JP2009159708A - Frequency converter and frequency conversion method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a frequency converter and a frequency conversion method, which omits a motor for rotation speed control of a frequency converter, or reduces the output of a motor for rotation speed control of a frequency converter. <P>SOLUTION: A frequency converter for converting power of some frequency into power of other frequency comprises: a rotary frequency converter having a stator winding, a rotor winding, and a rotor; a high frequency side power supply circuit connected with the stator winding of the rotary frequency converter; a low frequency side power supply circuit connected with the rotor winding of the rotary frequency converter; a braking apparatus connected mechanically with the rotor shaft of the rotary frequency converter; and a controller for generating a desired frequency from the rotor winding of the rotary frequency converter by controlling the braking force of the braking apparatus, and controlling the rotational speed of the rotary frequency converter. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a frequency conversion device that converts electric power of a certain frequency into electric power of another frequency, and more particularly to a rotary frequency conversion device and a frequency conversion method.

  A typical example of the rotational frequency conversion system is an induction asynchronous frequency converter described in Non-Patent Document 1 (see Non-Patent Document 1).

  In this method, the rotational speed of a rotary type (hereinafter referred to as “rotary type”) frequency converter is controlled by an electric motor directly connected to the frequency converter, and a desired frequency is determined from the rotor winding of the frequency converter. It is a method to obtain. The principle will be described below.

If the voltage frequency of the stator winding of the frequency converter is f1 Hz, the mechanical frequency of the magnetic pole of the rotor of the frequency converter is frHz, and the voltage frequency of the rotor winding of the frequency converter is f2 Hz,
f2 = f1-fr
There is a relationship. Therefore, f2 can be controlled by controlling fr.

Moreover, the electrical input of the stator of the frequency converter is P1, the mechanical output of the rotor of the frequency converter is Pr, and the electrical output of the rotor winding of the frequency converter is P2, and there is no loss of the frequency converter for convenience. Assuming
P2 = P1-Pr
From this,
Pr = P1 * (fr / f1) = P1 * {(f1-f2) / f1}
There is a relationship.

  For example, in a system in which a power supply frequency is 50 Hz, a load frequency is 0 to 50 Hz, and a load such as a power supply is connected to a motor or the like, when f1 = 50 Hz and f2 = 5 Hz, fr = 45 Hz and Pr = P1 × 0.9. The output of the motor for controlling the rotational speed of the frequency converter is as large as 90% of the output of the frequency converter.

  As a similar example using this method, “interconnection system of electric systems having different electric characteristics” is disclosed (see Patent Document 1).

  This interconnection system relates to an interconnection system that links power system A and power system B for the purpose of controlling power flow, and the frequency difference between power system A and power system B is usually within 1 Hz. The rotational speed fr of the rotor is a system controlled within 2% of the rotational speed f1 (50 Hz) of the rotating magnetic field of the stator.

Therefore, there is no disclosure of the above-described system for connecting a power source and a load such as an electric motor with a power frequency of 50 Hz and a load frequency of 0 to 50 Hz.
The Institute of Electrical Engineers of Japan Electrical Equipment Engineering I (for example, October 20, 1978, 24th edition) 3.19.5 JP 9-23651 A

  As described above, in the conventional method, when a low frequency lower than the power supply frequency (for example, 0 to 50 Hz) is required, the output of the rotation speed control motor of the frequency converter is the same as the output of the frequency converter. As a whole, the size of the frequency converter is increased, and the circuit configuration is complicated.

  In addition, when a semiconductor power conversion device is used for the rotation speed control of the motor for controlling the rotation speed of the frequency converter, the capacity of the semiconductor power conversion device is increased, the amount of generated harmonics is large, and the power system is adversely affected. In addition, the size of the semiconductor power conversion device is increased, and the installation space is increased.

  The present invention has been made in view of the above circumstances, and it is possible to omit the rotation speed control motor of the frequency converter or to reduce the output of the rotation speed control motor of the frequency converter. An object is to provide a conversion device and a frequency conversion method.

  In order to solve the above problems, a frequency conversion device according to claim 1 of the present invention is a frequency conversion device that converts power of one frequency into power of another frequency, in which a stator winding, a rotor winding, and A rotary frequency converter having a rotor, a high-frequency power circuit connected to the stator winding of the rotary frequency converter, and a low-frequency electric connected to the rotor winding of the rotary frequency converter The rotational frequency of the rotary frequency converter by controlling the rotational speed of the rotary frequency converter by controlling the circuit, the braking device mechanically connected to the rotor shaft of the rotary frequency converter, and the braking force of the braking device And a braking device control device that generates a desired frequency from the rotor winding of the converter.

  According to a second aspect of the present invention, there is provided the frequency converter according to the first aspect, wherein the gear is connected between the rotor shaft of the rotary frequency converter and the braking device. A mechanism is provided.

  According to a third aspect of the present invention, there is provided a frequency conversion device according to the second aspect, wherein the frequency conversion device is a gear mechanism composed of a spur gear and a worm gear, and a braking device. An electric motor connected to the worm gear and an electric motor control device that controls the rotational speed of the electric motor are provided.

  According to a fourth aspect of the present invention, there is provided the frequency converter according to the third aspect, wherein the motor, a newly added braking device, and a frequency generated by the rotary frequency converter are provided. A motor control device that increases the rotational speed of the motor, and a brake device control device that increases the braking force of the brake device when increasing the frequency generated by the rotary frequency converter. It is characterized by providing.

  According to a fifth aspect of the present invention, there is provided a frequency conversion method according to the fifth aspect of the present invention, wherein the frequency conversion method converts power of one frequency into power of another frequency, and includes a stator winding, a rotor winding and a rotor shaft. A rotary frequency converter, a braking device mechanically connected to a rotor shaft of the rotary frequency converter, a control device for a braking device for controlling the braking force of the braking device, and a rotary frequency converter A high-frequency power circuit connected to the stator winding and a low-frequency electric circuit connected to the rotor winding of the rotary frequency converter, and rotating by controlling the braking force of the braking device The rotational frequency of the type frequency converter is controlled, and the power supply frequency generated from the rotor winding of the rotary type frequency converter is controlled to a desired frequency.

  A frequency conversion method according to claim 6 of the present invention is the frequency conversion method according to claim 5, wherein the gear is connected between the rotor shaft of the rotary frequency converter and the braking device. It further has a mechanism.

  A frequency conversion method according to a seventh aspect of the present invention is the frequency conversion method according to the sixth aspect, wherein a gear mechanism including a spur gear and a worm gear is used instead of the braking device. The motor connected to the worm gear and the rotational speed of the motor by controlling the rotational speed of the motor to control the power frequency generated from the rotor winding of the frequency converter to a desired frequency It is characterized by doing.

  In addition, a frequency conversion method according to an eighth aspect of the present invention is the frequency conversion method according to the seventh aspect, comprising an electric motor and the newly added braking device, and a first-stage rotary frequency converter. When the frequency generated is reduced, the rotational speed of the electric motor is increased, and when the frequency generated by the rotary frequency converter is increased, the braking force of the braking device is increased to increase the frequency converter. The frequency generated from the rotor winding is controlled to a desired frequency.

  According to the frequency conversion device and the frequency conversion method of the present invention, the rotation speed control motor of the frequency converter can be omitted or the output of the rotation speed control motor of the frequency converter can be reduced. Moreover, when using a semiconductor power converter for speed control of the electric motor for rotational speed control of a frequency converter, the output of a semiconductor power converter can be reduced and the amount of harmonics can be reduced.

  A frequency conversion device and a frequency conversion method according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a configuration diagram of a frequency conversion device 10 according to the first embodiment of the present invention.
FIG. 1 shows a first electric circuit 101 and a second electric circuit 102 connected to the frequency converter 10.

  The frequency converter 10 includes a rotary frequency converter 20, a gear mechanism 30 connected to the rotor shaft 27 of the rotor 26 of the rotary frequency converter 20, a braking device 40 connected to the gear mechanism 30, A braking device control device 41 for controlling the braking force of the braking device 40; an electric motor 50 connected to the gear mechanism 30 via the braking device 40; an electric motor control device 51 for controlling the rotational speed of the electric motor 50; The frequency measuring device 103 detects the frequency 104 of the second electric circuit 102 and the frequency setting unit 105 sets the frequency command value 106 of the second electric circuit 102.

  The rotary frequency converter 20 has a structure similar to that of a winding induction motor, and includes a stator winding (primary winding) 21 and a rotor winding (secondary winding) 22.

  The gear mechanism 30 includes a spur gear 31 and a worm gear 32. The spur gear 31 is connected to the rotor shaft 27 of the rotary frequency converter 20, and the worm gear 32 includes a braking device 40 and an electric motor 50. It is connected to the.

  The braking device 40 includes, for example, a brake disc, a caliber, and a brake pad.

  A frequency signal 104 measured by the frequency measuring device 103 and a frequency command value 106 set by the frequency setting unit 105 are input to the braking device control device 41 and the motor control device 51.

  The braking device control device 41 calculates the optimum braking force of the braking device 40 from the frequency command value 106 and the frequency signal 104, and controls the braking force of the braking device 40 based on the calculation result.

  The motor control device 51 calculates the optimum rotation speed of the electric motor 50 from the frequency command value 106 and the frequency signal 104, and controls the rotation speed of the electric motor 50 based on the calculation result.

The operation of the frequency conversion device 10 configured as described above will be described below.
The rotor winding (secondary winding) 22 of the rotary frequency converter 20 has a frequency f2 determined from the frequency f1 of the stator winding 21 and the frequency fr of the rotor 26 on the same principle as that of the winding induction motor. appear. In the case of f1> f2, a rotational force is generated in the rotor 26 by the rotating magnetic field generated in the stator winding 21 on the same principle as that of the winding induction motor.

  The frequency f1 of the stator winding 21, the frequency fr of the rotor 26, and the frequency f2 of the rotor winding 22 have the following relationship.

f2 = f1-fr
If the rotational speed of the rotor 26 is controlled and the frequency fr of the rotor 26 corresponding to this is controlled, the value of the frequency f2 of the rotor winding 22 can be controlled.

When the frequency f2 of the frequency signal 104 detected by the frequency measuring device 103 is higher than the frequency f1 of the frequency command value 106, the braking device control device 41 sets the braking device 40 of the braking device 40 to bring f2 close to f1. The braking force is weakened and the frequency fr of the rotor 26 is increased. In addition, the motor control device 51 accelerates the rotation speed of the motor 50. Thus, when the braking force of the braking device 40 is weakened and the rotational speed of the electric motor 50 is accelerated, the rotational speed fr of the rotor 26 is accelerated and the frequency f2 of the rotor winding 22 is decreased.

  Conversely, when the frequency f2 of the frequency signal 104 detected by the frequency measuring device 103 is lower than the frequency f1 of the frequency command value 106, the braking device control device 41 performs braking to bring f2 closer to f1. The braking force of the device 40 is increased and the frequency fr of the rotor 26 is reduced. Further, the motor control device 51 decelerates the rotation speed of the motor 50. In this way, when the braking force of the braking device 40 increases and the rotational speed of the electric motor 50 decreases, the rotational speed fr of the rotor 26 decreases and the frequency f2 of the rotor winding 22 increases.

  As described above, based on the frequency signal 104 detected by the frequency measuring device 103, the braking device control device 41 controls the braking force of the braking device 40, and the motor control device 51 controls the rotational speed of the motor 50. Since the rotation speed of the rotor 26 can be controlled, the frequency f2 of the rotor winding 22 can be controlled to the value of the frequency command value 106.

  Next, the output reduction effect of the electric motor 50 in the frequency converter of the present invention will be described.

  A rotating force is generated in the rotor 26 by the rotating magnetic field of the stator winding 21. However, since the worm gear 32 connected to the electric motor 50 is used for the gear mechanism 30, the worm gear 32 and the spur gear 31 do not rotate and the rotor 26 does not rotate when the electric motor 50 is stopped.

  When the electric motor 50 is rotated, the worm gear 32 and the spur gear 32 are rotated, and the rotor 26 is also rotated. Originally, a rotational force is generated in the rotor 26 by the rotating magnetic field of the stator winding 21, so that the output that the electric motor 50 must generate in order to rotate the rotor 26 is the worm gear 42 and the spur gear 41. Only the amount of frictional force is sufficient.

On the other hand, when the rotor 26 is decelerated, since the braking device 40 is used, the electric motor 50 does not need to generate a force in the braking direction. Therefore, the output of the electric motor 50 is only an output determined from the frictional force of the worm gear 42 and the spur gear 41.

  As described above, according to the frequency converter according to the first embodiment, the output of the electric motor 50 can be significantly reduced as compared with the method of directly connecting the rotor of the rotary frequency converter and the electric motor shown in the conventional example. Can do.

Further, when a semiconductor power conversion device is used for the motor control device 51, the output of the semiconductor power conversion device can be greatly reduced, so that the amount of harmonics generated from the semiconductor power conversion device is also greatly reduced. can do.

In the first embodiment, an example in which a worm gear is used as the gear has been described. However, the type of gear is not limited to the worm gear, and other types of gears can be used. Further, the present invention can be realized by using speed change means other than gears, such as gears and chains, pulleys and belts, and rubber rollers.

  The second embodiment is a first modification of the first embodiment. As shown in FIG. 2, the second embodiment is configured without the braking device 40 and the control device 41 of the braking device 40 in FIG. 1.

  In the second embodiment, the electric motor 50 generates a braking force instead of the braking device 40 and decelerates the rotational speed of the rotor 26. For convenience, assuming that the transmission efficiency from the spur gear 31 to the worm gear 32 is 20%, the output of the electric motor 50 may be 20% of the shaft output of the rotor 26.

  In the second embodiment, the output of the electric motor 50 can be greatly reduced only by using the gear mechanism 30 as compared with the conventional method in which the rotor of the rotary type frequency converter and the electric motor are directly connected. .

  In the second embodiment, an example in which a worm gear is used as the gear has been described. However, the type of gear is not limited to the worm gear, and other types of gears can be used. Further, the present invention can be realized by using speed change means other than gears, such as gears and chains, pulleys and belts, and rubber rollers.

  The third embodiment is a second modification of the first embodiment. As shown in FIG. 3, the third embodiment has a configuration without the electric motor 50 and the electric motor control device 51, and the structure of the gear mechanism 30. Using a reversible drive worm gear capable of driving the worm gear 32 from the spur gear 31 to transmit the rotational force of the spur gear 31 on the rotor 26 side to the worm gear 32 on the braking device 40 side. It is.

The rotor 26 can be accelerated by weakening the braking force of the braking device 40, while the rotor 26 can be decelerated by increasing the braking force.

Thus, in Example 3, the electric motor 50 and the electric motor control apparatus 51 can be abbreviate | omitted, and a frequency converter can be simplified.

In the third embodiment, the worm gear is used as the gear. However, the type of the gear is not limited to the reversible drive worm gear, and other types of reversible drive gear can be used. Further, the present invention can be realized by using reversible transmission means other than gears, such as gears and chains, pulleys and belts, and rubber rollers.

  The fourth embodiment is a third modification of the first embodiment. As shown in FIG. 4, the fourth embodiment has a configuration without the gear mechanism 30, the motor 50, and the motor control device 51 in FIG. 1. Similarly to the second modification, the rotor 26 can be accelerated by weakening the braking force of the braking device 40, and the rotor 26 can be decelerated by increasing the braking force.

  In the present embodiment, the gear mechanism 30, the electric motor 50, and the electric motor control device 51 can be omitted, and the frequency conversion device can be simplified.

  In addition, this invention is not limited to each Example demonstrated above as it is, A component can be deform | transformed and embodied in the range which does not deviate from the summary in an implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, as described above, some components may be deleted from all the components shown in the first embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

It is a schematic block diagram of the frequency converter which concerns on Example 1 of this invention. It is a schematic block diagram of the frequency converter which concerns on Example 2 of this invention. It is a schematic block diagram of the frequency converter which concerns on Example 3 of this invention. It is a schematic block diagram of the frequency converter which concerns on Example 4 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Frequency converter, 20 ... Rotary type frequency converter, 21 ... Stator winding, 22 rotor winding, 26 ... Rotor, 27 ... Rotor shaft, 30 ... Gear mechanism, 31 ... Spur gear, 32 ... Worm gear, 40 ... braking device, 41 ... braking device control device, 50 ... electric motor, 51 ... electric motor control device, 101 ... first electric circuit, 102 ... second electric circuit, 103 ... frequency measuring device, 104 ... frequency signal, 105 ... frequency setter, 106 ... frequency command value.

Claims (8)

In a frequency converter that converts power at one frequency to power at another frequency,
A rotary frequency converter having a stator winding, a rotor winding and a rotor shaft;
A high frequency power supply circuit connected to the stator winding of the rotary frequency converter;
A low frequency electrical circuit connected to the rotor winding of the rotary frequency converter;
A braking device mechanically connected to the rotor shaft of the rotary frequency converter;
A control device for a braking device that controls the braking force of the braking device to control the rotational speed of the rotary frequency converter in order to generate a desired frequency from the rotor winding of the rotary frequency converter; ,
A frequency conversion device comprising:   The frequency converter according to claim 1, further comprising a gear mechanism connected between a rotor shaft of the rotary frequency converter and the braking device. The gear mechanism comprising a spur gear and a worm gear;
An electric motor connected to the worm gear instead of the braking device;
The frequency converter according to claim 2, further comprising: a motor control device that controls a rotation speed of the motor. The electric motor;
The braking device newly added;
When lowering the frequency generated by the rotary frequency converter, a motor control device for increasing the rotational speed of the motor;
The frequency converter according to claim 3, further comprising a braking device controller that increases a braking force of the braking device when the frequency generated by the rotary frequency converter is increased. In a frequency conversion method for converting power at one frequency to power at another frequency,
A rotary frequency converter having a stator winding, a rotor winding and a rotor shaft; a braking device mechanically connected to the rotor shaft of the rotary frequency converter; and a braking force of the braking device. A control device for a braking device to control;
A high frequency power circuit connected to the stator winding of the rotary frequency converter;
A low frequency electric circuit connected to the rotor winding of the rotary frequency converter,
By controlling the braking force of the braking device, the rotational speed of the rotary frequency converter is controlled, and the power supply frequency generated from the rotor winding of the rotary frequency converter is controlled to a desired frequency. A frequency conversion method characterized by that.   The frequency conversion method according to claim 5, further comprising a gear mechanism connected between a rotor shaft of the rotary frequency converter and the braking device.   The motor comprising: a gear mechanism comprising a spur gear and a worm gear; an electric motor connected to the worm gear instead of the braking device; and a motor control device for controlling the rotational speed of the electric motor. The power supply frequency generated from the rotor winding of the frequency converter is controlled to a desired frequency by controlling the rotational speed of the frequency converter by controlling the rotational speed of the frequency converter. Frequency conversion method. The electric motor and the newly added braking device,
When lowering the frequency generated by the rotary frequency converter, the rotational speed of the electric motor is increased,
The frequency conversion method according to claim 7, wherein when the frequency generated by the rotary frequency converter is increased, a braking force of the braking device is increased.

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