RU159869U1 - SYSTEM OF ENERGY EFFECTIVE TWO-ZONE REGULATION OF SPEED OF THE ASYNCHRONOUS MOTOR WITH DIRECT CONTROL OF THE MOMENT WITHOUT THE WINDING TEMPERATURE SENSOR - Google Patents

Abstract

A dual-zone induction motor speed control system using direct torque control (Direct Torque Control - DTC), containing a static voltage and frequency converter with an autonomous voltage inverter, supplying an asynchronous motor, a motor speed sensor, current sensors of phase A, B, C of the motor, a sensor voltage of the DC link of the static converter, direct torque control unit (DTC), to the corresponding inputs of which the signals of the motor current sensor, voltage sensor current, and the first output is connected to the control input of the static converter, and in the DTC block there is an adaptive motor model, including a thermal model, based on which the temperature of the stator windings of the motor is calculated; also containing an intensity adjuster connected to the first input of the subtraction unit, to the second input of which a signal is supplied from the engine speed sensor, and the output is connected to the input of the speed controller, the output of which is connected to the first input of the torque reference calculation unit, the second input of which is connected to the output the engine speed sensor, and the output is connected to the input of the torque reference of the DTC unit, characterized in that the following are introduced into the system: the set power calculation unit, the input of which is supplied with a temperature signal motor windings DTC from the second output unit, and an output connected to a third input of the calculation unit in the torque reference, a band-job stator flux linkage as a function of the electromagnetic motor torque, which is applied to the input of the time reference signal with a torque reference calculating unit, and an output connected to the reference input

Description

Energy-efficient dual-zone induction motor speed control with direct torque control without winding temperature sensor

The utility model relates to an asynchronous electric drive and can be used in industry and transport in electric drive systems with direct control of the torque of asynchronous motors (HELL).

The known system of direct torque control (Direct Torque Control, - DTC) (Kozyaruk AE, Rudakov VV Systems of direct torque control in variable frequency AC electric drives / edited by A. Naroditsky - St. Petersburg: St. Petersburg Electrotechnical company, 2005 - prototype). The direct torque control system implements direct highly dynamic relay control of stator flux linkage and motor torque by deviation. The distinctive features of DTC include the presence in the system (Fig. 1):

- hysteresis relay regulators of stator flux linkage (PPP) and torque (PPm) of an induction motor;

- an electronic adaptive motor model (AMD) for calculating the current controlled coordinates of an induction motor (stator flux linkage, electromagnetic torque, temperature, etc.) based on the value of phase currents, voltage in the DC link and switching function of the autonomous voltage inverter (AIN);

- a phase sector calculation unit (BVFS), in which at the current moment of time is the stator flux linkage vector of the motor;

- tabular (matrix) calculator of the optimal motor voltage vector, performed in the form of a block of a logical automaton (UAV) and determining the switching function of the AIN valves.

The DTC system has high speed, it is resistant to disturbances and inaccuracy of information about the state variables of the control object, however, for DTC systems, energy-saving methods for controlling engines are not well developed, which does not allow to fully realize all the advantages of DTC.

The purpose of the utility model is the implementation of energy-efficient dual-zone regulation of an induction motor in a direct torque control system with the most full use of heating and engine power, not equipped with a temperature sensor for the windings.

The technical result is achieved by the fact that in a dual-zone speed control system of an induction motor using direct torque control (Direct Torque Control - DTC), containing a static voltage and frequency converter with an autonomous voltage inverter, supplying an asynchronous motor, a motor speed sensor, phase current sensors A , B, C of the motor, voltage sensor of the DC link of the static converter, direct torque control unit (DTC), to the corresponding inputs of which the sensor signals in the motor current, a DC-link voltage sensor, and the first output is connected to the control input of the static converter, moreover, in the DTC block there is an adaptive motor model, including a thermal model, based on which the temperature of the motor stator windings is calculated; also containing an intensity adjuster connected to the first input of the subtraction unit, to the second input of which a signal is supplied from the engine speed sensor, and the output is connected to the input of the speed controller, the output of which is connected to the first input of the torque reference calculation unit, the second input of which is connected to the output engine speed sensor, and the output is connected to the input of the DTC unit torque reference, the following are entered:

a set power calculation unit, to the input of which a temperature signal of the motor windings is supplied from the second output of the DTC unit, and the output is connected to the third input of the torque reference calculation unit, and

the stator flux link assignment unit, depending on the electromagnetic moment of the motor, the input of which is supplied with a torque reference signal from the torque reference calculation unit, and the output is connected to the flux link input input of the DTC block.

The functional diagram of the dual-zone speed control system of an induction motor (AM) is shown in Fig. 1. The system contains a three-phase HELL 1 with a speed sensor DCHV 2; rectifier-inverter static converter 3, from which the HELL is powered; a DTC 4 unit that controls the semiconductor switches of converter 3; unit for calculating the task of the moment 5; speed controller 6; a subtraction unit 7, in which the mismatch between the speed reference and the actual engine speed measured by the sensor 2 is determined; intensity adjuster 8; a unit for calculating a given power 9 and a unit for calculating a task for flux link 10.

Let us dwell on the design of the device. In the presented system (Fig. 1) there is an external circuit for controlling the rotational speed (angular velocity) of blood pressure. The rate of increase of the task at the rotation frequency ω _s is determined by the intensity adjuster 8 (ZI). The actual angular velocity of the rotor HELL is measured by a speed sensor 2 (DF). The mismatch between the given (ω _h ) and the actual angular speed of the engine (ω), determined in the subtraction unit 7, is fed to the speed controller, which generates a preliminary task at the moment of the traction motor (Ms _ω ). In the block for calculating the task of the moment 5 (BVZM), taking into account the constraints, the restrictions and the final task at the moment M _s , arriving at the DTC block, are determined according to the equations

where M _zogr - job restriction at the time of blood pressure; M _zmax - _torque limit, usually set based on the permissible current of the AIN valves of the static converter (SP); M _ω - preliminary task at the moment calculated by the speed controller; P _s - set engine power.

In the unit for calculating the set power 9 (BV_P _s ), the value of the set power P _s is determined depending on the temperature θ of the stator windings of the motor according to the following equations:

where θ _add - allowable temperature of the stator winding HELL, R _n - rated motor power.

In this system, there is no temperature sensor for the motor windings, and the temperature is determined by the thermal model of the motor, which is part of the adaptive model of the motor of the DTC unit. This reduces the accuracy of determining the temperature, but does not require the installation of a sensor in an induction motor.

In block 10, the task for stator flux linkage ψ _sЗ in the first and second zone for controlling the BP speed is determined by the task found using equations (1, 2) at the moment M _s based on the previously calculated dependence of stator flux linkage on the motor moment ψ _sз = f (M _з ) by the condition of minimum stator current, which has the form of a curve with saturation. The found reference for flux linkage, as well as the reference for the moment, enters the DTC block. The use of DTC allows you to separately control the electromagnetic moment and flux linkage of the motor stator according to the energy-saving law with high speed.

When the device is operating, block 3 is connected to a three-phase network, preliminary magnetization is performed (which is described in more detail below), block 8 generates a speed reference signal, from which the speed signal measured by sensor 2 is subtracted in block 7, the resulting mismatch is transmitted to the speed control unit 6, which calculates the preliminary task for the moment that arrives at block 5. The value of the set power, determined in block 9 by expressions (2) taking into account the temperature s of windings, and then in block 5, using the value of the set power and the value of the preliminary reference for the moment, expressions (1) determine the final reference for the moment arriving at block 4 (DTC) and block 10, in which the reference for flux coupling is determined in advance calculated energy-saving dependence of stator flux linkage from the moment ψ _sз = f (M _з ). The building for flux linkage, as well as the task at the moment, goes to block 4 (DTC), which generates control signals supplied to block 3 (SP), which feeds the induction motor.

In the first zone of speed regulation, when low speeds and low tasks are implemented at the moment (in case of a reduced motor load), the stator flux linkage automatically decreases according to a given curve ψ _sз = f (M _з ) (Fig. 1, block 10). When the load increases, the task at the moment increases (up to M _zmax ) and, accordingly, the task for stator flux linkage increases.

As the engine acceleration and to increase the rotational speed ω upwards from the nominal value assignment at the time of taking into account the accepted limits (see. The expression 1) inevitably decreases with increasing ω and simultaneously decreases job stator flux linkage on the same design expression ψ _sz = f (M _s ) In this case, the engine automatically goes into the field weakening zone (into the second zone).

It should be noted that in this electric drive system, before starting the engine, it is necessary to set a given level of flux linkage. For this, the pre-magnetization mode is used, which consists in setting the task for flux linkage at a given initial level when the task at the moment is zero. After magnetization of the blood pressure, the task increases with the required intensity and then the calculated dependence ψ _sз = f (M _з ) is realized.

Thus, in the first and second zones, the stator flux linkage is regulated according to the energy-saving law, and at the same time, the maximum permissible motor power is implemented depending on the temperature of the windings, allowing it to be dosed to change its overload capacity.

Changing the set power _Pz depending on the temperature of the windings allows to increase the motor power without reducing the service life, temporarily overloading it if necessary, for example, when overcoming lifting by a vehicle or lowering the pressure in the line when increasing the flow rate of the liquid, and also to protect the motor from exceeding temperature . At the same time, the proposed implementation of energy-saving dual-zone regulation in a direct torque control system allows to reduce losses and increase efficiency induction motor.

Claims (1)

A dual-zone induction motor speed control system using direct torque control (Direct Torque Control - DTC), containing a static voltage and frequency converter with an autonomous voltage inverter, supplying an asynchronous motor, a motor speed sensor, current sensors of phase A, B, C of the motor, a sensor voltage of the DC link of the static converter, direct torque control unit (DTC), to the corresponding inputs of which the signals of the motor current sensor, voltage sensor current, and the first output is connected to the control input of the static converter, and in the DTC block there is an adaptive motor model, including a thermal model, based on which the temperature of the stator windings of the motor is calculated; also containing an intensity adjuster connected to the first input of the subtraction unit, to the second input of which a signal is supplied from the engine speed sensor, and the output is connected to the input of the speed controller, the output of which is connected to the first input of the torque reference calculation unit, the second input of which is connected to the output engine speed sensor, and the output is connected to the input of the torque reference of the DTC unit, characterized in that the following are entered into the system: a set power calculation unit, to the input of which a temperature signal of the motor windings is supplied from the second output of the DTC unit, and the output is connected to the third input of the torque reference calculation unit, and the stator flux link assignment unit, depending on the electromagnetic moment of the motor, the input of which is supplied with a torque reference signal from the torque reference calculation unit, and the output is connected to the flux link input input of the DTC block.

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