CN202176498U - Surge-preventing generalized predictive control system of air compressor - Google Patents

Abstract

A surge-preventing generalized predictive control system of an air compressor relates to the field of surge-preventing predictive control of air compressor control systems in steel and chemical industries. The surge-preventing generalized predictive control system comprises a forward collector, a predictor and a backward actuator, wherein the forward collector monitors the inlet-outlet pressure and flow rate of a pipe network and is connected with the predictor in a PCI (Peripheral Component Interconnect) bus way; the backward actuator controls an emptying valve, has a sound-light alarming function and is connected with the predictor in an RS485 way; and the predictor calculates, displays and storing the operation parameters of the air compressor by adopting a surge-preventing generalized predictive control method of the air compressor and combining the production burthen set information input from a keyboard and the on-site operation data obtained by the forward collector, and outputs predictive control information to the backward actuator in the RS485 way, thereby realizing the surge-preventing predictive control on the air compressor. The surge-preventing generalized predictive control system is moderate in adjusting process, high in control precision and dynamic quality, stable and reliable in operation, and capable of effectively avoiding the surge of the air compressor.

Description

A kind of air compressor anti-surge generalized predictable control system

Technical field

The utility model relates to the anti-surge predictive control field of iron and steel, chemical industry air compressor control system, relates in particular to a kind of air compressor anti-surge generalized predictable control system.

Background technique

The prediction of air compressor surging phenomenon and strick precaution are air compressor control hot research fields.Prediction is exactly how to set up practicality, effective air compressor dynamic model with the most basic problem of generation of taking precautions against surging phenomenon.At present the research method majority of this problem concentrates on the LTI process, with collection in worksite to data such as pipe network air displacement, pressure, flow be expressed as time series independent of each other, realize the stationary process of LTI function.Yet; Actual compressor operation process has to a certain degree time variation and non-linear, itself has certain self correlation like the sampling analysis data, does not satisfy that statistics is independent each other; The pipe network flow rate disturbance changes, pressure, flow, temperature transducer and motor, stator valve actuator non-linear etc.Therefore, reflect that for true surge receives the complex process of factor affecting such as the factor of unit own, ductwork pressure, temperature, flow, the mathematical model that becomes when setting up is very important.

Because this utilization changes the regulative mode of field current; Inevitably can receive the influence of mains by harmonics disturbance, gas flows in the runner of impeller and Diffuser in addition, utilizes centrifugal boosting and reduction of speed diffusion action; Gas compression; Pressure improves, and entrained energy before and after compression variation has taken place, and promptly specific volume, entropy, enthalpy all change.According to law of conservation of energy and bernoulli equation, consider that pipeline presses many practical factors such as becoming resistance, ambient temperature, gas leakage, show between pipe network inlet, outlet pressure ratio and the flow and become when tangible and non-linear.If adopt the LTI controlling method to regulate simply to the air compressor variable load operation; Air compressor is prone to the operation point and moves into Critical Control district or dangerous surge area from the smooth working district so; Cause that performance of air compressor worsens; Pressure and efficient significantly reduce, and can cause the strong vibrations of parts such as swivel bearing, blade or rotor, even damage.

The model utility content

In order to solve the problem that moves into Critical Control district or dangerous surge area by caused by factors air compressor real work points such as the adjustment of producing load, pipe network gas leakage, mains by harmonics disturbances; The utility model provides a kind of air compressor anti-surge generalized predictable control system; This system is foundation with the flow change rate, whether the compressor operation operation point is got into surge region carry out Generalized Prediction and control.Air compressor anti-surge generalized forecast control method is based on to the analysis of correlation between many parameters in the air compressor Anti-surge Control process; Set up air compressor anti-surge controlled autoregressive integration overlapping averages system model; The harmful effect of uncertain interference and non-linear factor can be suppressed, the generation of surging phenomenon can be effectively prevented system.

The technological scheme that the utility model technical solution problem is taked is following:

A kind of air compressor anti-surge generalized predictable control system comprises forward direction collector, fallout predictor and back to final controlling element, and said forward direction collector monitoring pipe network is gone into, outlet pressure and flow, links to each other with fallout predictor with the pci bus mode; Said back has sound and light of alarm to final controlling element control atmospheric valve, links to each other with fallout predictor with the RS485 mode; Said fallout predictor adopts air compressor anti-surge generalized forecast control method; In conjunction with the production load setting information of keyboard input and the on-the-spot service data of forward direction collector acquisition; Calculate, show and storage compressor operation parameter; Backward to final controlling element prediction of output control information, realize the predictive control of air compressor anti-surge with the RS485 mode.

Above-mentioned fallout predictor is the system core; Select industrial control computer for use; Be connected with the forward direction collector with the pci bus mode, be connected to final controlling element with the back, can receive production load setting information by the keyboard input with the RS485 mode; Embedded a kind of air compressor anti-surge generalized forecast control method has functions such as information processing, demonstration, storage, generation form, printing, output control information;

Above-mentioned forward direction collector is the forward path of system, and it comprises flow transducer, pressure transducer, RS485 standard interface circuit and capture card; Said flow transducer is connected with capture card, and its monitoring pipe network is gone into, the exit gas flow information; Said pressure transducer is connected with capture card, and its monitoring pipe network is gone into, the exit gas pressure information; Said RS485 standard interface circuit becomes the RS485 level of standard with the information translation of above-mentioned flow transducer and pressure transducer, realizes the information transmission between above-mentioned flow transducer and pressure transducer and the capture card; Said capture card is a data collecting card, is connected with fallout predictor with the pci bus mode.

Above-mentioned back is the backward channel of system to final controlling element, and it comprises controller, audible-visual annunciator, 4-20mA change-over circuit and atmospheric valve; Said controller is connected with fallout predictor with the RS485 mode, receives the information of forecasting that fallout predictor sends; Said audible-visual annunciator is connected with controller, carries out acoustooptic alarm according to the instruction of controller; Said 4-20mA change-over circuit is connected with atmospheric valve, and it provides the operating current of 4-20mA for atmospheric valve; The gas flow of said atmospheric valve control pipe network.

The beneficial effect of the utility model is: overcome the caused unit gas of air compressor variable load operation and introduced, derive factors such as loine pressure, flow, temperature and each inter-stage system balance significantly change; Become and nonlinear problem when having solved between gas pressure ratio and the flow velocity, realize prediction of air compressor varying duty anti-surge and control.This system's adjustment process is gentle, and control accuracy, dynamic quality promote to some extent, and stable and reliable operation can effectively prevent the generation of air compressor surging phenomenon.Compare with existing systems,, all be significantly improved at aspects such as stability, reliability and the prediction of system and control abilities.

Description of drawings

Fig. 1 is the structured flowchart of the utility model air compressor anti-surge generalized predictable control system.

Fig. 2 is the workflow diagram of the utility model air compressor anti-surge generalized predictable control system.

Embodiment

Below in conjunction with accompanying drawing the utility model is done further explain.

As shown in Figure 1, the utility model air compressor anti-surge generalized predictable control system comprises that fallout predictor, forward direction collector and back are to final controlling element.With pipeline delivery outlet pressure is constant, with the variation of production logistics, is principle according to pipe network flow minimum, and prediction region, compressor operation operation point is implemented under the condition of varying duty, and the air compressor safe and stable operation is avoided the generation of surging phenomenon.

Fallout predictor is the system core, selects industrial control computer for use, is furnished with AMD PHENOM 8400CPU; The 2G internal memory, 250G hard disk, pci bus interface, RS485 communication interface; Operation Windows operation system, a kind of air compressor anti-surge generalized forecast control method that embedded c programming language is write.Be connected with the forward direction collector with the pci bus mode, be connected to final controlling element with the back, can receive production load setting information, have functions such as information processing, demonstration, storage, generation form, printing, output control information by the keyboard input with the RS485 mode.

The forward direction collector is the forward path of system, mainly is made up of flow transducer, pressure transducer, RS485 standard interface circuit and capture card.Flow transducer is furnished with RS485 standard interface circuit, and the monitoring pipe network is gone into, the exit gas flow information, sends capture card to the RS485 fiduciary level; Pressure transducer also is furnished with RS485 standard interface circuit, and the monitoring pipe network is gone into, the exit gas pressure information, sends capture card to the RS485 fiduciary level; Capture card is selected the PCI1716 data collecting card for use, is connected with fallout predictor with the pci bus mode.

The back is the backward channel of system to final controlling element, mainly is made up of controller, audible-visual annunciator, 4-20mA change-over circuit and atmospheric valve.Controller is selected the AT89C58 single-chip microcomputer for use, is furnished with RS485 standard interface circuit, is connected with fallout predictor with the RS485 bus mode; Audible-visual annunciator is selected industrial warning light and electric bell for use, after controller sends low level signal, and alarm equipment alarm, after device to be controlled sends high level signal, alarm release; The 4-20mA change-over circuit is made up of technical grade DA conversion chip MAX7541, amplifier LM358; Atmospheric valve is selected continuous electric control valve for use, realizes prediction of air compressor anti-surge and control.

As shown in Figure 2, it is three steps as follows that the controlling method of the utility model air compressor anti-surge generalized predictable control system is mainly divided:

Step 1, set up air compressor anti-surge generalized predictive control model

Suppose that the pressurized gas state is even, pressure, the temperature of each point are identical, specific heat, interior can be only relevant with gas temperature, according to the on-the-spot roadability of air compressor system, can set up dynamical equation:

$\frac{\mathrm{d\ϵ}}{\mathrm{dt}}=\frac{q-q_l}{S}\mathrm{\ϵ}+\underset{j=1}{\overset{4}{\mathrm{\Σ}}}{\mathrm{\μ}}_j{\mathrm{\ϵ}}_j+{\mathrm{\ω}}_l---\left(1\right)$

$\frac{{\mathrm{d\ϵ}}_j}{\mathrm{dt}}=\frac{q_l}{S}\mathrm{\ϵ}-{\mathrm{\μ}}_j{\mathrm{\ϵ}}_j$ j＝1，2，Λ4 (2)

In the formula: ε is a pressure ratio,

P _iBe the air inlet ductwork pressure; P _oBe the exhaust ductwork pressure; Q is the pipe network gas mass flow; q _lBe pipe network gas leakage or decay mass flow rate; S is the gas compression time; μ _jBe corresponding pressure ratio coefficients at different levels; ε _jBe corresponding pressure ratios at different levels; J is compression sequence numbers at different levels; ω _lFor disturbing.

Formula (1) both sides are to the t differentiate, substitution formula again (2), put in order:

$\frac{d{\mathrm{\ϵ}}^2}{d^{2}t}=-(\frac{q_l}{S}+\mathrm{\η})\frac{\mathrm{d\ϵ}}{\mathrm{dt}}+\frac{{\mathrm{\ϵ}}_0}{S}\frac{\mathrm{dq}}{\mathrm{dt}}+\frac{\mathrm{\η}{\mathrm{\ϵ}}_0}{S}q+\mathrm{\ξ}---\left(3\right)$

In the formula: η is the mean value of decay constant; ε ₀Be air compressor surge critical pressure ratio; ξ is that white noise disturbs.

Formula (3) discretization is got:

$\mathrm{\ϵ}\left(k\right)+\frac{q_{l}T+\mathrm{S\ηT}-2S}{S}\mathrm{\ϵ}(k-1)+\frac{S-q_{l}T-\mathrm{\ηST}}{S}\mathrm{\ϵ}(k-2)=$ (4)

$\frac{{\mathrm{\ϵ}}_{0}T+\mathrm{\η}{\mathrm{\ϵ}}_0{T}^2}{S}q(k-1)-\frac{{\mathrm{\ϵ}}_{0}T}{S}q(k-2)+T^2\mathrm{\ξ}(k-1)$

In the formula: T is the sampling period; K is the integral multiple moment of T.

Can set up controlled autoregressive integration moving average model by formula (4):

A(z ^-1)ε(k)＝B(z ^-1)q(k-1)+C(z ^-1)ξ(k)/Δ (5)

In the formula: z ^-1Backward shift operator for discrete system; Δ is a difference operator, Δ=1-z ^-1A (z ^-1), B (z ^-1), C (z ^-1) be z ^-1Multinomial;

A(z ^-1)＝1+a ₁z ^-1+a ₂z ^-2

$a_1=\frac{q_{l}T+\mathrm{S\ηT}-2S}{S};$

$a_2=\frac{S-q_{l}T-\mathrm{\ηST}}{S};$

B(z ^-1)＝b ₀+b ₁z ^-1

$b_0=\frac{{\mathrm{\ϵ}}_{0}T+\mathrm{\η}{\mathrm{\ϵ}}_0{T}^2}{S};$

$b_1=-\frac{{\mathrm{\ϵ}}_{0}T}{S};$

C(z ^-1)＝c ₁z ^-1+c ₂z ^-2

c ₁＝T ²；

c ₂＝-T ²。

Step 2, design object function

Fallout predictor is according to the production load value of keyboard input, and inquiry compressor operation performance table is confirmed air compressor surge critical pressure ratio ε ₀Sampling time is chosen 5 minutes, by flow transducer, the pressure transducer of forward direction collector record that current pipe network is gone into, exit gas flow and pressure information, according to the formula in the step 1, calculate current air compressor steady operational status parameter ε, a ₁, a ₂, b ₀, b ₁, c ₁, c ₂

Is target with compressor operation at stable operating point, is principle with pipe network flow minimum, the design object function:

$J(N_1,N_2)=\underset{k=1}{\overset{N_1}{\mathrm{\Σ}}}{[\mathrm{\ϵ}(k+j)-{\mathrm{\ϵ}}_0]}^2+\mathrm{\λ}\underset{k=1}{\overset{N_2}{\mathrm{\Σ}}}{\left[\mathrm{\Δq}(k+j-1)\right]}^2---\left(6\right)$

In the formula: N ₁Be pressure ratio predicted time length; N ₂Be control time length; λ is a control coefrficient.

The prediction of step 3, surge and control

According to the design object of step 2, when pipe network gas pressure ratio was approached air compressor surge critical value, the gas mass velocity variable quantity reached minimum and is:

Δq(k)＝P(Z ^-1)ε ₀-α ₁(Z ^-1)ε(k)-α ₂(Z ^-1)ε(k-1) (7)

In the formula:

$P\left(Z^{-1}\right)=P_{N_1}+P_{N_1-1}{Z}^{-1}+\mathrm{\Λ}+P_1{Z}^{-N_1+1}$

${\mathrm{\α}}_1\left(Z^{-1}\right)=\underset{j=1}{\overset{N_Y}{\mathrm{\Σ}}}{P}_j{F}_j\left(Z^{-1}\right)$

${\mathrm{\α}}_2\left(Z^{-1}\right)=\underset{j=1}{\overset{N_Y}{\mathrm{\Σ}}}{P}_j{H}_j\left(Z^{-1}\right)$

Recursive form that accounting equation is separated and correlation matrix are:

$F_j\left(Z^{-1}\right)={F_0}^j+{F_1}^j{Z}^{-1}+{F_2}^j{Z}^{-2}$

$H_j\left(Z^{-1}\right)={H_0}^j+{{H_1}^{j}Z}^{-1}$

${F_1}^{j+1}={F_2}^j-(a_2-a_1){F_0}^j$

${F_2}^{j+1}=a_2{F_0}^j$

${H_0}^{j+1}={H_1}^j-\frac{b_1}{b_0}{H_0}^j-c_1{G}_j$

H ₁ ^j+1＝-c ₂G _j

G _j＝b ₀

F ₀ ¹＝c ₁

F ₁ ¹＝c ₂

F ₂ ¹＝0

H ₀ ¹＝-b ₀c ₁

H ₁ ¹＝-b ₀c ₂

Can get Δ q (k) by the aforementioned calculation formula, whether Δ q (k) moves into the Generalized Prediction parameter of surge region for current compressor operation operation point.If forward direction collector flow transducer records that current pipe network is gone into, the exit gas flow change rate is greater than Δ q (k), then measurablely go out air compressor and surging phenomenon will occur, low level signal is sent to the controller of final controlling element in the back; Start audible-visual annunciator, and open atmospheric valve, treat the forward direction collector monitor the gas flow variance ratio less than Δ q (k) after; Controller sends high level signal; Alarm release is closed atmospheric valve, realizes the anti-surge prediction and the control of air compressor.

In sum; The air compressor anti-surge generalized predictable control system of the utility model is analyzed the correlation between many parameters in the air compressor Anti-surge Control process, sets up air compressor anti-surge controlled autoregressive integration overlapping averages system model; A kind of air compressor anti-surge generalized forecast control method is proposed; Realize the reliable operation of air compressor varying duty energy-saving run, avoid the generation of surging phenomenon, can be applicable to the control system of iron and steel, chemical enterprise air compressor.

Claims (4)

1. air compressor anti-surge generalized predictable control system is characterized in that this system comprises: forward direction collector, fallout predictor and back be to final controlling element, and said forward direction collector monitoring pipe network is gone into, outlet pressure and flow, links to each other with fallout predictor with the pci bus mode; Said back has sound and light of alarm to final controlling element control atmospheric valve, links to each other with fallout predictor with the RS485 mode; Said fallout predictor adopts air compressor anti-surge generalized forecast control method; In conjunction with the production load setting information of keyboard input and the on-the-spot service data of forward direction collector acquisition; Calculate, show and storage compressor operation parameter; Backward to final controlling element prediction of output control information, realize the predictive control of air compressor anti-surge with the RS485 mode.

2. a kind of air compressor anti-surge generalized predictable control system as claimed in claim 1 is characterized in that said fallout predictor is an industrial control computer.

3. a kind of air compressor anti-surge generalized predictable control system as claimed in claim 1 is characterized in that said forward direction collector comprises flow transducer, pressure transducer, RS485 standard interface circuit and capture card; Said flow transducer is connected with capture card, and its monitoring pipe network is gone into, the exit gas flow information; Said pressure transducer is connected with capture card, and its monitoring pipe network is gone into, the exit gas pressure information; Said RS485 standard interface circuit converts sensor information the RS485 level of standard to, realizes the information transmission between sensor and the capture card; Said capture card is a data collecting card, is connected with fallout predictor with the pci bus mode.

4. a kind of air compressor anti-surge generalized predictable control system as claimed in claim 1 is characterized in that, said back comprises controller, audible-visual annunciator, 4-20mA change-over circuit and atmospheric valve to final controlling element; Said controller is connected with fallout predictor with the RS485 mode, receives the information of forecasting that fallout predictor sends; Said audible-visual annunciator is connected with controller, carries out acoustooptic alarm according to the instruction of controller; Said 4-20mA change-over circuit is connected with atmospheric valve, and it provides the operating current of 4-20mA for atmospheric valve; The gas flow of said atmospheric valve control pipe network.

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