on maximal efficiency, but because the calculating formula more complicated of efficient, if directly solve an equation again after the partial differential computing, then operand will be very huge, arithmetic speed and performance to numerical control system have higher requirement, be unfavorable for actual application, in the present invention, adopted a kind of searching algorithm, utilize the supply frequency when progressively the method for increment is searched for given rotating speed, thereby avoided solving an equation, ask loaded down with trivial details computings such as partial differential, operand has obtained reducing greatly.With the input of the asynchronous machine rotating speed that picks out in the step (1) as this algorithm, obtain the required supply frequency of asynchronous machine optimized operation through the numerical control system calculation process, with the given signal of operation result as frequency converter frequency, more than two steps guarantee that the operational efficiency of asynchronous machines is optimum.

(3), set the pressure set points of network pressure superposition water supply system, and do difference with the detected water-aspirator pressure of pressure sensor and obtain the error signal Δ H of hydraulic pressure, Δ H is carried out the PI computing, after the numerical control system calculation process as the given signal of frequency converter voltage, the exit of pump pressure of this step assurance laminating water service system is kept constant, to satisfy user's water requirement.

Fig. 5 is the schematic diagram of method of the present invention in laminating water service system is used.

Claims (3)

1. based on the method for controlling pipe network pressure-superposed water supply system of efficiency optimization of asynchronous motor, it is characterized in that: described rotating speed based on water pump Model Distinguish asynchronous machine, and with the input of the rotating speed that picks out as asynchronous machine minimal losses efficiency optimization control algolithm, above computing is finished in digital control unit, and through D A transform the frequency given side output to frequency converter, it is poor that the water-aspirator pressure value of pressure sensor collection and pressure design value are done, obtain the error signal Δ H of hydraulic pressure, Δ H is carried out the PI computing, through D A transform the voltage given end output to frequency converter.

2. the method for controlling pipe network pressure-superposed water supply system based on efficiency optimization of asynchronous motor according to claim 1, it is characterized in that: described network pressure superposition water supply system based on efficiency optimization of asynchronous motor control, the structure of this system comprises: frequency converter, water pump assembly, pressure sensor, flow meter and based on the digital control unit of asynchronous machine minimal losses efficiency optimization control algolithm.

3. according to claim 1 and 2 described method for controlling pipe network pressure-superposed water supply system based on efficiency optimization of asynchronous motor, it is characterized in that: described digital control unit based on asynchronous machine minimal losses efficiency optimization control algolithm is with the force value of the pressure sensor input that receives and the flow value of flow meter input, after A/D conversion and internal efficiency optimal control routine processes, output to frequency converter with the form of analog voltage signal and analog frequency signal; The input of inverter output terminal water pump unit, water pump assembly carries out speed governing according to frequency converter given voltage and frequency signal, and exit of pump pressure is regulated.

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