JP4604595B2 - PWM cycloconverter - Google Patents

Description

  The present invention relates to an AC motor and a PWM cycloconverter that drives a DC motor at a variable speed.

  Conventionally, there is an example using a three-phase inverter as a method of driving a single motor control device using a DC motor and an AC motor (see, for example, Patent Document 1). This is because when the motor to be driven is a DC motor, the armature winding of the DC motor is placed between the first phase output line and the second phase output line among the AC output lines of the three-phase voltage source inverter. And connecting a field winding of a DC motor between the third phase output line and one end on the DC input side of the inverter, and connecting the power converter composed of the first phase and the second phase of the inverter to a four-quadrant chopper When the motor to be driven is an AC motor, the AC output line of the three-phase voltage source inverter is switched to AC when the motor to be driven is an AC motor. The AC motor is inverter-driven by connecting to the armature winding of the motor.

The inverter realizes frequency conversion through two stages, first converting alternating current of commercial frequency to direct current, and then converting it to alternating current of a desired frequency.
In recent years, PWM cycloconverters (also referred to as matrix converters) using reverse blocking IGBTs (Insulated Gate Bipolar Transistors) have been used instead of inverters (see Patent Document 2). This PWM cycloconverter is a device that directly converts power of a three-phase commercial frequency into power of a desired frequency by PWM (pulse width modulation) of a bidirectional switch such as a reverse blocking IGBT. Since no power storage elements such as large-capacity electrolytic capacitors and DC reactors are required in the part, the power converter can be downsized, the conversion efficiency can be increased, and the life can be extended compared to conventional inverters. It is expected that the waveform of the input current can be improved by PWM of the switch, and harmonics can be reduced and the efficiency can be improved.

JP-A-8-256497 JP 2000-139076 A

As disclosed in Patent Document 1 described above, a three-phase inverter is conventionally used as a motor control device that can drive both a DC motor and a three-phase AC motor.
On the other hand, as an electric motor, it is known that an AC motor is easier to maintain and has a longer life than a DC motor.
In recent years, controllability and efficiency similar to those of a DC motor have been realized by vector control of the AC motor using an inverter. Therefore, when replacing the existing DC motor due to the life of the existing DC motor or the like, the AC motor is updated. By the way, the life of the motor and its control device is generally shorter in the control device. Therefore, conventionally, as shown in FIG. 5, in a facility using a DC motor and a DC motor control device (1), when the DC motor control device (1) reaches the end of its life, the DC motor is left as it is. Then, when the DC motor control device (2) is newly updated and then the life of the DC motor is reached, the DC motor is updated to an AC motor, and the control device is also updated to the AC motor control device.

  Under such circumstances, as described above, when a three-phase inverter capable of driving both a DC motor and a three-phase AC motor appears, an updating method as shown in FIG. 6 could be adopted. That is, at first, in a facility using a DC motor and a DC motor control device, when the DC motor control device has reached the end of its life, the DC motor remains unchanged, but when the DC motor reaches the end of its life, the AC motor The three-phase inverter is adopted as the control device for the DC motor in anticipation of switching to the DC motor, and when the DC motor reaches its end of life, the DC motor is updated to an AC motor. However, the control device remains a three-phase inverter. In this case, the AC motor was controlled.

However, if the DC motor control device is a thyristor converter, changing this to a three-phase inverter has the problem that the harmonics contained in the current flowing to the input side will increase. Then, it is necessary to provide a PWM converter in the inverter, and there is a problem that the apparatus becomes large and expensive.
The present invention has been made in view of such problems, and by using a PWM cycloconverter as a motor control device that can control both a three-phase AC motor and a DC motor, the motor is a small and inexpensive device. It is an object of the present invention to reduce the harmonics contained in the current flowing on the input side as compared to the thyristor conversion device.

In order to achieve the above object, the first configuration of the present invention uses a multi-phase AC power source as an input power source and performs PWM control on a converter main body configured by a bidirectional switch, so that a desired configuration can be obtained from three main circuit wires. In a PWM cycloconverter that outputs three-phase power at a frequency, the voltage command generation circuit for PWM control of the converter body is provided with a selection switch for selecting between AC motor control and DC motor control, and the main circuit wiring When AC motor control is selected by the selection switch while all three are connected to a three-phase AC motor, the three-phase AC motor is driven at a variable speed, and two of the three main circuit wirings are DC motors. When the direct current motor control is selected by the selection switch in a state where the direct current motor is connected, the direct current motor is driven at a variable speed.
In the present invention, it is possible to select whether to control the AC motor or the DC motor with one selection switch. When the AC motor control is selected, the three-phase AC is output from the three output lines. When the motor is driven at a variable speed and DC motor control is selected, a PWM cycloconverter that can output a DC voltage from two of the three output lines and drive the DC motor at a variable speed can be realized.
As the bidirectional switch, a reverse blocking IGBT connected in reverse parallel can be used.

According to the PWM cycloconverter of the present invention, when the AC motor control is selected by the selection switch attached to the main body, the three-phase AC motor is driven at a variable speed by outputting the three-phase AC from the three output main circuit lines. When the DC motor control is selected with the selection switch, the DC motor can be driven at variable speed by outputting DC from two of the three output main circuit lines, so that both the three-phase AC motor and the DC motor can be driven. Can be controlled.
As a result, when the electrical equipment of the DC motor drive equipment is updated to the three-phase AC motor drive, using this PWM cycloconverter, the motor control device with a short life is updated first, and the DC motor three times later at a later time. It is possible to update to a phase AC motor and to reduce the harmonics flowing to the input power supply when the motor control device is updated, compared to an existing DC machine driving thyristor conversion device.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a basic configuration of an electric motor control device using a PWM cycloconverter according to an embodiment of the present invention, FIG. 2 is a block diagram of the PWM cycloconverter according to the embodiment, and FIG. FIG. 4 is a time chart of DC motor drive equipment update by the PWM cycloconverter according to the embodiment.

  As shown in FIG. 1, an electric motor control apparatus according to an embodiment of the present invention uses a multiphase AC power supply 1 as an input power supply, three main circuit wires 4, a speed detection signal input circuit 17 and a current detection for output. The PWM cycloconverter 2 having a signal input circuit 18 and an input voltage detection signal input circuit 20 is provided. The PWM cycloconverter 2 has an AC motor control / DC motor control selection switch 3 (hereinafter simply referred to as “selection switch 3”) for selecting between AC motor control and DC motor control. All three of the main circuit wiring 4 of the PWM cycloconverter 2 are connected to the three-phase AC motor 7 by the main circuit connection line 5, and the speed detection signal line from the speed detector 8 provided in the three-phase AC motor 7. 9 is connected to the PWM cycloconverter 2 via the speed detection signal input circuit 17. Further, a current detection signal line 10 from the current detector 6 of the three-phase AC motor 7 is connected to the PWM cycloconverter 2 via a current detection signal input circuit 18.

On the other hand, two of the three main circuit wires 4 are connected to the DC motor 13 by the main circuit connection line 11, and the speed detection signal line 15 from the speed detector 14 provided in the DC motor 13 is The PWM cycloconverter 2 is connected via the detection signal input circuit 17. Further, a current detection signal line 16 from the current detector 12 of the DC motor 13 is connected to the PWM cycloconverter 2 via a current detection signal input circuit 18.
Here, when the AC motor control is selected by the selection switch 3, the three-phase AC motor 7 can be driven at a variable speed, and when the DC motor control is selected by the selection switch 3, the DC motor 13 is driven at a variable speed. be able to.

  FIG. 2 is a block diagram of the PWM cycloconverter 2 according to the embodiment. In FIG. 2, the PWM cycloconverter 2 has a converter main body 21 that receives power supply voltage from the multiphase AC power supply 1 and has three main circuit wires 4 of u phase, v phase, and w phase. The PWM cycloconverter 2 is provided with a switch 3 that selects between AC motor control and DC motor control. Further, a signal from the switch 3, a current detection signal input circuit 18, a speed detection signal input circuit 17 and an input voltage detection signal input circuit 20 are connected to the control board 22 attached to the PWM cycloconverter 2. Three voltage commands 25 for the u-phase, v-phase, and w-phase are output from a voltage command generation circuit 23 in the control board 22 to a PWM signal generation circuit 24 that outputs a drive signal for the power element. The PWM signal generation circuit 24 generates a PWM cycloconverter drive signal that reduces harmonics of the input-side current and generates an output voltage according to the command, based on the signal from the input voltage signal input circuit 20 and the voltage command 25.

  The voltage command generation circuit 23 outputs a three-phase AC voltage command necessary for controlling the three-phase AC motor 7 to all three voltage commands 25 when the AC switch control is selected by the selection switch 3. A three-phase AC voltage is output to the main circuit wiring 4 of the book, and the three-phase AC motor 7 is driven at a variable speed. Further, the voltage command generation circuit 23 outputs a DC voltage command necessary to control the DC motor 13 to two of the three voltage commands 25 when the DC motor control is selected by the selection switch 3. A DC voltage is output to two of the main circuit wires 4 and the DC motor 13 is driven at a variable speed.

  FIG. 3 is a block diagram of the voltage command generation circuit 23 in the control board 22 of the PWM cycloconverter 2 capable of controlling both the three-phase AC motor 7 and the DC motor 13 shown in FIG. In the figure, 31 is a phase command device that outputs a phase command φref, 32 is a scale conversion unit that converts the phase command into a d-axis current command Id, and 33 calculates a deviation between the d-axis current command Id and the actual d-axis current Idfb. Subtractor 34, a current controller 34, an adder 35 for adding the output of the current controller 34 and the output of the q-axis → d-axis induced voltage calculator 43 described later, 36 for driving an AC motor and DC A changeover switch for switching the case of driving the electric motor, 37 is a 0 setter for setting the d-axis voltage to 0 when the changeover switch 36 is switched to the DC side, 38 is a rotation coordinate / fixed coordinate rotation conversion unit, and 39 is a two-phase switch / Three-phase converter, 40 is a speed command device that outputs a speed command Nref, 41 is a subtractor that calculates the deviation between the speed command Nref and the detected speed value Nfb, 42 is a speed controller, and 43 is a q-axis → d-axis Induced voltage calculator 44 is q-axis The subtractor for calculating the deviation between the current command Iq and the actual q-axis current Iqfb, 45 is the current controller, 46 is the output of the current controller 45 and the output of the d-axis → q-axis induced voltage calculator 47 described later. Adder, 47 is d-axis → q-axis induced voltage calculation unit, 48 is slip calculation unit, 49 is a selector switch for switching between driving an AC motor and controlling a DC motor, 50 is a 0 setter, 51 is An adder that adds the speed detection value Nfb and the slip frequency ωslip, 52 is an integrator, 53 is a selector switch that switches between driving an AC motor and controlling a DC motor, 54 is a phase lock setting device, and 55 is an actual d. A subtractor that subtracts the axial current Idfb and the actual q-axis current Iqfb, 56 is a three-phase / two-phase converter, and 57 is a fixed coordinate / rotational coordinate rotation converter.

  In FIG. 3, a signal from the selection switch 3 for selecting between the AC motor control and the DC motor control is used for switching values of the slip frequency command ωslip, the phase θs, and the d-axis voltage command Vd. When the signal from the selection switch 3 is AC motor control selection (AC side of the changeover switches 36, 49, 53 in FIG. 3), this block diagram matches the vector control block diagram of a normal induction motor. The voltage command output obtained as the output of the two-phase / three-phase converter 39 is a three-phase AC voltage.

On the other hand, when the signal from the selection switch 3 is DC motor selection (DC side of the changeover switches 36, 49, 53 in FIG. 3), the value of the slip frequency command ωslip is 0, and the frequency command value is the speed feedback signal. It matches the value of Nfb. The slip frequency command ωslip is used for the calculation of the q-axis → d-axis induced voltage calculation unit 43 and the d-axis → q-axis induced voltage calculation unit 47, the d-axis voltage command Vd becomes 0, and the voltage command is the q-axis voltage. Only the command Vq is provided. This coincides with a control block diagram of a DC motor in which the q axis is regarded as an armature. In the case of direct current motor control, the phase θs is a fixed value θ ₀ by the phase fixing setter 54. This is control of only the q axis, and the output of the two-phase / three-phase converter 39 is two of the three voltage outputs. This is to output only one of them. For example, when the phase fixed value θ ₀ is 60 degrees, the rotation coordinate / fixed coordinate rotation conversion unit 38 and the two-phase / three-phase conversion unit 39 will be obtained. In the rotation coordinate / fixed coordinate rotation conversion unit 38, if the d-axis voltage command is 0 and the q-axis voltage command is Vq, the following equation is converted.

Vα = −Vq × sin 60 ° = −√3 / 2 × Vq
Vβ = Vq × cos 60 ° = 1/2 × Vq
In the two-phase / three-phase converter 39, the following conversion is performed.
Vu = Vα = −√3 / 2 × Vq
Vv = −1 / 2 × Vα + √3 / 2 × Vβ = √3 / 2 × Vq
Vw = −1 / 2 × Vα−√3 / 2 × Vβ = 0

  As described above, the three voltage command outputs of the two-phase / three-phase conversion unit 39 are such that only two of the u-phase voltage command Vu and the v-phase voltage command Vv have voltage command values proportional to the q-axis voltage command 38, and w It can be seen that the phase voltage command Vw is zero. This also shows that a DC voltage of √3 × Vq is output in proportion to the q-axis voltage command 38 between the u-phase and v-phase lines.

  When the AC motor control is selected by the selection switch 3 shown in FIG. 3 by the operation as described above, three-phase AC is output from the three main circuit wirings 4 of u phase, v phase, and w phase. The phase AC motor 7 is driven at a variable speed. When the DC motor control is selected by the selection switch 3, a DC voltage is output from two phases of the three main circuit wirings 4 of the u phase, the v phase, and the w phase, and the DC motor 13 is variably driven. In this way, both the AC motor and the DC motor can be controlled by one PWM cycloconverter 2.

  As described above, in the embodiment of the present invention, as shown in FIG. 4, when the life of the DC motor control device is first reached in the equipment using the DC motor and the DC motor control device first, as shown in FIG. The DC motor remains the same, but in the future when the life of the DC motor comes to an end, it will be replaced with an AC motor, and the PWM cycloconverter will be used as a controller for the DC motor. In addition, the DC motor is updated to an AC motor, and the control device can subsequently use the PWM cycloconverter as a control device for the AC motor. Thus, when the motor control device is updated, the update is performed without using the control device capable of driving both the DC motor and the AC motor as shown in FIG. 5, and the DC motor and the AC motor as shown in FIG. Compared with the existing DC machine driving thyristor converter as in the case of renewal using a three-phase inverter capable of driving both, the harmonics flowing to the input power supply can be reduced.

  The present invention is used as a PWM cycloconverter capable of lowering harmonics flowing to an input power source when compared with an existing DC machine driving thyristor conversion apparatus when the motor control apparatus is updated, and is used for a DC motor and an AC motor control apparatus. Can do.

1 is a block diagram showing a basic configuration of an electric motor control device using a PWM cycloconverter according to an embodiment of the present invention. 1 is a block diagram of a PWM cycloconverter according to an embodiment of the present invention. It is a block diagram of a voltage command generation circuit according to an embodiment of the present invention. It is a time chart of DC motor drive equipment update by the PWM cycloconverter concerning an embodiment of the invention. It is a time chart of DC motor drive equipment renewal when not using a control device which can drive both a DC motor and an AC motor. It is a time chart of the DC motor drive equipment update by the three-phase inverter which can drive both a DC motor and an AC motor.

Explanation of symbols

1 Multiphase AC power supply 2 PWM cycloconverter 3 (AC motor control / DC motor control) selection switch 4 Main circuit wiring 5 Main circuit connection line 6 Current detector 7 (Three phase) AC motor 8 Speed detector 9 Speed detection signal line DESCRIPTION OF SYMBOLS 10 Current detection signal line 11 Main circuit connection line 12 Current detector 13 DC motor 14 Speed detector 15 Speed detection signal line 16 Current detection signal line 17 Speed detection signal input circuit 18 Current detection signal input circuit 19 Input voltage detector 20 Input Voltage detection signal input circuit 21 Converter main body 22 Control board 23 Voltage command generation circuit 24 PWM signal generation circuit 25 u-phase, v-phase, w-phase voltage command 31 Phase commander 32 Scale converter 33 Subtractor 34 Current controller 35 Adder 36 selector switch 37 0 setter 38 rotation coordinate / fixed coordinate rotation conversion unit 39 two-phase / Three-phase converter 40 Speed command unit 41 Subtractor 42 Speed controller 43 q-axis → d-axis induced voltage calculation unit 44 Subtractor 45 Current controller 46 Adder 47 d-axis → q-axis induced voltage calculation unit 48 Slip calculation unit 49 changeover switch 50 0 setter 51 adder 52 integrator 53 changeover switch 54 phase fixed setter 55 subtractor 56 three-phase / two-phase converter 57 fixed coordinate / rotary coordinate rotation converter ωslip slip frequency command θs phase Vd d axis Voltage command Vq q-axis voltage command Nfb Speed feedback signal

Claims (2)

In a PWM cycloconverter that outputs a three-phase power of a desired frequency from three main circuit wires by using a multiphase AC power supply as an input power supply and PWM controlling a converter body configured by a bidirectional switch.
A voltage command generation circuit for PWM control of the converter body ;
And a selection switch for selecting whether AC motor control or DC motor control is provided,
The voltage command generation circuit has switching means for switching the phase of the output voltage, the slip frequency command, and the d-axis voltage command in accordance with a signal from the selection switch,
When AC motor control is selected by the selection switch with all three main circuit wirings connected to a three-phase AC motor, the three-phase AC motor is driven at a variable speed, A PWM cycloconverter characterized in that the DC motor is driven at a variable speed when DC motor control is selected by the selection switch in a state where two are connected to the DC motor.   The PWM cycloconverter according to claim 1, wherein the bidirectional switch is a reverse blocking IGBT connected in reverse parallel.

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