RU2493437C1 - Turbine unit control system - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: control system includes a centrifugal pump, an electric motor, a rotation frequency variation unit of a centrifugal pump rotor, an automatic control system providing the specified rotation frequency of the pump rotor. At the automatic control system inlet there installed is a frequency comparison element, a demand formation unit and an automatic correction unit. Demand formation unit consists of a rotor rotation frequency calculation unit, a solver, a unit for determining maximum efficiency line of the pump, a calculator of pump maximum efficiency, and approximation unit of pump efficiency characteristic, an approximation unit of pump pressure characteristic and an approximation unit of pipeline pressure characteristic. Automatic correction unit consists of pressure sensor at centrifugal pump inlet, pressure sensor at pump outlet, unit for determining differential head of pump, measuring device of liquid flow rate through pump, unit for determining pump operating efficiency, comparison element of pump efficiency, signal converter and watt-metre.

EFFECT: providing operation of turbine units with maximum possible efficiency coefficient irrespective of variation of pipeline characteristic.

1 dwg

Description

The invention relates to the field of control of turbine units, in particular oil pumping, sump and compressor units, including centrifugal or axial machines, and is intended to ensure their operation with the highest possible efficiency, regardless of changes in the characteristics of the pipeline.

A known control system of an external electric centrifugal pump (patent RU No. 2341004, publ. 10.12.2008), comprising a block for setting a diagram of a dynamic fluid level, a comparison unit, a dynamic fluid level sensor, a unit for calculating the required frequency, a frequency converter, a submersible electric centrifugal pump, a differentiation unit, adder.

The disadvantage of this device is the reduction in efficiency when changing productivity or pressure.

A control device for a pumping unit is known (patent RU No. 2095633, publ. 10.11.1997) containing a pressure sensor and a magnetic actuator, which turns on the electric drive of the pumping unit. It is equipped with a signal conversion unit, a setting unit, software and memory units, and an amplifier. The pressure sensor is made analog and connected to the first input of the signal conversion unit, the second input of which is connected to the output of the setting unit, and the third input to the first output of the program unit, its first input is connected to the output of the signal conversion unit, the second output of the program unit is connected to the input of the storage unit, the output of which is connected to the second input of the program unit, the third output of which is connected to the input of the amplifier, the output of which is with a magnetic starter.

The disadvantages of this device is that it does not provide for the regulation of a given flow rate by changing the number of revolutions of the pump shaft, this does not allow it to be used as a flow regulator. Therefore, its use as a flow regulator requires an additional installation of a pressure regulator in the fluid flow, which leads to additional capital and operating costs.

A known control system of a centrifugal pump (patent RU No. 2418990, publ. 05/20/2011), adopted as a prototype. The system contains a control parameter setting unit, the output of which is connected to the first input of the comparison unit, the output of the centrifugal pump is connected to the adjustable parameter sensor, an adjustable parameter sensor, an adder, a differentiation unit, the second input of the comparison unit is connected to the output of the adder, the integration unit is connected to the output of the comparison unit , the output of the integration unit is connected to the input of an induction motor, the output of which is connected to the input of a centrifugal pump, the asynchronous motor is connected speed sensor, an output connected to the second differential unit whose output is connected to a first input of an adder controlled parameter sensor is connected to the input differential unit whose output is coupled to a second input of the adder, a third input coupled to an output of the sensor control parameter.

The disadvantage of this device is the reduction in efficiency when changing productivity or pressure.

The technical result is to increase the efficiency of the turbine unit to the maximum possible.

The technical result is achieved by the fact that in the control system of the turbine unit, including a centrifugal pump, an electric motor, a unit for changing the rotor speed of a centrifugal pump, an automatic control system providing a predetermined rotational speed of the centrifugal pump rotor, a frequency comparison element, a task formation unit are installed at the input of the automatic control system consisting of a unit for calculating the rotor speed, a solver, a line determination unit for a maximum centrifugal efficiency n a sucker, a calculator of the maximum efficiency of a centrifugal pump, an approximation block of a characteristic of an efficiency of a centrifugal pump, a block of approximation of a pressure characteristic of a centrifugal pump and a block of approximation of a pressure characteristic of a pipeline, and an automatic correction unit consisting of a pressure sensor at the inlet of the centrifugal pump, a pressure sensor at the outlet of the centrifugal pump , unit for determining the differential pressure of a centrifugal pump, a device for measuring the flow of liquid through the pump, a unit for determining the working its efficiency of a centrifugal pump, an element of comparison of the efficiency of a centrifugal pump, a signal converter, a wattmeter, while one output of the approximation block of the efficiency characteristic of a centrifugal pump is connected to a calculator of the maximum efficiency of a centrifugal pump, which is connected to the inputs of the approximation block of the pressure characteristic of a centrifugal pump, a block for determining the maximum efficiency line a centrifugal pump and with a comparison element of the efficiency of a centrifugal pump, the output of the approximation block of the pressure characteristic of a centrifugal pump with is dined to the input of the maximum efficiency line determination unit of the centrifugal pump, which is connected to the solver input, the solver input is connected to the approximation of the pressure characteristic of the pipeline, and the output to the rotor speed calculation unit, the input of which is connected to the frequency comparison element, the input of the differential pressure determination unit of the centrifugal pump the pump is connected to the outputs of the pressure sensors at the inlet to the pump and the outlet of the pump, the output is connected to the input of the unit for determining the operational efficiency of the centrifugal pump, the input of which о is connected to the output of the device for measuring fluid flow through the pump and to the wattmeter, and the output is connected to a centrifugal pump efficiency comparison element, the input of which is connected to the output of the centrifugal pump maximum efficiency calculator, and the output is connected to a signal converter, the output of which is connected to the frequency comparison element, which is connected to the input of the automatic control system, the input of which is connected to the unit for changing the rotational speed of the rotor of the centrifugal pump connected to the electric motor, and the electric motor l with a centrifugal pump.

A turbine unit is a combination of a centrifugal compressor, an electric pump or a turbine and an electric generator driven by it. In this case, the turbine unit includes a centrifugal pump, an electric motor as a drive and a unit for changing the speed of the rotor of the centrifugal pump.

According to the proposed formulas known from the prior art, the regulating parameter is calculated in the task forming unit - the pump rotor speed depending on the passport parameters, then in the automatic correction unit the calculated pump rotor speed is corrected by its actual speed, and then the corrected speed value is fed to speed change unit. This provides an increase in the efficiency of the turbine unit to the maximum possible.

The system is illustrated in the drawing, which shows a functional diagram. The system includes: a centrifugal pump 1, an electric motor 2, a change unit 3 of the rotor speed of the centrifugal pump 1, an automatic control system 4 providing a predetermined rotor speed of the centrifugal pump 1, a frequency comparison element 5, a wattmeter 6, a rotor speed setting task generating unit, corresponding to the maximum efficiency of the centrifugal pump, and the automatic correction of the maximum efficiency unit when changing external factors affecting the operation of the turbine unit.

The unit for forming the rotor speed reference includes a centrifugal pump efficiency factor approximation unit 7, a centrifugal pump maximum efficiency calculator 8, a centrifugal pump pressure head approximation unit 9 and a centrifugal pump maximum efficiency line determination unit 10, a pipeline characteristic approximation unit 11, a solver 12, unit 13 for calculating the rotor speed, made in the form of a set of known elements of addition, multiplication, differentiation, respectively, used to calculate laziness formulas.

The automatic correction unit includes a pressure sensor 14 at the inlet of the centrifugal pump 1 and a pressure sensor 15 at the outlet of the centrifugal pump 1, a differential pressure determination unit 16 for the centrifugal pump 1, a liquid flow measuring device 17, a working efficiency determination unit 18 for the centrifugal pump 1, and an electric meter power - a wattmeter 6, an element 19 for comparing the efficiency values of a centrifugal pump 1, a signal converter 20.

The system operates as follows. On the block 7 approximating the characteristics of the efficiency of a centrifugal pump, the operator enters the values of the efficiency coefficients of the efficiency of the centrifugal pump c ₁ , c ₂ , c ₃ , and generates a signal of the efficiency characteristic of the centrifugal pump according to the formula:

η = c ₁ Q + c ₂ Q ² + c ₃ Q ³ ,

where η is the efficiency of the main pump;

c ₁ , c ₂ c ₃ , are constant coefficients of the efficiency characteristic of a centrifugal pump, determined by the passport characteristics of turbine units or when conducting regulated tests during operation, respectively s / m ³ , s ² / m ⁶ , s ³ / m ⁹ ;

Q is the actual flow rate of the centrifugal pump, m ³ / s.

for the passport speed supplied to the calculator 8 of the maximum efficiency of the centrifugal pump, which calculates the performance of the centrifugal pump at the maximum efficiency Q _ηmax according to the formula:

, $$Q_{\eta \max }=\frac{-c_2-\sqrt{c_2^2-3c_{\mathrm{one}}{c}_3}}{3c_3}$$

,

where Q _ηmax is the feed at the maximum efficiency of the centrifugal pump, m ³ / s;

and generates a signal supplied to block 9 approximation of the pressure characteristics of the centrifugal pump 1 and block 10 determining the line of maximum efficiency of the centrifugal pump 1,

, $$H=\frac{H_{\eta \max }}{Q_{\eta \max }^2}{Q}^2$$

,

where Q _ηmax and H _ηmax , respectively, flow, m ³ / s and pressure, m at maximum efficiency of a centrifugal pump;

Q and H - respectively, the actual flow, m ³ / s and the actual pressure, m of a centrifugal pump.

and also determines the maximum efficiency _ηmax , but the formula:

, $${\eta }_{\max }=c_{\mathrm{one}}{Q}_{\eta \max }+c_2{Q}_{\eta \max }^2+c_3{Q}_{\eta \max }^3$$

,

which is fed to the element 19 for comparing the efficiency values of the centrifugal pump 1. In block 9 for approximating the pressure characteristic of the centrifugal pump 1, the values of the coefficients of the pressure characteristic of the boom a ₀ are also entered, and where the pump characteristic H is formed according to the formula

$$H=a_0+a_{\mathrm{one}}Q+a_2{Q}^2$$

where a ₀ , a ₁ , a ₂ are the constant coefficients of the pressure characteristics of the centrifugal pump, determined by the passport characteristics of the turbine units or during regulated tests during operation, respectively, m, s / m ² , s ² / m ⁵ ;

Q - centrifugal pump feed, m ³ / s.

for the passport rotational speed of the pressure and calculate the pressure signal of the centrifugal pump 1 at the maximum efficiency H _ηmax , but the formula

, $$H_{\eta \max }=a_0+a_{\mathrm{one}}{Q}_{\eta \max }+a_2{Q}_{\eta \max }^2$$

,

supplied to the block 10 line determination of the maximum efficiency of the centrifugal pump 1.

In the block 11 approximation of the characteristics of the pipeline are entered values of the coefficients of the characteristics of the pipeline b ₀ , b ₁ , b ₂ , where the equation is formed characteristics of the pipeline

, $$H=b_0+b_{\mathrm{one}}Q+b_2{Q}^2$$

,

where b ₀ , b ₁ , b ₂ - constant coefficients of the characteristics of the pipeline, respectively m, s / m ² , s ² / m ⁵ .

The signals from block 10 determining the line of maximum efficiency of the centrifugal pump 1 and from block 11 of approximating the characteristics of the pipeline are fed to the input of solver 12, where the system of equations for the characteristics of the pipeline and the line of maximum efficiency are solved. The resulting productivity decisions, Q ₀ and pressure H _{0, of} the operation mode of the centrifugal pump 1 are formed into signals supplied to the input of the rotor speed calculation unit 13, in which the rotor speed is determined corresponding to the maximum efficiency of the centrifugal pump 1

, $$n=n_{P\mathrm{but}\mathrm{from}P}\frac{-Q_0{a}_{\mathrm{one}}+\sqrt{Q_0^2(a_{\mathrm{one}}^2-\mathrm{four}{a}_0{a}_2)+\mathrm{four}{a}_0{H}_0}}{2a_0}$$

,

where n _passport is the nominal (passport) rotational speed of the rotor of the centrifugal pump, s ^-1 ;

Q ₀ and H ₀ - respectively, the working flow, m ³ / s and pressure, m

and which generates a signal of the rotational speed of the rotor of the centrifugal pump 1, supplied to the frequency comparing element 5. Also in the block 13 for calculating the rotor speed are entered values of the coefficients of the pressure characteristic a ₀ , a ₁ , a ₂ .

The automatic correction unit operates as follows. A pressure sensor 14 at the inlet of the centrifugal pump 1 and the sensor 15, the outlet pressure of the centrifugal pump 1 is fed signals respectively, P _Rin and P _O to the block 16 determines the pressure of the centrifugal pump 1, which supplies the signal H _n to the block 18, determining the operating efficiency of the centrifugal pump 1 The fluid flow measuring device 17 supplies a signal Q to a unit 18 for determining the operational efficiency of a centrifugal pump 1. Also, a signal for the power consumption of the electric motor from a wattmeter 6 is supplied to this unit 18. The signals generated in the calculator 8 of the centrifugal efficiency Asosa 1 as η _max and in block 18 determine the operating efficiency of the centrifugal pump 1 in the form η fed to the comparing element 19 values of the centrifugal pump efficiency 1 wherein formed in Δη signal which is supplied to inverter 20 signal forming corrective value of rotor Δn speed a centrifugal pump 1 supplied to the input of the frequency comparison element 5.

The frequency comparing element 5 generates a signal of the operating rotational speed of the rotor of the centrifugal pump 1, which is supplied to the automatic control system 4 of the frequency converter, where a signal is generated for the frequency converter 3. This signal is supplied to an electric motor 2, which is mechanically connected to a centrifugal pump 1.

Thus, it is possible to operate the turbine unit with the highest possible efficiency, regardless of the characteristics of the pipeline.

Claims (1)

A control system for a turbine unit, including a centrifugal pump, an electric motor, a centrifugal pump rotor rotational speed change unit, an automatic control system providing a predetermined rotational speed of a centrifugal pump rotor, characterized in that a frequency comparison element and a task generating unit are installed at the input of the automatic control system, unit for calculating the rotor speed, solver, unit for determining the maximum efficiency line of a centrifugal pump, maxi calculator the total efficiency of the centrifugal pump, the approximation block of the efficiency characteristic of the centrifugal pump, the approximation block of the pressure characteristic of the centrifugal pump and the approximation block of the pressure characteristic of the pipeline, and the automatic correction unit, consisting of a pressure sensor at the inlet to the centrifugal pump, a pressure sensor at the outlet of the centrifugal pump, a determination unit differential pressure of a centrifugal pump, a device for measuring fluid flow through a pump, a unit for determining the operational efficiency of a centrifugal pump a sucker, an element of comparison of the efficiency of a centrifugal pump, a signal converter, a wattmeter, while one output of the approximation block of a characteristic of efficiency of a centrifugal pump is connected to a calculator of the maximum efficiency of a centrifugal pump, which is connected to the inputs of the approximation block of a pressure characteristic of a centrifugal pump, a block for determining the line of maximum efficiency of a centrifugal pump and with a comparison element of the centrifugal pump efficiency, the output of the approximation block of the pressure characteristic of the centrifugal pump is connected to the input of the op determining the line of maximum efficiency of a centrifugal pump, which is connected to the input of the solver, the input of the solver is connected to the approximation unit of the pressure characteristic of the pipeline, and the output to the rotor speed calculation unit, the input of which is connected to the frequency comparison element, the input of the differential pressure determination unit of the centrifugal pump is connected to the outputs pressure sensors at the inlet to the pump and the outlet of the pump, the output is connected to the input of the unit for determining the working efficiency of a centrifugal pump, the input of which is connected to the output of the device for measuring the flow rate of the liquid through the pump and with the wattmeter, and the output is connected to the comparison element of the efficiency of the centrifugal pump, the input of which is connected to the output of the calculator of the maximum efficiency of the centrifugal pump, and the output is connected to the signal converter, the output of which is connected to the frequency comparison element, which is connected to the input automatic regulation system, the input of which is connected to the rotor speed change unit of the centrifugal pump rotor, connected to the electric motor, and the electric motor to the centrifugal pump th.