RU2424612C1 - Speed control device of asynchronous electric motor (versions) - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: speed control device of asynchronous electric motor includes active rectifier made as per bridge circuit the ac input of which is connected to outputs of secondary winding of network transformer. Capacitance divider in constant voltage circuit of frequency converter is connected to output of active rectifier. Middle point of secondary transformer winding is connected to middle point of capacitance divider in dc circuit of converter. For the purpose of further simplification of the device two phases of asynchronous electric motor are connected to two arms of voltage inverter, and the third phase of asynchronous electric motor is connected to middle point of capacitance voltage divider in dc circuit of frequency converter. Active bridge rectifier of supply voltage is made on two diodes the two in-series connected arms of which are shunted with opposite connected transistors.

EFFECT: increasing output during power supply from single-phase network.

3 cl, 4 dwg

Description

The proposed device for controlling the speed of an asynchronous electric motor is intended for use in electric locomotive drives with asynchronous electric motors powered by alternating current or direct current networks, which is typical for extended high-speed highways with sections of alternating and direct current mains.

Known two-link frequency converter with a bridge three-phase voltage inverter for IGBT transistors with a DC link and an active rectifier. [one]

The disadvantage of this frequency converter is complexity, a large number of power transistors, including when powered by a single-phase network.

Known two-link frequency converter with a bridge three-phase voltage inverter for IGBT transistors with a DC link and an active rectifier on thyristors powered by a single-phase AC network to power a traction asynchronous electric drive of the Sokol high-speed train. [2]

The disadvantage of this device is its complexity.

Known two-link frequency converter on a fully controlled power semiconductor switches with a PWM rectifier. [3]

Its positive qualities are providing a high value of the input power factor (0.99) in a wide range of load changes, ensuring bi-directional energy transfer - recovery. The voltage equalizer (DC) on the DC buses of the inverter power is made on two IGBT transistors VT3, VT4 and a choke with inductance L2 connected to the midpoint of the storage capacitors C1, C2. It is a device that ensures equal DC voltages of capacitors C1 and C2, which is necessary to exclude the DC component of the supply voltage at the inverter output. The equalizer reduces the ripple current in the storage capacitors. This allowed us to solve switching problems, ensured sinusoidality of the output and input currents, a single power factor over the network, the ability to recover electric energy to the network, improved electromagnetic compatibility with the mains, increased the dynamics of the electric drive, and improved weight and size parameters.

The disadvantages of a two-link frequency converter on fully controllable power semiconductor switches with a PWM rectifier include:

- the complexity of the device, a large number of power IGTB transistors and the possibility of significant transient overvoltages on closed transistors;

- the complexity of the control system of transistors of a PWM rectifier, requiring information not only about the magnitude of currents and voltage, but also about their phase shift;

- the presence of electric capacitors of large capacity and high operating voltage.

Known matrix frequency converter. [four]

It is performed on 9 bi-directional switches that are capable of connecting any of the three phases of the input voltage to any of the three phases of the load. As a fully controlled key element of two-sided conductivity, two IGBT transistors (or MOSFETs), connected in series and counterclockwise, each of which is shunted by a diode connected counterclockwise to the transistor, can be used.

The disadvantage of this device is the complexity, a large number of key elements, the occurrence of large overvoltages on semiconductor fully controllable key elements at the moments of interruption of current in the branches of the system with inductive elements. Limiting the amount of overvoltage that occurs when the keys are opened leads to the inevitable complication of the circuit with additional elements to limit the voltage and to additional losses.

A known frequency converter with a bridge three-phase inverter with an additional (neutral) arm and with a capacitive divider in the DC circuit. [5]

The disadvantage of this device is the large number of IGBT transistors in the voltage inverter, the instability of the capacitance of the capacitor divider, which leads to the appearance of a constant component of the voltage on the phases of the induction motor, the limitation of the power of the voltage inverter to the capacitance in the capacitive divider of the DC link.

A prototype of the proposed device is a frequency converter with an active half-bridge single-phase half-wave rectifier of the mains voltage, a bridge voltage inverter and a capacitive voltage divider in the DC link (Figure 1). [6]

The output 1 of the AC single-phase voltage source through the inductor 3 is connected to the middle (common) point of the active half-bridge single-phase half-wave rectifier, which is made on IGBT transistors 5, 6. The output 2 is connected to the middle (common) point 4 of the capacitive divider 7, 8 and phase A of the asynchronous electric motor 13. Phases B and C are connected to a bridge voltage inverter, which is made on IGBT transistors 9, 10, 11, 12.

The disadvantage of this device is the limitation on the power of the voltage inverter due to the uneven distribution of voltage across the capacitors of the divider in the DC circuit, which is associated with the half-wave rectification of the single-phase voltage, as well as charging the capacitors in different half-periods of the mains voltage.

The aim of the proposed device is to increase the permissible power of the frequency converter when powered by a single-phase AC voltage network.

This goal is achieved by the fact that the active rectifier of the mains voltage is made according to the bridge circuit, the AC input of the active rectifier is connected to the terminals of two in series and according to the included secondary windings of the network transformer, a capacitive divider is connected to the output of the active rectifier in the DC link of the frequency converter, medium (total ) the point of the secondary windings of the transformer is connected to the midpoint (common) point of the capacitors of the capacitive divider in the DC link of the frequency converter, and When the phase of the induction motor are connected to the corresponding arms of inverter voltage (Figure 2).

The primary winding 15 of the network transformer 14 is connected to a single-phase alternating voltage source 1, 2 (contact network). The input of the active bridge rectifier, made on the key elements 5, 6, 19, 20, is connected in series and according to the included secondary windings 16, 17 of the network transformer 14. The middle (common) point 18 of the secondary windings of the network transformer is connected to the middle (common) point of the capacitive a divider 7, 8, which is connected to the output of the active bridge rectifier. Phases A, B, C of the induction motor 13 are connected to the corresponding shoulders of the voltage inverter made on the key elements 9, 10, 11, 12, 21, 22.

As key elements, IGBT or MOSFET transistors with built-in reverse diodes can be used.

A single-phase alternating voltage through a network transformer 14 is fed to the input of an active bridge rectifier, made on the key elements 5, 6, 19, 20, the inverse diodes of which charge a capacitive voltage divider 7, 8. If, as a result of the converter, the equality of voltages across the capacities 7 and 8 is violated , or the input voltage decreases to such an extent that it is necessary to further increase the voltage of the DC link, then the key elements of the active rectifier come into operation. The use of an active bridge rectifier and, at the same time, the connection of the middle (common) point of the transformer with the middle (common) point of the capacitive divider allows for more accurate equality of voltages at capacities 7 and 8, since two-half-period rectification of the alternating mains voltage is carried out, which, in turn, allows increase the power of the frequency converter.

If a frequency converter is used to control the speed of auxiliary AC drives of an electric locomotive, the goal is to simplify the device.

This goal is achieved by the fact that two phases of the asynchronous electric motor are connected to two shoulders of the voltage inverter, and the third phase of the asynchronous electric motor is connected to the midpoint of the capacitors of the capacitive voltage divider in the DC link of the frequency converter (Figure 3).

The primary winding 15 of the network transformer 14 is connected to a single-phase alternating voltage source 1, 2 (contact network). The input of the active bridge rectifier, made on the key elements 5, 6, 19, 20, is connected in series and according to the included secondary windings 16, 17 of the network transformer 14. The middle (common) point 18 of the secondary windings of the network transformer is connected to phase A of the induction motor 13 and the middle (common) point of the capacitive divider 7, 8, which is connected to the output of the active bridge rectifier. Phases B, C of the induction motor 13 are connected to the corresponding shoulders of the voltage inverter made on the key elements 9, 10, 11, 12.

As key elements, IGBT or MOSFET transistors with built-in reverse diodes can be used.

A single-phase alternating voltage through a network transformer 14 is fed to the input of an active bridge rectifier, made on the key elements 5, 6, 19, 20, the inverse diodes of which charge a capacitive voltage divider 7, 8. If, as a result of the converter, the equality of voltages across the capacities 7 and 8 is violated , or the input voltage is reduced to such an extent that it is necessary to additionally increase the voltage of the DC link, then the key elements of the active rectifier come into operation, which performs a half th straightening. The formation by the control system of the pulse width modulation (PWM) method of sinusoidal currents in phases B, C of the asynchronous electric motor 13 and the connection of phase A to the middle (common) point 18 of the capacitive voltage divider 7, 8 allows you to get a sinusoidal current in phase A of the electric motor, which, in in turn, simplifies the frequency converter.

In order to further simplify the device, the active bridge rectifier of the mains voltage is made on diodes, two series-connected arms of which are shunted by counter-connected transistors (Figure 4).

The primary winding 15 of the network transformer 14 is connected to a single-phase alternating voltage source 1, 2 (contact network). The input of the active bridge rectifier, made on the key elements 5, 6 and diodes 19, 20, is connected in series and according to the included secondary windings 16, 17 of the network transformer 14. The middle (common) point 18 of the secondary windings of the network transformer is connected to phase A of the induction motor 13 and the middle (common) point of the capacitive divider 7, 8, which is connected to the output of the active bridge rectifier. Phases B, C of the induction motor 13 are connected to the corresponding shoulders of the voltage inverter made on the key elements 9, 10, 11, 12.

As key elements, IGBT or MOSFET transistors with built-in reverse diodes can be used.

A single-phase alternating voltage through a network transformer 14 is fed to the input of an active bridge rectifier, which, through the reverse diodes of the key elements 5, 6 and diodes 19, 20, charges a capacitive voltage divider 7, 8. If, as a result of the converter’s operation, the equality of voltages across capacities 7 and 8 is violated, or the input voltage is reduced to such an extent that it is necessary to further increase the voltage of the DC link, then the key elements 5, 6 of the active rectifier come into operation. In this case, the capacitive divider charge is also carried out according to a two-half-wave scheme, and to maintain the equality of voltages at capacities 7 and 8, two key elements 5 and 6 are sufficient, which makes it possible to simplify the frequency converter.

Information sources

1. A textbook for university students enrolled in specialty 140604 “Electric drive and automation of industrial plants and technological complexes”, training direction 140600 “Electrical engineering, electromechanics and electrotechnology”. - M .: ACADEMA, 2006; fig. 4.1.

2. "Microprocessor control systems for traction asynchronous electric drive" Bogatyrev D.E., Makhonin S.V., Makhonin Yu.S., Moskalev I.A., Nikolaev M.A. - Central Research Institute of Electric Networks, St. Petersburg.

3. V. Klimov, A. Moskalev Three-phase uninterruptible power supplies: circuitry and technical specifications, Electronic components, No. 8, 2005

4. A. Alesina, M. Venturini Analysis and Design of Optimum-amplitude Nine-switch Direct AC-AC Converters, IEEE Trans. On Power Electronics, vol. 4, no. 1, 1989.

5. Zinoviev G.S. Fundamentals of power electronics // Textbook. Ed. 2nd, rev. and add. Novosibirsk, 2003, Fig. 13.6.1.

6. Zinoviev G.S. Fundamentals of power electronics // Textbook. Ed. 2nd, rev. and add. Novosibirsk, 2003, Fig. 13.6.4.

Claims (3)

1. A device for controlling the speed of an asynchronous electric motor, containing an active rectifier of the mains voltage, a voltage inverter, a capacitive voltage divider in the DC link, characterized in that the active rectifier of the mains voltage is made according to the bridge circuit, the AC input of the active rectifier is connected to the terminals of two in series and according to the included secondary windings of the network transformer, a capacitive divider in the DC link is connected to the output of the active rectifier Vatel frequency, the average (common) point of the secondary windings of the transformer is connected to the middle (common) point of the capacitive divider capacitors of the DC link current of the frequency converter, and three phase induction motor are connected to the corresponding arms of inverter voltage. 2. A device for controlling the speed of an asynchronous electric motor containing an active rectifier of the mains voltage, a voltage inverter, a capacitive voltage divider in the DC link, characterized in that the active rectifier of the mains voltage is made according to the bridge circuit, the AC input of the active rectifier is connected to the terminals of two in series and according to the included secondary windings of the network transformer, a capacitive divider in the DC link is connected to the output of the active rectifier frequency converter, the middle (common) point of the secondary windings of the transformer is connected to the middle (common) point of the capacitors of the capacitive divider in the DC link of the frequency converter, and the two phases of the induction motor are connected to the two arms of the voltage inverter, and the third phase of the asynchronous motor is connected to the midpoint of the capacitors capacitive voltage divider in the DC link of the frequency converter. 3. The device according to claim 1 or 2, characterized in that the active bridge rectifier of the mains voltage is made on diodes, two series-connected arms of which are shunted by counter-connected transistors.

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