SU866683A1 - Device for control of magnetic flux of induction machine - Google Patents

Description

(54) DEVICE FOR MANAGING THE MAGNETIC FLOW OF THE ASYNCHRONOUS MACHINE

The invention relates to electrical engineering, in particular, to a frequency-controlled electric drive and can be used to control the magnetic flux in asynchronous machines. A device is known for stabilizing the magnetic flux of an asynchronous machine by the emf of a measuring saturation covering the pole division of the stator Jl. However, the known device, having a low accuracy in static modes, has a very large error in transient modes and is therefore completely unacceptable in devices where it is necessary to control the transient modes. It is also known a device for controlling the magnetic flux, in which the initial flow information is generated using Hall sensors located in the air gap of the machine, the magnetic flux current control of the machine, all measured variables are converted into a coordinate system related to the flux vector, and then flow control. The Jlffin conversion uses a device for the non-linear measurement of the direction of the flow vector — a trigonometric analyzer, which is a two-phase generator following the two-phase system, formed by the flow vector and the special C23 scaling units. A disadvantage: the devices are its complexity, since in addition to devices for direct measurement and flow control, more sophisticated devices are required for the double conversion of coordinates. In addition to TOio, the control of the magnetic flux in the device described is conducted through the first harmonic of the magnetic lol, and when powered by converters, the highest harmonic frequency is up to 40-50% of the total flux; All this reduces the accuracy of the device. The closest to the invention is the device for controlling the magnetic flux in an asynchronous motor with three measuring coils, located in the stator slots, the outputs of which are connected to the inputs of three integrators, the outputs of which are connected to rectifiers, and the drivers of the rectifiers are connected to the input of the adder, the output of which is connected to another C5gmmator, with which the flow reference unit is connected, and the output of this adder is connected to the input of the regulator, the output of which is connected to the first input of the unit scabbard. The second input of the multiplication unit is connected to the frequency adjuster. The output of the multiplier unit is connected to the first input of the split unit, the second input of which is connected to the output of the DC source supplying the frequency converter, and the output of the division unit is connected to the first input of the frequency converter. Insegrators produce signals that are proportional to the magnetic flux. These signals are rectified, summed, compared to a reference, and an error is sent to the controller. The signal received from the controller is multiplied by using a multiplier by the set voltage frequency of the stator and transmitted to the control unit of the thyristor converter, In a known device, the reference to the voltage on the stator of the engine provides sufficiently precise control of the magnetic flux in the established mode . However, in transients, such a device does not provide accurate direction, i.e. the voltage is determined not by the frequency of rotation of the machine flux vector, but by the frequency that is set and which in transient conditions may differ significantly from the actual frequency of rotation of the flux vector of the asynchronous machine. In addition, the determination of the resultant flux is performed by rectifying the signals, i.e. without taking into account the phase relations between the vectors, the ot module may differ significantly, i.e. flux vector values. The purpose of the invention is to improve the accuracy of work. The goal is achieved by the fact that, in a device containing integrators connected to measuring coils, dividing and multiplying units, the first and second adders, a flow controller connected to the output of the second equalizer, the input of which is connected to the output of the calculator of the flow vector module, whose inputs connected to the outputs of the integrator, the frequency converter, the output of which is connected to the asynchronous matine, the calculator of the square of the derivative of the flow module, the determinant of the frequency of rotation of the flow vector, and the inputs The squared modulus of the derivative of the stream is connected cooler with the measuring coils, and the output is connected to the first input of the division unit, the inputs for determining the rotation frequency of the flow vector are connected to the outputs of the flow integrator and measuring coils, and its output is connected to the first input of the multiplication unit, the second input of which is connected to the output flow controller, and the input is connected respectively with the second input of the division unit and the first input of the first adder, the second input of which is connected to the output of the Division unit, and the output of the adder By connecting to the control voltage input of the frequency converter. The drawing shows a block diagram of a device for controlling the flux of an asynchronous machine. The device for controlling the magnetic flux of the asynchronous machine 1, equipped with measuring coils 2 and 3, contains integrators 4 and 5 of the flow, calculator 6 modulus of the flux vector, calculator 7 of the square of the modulus of the derivative of flux, determinant 8 of the rotation frequency of the flux vector, first and second cy atopov 9 and 10, the flow controller P, the conciliation unit 12, the division unit 13 and the frequency converter 14. The measuring coils 2 and 3 are connected to the inputs of the integrators 4 and 5 of the flow and the determinant 8 of the rotation frequency of the flow vector, to the inputs of which also connect the outputs of the integrators 4 and 5 of the flow. The moves of integrators 4 and 5 of the flow are connected to the input of the calculator 6 module of the flow vector, the output of which is connected to the input of the second adder 10, to another input

Which feed flow is applied. The output of the second adder 10 is fed to the input of the flow controller 1, you, whose course is fed to the first input of the multiplication unit 12, the other input of which is connected to the output of the determinant 8 of the rotation frequency of the flow vector. The measuring coils 2 and 3 are connected to the inputs of the calculator 7 of the square of the module of the derivative of the flow, the output of which is connected to the first input of the block 13 division. The second input of division unit 13 is connected to the output of multiplication unit 12. The output of multiplication unit 12 is connected to the input of adder 9, with the other inputs of which is connected the output of the block {3 divisions, and the output of adder 9 is connected to the first input of frequency converter 14, to the second input of which a frequency reference signal is applied.

The device works the following way;

The magnetic flux of the asynchronous machine 1 induces an emf in the measuring coils 2 and 3, which is installed. on the stator of the machine. The emf integrator in these coils is determined by the flow integrators 4 and 5 instantaneous values of the fluxes by the axes. The calculator 6 modulus of the flux vector by the signals taken from the integrators 4 and 5 of the flux finds the magnitude of the modulus of the flux and transmits it to the adder 10, in which the signal is compared with the modulo flux reference. The error is transmitted to the controller 11. The signal taken from the controller 11 is multiplied by the unit 12 by multiplying the signal npdpional to the instantaneous value of the rotation frequency of the flux vector, which is generated by the determinant B of the rotation frequency of the flux vector. Signals from the measuring coils 2 and 3 and from the integrators 4 and 5 of the flow, which allow to determine the frequency of rotation of the flow vector, are sent to the input of the determining frequency of rotation of the flow vector. As a result, at the output of multiplication unit 12, a signal is formed that is proportional to the set voltage, which is transmitted to adder 9. A signal from division unit 13 is supplied to another input of adder 9. At the input of the dividing unit 13, a signal is given from the calculator 7 of the square of the module of the derivative of magnetically. th stream, to the input of which signals from measuring coils are supplied

2 and 3. The input of the division unit 13 is given a signal produced by the multiplication unit 12. In the adder 9, a signal is added that maintains the specified flow in transients. The signal generated by the accumulator 9 is transmitted to the channel of the control system of the frequency converters 14, which controls

the value of the output voltage of the converter ..

Thus, the specified voltage "B" is normalized to the instantaneous frequency of rotation of the vector of the flow torus, and in addition, the signal generated by the block creates an additional component of the voltage that keeps the flow constant in transient conditions caused by disturbances when the resistance moment changes or change assignment. Due to the introduction of a signal proportional to the instantaneous value of the frequency of rotation of the vector

5, as well as introducing a component into the voltage reference, which compensates the transient component, the proposed device allows to increase the accuracy of operation both in the steady state and in the transient operating modes of the asynchronous machine.

Claims (1)

Invention Formula 5 Device for controlling the flow of an asynchronous machine with measuring coils; it contains integrators connected to the measuring coils; a division unit 0 and multiply, the first and second adders, the flow controller connected to the output of the second adder, the input of which is connected to the output of the calculator MODULE of the flow vector, input  which is connected to the outputs of the flow integrator, the frequency converter, the output of which is connected to an asynchronous machine, differs from the fact that, in order to improve accuracy, you have been entered into it the numerator of the square of the derivative of the flow modifier, the frequency determinant of the return of the flow vector, and sx.o} j the calculator of the square of the derivative of the flow modulus are connected to the measuring input and the output to the first input of the flow block are connected