RU2589718C1 - System for automatic control of rotor - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to electrical engineering and can be used in injectors, compressors, turboexpanders of gas transfer units with heavy rotors of horizontal design weighing, for example, at least 900 kg. In system for automatic control of rotor electromagnetic suspension, each channel comprises rotor position sensor (1), shaft position setting unit (2), comparison element (3), vibration signal processing unit (4), proportional (5), integrated (6), differential (7), proportional-differential (8) regulators, comparison element (9), proportional to current regulator (10), current sensor (11), power converter (12) and two electromagnets (13 and 14). Output value of rotor position sensor (1) is subtracted from value of setting unit (2) of rotor position in comparison element (3). Difference is supplied to input of signal processing unit (4) vibration output signal of which is supplied simultaneously to inputs of proportional (5), reset control (6) and differential (7) controls. Total output values of controls (5, 6, 7) is supplied to input of proportional-differential controller (8), from output value of which in comparison element (9) is subtracted current value measured by current sensor (11) in windings of electromagnets (13, 14). Difference is supplied to input of proportional current regulator (10), output of which is connected to input of power converter (12), to output of which are connected to windings of electromagnets (13 and 14).

EFFECT: technical result is providing low vibration level, high speed of operation.

2 cl, 5 dwg

Description

The invention relates to mechanical engineering and can be used in rotor mechanisms on electromagnetic supports. Scope are superchargers, compressors, turbo expanders of gas pumping units.

Electromagnetic suspension control systems have their own specifics for heavy horizontal rotors weighing, for example, at least 900 kg, used, for example, in centrifugal blowers of gas pumping units. With increasing mass of the rotor, the mass and electric power of magnetic bearings proportionally increase, and their speed decreases, which reduces the speed of the control system as a whole.

The well-known "Control system of electromagnetic rotor suspension" according to the patent for invention RU 2460909 C1, IPC F16C 32/04, Н02K 7/09, Н02Р 6/16, G05B 6/00, G05B 11/36 (application 2011103758/07 from 02.02.2011 , date of commencement of the term of validity of the patent 02.02.2011, published 10.09.2012, patent holder - State Educational Institution of Higher Professional Education "Samara State Technical University", authors Starikov Alexander Vladimirovich, Starikov Stanislav Aleksandrovich).

In the rotor electromagnetic suspension control system, each control system channel contains a rotor position sensor, an integral regulator, a proportional regulator, a differential regulator, a proportional-differential regulator, a power converter, two electromagnets, a proportional link, a module selection unit, a reference unit, an adder and a division unit.

The disadvantages of the control system of the electromagnetic suspension of the rotor are as follows. Firstly, the required performance is not ensured, i.e. rapid change in the magnetic field of electromagnets, which is important for controlling highly inductive windings of electromagnets in the magnetic suspension system of heavy horizontal rotors with a mass of, for example, at least 900 kg, used, for example, in centrifugal blowers of gas pumping units. Secondly, all elements of each channel of the rotor electromagnetic suspension control system operate on analog microcircuits, which do not provide flexible parameter changes during setup, and are also difficult to maintain. Thirdly, the complex technical implementation of the circuit of the control system of the electromagnetic suspension of the rotor. Fourth, the lack of the ability to smoothly change the coefficients of the regulators depending on the frequency of vibration of the rotor to stabilize the position of the rotor at critical speeds.

The well-known "Method of controlling electromagnetic bearings and a device for its implementation" according to the patent for invention RU 2290746 C1, IPC Н02Р 6/16, G05B 11/26 (application 2005118005/09 from 06/10/2005, the start date of the patent validity date 10.06.2005, published December 27, 2006, patent holders - Elena Kravtsova, Dmitry Kochetov, Dmitry Viktorovich Kravtsov, authors Elena Kravtsova, Dmitry Kochetov, Dmitry Viktorovich Kravtsov.

The method for controlling electromagnetic bearings and the device for its implementation is characterized by the following. In this method of controlling electromagnetic bearings, the formation of currents necessary to stabilize the rotor in space is carried out in two frequency regions, low-frequency and high-frequency. The method is implemented in a device containing a rotor position sensor, an integral controller, a multiplying unit, a boost controller, a power converter, and at the input of an integral controller consisting of proportional differential and integral regulation blocks and a first adder block, an analog-to-digital converter unit with an upstream a low-pass filter unit, and a notch filter or a group of notch filters, a block of the second adder, bl ok inverting and pulse-width modulation signal generation blocks.

The disadvantages of the method of controlling electromagnetic bearings and devices for its implementation are as follows.

The inability to smoothly change the coefficients of the regulators depending on the frequency of vibration of the rotor to stabilize the position of the rotor at critical speeds.

Known "Magnetic bearing systems and methods for controlling them" by US application No. 20140145534 A1. "Magnetic bearing system and methods of controlling the same", pub. No: US 2014/0145534 A1, pub. Data: May 29, 2014, Applicant: General Electric Company, Inventor: Leonardo Cesar Kammer, Appl. No: 13 / 689,249, Filed: Nov. 2012.2012.

The magnetic bearing system consists of two electromagnets located on the same axis on opposite sides of the rotor. The system includes a controller that calculates the control action necessary to maintain the rotor in a given position. The system also includes a non-linearity compensation device that calculates the magnitude of the current in the first electromagnet and the second electromagnet to maintain the required stiffness during starting, nominal operating modes and during shutdown.

The disadvantages of the magnetic bearing system and their control methods are as follows. All elements of the magnetic bearing control system are digital. However, the system does not have the ability to smoothly change the coefficients of the regulators (including damping) depending on the frequency of vibration of the rotor to stabilize the position of the rotor at critical speeds.

The closest adopted for the prototype is the "Control system of the electromagnetic suspension of the rotor" according to the patent for the invention RU 2460909 C1.

The known system cannot be applied due to disadvantages, which include the following.

Firstly, performance is not ensured, i.e. rapid change in the magnetic field of electromagnets, which is important for controlling highly inductive windings of electromagnets in the magnetic suspension system of heavy horizontal rotors with a mass of, for example, at least 900 kg, used, for example, in centrifugal blowers of gas pumping units. Secondly, all elements of each channel of the rotor electromagnetic suspension control system operate on analog microcircuits, which do not provide flexible parameter changes during setup, and are also difficult to maintain. Thirdly, a complex technical implementation of the control system of the electromagnetic rotor suspension. Fourth, the lack of the ability to smoothly change the coefficients of the regulators depending on the frequency of vibration of the rotor to stabilize the position of the rotor at critical speeds.

The objectives of the present invention are to provide a system for automatic control of the electromagnetic suspension of the rotor, which provides the required criteria for the quality of regulation, consisting in a low level of vibration, in high speed of the system, as well as simplification of the circuit, configuration and maintenance of the control system.

The proposed automatic control system of the rotor electromagnetic suspension allows to achieve a technical result when using the automatic control of the large mass rotor electromagnetic suspension by creating such an automatic control circuit that will simplify setup and maintenance by digitally implementing the automatic control of the rotor electromagnetic suspension, using digital adaptive design circuits regulators, in a new set of relationships between e ementami devices in the new scheme of connection of the windings of the electromagnets to the power converter.

To solve this problem and achieve a technical result, a system is proposed for automatic control of the rotor electromagnetic suspension, each channel of which contains a rotor position sensor, an integral controller, a proportional controller, a differential controller, a proportional differential controller, a power converter, two electromagnets, a task unit, characterized in that each channel is additionally equipped with a vibration signal processing unit, a proportional current regulator and a current sensor, with than the rotor position sensor is connected to the input of the vibration signal processing unit, the output of which is connected to the inverse input of the proportional controller, integral controller, differential controller, the outputs of which are connected to the input of the proportional-differential controller, the output of which is connected to the proportional controller with feedback according to the current value in the windings of electromagnets, the output of this controller is connected to the input of the power converter, to the output of which the windings of the electromagnets are connected, When this setting is performed adaptive controllers (proportional control, differential control) depending on the signal obtained at the output of the vibration signal processing unit.

The connection of the electromagnet windings to the three-phase diode-transistor bridge is made in such a way that the common point of the electromagnet windings is connected through the transistor switch to the "minus" of the power supply.

Thus, the proposed automatic control system for the electromagnetic suspension of the rotor allows to reduce the vibration level, improve the system performance for heavy rotors weighing, for example, at least 900 kg, by solving the layout scheme for connecting the electromagnet windings, in which the electromagnet windings are connected to a three-phase diode-transistor bridge so that the common point of the electromagnet windings is connected through a transistor switch to the “minus" of the power supply, as a result of which one can not use one key and simplify the circuit. To simplify the configuration of the technical system by using a digital controller instead of analog elements, in which the mathematical blocks are implemented in software with the ability to quickly configure, reduce the vibration level by introducing a vibration signal processing unit, which analyzes the frequency spectrum of the rotor vibration and, depending on the results, automatically adjusts the parameters regulator settings.

To clarify the described object in the drawings (figures), a list of drawings and the names of the images on them are given:

FIG. 1 is a functional diagram of each channel of the automatic control system of the rotor electromagnetic suspension;

FIG. 2 - connection diagram of electromagnet windings to a power converter;

FIG. 3 is a structural diagram of one channel of a system for automatically controlling an electromagnetic suspension of a rotor;

FIG. 4 is a graph of the transition process when the rotor emerges from the safety bearings;

FIG. 5 is a graph of a transient perturbation process at a central rotor position.

Each channel (Fig. 1) contains a rotor position sensor 1, a shaft 2 position setting unit, a comparison element 3, a vibration signal processing unit 4, a proportional controller 5, an integral controller 6, a differential controller 7, a proportional differential controller 8, a comparison element 9 , proportional current controller 10, current sensor 11, power converter 12, two electromagnets 13 and 14. The output value of the rotor position sensor 1 is subtracted from the value of the reference unit 2 of the rotor position in the comparison element 3. The difference is applied to input b An eye for processing the vibration signal 4, the output signal of which is supplied simultaneously to the inputs of the proportional controller 5, the integral controller 6 and the differential controller 7. The sum of the output values of the regulators 5, 6, 7 is fed to the input of the proportional-differential controller 8, from the output value of which in the comparison element 9, the value of the current strength measured using the current sensor 11 in the windings of the electromagnets 13, 14 is subtracted. The difference is applied to the input of the proportional current controller 10, the output of which is connected to the power input transformer 12. The output of the power transducer 12 is connected to the windings of the electromagnets 13 and 14.

The above blocks 2 ... 10 of the system for automatic control of the electromagnetic suspension of the rotor are made programmatically in a digital controller.

As the rotor position sensor 1, for example, an inductive eddy current sensor with a measurement unit can be used.

The power converter 12 is, for example, a transistor pulse-width converter, consisting of a pulse-width modulator and a transistor bridge assembled in a three-phase half-bridge circuit.

As the current sensor 11, for example, a sensor based on the Hall effect with high speed can be used.

The electromagnets 13 and 14 are located on the stator of the rotor machine, for example, on the same axis on opposite sides of the rotor and can be performed, for example, as explicit pole or with distributed windings.

The windings of the electromagnets are connected to a diode-transistor bridge, for example, as shown in FIG. 2. Thus, the common point of the electromagnet windings is connected through a transistor switch to the "minus" of the power supply, which eliminates the need for a single transistor switch and simplifies the circuit.

The proposed system for automatic control of the electromagnetic suspension of the rotor operates as follows. Initially, the rotor is located on safety bearings. When the control system is turned on in each channel, the rotor 1 position sensor measures the deviation of the rotor from its central position. The difference between the supported central value of the rotor position in the reference unit 2 and the measured value is fed to the input of the vibration signal processing unit 4, the output of which is fed to the input of the proportional 5, integral 6 and differential 7 controllers. In accordance with the transfer functions implemented in the controllers 5 ... 7, the sum of the output values of these controllers is fed to the input of the proportional-differential controller 8. In accordance with the transfer function implemented by the controller 8, the output value is supplied to the input of the comparison element 9, where from this value the value of the current strength measured in the electromagnet windings measured using the current sensor 11 is subtracted. The difference is fed to the input of the proportional current controller 10. The purpose of this controller is to maintain a current value proportional to the output value of the controller 8, as well as compensation for the time constant T _{E of the} electromagnet windings. The output value of the proportional current controller 10 is the value for the pulse-width power converter 12, in proportion to which the power converter regulates the voltage across the windings of the electromagnets 13 and 14.

As a result, such currents are formed in the windings of the electromagnets 13 and 14 that create the resulting force that lifts the rotor from the safety bearings and keeps it in a central position (by sensor 1) in operating modes.

The automatic control system of the electromagnetic rotor suspension is fully digital. The mathematical implementation of the transfer functions of the vibration signal processing unit 4, controllers 5 ... 8, 10, as well as reference and comparison units 2, 3, 9, is performed in software on the basis of an industrial digital controller with high speed. The signals from the rotor position sensor 1 and current sensor 11 are digitized using analog-to-digital converters. The power Converter 12 operates with a digital input signal of a pulse-width modulator.

- передаточная функция интегрального регулятора 6; Т_Д1р - передаточная функция дифференциального регулятора 7; k_П2 - коэффициент передачи пропорционально-дифференциального регулятора 8; k_П2(1+Т_Д2p) - передаточная функция пропорционально-дифференциального регулятора 8; k_ШИМ - коэффициент передачи силового широтно-импульсного преобразователя 12, является также коэффициентом передачи пропорционального регулятора тока 10; k_ДТ - коэффициент передачи датчика тока 11; x_З, F_ВХ и x - сигналы задания (поддерживаемое центральное положение ротора от блока задания 2), возмущающей силы и текущего положения ротора, соответственно. Остальные динамические звенья в совокупности представляют собой линеаризованную математическую модель процесса перемещения ротора в поле электромагнитного подшипника под действием управляющего сигнала на входе силового преобразователя 12. Коэффициенты передачи k_ШИМ и U характеризуют параметры силового преобразователя 12: коэффициент передачи широтно-импульсного преобразователя и напряжение питания транзисторного моста. Динамическое звено с передаточной функцией $$\frac{1}{U\left(T_{Э}p+1\right)}$$

(T_Э - постоянная времени электрической цепи обмоток электромагнитов) связывает приращение соотношения токов в электромагнитах 13 и 14 с приращением напряжения на обмотках, причем заведомо принимается такой закон коммутации транзисторов моста, что увеличение напряжение на одной из обмоток приводит к такому же уменьшению напряжения на другой. Коэффициент передачи k_ЭМ связывает силу, действующую со стороны электромагнитов на ротор при его центральном положении, с соотношением токов в электромагнитах. Коэффициент передачи k_F характеризует изменение силы, действующей на ротор, при его отклонении от центрального положения. Динамическое звено $$\frac{1}{m{p}^2}$$

в соответствии со вторым законом Ньютона определяет перемещение ротора под действием результирующей силы. Коэффициент передачи k_Е характеризует приращение наводимой в обмотках электромагнитов эдс со скоростью перемещения ротора в магнитном поле.The processes occurring during the operation of the proposed system of automatic control of the electromagnetic suspension of the rotor can be represented by a structural diagram (Fig. 3). Here k _DP is the transmission coefficient of the position sensor 1; k _P1 - gear ratio of the proportional controller 5; $$\frac{\mathrm{one}}{T_{\mathrm{AND}}p}$$

- transfer function of the integral controller 6; T _D1 p - the transfer function of the differential controller 7; k _P2 - transmission coefficient of the proportional differential controller 8; k _P2 (1 + T _D2 p) - transfer function of the proportional differential controller 8; k _PWM - transmission coefficient of the power pulse-width converter 12, is also the transmission coefficient of the proportional current controller 10; k _DT is the transfer coefficient of the current sensor 11; x _З , F _ВХ and x are the reference signals (the supported central position of the rotor from the reference block 2), the disturbing force and the current position of the rotor, respectively. The remaining dynamic links in the aggregate are a linearized mathematical model of the process of moving the rotor in the field of the electromagnetic bearing under the action of a control signal at the input of the power converter 12. The transmission coefficients k _PWM and U characterize the parameters of the power converter 12: the transmission coefficient of the pulse-width converter and the supply voltage of the transistor bridge . Dynamic link with transfer function $$\frac{\mathrm{one}}{U\left(T_{E}p+\mathrm{one}\right)}$$

(T _E is the time constant of the electric circuit of the electromagnet windings) relates the increment in the ratio of currents in electromagnets 13 and 14 to the increment of voltage on the windings, and the law of switching transistors of the bridge is obviously adopted such that an increase in voltage on one of the windings leads to the same decrease in voltage to the other . The transmission coefficient k _EM connects the force acting from the side of the electromagnets to the rotor with its central position, with the ratio of currents in the electromagnets. The gear coefficient k _F characterizes the change in the force acting on the rotor when it deviates from its central position. Dynamic link $$\frac{\mathrm{one}}{\mathrm{<figure-callout\; id="2"\; label="m\; p"\; filenames="00000007.png,00000010.png"\; state="\{\{state\}\}">m\; </figure-callout>}{p}^{}{}^2}$$

in accordance with the second law of Newton determines the movement of the rotor under the action of the resulting force. The transmission coefficient k _E characterizes the increment induced in the windings of the electromagnet electromotive force with the speed of movement of the rotor in a magnetic field.

- для коэффициента передачи k_П1 пропорционального регулятора 5 и в соответствии с передаточной функцией фильтра низких частот второго порядка

- для постоянной времени дифференцирования T_Д1 дифференциального регулятора 7. k_ф1, k_ф2 - весовые коэффициенты, определяющие степень влияния фильтров на выходной сигнал блока обработки вибрации. Адаптивные по частоте входного сигнала регуляторы 5, 7 позволяют обеспечить устойчивость системы автоматического управления во всем рабочем диапазоне частот вращения ротора.In the vibration signal processing unit 4, the gain of the control system automatically changes depending on the frequency of the rotor position deviation signal in accordance with the transfer characteristic of the second-order low-pass filter

- for the transmission coefficient k _{П1 of the} proportional controller 5 and in accordance with the transfer function of the second-order low-pass filter

- for the differentiation time constant T _{D1 of the} differential controller 7. k _f1 , k _f2 - weighting factors that determine the degree of influence of the filters on the output signal of the vibration processing unit. Regulators 5, 7, adaptive in frequency of the input signal, make it possible to ensure the stability of the automatic control system in the entire working range of rotor speed.

The value of the time constant of the proportional differential controller 8

W _PD (p) = k _P2 (1 + T _D2 )

is determined, for example, from the relation T _D2 = 3T _E , and the transfer coefficient k _{P2 of} this regulator can vary within wide limits. The values of the transfer coefficient k _{P1 of the} proportional controller 5 and the time constant T _{AND of the} integral controller 6 in accordance with the stability condition can also be selected from a wide range of values.

Computer simulation shows the achievable performance of the proposed rotor electromagnetic suspension control system. In FIG. Figures 4 and 5 show graphs of transients during the ascent of the rotor from the safety bearings and under the action of a disturbing force at the initial central position of the rotor. In the calculations, the following parameters of the electromagnetic suspension of the rotor, for example, a turbine, were taken: k _E = 1461 Vs / m; k _EM = 1306 N; k _F = 1315900 N / m; m = 900 kg; T _e = 0.038233 s; k _PWM = 1.9608 · 10 ^-3 ; U = 247 V; k _P1 = 0.01; T _D1 = 0.000115 s; k _P2 = 1; T _D2 = 0.112 s; T _And = 0.5 s; k _DP = 4096000 discrete / m; k _DT = 2048 discrete / A; k _f1 = 0.5; k _f2 = 0.5; a ₁ = 3948; b ₁ = 0.6547; c ₁ = 0.0001081; d ₁ = 3948; e ₁ = 88.86; f ₁ = 1.0; a ₂ = 194100; b ₂ = 31.13; c ₂ = 0.004862; d ₂ = 194100; e ₂ = 622; f ₂ = 1.0. Analysis of the graphs shows that in the control system of the electromagnetic suspension of the rotor there is a high speed in all operating modes. The rotor emerges from the safety bearings having a clearance in the working condition δ = 0.25 mm, for a time t _PP = 0.5 s. The dynamic failure of the rotor during an impact force application of 1 N is Δx _max = 0.0018 μm. It should also be noted that the rotor returns to its center position after applying a load.

The correctness of the claimed technical solution is confirmed by putting into commercial operation an automatic control system for NTs-16 type superchargers with electromagnetic rotor bearings at KS-22 Pomarskaya of the Volzhsky MPI of the Moscow branch of Gazprom transgaz Nizhny Novgorod LLC.

Thus, the proposed system of automatic control of the electromagnetic suspension of the rotor provides a low level of vibration, high system performance, as well as simplifying the circuit, configuration and maintenance of the control system.

Claims (2)

1. The automatic control system of the electromagnetic suspension of the rotor, each channel of which contains a rotor position sensor, an integral controller, a proportional controller, a differential controller, a proportional differential controller, a power converter, two electromagnets, a reference unit, characterized in that each channel is additionally equipped with a processing unit a vibration signal, a proportional current controller and a current sensor, the rotor position sensor being connected to the input of the vibration signal processing unit, the output of which is connected to the inverse input of the proportional controller, integral controller, differential controller, the outputs of which are connected to the input of the proportional differential controller, the output of which is connected to the proportional controller with feedback on the value of the current in the electromagnet windings, the output of this controller is connected to the input of the power converter , to the output of which the windings of electromagnets are connected, while adaptive adjustment of the regulators (proportional control torus, differential controller) depending on the signal obtained at the output of the vibration signal processing unit. 2. The automatic control system of the rotor electromagnetic suspension according to claim 1, characterized in that the connection of the electromagnet windings to the three-phase diode-transistor bridge is made in such a way that the common point of the electromagnet windings is connected through the transistor switch to the "minus" of the power supply.

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