RU2361357C2 - Device for controlling asynchronous engine in vehicles - Google Patents

Abstract

FIELD: radio engineering. ^ SUBSTANCE: invention relates to electric engineering and may be used in a.c. electric locomotives, shaft-driven generators of water-crafts, invertible power supply systems of water-crafts, wind plants generators. The invention may be also used in break-in benches of tractor engines and in other cases where mechanical energy from variable speed drive movers is used. The d.c. voltage-to-three-phase voltage converter and pick-off diode in the asynchronous electric engine control unit are connected to the output of invertible single-phase or three-phase full-wave rectifier. The input of the said invertible single-phase or three-phase full-wave rectifier is connected to autotransformer terminals. The above-mentioned autotransformer is connected to a.c. contact of industrial mains. The unit is provided with a simple system of automated control and stable tetra-quadrant mode of drive operation. The regenerative breaking mode of the vehicles allows for delivering significant part (to 40%) of energy into a.c. mains. Previously, that energy was used during mechanical breaking. As a result, short pay-back period is ensued. Due to invertible growth of electric power cost, the above-mentioned becomes more valuable. ^ EFFECT: vehicle can operate from ac mains. ^ 5 cl; 5 dwg

Description

The invention is intended for use in drives of vehicles operating in dynamic modes in a wide speed range, when powered by AC voltage sources, and can also be used as a converter of mechanical energy into electrical energy.

A device is known for controlling an asynchronous electric motor of a vehicle, powered by a constant voltage source, comprising a constant voltage to three-phase voltage converter with adjustable amplitude, adjustable frequency and a variable phase sequence, characterized in that a phase-rotor motor, windings are used as an asynchronous electric motor the stator of which is connected to the output of the aforementioned converter, its rotor windings are connected to a three-phase bridge rectifier, and the output of this rectifier is connected to the aforementioned DC voltage source through a choke, a pulse chopper and a cut-off diode.

The disadvantage of this device is that it can only work from a constant voltage source and cannot work from an AC network, receive energy from an AC network and return it to this network.

The purpose of the proposed device is to ensure the possibility of the vehicle from AC power.

This goal is achieved by the fact that the input of the DC-DC converter to the three-phase voltage and the cut-off diode are connected to the output of the reversing single-phase or three-phase two-half-wave rectifier, and the input of the single-phase or three-phase two-half-wave rectifier is connected to the terminals of the autotransformer, which is connected to the AC network.

A reversible single-phase or three-phase half-wave rectifier is formed by a bridge circuit, in each arm of which thyristors are connected in parallel-parallel, one of which is used in the rectification circuit of an alternating voltage coming from an autotransformer, and the other in a circuit driven by an inverter.

If in the rectification mode it is not necessary to regulate the rectified voltage, then instead of the thyristors operating in the rectification circuit, diodes are used.

In order to improve the mode of inverting energy from a DC voltage circuit to an AC network, IGBT transistors are used instead of the thyristors operating in the network-driven inverter circuit.

In order to simplify the circuit, instead of one bridge reversible rectifier, two half-wave reversible rectifiers with a common point at the output of the autotransformer are used.

In order to simplify the frequency converter, as well as to obtain a pulsating engine torque for starting from the vehicle without slipping, a two-phase frequency converter is used instead of a three-phase frequency converter, and the asynchronous electric motor has a two-phase stator winding.

The control device of the asynchronous motor (Figure 1) receives power from a constant voltage source - terminals 1 and 2 (with polarity + and -). A converter 3 is connected to points 1 and 2 to a three-phase voltage with an adjustable amplitude, an adjustable frequency and a variable phase sequence.

Three-phase voltage is supplied from the converter 3 to the stator windings of the asynchronous electric motor 4 with a phase rotor (with slip rings). The rotor voltage of the induction motor 4 through the contact rings is fed to the input of a three-phase bridge rectifier 5, the output of which is connected through a low-pass filter (inductor 6 and capacitor 7) to a pulse regulator formed by inductor 8 and commutator (chopper) 9.

The output of the pulse regulator (8 and 9) through the cut-off diode 10 and the low-pass filter (capacitor 11 and inductor 12) is connected to points 1 (+) and 2 (-) of the DC circuit.

The input of the DC-DC converter to three-phase voltage 3 and the cut-off diode 10 are connected at points 1 (+) and 2 (-) to the output of the reversing single-phase two-half-wave rectifier formed by semiconductor elements 18-25 (Figure 2).

The input of a single-phase, half-wave bridge rectifier is connected to the terminals 0 and 16 of the autotransformer 14, which is connected through the terminal 15 and the sliding contact 13 to the AC network.

To the terminals 0 and 16 (FIG. 2) of the autotransformer 14 are connected a reversible single-phase rectifier according to a bridge circuit on controlled semiconductor elements - thyristors 18, 19, 20 and 21 (for transmitting power in the forward direction from the AC mains to the motor) and a network-driven inverter on thyristors 22, 23, 24 and 25 (for transferring power in the opposite direction to the alternating current network). At the output of the reversible rectifier from the DC voltage side, a capacitor 26 is connected as a low-pass filter.

In a simplified version (Figure 3), the reversible rectifier is created according to the scheme of two reversible half-wave rectifiers with a common point at terminal 0 of the autotransformer 14. The voltage is supplied to the reverse rectifier from terminal 16 of the autotransformer and terminal 17 of the additional autotransformer winding, as a result of which a half-wave rectification mode is provided and inverting with half the number of semiconductor elements in the circuit. Thyristors 27 and 28 provide a rectification mode for the direct direction of power transmission from the AC network, and thyristors 29 and 30 operate in the mode of a network-driven inverter for the reverse direction of power transmission to the AC network.

If regulation of the rectified voltage is not required, diodes instead of thyristors are used as elements 27 and 28 (Figure 4).

The switching mode during inverting and control of the inverter mode can be improved if IGBT transistors are used as elements 29 and 30 instead of thyristors (Figure 5).

In order to simplify the frequency converter, as well as create a pulsating torque of rotation of the induction motor, to move the vehicle away without slipping, a two-phase frequency converter is used instead of a three-phase frequency converter, and the asynchronous electric motor has a two-phase stator winding.

The proposed device operates as follows. It is possible to operate an asynchronous electric motor in the motor mode, regenerative regenerative braking mode, in the opposition mode with the recovery of sliding power.

In the motor mode, the energy from the AC network through terminal 13, the autotransformer 14 and the rectifier on the elements 18, 19, 20 and 21 enters the DC voltage circuit (points 1 (+) and 2 (-)). The rectified voltage is partially smoothed by the capacitor 26. The DC voltage circuit is connected to the input of the frequency converter 3, the three-phase voltage from the output of which is supplied to the stator windings of the three-phase asynchronous motor 4. The voltage of the phase rotor through the contact rings is fed to the input of the three-phase bridge rectifier 5.

When the breaker 9 is open, the voltage from the output of the rectifier 5 enters through the rectified current circuit of the rotor to the cut-off diode 10. If the voltage at the output of the rectifier 5 is less than the voltage of the DC circuit (voltage across the capacitor 11), then the cut-off diode 10 is biased in the opposite direction and the current in the circuit of the rectified current of the rotor (through the inductor 8, rectifier 5) is absent. Accordingly, there is no current in the windings of the rotor and the moment of rotation of the motor 4 is not created.

If the voltage at the output of the rectifier 5 is greater than the voltage of the DC circuit (more than the voltage at the capacitor 11), which is possible with a large slip of the asynchronous motor 4 (for example, when the vehicle is lowered downhill and the engine is in the opposite mode), then the diode 10 will be shifted to forward direction and through it starts to flow current with open interrupter 9, and also starts to flow current through the rectified current circuit of the rotor (inductor 8), through the rectifier 5 and the windings of the rotor of the motor 4. etstvii to the principle of the asynchronous (induction) motor 4 appearing therein yaw moment is directed so as to reduce engine sliding of 4 to bring the speed of the rotor to the stator magnetic field rotational speed. The speed and direction of rotation of the magnetic field of the stator are set by the frequency converter 3. By changing the frequency and voltage at the output of the frequency converter 3, at the same rotation speed of the rotor of the motor 4, you can change the slip value of the motor, the rectified voltage of the rotor and thereby change the magnitude of the current flowing through the cut-off diode 10, through the inductor 8, the current through the rectifier 5 and along the rotor windings even without the use of a chopper 9.

If the chopper 9 enters operation, then when the chopper 9 is closed, the inductor 8 is connected to the voltage at the output of the rectifier 5 and the current of the inductor 8, the current of the rectifier 5, the current through the rotor windings begin to increase. A long circuit breaker 9 is equivalent to short-circuiting the rotor of the motor 4 (through the rectifier 5 and the inductor 8), which leads to the transition of the motor to a mechanical characteristic close to the natural mechanical characteristic.

As a result of the opening of the chopper 9 due to the self-induction EMF of the inductor 8, the current in the inductor 8 continues to flow through the cut-off diode 10 and enters the DC voltage circuit (1-2), creating an increase in voltage across the capacitors 11 and 26. As a result, recovery (return) to a constant voltage circuit (1-2) of the part of the energy received by the motor 4 through the converter 3 from the constant voltage source. If the engine 4 operates in generator braking mode (at a speed above the synchronous rotor speed determined by the frequency at the output of the converter 3), mechanical energy is transferred from the vehicle through the rotary pulse chopper to the DC voltage circuit (1-2). The recoverable slip power passes through the rectified current circuit of the rotor.

Increasing the voltage on the capacitors 11 and 26 to a level above the level of the rectified voltage of the AC network causes the thyristors of the network rectifier to lock (on the elements 18, 19, 20 and 21) and creates the possibility of the inverter driven by the network on the elements (22, 23, 24 and 25 ) The transition from the rectifier mode to the invert mode to the AC network is also possible due to the grid control of the rectifier and inverter thyristors.

Changing the duty cycle of the on state of the chopper 9 from the complete opening of the rotor circuit to the complete closure of its circuit through the rectifier 5, inductor 8 and chopper 9, you can smoothly adjust the average current value of the inductor 8, smoothly control the current of the rotor windings of the motor 4 and the rotational speed of the motor 4 regardless of stator control.

The rotational speed of the motor is controlled by changing the frequency of the stator voltage using a frequency converter 3. The rotational moment of the motor (rectified rotor current) is set at a constant slip value (the magnitude of the rectified rotor voltage) by changing the duty cycle of the breaker 9, by PWM (pulse-width modulation) regulation. In the anti-inclusion mode, the speed control corresponds to the slip control (control of the rectified rotor voltage).

A smaller moment of load resistance in the motor mode corresponds to a smaller steady-state amount of sliding, a smaller value of the rectified voltage of the rotor, less current of the rotor. In regenerative braking mode, the engine torque counteracts the motor torque of the mechanism.

The mechanical characteristics of the engine can thus be located in all 4 quadrants and are stable at all points, providing a motor operating mode of the drive, a generator mode and an anti-switching mode.

If it is not necessary to adjust the rectified voltage with a mains voltage rectifier (elements 18, 19, 20 and 21), instead of thyristors, diodes can be used for rectification.

If an additional winding is added to the autotransformer 14 (Figs. 3 and 4), then the mains rectifier and the inverter driven by the network can be constructed with fewer elements (27 and 28 for the rectifier, 29 and 30 for the inverter). This reduces almost 2 times the loss in the elements of the rectifier and inverter. Losses due to the use of an additional autotransformer winding with an appropriate choice of the cross section of its wire will not increase. Reducing losses in converting devices helps to reduce their size.

If a three-phase network is used, then instead of single-phase rectifiers, the corresponding three-phase rectification and inversion circuits are used (three-phase bridge, two three-phase rectification schemes with a zero wire in the presence of the corresponding three-phase transformer or autotransformer).

In the case of using zero voltage rectification circuits, the frequency converter can be made not according to bridge, but according to known zero circuits with fewer semiconductor elements. In this case, a two-phase frequency converter and a two-phase stator winding of an asynchronous electric motor are preferred, the phase rotor of which remains three-phase. Asymmetric phase voltage control of the frequency converter creates an elliptical rotating magnetic field of the stator. When starting the vehicle at a low output frequency of the inverter by the motor, in this case a semblance of a jogging mode is created, which helps to move the vehicle (accelerate) without slipping.

The steady mode of regenerative braking of the vehicle, provided by the proposed device, allows you to give a significant part of the energy (about 40%) to the AC network, which is currently absorbed by mechanical braking, which gives a short payback period of the proposed device, even taking into account the cost of the proposed device for Compared with similar in purpose simpler devices that do not have the ability to operate stably in generator braking mode.

Due to the inevitable increase in the cost of electricity, the value of this preferred property of the proposed device increases.

The source of information:

1. RF patent for utility model No. 57990. IPC: Н02Р 7/00; Н02К 17/34 “Device for controlling an asynchronous electric motor” (priority 26.05.06, publication Bulletin No. 30 of 10.27.06).

Claims (5)

1. Device for controlling an asynchronous electric motor of a vehicle, comprising a DC-to-three-phase voltage converter with adjustable amplitude, adjustable frequency and a variable phase sequence, where a phase-rotor motor is used as an asynchronous electric motor, the stator windings of which are connected to the output of the said converter, windings rotors are connected to a bridge three-phase rectifier, and the output of this rectifier is connected to the aforementioned converter with on the side of the DC voltage circuit through a choke, a pulse chopper and a cut-off diode, characterized in that the input of the DC-DC converter to a three-phase voltage and a cut-off diode are connected to the output of the reversing rectifier, and the input of the reversing rectifier is connected to the terminals of the autotransformer, which is connected to the contact AC network . 2. The device according to claim 1, characterized in that the reversing rectifier is made according to a bridge circuit, in each arm of which thyristors are turned in parallel-parallel, one of which operates in the rectification mode of the AC voltage coming from the autotransformer, and the other in the mode driven by the network inverter. 3. The device according to claim 1, characterized in that the reversing rectifier has a counter-parallel diode in each arm, which operates in the rectification mode of the AC voltage coming from the autotransformer, and a thyristor operating in the mode of a network-driven inverter. 4. The device according to claim 1, characterized in that the reversing rectifier has in each arm counter-parallel connected thyristor operating in the rectification mode of the alternating voltage coming from the autotransformer, and an IGBT transistor operating in the mode of a network-driven inverter. 5. The device according to claim 1, characterized in that the reversible half-wave rectifier is formed of two half-wave reverse rectifiers with a common point at the output of the autotransformer.

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