UA151236U - Method of frequency control of asynchronous traction electric motor - Google Patents

Abstract

The method of scalar frequency control of an asynchronous traction electric motor, according to which the optimal control characteristics of the power electric drive of a hybrid car are determined, and with uniform movement of the car on the electric drive at a speed of 30-60 km/h. a frequency control channel is used, with the help of which a frequency proportional to the speed of the car is selected, and with the help of a phase voltage control channel, such a three-phase alternating voltage is selected, when it is applied to all three phases on one of them, a given power factor is provided.

Description

The useful model belongs to automotive technology and can be used in mild hybrid cars.

A known method of frequency control of an asynchronous electric motor in the scalar mode (Anuchin A.S. System! upravlenie zlektroprivodov - Izdatelsky dom MZY; IZVM: 978-5-383-00918-5; 2015, 373 p.). Today, despite the competition with vector control methods, it is quite common, as it allows solving many technical tasks of a mass electric drive more easily and efficiently. In the case of scalar control while keeping the voltage-to-frequency ratio constant, it is necessary to increase the stator supply voltage as the rotation speed increases. However, the synchronous frequency of the induction motor is not equal to the shaft rotation frequency, and the slip of the induction motor depends on the load. Thus, a control system with scalar control without additional feedback cannot accurately control the operation of the engine under a changing load.

The scalar control method is relatively simple to implement, but has significant disadvantages: - it has poor dynamics when starting the engine from a stationary state - it has a relatively narrow range of rotation speed adjustment (no more than 1:10) - it does not adapt well to changing load.

The closest analogue is the technical solution used in the power electronics of Tevia 5, Tezia X, EP ABA cars. In them, the frequency control of the traction asynchronous electric motor is produced by an inverter with vector regulation (Tevzia 5 and Tevia H. porz //amiodmidaieii.sot/tagkKi/dmidaie!I-ievia. PITTI, EPAVA Or /Llymly.agime2.gy/6/966580/) .

A distinctive feature of the vector control system of the asynchronous traction electric drive is the need to use an additional computing unit, which evaluates the rotor flux coupling vector module and the current angular position. This is done by solving the system of differential equations in real time, compiled according to the mathematical model of an asynchronous electric motor.

Compared to the scalar one, the vector control method has the following advantages: - a wide range of speed regulation; - smooth adjustment of engine rotation speed in the entire frequency range; - the possibility of maintaining a constant speed when the load of the electric drive changes;

Zo - reduction of losses during transient processes in the drive (in this connection, some increased

engine efficiency).

The vector frequency converter is used where it is necessary to provide a wide range of adjustment, especially at low rotation frequencies.

Despite a number of significant advantages, it is worth noting that the computational complexity of the vector control method is high, and when calculating the optimal operating modes of the drive, it is necessary to take into account a large number of parameters of the electric drive. Briefly, the disadvantages of vector control can be said as follows: expensive in development, production and maintenance.

In addition, speed fluctuations at constant load are greater than with the scalar control method. Therefore, where there is no need for a large depth of adjustment and there is no requirement to provide a high torque, at a low speed of rotation, the scalar method is used.

The task of the proposed useful model is to reduce the cost of implementing the proposed method using a traction electric drive system by reducing the computing power of the control system and the number of sensors of the current state of the electric drive.

To solve the problem in the method of scalar frequency control of an asynchronous traction electric motor in a mild hybrid car, with uniform movement of the car on an electric drive at a speed of 30-60 km/h. the frequency control channel is used, which selects a frequency proportional to the speed of the vehicle, and the phase voltage control channel selects such a three-phase alternating voltage, when applied to all three phases, at least one of them provides the specified power factor.

To implement this method in a mild hybrid car, which consumes the electric energy of the traction battery only for uniform movement or movement with small accelerations at a speed of 30-60 km/h (Dvadnenko V.Ya., Pushkar O.B. Улучшение зкономический и zcological characteristics of a microhybrid car. / Automotive transport: scientific journal - 2019. - Issue 45. - pp. 12-22). Such a mild hybrid car does not use the operation of the electric motor at low speeds and operates in a relatively narrow range of revolutions. In such a car, the asynchronous traction electric motor is kinematically connected by means of a polyclinic transmission to the secondary shaft of the mechanical gearbox.

A frequency control channel and a phase voltage control channel are used to control an asynchronous motor.

In order to control the frequency, a car speed sensor is used, since the signal is proportional to the rotation frequency of the asynchronous motor axis. Knowing the number of pairs of stator poles and the proportionality factor between the frequency of the vehicle speed sensor signal and the frequency of rotation of the shaft of the induction motor, the frequency of the three-phase alternating voltage that must be supplied to the induction motor is obtained by adding the nominal absolute slip. The essence of the useful model is explained by the drawing, which shows the block diagram of the system for implementing the proposed method of controlling the traction asynchronous electric motor in a mild hybrid car, where the following are marked: 1 - traction battery, 2 - power three-phase inverter, C - asynchronous electric motor, 4 - control channel voltage, 5 - frequency control channel, 6 - vehicle speed sensor, 7 - phase current sensor.

To determine the optimal voltage, which in general depends not only on the frequency, but also on the load of the electric motor, use the law of M.P. Kostenko (Kostenko

M.P. Operation of a multiphase asynchronous motor with a variable number of periods. -

Zlektrychestvo, 1925. - Mo 2. - P. 85-95). If the saturation in the engine is weak, then for optimal operating conditions, the relative voltage must be changed in proportion to the product of the relative frequency by the square root of the relative moment. At the same time, the asynchronous motor will work with a constant absolute slip, a constant reserve of static stability and a constant power factor (Usoltsev A.A. Частотное управление асинхронньмы двигатиями / Uchebnoe posobie. - St. Petersburg: SPOGU ITMO, 2006. - 94 p.).

Since determining the moment using sensors is a difficult task, we use the fact that the load moment of an asynchronous motor depends on its power factor. The power factor is determined using inexpensive specialized microcircuits (microcontrollers for electronic kilowatt-hour meters, for example, AOE7755).

The voltage control channel uses signals from the current and voltage sensors of the motor phase, which are processed by a specialized controller and then sent to the microcontroller of the control unit. With the help of the control unit, the voltage of the motor phases is changed relative to the voltage set by the frequency in such a way as to maintain the set value of the power factor, since a small reactive power is required for the formation of the magnetic field of the rotor for an asynchronous motor.

The technical result of the useful model, which is achieved by the above-mentioned distinctive features, is the possibility of using a low-power asynchronous motor with frequency scalar control in a mild hybrid car, which reduces the cost of implementing the specified method of frequency control of the asynchronous traction electric motor of the power plant of a hybrid car.

Claims (1)

USEFUL MODEL FORMULA The method of scalar frequency control of an asynchronous traction electric motor, according to which the optimal control characteristics of the power electric drive of a hybrid car are determined, which is distinguished by the fact that with uniform movement of the car on an electric drive at a speed of 30-60 km/h. a frequency control channel is used, with the help of which a frequency proportional to the speed of the car is selected, and with the help of a phase voltage control channel, such a three-phase alternating voltage is selected, when it is applied to all three phases on one of them, a given power factor is provided. i and xx Y zve Y: Ov