RU2532090C2 - Adaptive control system of oil air cooling unit - Google Patents

Abstract

FIELD: heating.

SUBSTANCE: invention relates to air cooling units and can be used for oil cooling of gas pumping units. An adaptive control system of an oil air cooling unit includes temperature setting unit 1, proportional-integral controller 2, multiplier unit 3, frequency converter 4, asynchronous motor 5, fan 6, heat exchanger 7, oil temperature sensor 8, forcing unit 9, air temperature sensor 10, and proportional link 11.

EFFECT: proposed adaptive control system of an oil air cooling unit allows providing operation without any readjustment of controllers.

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Description

The invention relates to air cooling apparatuses (ABOs) and, in particular, can be used to cool gas pumping units.

The closest in technical essence is the control system of the apparatus for air cooling of oil (see. Rosseyev N.N. Creation of an energy-efficient system for automatic control of apparatus for air cooling of oil based on a frequency-controlled electric drive // The dissertation for the degree of candidate of technical sciences. - Samara: Samara State Technical University, 2006, pp. 60-72), containing a temperature setting unit, proportional-integral-differential controller, frequency converter , induction motor, fan, heat exchanger and temperature sensor.

The disadvantage of the closest in technical essence to the control system of the oil air cooling apparatus is that when the temperature of the cooling air changes over a wide range, it requires reconfiguration of the regulators.

The essence of the invention lies in the fact that the adaptive control system of the air-cooled oil cooler, comprising a temperature setting unit, a proportional-integral controller, a frequency converter, an induction motor, a fan, a heat exchanger and an oil temperature sensor, the output of the temperature setting unit being connected to the first input in proportion integral controller, the output of the frequency converter is connected to an asynchronous motor kinematically connected to the fan, the fan is affected by the flow ohm of air to a heat exchanger equipped with an oil temperature sensor is additionally equipped with a forcing unit, an air temperature sensor, a proportional link and a multiplication unit, the output of the oil temperature sensor being connected to the forcing unit input, the output of which is connected to the second input of the proportional-integral controller, the temperature sensor output air is connected to the input of the proportional link, the output of which is connected to the first input of the multiplication unit, the output of the proportional-integral controller is connected with the second input of the multiplication unit, the output of which is connected to the input of the frequency converter.

Significant differences are expressed in a new set of connections between the elements of the device. The specified set of connections allows you to ensure the operation of the control system of the apparatus for air cooling of oil without reconfiguring the regulators.

Figure 1 shows a functional diagram of an adaptive control system of an apparatus for air cooling of oil; figure 2 is a structural diagram of an adaptive control system of an apparatus for air cooling of oil, figure 3 is a calculation model of an adaptive control system of an apparatus for air cooling of oil; figure 4 - transient control action.

The adaptive control system of the oil air cooling apparatus (Fig. 1) contains a temperature setting unit 1, a proportional-integral controller 2, a multiplication unit 3, a frequency converter 4, an induction motor 5, a fan 6, a heat exchanger 7, an oil temperature sensor 8, a boost unit 9 , air temperature sensor 10, proportional link 11.

The output of the temperature setting unit 1 is connected to the first input of the proportional-integral controller 2. The output of the frequency converter 4 is connected to an asynchronous motor 5 kinematically connected to the fan 6. The fan 6 acts by the air flow on the heat exchanger 7, equipped with an oil temperature sensor 8. The output of the oil temperature sensor 8 is connected to the input of the boosting unit 9, the output of which is connected to the second input of the proportional-integral controller 2. The output of the air temperature sensor 10 is connected to the input of the proportional link 11, the output of which is connected to the first input of the multiplication unit 3. The output of the proportional-integral controller 2 is connected to the second input of the multiplication unit 3, the output of which is connected to the input of the frequency converter 4.

Parameter block 1, proportional-integral controller 2, multiplication block 3, frequency converter 4, forcing block 9 and proportional link 11 can be implemented, for example, on the MICROMASTER 430 frequency converter from Siemens using its internal functionality and BICO programming technology . In particular, using parameter P2200, the use of, for example, a process controller can be enabled. Parameters P2201 and P2253 form a fixed task for the controller, parameter P2264 - a feedback source for the technological controller, for example, the first analog input. Parameter P2280 sets the gain, and parameter P2285 sets the time constant of the proportional-integral controller 2. Parameter P2263 selects the type of technological controller that allows the use of boost unit 9 in the feedback circuit, and parameter P2271 sets the type of feedback. Parameter P2274 determines the value of the time constant of the boost unit 9. Parameters P2800 and P2802 enable the use of multiplication block 3. The proportional link 11 can be realized, for example, by scaling the second analog input, through which, for example, the signal from the air temperature sensor 10 is brought in. Scaling is done using parameters P0757-P0760. It should be noted that the parameter setting unit 1, the proportional-integral controller 2, the multiplication unit 3, the forcing unit 8 and the proportional link 11 can also be implemented in software on a microprocessor controller. As an asynchronous motor 4 can be taken, for example, the motor 4A132M8U3, used in air-cooled oil coolers. The fan 5 is, for example, a GAC-12,4-6 impeller mounted on the shaft of an asynchronous motor 4. The heat exchanger 6 can be implemented, for example, similarly to a Hungarian type 06-10 heat exchanger. As sensors 8 and 10, the temperature of the oil and air, for example, can be used sensors KORUND-TM-01-2. An oil temperature sensor 8 is installed at the outlet of the heat exchanger, and an air temperature sensor 10 is installed at the inlet of the ABO air intake.

The adaptive control system of the air oil cooler operates as follows. In accordance with the magnitude of the driving signal coming from the output of the temperature setting unit 1 and the signal from the oil temperature sensor 8, the forcing unit 9, together with the proportional-integral controller 2, form a signal at the second input of the multiplication unit 3. At the same time, the signal from the air temperature sensor 10, passing through the proportional link 11, is fed to the first input of the multiplication unit 3. The resulting signal received at the output of the multiplication unit 3 is fed to the input of the frequency converter 4. The frequency converter 4 converts this signal to a voltage of a certain amplitude and frequency on the stator windings of the induction motor 5. In this case, the shaft of the asynchronous motor 5 starts to rotate and drives the fan 6 , which acts on the heat exchanger 7 by the flow of cooling air. The change in the rotation speed of the induction motor 5 and, therefore, of the fan 6 continues until the signal value from the forcing unit 9 is equal to the signal value at the output of the task unit 1. As a result, the temperature of the oil at the outlet of the heat exchanger 7 is stabilized at a predetermined level and there is a thermal balance between the air flow and the oil flow in the heat exchanger at the required temperature.

The proportional-integral controller 2 is designed to compensate for the greatest inertia of the heat exchanger 7 and all the interference covered by the oil temperature sensor 8. The forcing unit 9 performs the function of compensating for the inertia of the oil temperature sensor 8. The air temperature sensor 10, the proportional link 11 and the multiplication unit 3 are designed to adapt the output signal of the proportional-integral controller 2 when the temperature of the cooling air changes. The correct choice of the settings of the proportional-integral controller 2 and the gear ratio of the proportional link 11 provides a stable mode of operation of the control system and the required accuracy of maintaining the oil temperature at the outlet of the air cooling apparatus at any ambient temperature.

To confirm the last statement, we consider the structural diagram of the proposed adaptive control system of the apparatus for air cooling of oil (figure 2). It contains a proportional-integral regulator with a transfer function

$$W_{P\mathrm{AND}}\left(p\right)=-\left(k_P+\frac{\mathrm{one}}{T_{\mathrm{and}}p}\right)=-\frac{k_P{T}_{\mathrm{and}}p+\mathrm{one}}{T_{\mathrm{and}}p},\left(\mathrm{one}\right)$$

where k _p and T _and are the transmission coefficient and time constant of the proportional-integral controller, respectively.

The minus sign in the transfer function of the controller takes into account that an increase in its signal leads to a decrease in the output value. Oil and air temperature sensors represented by transfer functions

$$W_{dTm}\left(p\right)=\frac{k_{dTm}}{T_{dTm}p+\mathrm{one}};\left(2\right)$$

$$W_{dT\mathrm{at}}\left(p\right)=\frac{k_{dT\mathrm{at}}}{T_{dT\mathrm{at}}p+\mathrm{one}},\left(3\right)$$

where k _dTm and T _dTm - transmission coefficient and time constant of the oil temperature sensor; k _dTv and T _dTv - transmission coefficient and time constant of the air temperature sensor.

The transfer function of the boost unit has the form:

$$W_f\left(p\right)=T_{f}p+\mathrm{one,}\left(\mathrm{four}\right)$$

where the time constant is chosen equal to

$$T_f=T_{dTm}.\left(5\right)$$

The structural diagram also shows the transfer function of the heat transfer process with respect to the control action - the volumetric air flow G _in (p)

$$W_{\mathrm{at}}\left(p\right)=\frac{T_m\left(p\right)}{G_{\mathrm{at}}\left(p\right)}=-\frac{k_G}{a_0{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="00000026.png,00000027.png"\; state="\{\{state\}\}">p</figure-callout>}}^2+a_{\mathrm{one}}p+\mathrm{one}},\left(6\right)$$

Where

; $$a_0=\frac{m_m{C}_m{m}_{tR}{C}_{tR}}{\left(G_m{\rho }_m{C}_m+{\alpha }_m{F}_{\mathrm{at}n}\right)\left({\alpha }_m{F}_{\mathrm{at}n}+{\alpha }_{\mathrm{at}}{F}_{n\mathrm{but}R}-\frac{{\alpha }_{{}_{\mathrm{at}}}^2{F}_{{}_{n\mathrm{but}R}}^2}{G_{\mathrm{at}0}{\rho }_{\mathrm{at}}{C}_{\mathrm{at}}+{\alpha }_{\mathrm{at}}{F}_{n\mathrm{but}R}}\right)-{\alpha }_{{}_{\mathrm{at}}}^2{F}_{{}_{\mathrm{at}\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="00000026.png,00000027.png"\; state="\{\{state\}\}">n</figure-callout>}}}^2}$$

;

; $$a_0=\frac{m_m{C}_m\left({\alpha }_m{F}_{\mathrm{at}n}+{\alpha }_{\mathrm{at}}{F}_{n\mathrm{but}R}-\frac{{\alpha }_{{}_{\mathrm{at}}}^2{F}_{{}_{n\mathrm{but}R}}^2}{G_{\mathrm{at}0}{\rho }_{\mathrm{at}}{C}_{\mathrm{at}}+{\alpha }_{\mathrm{at}}{F}_{n\mathrm{but}R}}\right)+m_{tR}{C}_{tR}\left(G_m{\rho }_m{C}_m+{\alpha }_m{F}_{\mathrm{at}n}\right)}{\left(G_m{\rho }_m{C}_m+{\alpha }_m{F}_{\mathrm{at}n}\right)\left({\alpha }_m{F}_{\mathrm{at}n}+{\alpha }_{\mathrm{at}}{F}_{n\mathrm{but}R}-\frac{{\alpha }_{{}_{\mathrm{at}}}^2{F}_{{}_{n\mathrm{but}R}}^2}{G_{\mathrm{at}0}{\rho }_{\mathrm{at}}{C}_{\mathrm{at}}+{\alpha }_{\mathrm{at}}{F}_{n\mathrm{but}R}}\right)-{\alpha }_{{}_{\mathrm{at}}}^2{F}_{{}_{\mathrm{at}\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="00000026.png,00000027.png"\; state="\{\{state\}\}">n</figure-callout>}}}^2}$$

;

$$k_G=\frac{{\alpha }_m{F}_{\mathrm{at}n}{\alpha }_{\mathrm{at}}{F}_{n\mathrm{but}R}{\rho }_{\mathrm{at}}{C}_{\mathrm{at}}\left(T_{\mathrm{at}0}-T_{\mathrm{at}.\mathrm{at}x0}\right)}{\left(G_{\mathrm{at}0}{\rho }_{\mathrm{at}}{C}_{\mathrm{at}}+{\alpha }_{\mathrm{at}}{F}_{n\mathrm{but}R}\right)\left[\begin{array}{l}\left(G_m{\rho }_m{C}_m+{\alpha }_m{F}_{\mathrm{at}n}\right)\left({\alpha }_m{F}_{\mathrm{at}n}+{\alpha }_{\mathrm{at}}{F}_{n\mathrm{but}R}-\frac{{\alpha }_{{}_{\mathrm{at}}}^2{F}_{{}_{n\mathrm{but}R}}^2}{G_{\mathrm{at}0}{\rho }_{\mathrm{at}}{C}_{\mathrm{at}}+{\alpha }_{\mathrm{at}}{F}_{n\mathrm{but}R}}\right)-\\ -{\alpha }_{{}_{\mathrm{at}}}^2{F}_{{}_{\mathrm{at}n}}^2\end{array}\right]}$$

G _m and G _in - volumetric flow rates of oil and air; ρ _in and ρ _m - the density of air and oil; m _m and m _in - the mass of oil and heat exchanger tubes; C _m , C _in and C _Tr - specific heat of air, oil and tube material of the heat exchanger, respectively; α _m and α _in - convective heat transfer coefficients from the tube wall to the air and from oil to the tube wall, respectively; F _VN and F _NAR - internal and external heat transfer area; T _m and T _in - average temperatures of oil and air at the outlet of the air-cooling apparatus; T _in.in - the average value of the air temperature at the inlet of the air cooling apparatus;

G _in0 , T _in0 and T _in.in0 are the initial conditions.

An analysis of the roots of the denominator (6) shows that this transfer function can be written as a double aperiodic link

$$W_{\mathrm{at}}\left(p\right)=\frac{T_m\left(p\right)}{G_{\mathrm{at}}\left(p\right)}=-\frac{k_G}{\left(T_{\mathrm{eleven}}p+\mathrm{one}\right)\left(T_{22}p+\mathrm{one}\right)},\left(7\right)$$

, $$T_{22}=\frac{2a_0}{a_1-\sqrt{a_1^2-4a_0}}$$

, причем будем считать, что T₂₂≥T₁₁.Where $$T_{\mathrm{eleven}}=\frac{2a_0}{a_{\mathrm{one}}+\sqrt{a_{\mathrm{one}}^2-\mathrm{four}{a}_0}}$$

, $$T_{22}=\frac{2a_0}{a_{\mathrm{one}}-\sqrt{a_{\mathrm{one}}^2-\mathrm{four}{a}_0}}$$

, and we assume that T ₂₂ ≥T ₁₁ .

The transfer function of the fan together with the duct is represented by an aperiodic link

$$W_V\left(p\right)=\frac{k}{\left(T_{V}p+\mathrm{one}\right)}\left(8\right)$$

и постоянной времени $$T_V=-\frac{{\rho }_{в}{l}_{в}}{\left(2a{G}_{в0}+b{\omega }_{00}\right)S_{в}}$$

, где a, b и c - коэффициенты аэродинамической характеристики вентилятора; l_в и S_в - длина и площадь поперечного сечения воздуховода; ω₀₀ - начальное значение скорости вращения вентилятора.with variable gear ratio $$k_V=-\frac{\left(2c{\omega }_{00}+b{G}_{\mathrm{at}0}\right)}{2a{G}_{\mathrm{at}0}+b{\omega }_{00}}$$

and time constant $$T_V=-\frac{{\rho }_{\mathrm{at}}{l}_{\mathrm{at}}}{\left(2a{G}_{\mathrm{at}0}+b{\omega }_{00}\right)S_{\mathrm{at}}}$$

where a , b and c are the aerodynamic characteristics of the fan; l _in and S _in - the length and cross-sectional area of the duct; ω ₀₀ - the initial value of the fan speed.

The transfer function of an induction motor is represented by a second-order dynamic link

$$W_{d\mathrm{at}}\left(p\right)=\frac{k_{d\mathrm{at}}}{a_{00}{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="00000026.png,00000027.png"\; state="\{\{state\}\}">p</figure-callout>}}^2+a_{10}p+\mathrm{one}},\left(9\right)$$

where the values of the coefficients a ₀₀ and a ₁₀ depend on the parameters of the motor equivalent circuit, the frequency of the supply voltage and the law of regulation of the voltage amplitude as a function of frequency.

The frequency converter in the structural diagram is represented by an inertia-free link with a transmission coefficient k _cn , since its inertia in comparison with the inertia of the heat exchanger can be neglected.

The settings of the proportional-integral controller are selected so that the equality

$$k_P{T}_{\mathrm{and}}=T_{22}.\left(10\right)$$

Formula (10) has two degrees of freedom. Therefore, setting the value of the time constant T _and , for example, from the relation:

$$T_{\mathrm{and}}=\mathrm{1,5}{T}_{\mathrm{eleven}}{k}_{\mathrm{from}P}{k}_{d\mathrm{at}}{k}_V{k}_G{k}_{dT},\left(\mathrm{eleven}\right)$$

you can find the desired value of k _p :

$$k_P=\frac{T_{22}}{T_{\mathrm{and}}}.\left(12\right)$$

The transmission coefficient of the proportional link k _a is selected based on the transmission coefficient of the air temperature sensor and the range of temperature changes of the cooling air.

In accordance with expressions (1) - (12), the transfer functions of all elements of the adaptive oil ABO control system with an 4A132M8U3 induction motor, GAC-12.4-6 fan impeller were calculated, with heat exchanger parameters: G _m = 0.0166 m ³ / from; ρ _m = 843 kg / m ³ ; C _m = 1670 J / kgK; C _mp = 460 J / kgK; C _in = 1005 J / kgK; m _m = 434 kg; m _tr = 1544 kg; α _m = 286 W / m ² K; F _int = 144 m ² ; F _nar = 1135 m ² . Transfer functions found for two modes.

In the first mode, the initial conditions are taken G _в0 = 0.54 m ₃ / s; T _in.in0 = -30 ° C; _0O T = 9,089 ° C; α _in = 0.504 W / m ² K; ρ _in = 1,452 kg / m ³ . In this case, the transfer functions of the elements of the control system take the following numerical values:

; $$W_{\mathrm{at}\mathrm{one}}\left(p\right)=-\frac{\mathrm{1,0043}}{412.1345{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="00000026.png,00000027.png"\; state="\{\{state\}\}">p</figure-callout>}}^2+67.2848p+\mathrm{one}}$$

;

; $$W_{V1}\left(p\right)=\frac{\mathrm{0,4042}}{\left(\mathrm{1,202}p+1\right)}$$

. $$W_{d\mathrm{at}\mathrm{one}}\left(p\right)=\frac{\mathrm{1,57}}{0.1101{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="00000026.png,00000027.png"\; state="\{\{state\}\}">p</figure-callout>}}^2+0.5939p+\mathrm{one}}$$

; $$W_{V\mathrm{one}}\left(p\right)=\frac{0.4042}{\left(\mathrm{1,202}p+\mathrm{one}\right)}$$

.

In the second mode, the initial conditions are accepted: G _в0 = 27.2 m ² / s; T _in.in0 = 40 ° C; _0O T = 45,923 ° C; α _in = 23 W / m ² K; ρ _in = 1,118 kg / m ³ . In this case, the transfer functions of the elements of the control system take the following numerical values:

; $$W_{\mathrm{at}2}\left(p\right)=-\frac{0.0675}{\mathrm{216,682}{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="00000026.png,00000027.png"\; state="\{\{state\}\}">p</figure-callout>}}^2+40.7052p+\mathrm{one}}$$

;

; $$W_{V2}\left(p\right)=\frac{\mathrm{0,4042}}{\left(\mathrm{0,024}p+1\right)}$$

. $$W_{d\mathrm{at}2}\left(p\right)=\frac{\mathrm{1,557}}{0.0024{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="00000026.png,00000027.png"\; state="\{\{state\}\}">p</figure-callout>}}^2+\mathrm{0,0755}p+\mathrm{one}}$$

; $$W_{V2}\left(p\right)=\frac{0.4042}{\left(0.024p+\mathrm{one}\right)}$$

.

The transmission coefficient of the frequency Converter is fundamentally equal to k _SP = 1. Temperature sensors are characterized by time constants T _dTm = T _dTv = 40 s. Since the driving signal in the control system is formed in the same quantities as the output quantity, the transmission coefficient of the oil temperature sensor k _dTv = 1.

The parameters of the regulators are calculated for the second mode: T _and = 6.52 s; k _p = 9.28; T _f = 40 s. The transmission coefficient of the proportional link (in fact, the adaptation coefficient) is taken equal to k _a = 0.1.

In accordance with the obtained transfer functions in the software environment "Matlab Simulink" developed a calculation model of the adaptive control system ABO oil (figure 3). The calculation model allows the study of the adaptive control system of the oil cooler in relation to the control action T _s , taking into account the variation of the parameters of the control object. With the settings of the regulators selected for the mode T _in.input = -30 ° C, G _in0 = 0.54 m ² / s, at the same time, modeling is carried out for the opposite case with the initial conditions T _in.in = 40 ° C, G _в0 = 27 , 2 m ² / s. The absence of the inertia of the air temperature sensor in the design diagram is explained by the fact that by the time the driving action changes, the sensor output signal has an already established value.

Analysis of the graphs shown in figure 4, shows that the developed adaptive control system ensures the health of the ABO oil in the entire possible range of parameters of the control object. Curve 1 corresponds to the initial conditions T _in.input = -30 ° C, G _in0 = 0.54 m ² / s, and curve 2 - T _in.input = 40 ° C, G _in0 = 27.2 m ³ / s. The time of the transition process varies within t _pp = 86.5 ÷ 127 s, despite the fact that the transmission coefficient of the control object changes by almost 15 times.

Thus, the proposed adaptive control system for the oil air cooler allows for operation without reconfiguring the regulators.

Claims (1)

An adaptive control system for an oil air cooling apparatus, comprising a temperature setting unit, a proportional-integral controller, a frequency converter, an induction motor, a fan, a heat exchanger and an oil temperature sensor, the output of the temperature setting unit being connected to the first input of the proportional-integral controller, the output of the frequency converter with an asynchronous motor kinematically connected to the fan, the fan acts on the heat exchanger equipped with a stream of air oil temperature sensor, characterized in that it is additionally equipped with a boost unit, an air temperature sensor, a proportional link and a multiplication unit, the output of the oil temperature sensor being connected to the input of the boost unit, the output of which is connected to the second input of the proportional-integral controller, the output of the air temperature sensor connected to the input of the proportional link, the output of which is connected to the first input of the multiplication unit, the output of the proportional-integral controller is connected to the second input m of the multiplication unit, the output of which is connected to the input of the frequency converter.

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