JP2003244960A - PWM cyclo converter - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To improve the input current waveform by suppressing the resonance current of a PWM cycloconverter. Also, surge energy generated at the time of switching of the bidirectional semiconductor switching elements constituting the main circuit of the PWM cycloconverter is regenerated to the power system. Each phase of an AC power supply and each phase on an output side are directly connected by a bidirectional switch having a self-extinguishing ability, and PWM control of an AC power supply voltage is performed according to an output voltage command, so that arbitrary AC and DC A PWM cycloconverter for outputting a voltage has a PWM converter device connected to a DC voltage system, and an output part of the PWM converter device is connected to an input power supply side of the PWM cycloconverter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a PWM converter connected to the input section of a PWM cycloconverter to realize an arbitrary current waveform and improve input current of a PWM cycloconverter for suppressing input current distortion. It is about.

[0002]

2. Description of the Related Art A PWM cycloconverter is an AC-A that directly converts a three-phase AC power supply voltage into an arbitrary voltage / frequency.
C direct power converter. In principle, the PWM cycloconverter causes a pulsed current to flow through the input portion of the power semiconductor element. In order to prevent the pulse current from being returned to the power supply system, a low pass filter is generally provided using an AC reactor and an AC capacitor. However, when a current flows through the filter, the reactor and the capacitor cause a resonance phenomenon, and a resonance current flows through the input section. Due to this resonance current, the distortion rate of the input current deteriorates. Also, PW
Even when the M cycloconverter is not operating, a resonance current is generated because a current flows through the capacitor and a current flows. As a conventional example of a method for suppressing this resonance current, AC
There is a method of providing a resistor in parallel with the reactor for damping. This conventional example is shown in FIG. In FIG.
1 is a 3-phase AC power supply, 2 is a 3-phase AC reactor, 3 is a 3-phase AC capacitor, 4 is a bidirectional switch group, 5 is a motor,
18 is a damping resistor. Next, the configuration will be described so that the connection relationship in FIG. 6 can be understood. Damping resistor 18
Is connected in parallel with the three-phase AC reactor 2. One end of the damping resistor 18 is connected to the three-phase AC power supply, and the other end is connected to the three-phase AC capacitor 3. Three-phase AC capacitor 3
The other end of is connected to each phase terminal on the input side (power supply side) of the bidirectional switch group 4. The output terminal side (load side) of the bidirectional switch group 4 is connected to the motor 5 serving as a load. The three-phase AC reactors 2 and 3 are three-phase AC capacitors that form an LC low-pass filter. The damping resistor 18 consumes the input current harmonic component as a loss.

[0003]

However, in the above-described damping method using the resistor, a loss occurs because the damping is performed by using the heat loss of the resistor, the energy efficiency is deteriorated, and the PWM which is the power converter is used. It also affects the life of the cycloconverter. The present invention has been made in view of the above problems, and its objects are (1) suppressing the resonance current of the PWM cycloconverter and improving the input current waveform, and (2) providing a main circuit of the PWM cycloconverter. The purpose is to regenerate the surge energy generated at the time of switching of the bidirectional semiconductor switching element to be regenerated into the power system.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention directly connects each phase of an AC power supply and each phase on the output side with a bidirectional switch having a self-extinguishing capability to output an output voltage command. In a PWM cycloconverter that PWM-controls an AC power supply voltage in accordance with the above, and outputs arbitrary AC and DC voltages, a PWM converter device connected to a DC voltage system is provided, and an output unit of the PWM converter device is the PW.
It is connected to the input power source side of the M cycloconverter. Further, a diode rectifying device for full-wave rectifying the input voltage of the PWM cycloconverter, a smoothing capacitor for smoothing a DC voltage created by the diode rectifying device, and a smoothing voltage detecting device for detecting a smoothing voltage of the smoothing capacitor. It is characterized by having.
In addition, one or more snubber devices connected to the input / output terminals of the power semiconductor element of the PWM cycloconverter and provided with a diode and a capacitor, and a snubber voltage detection device for detecting the voltage across the snubber capacitor. It is characterized by that. In addition, each phase of the AC power supply and each phase on the output side are directly connected by a bidirectional switch having a self-extinguishing capability, and the AC power supply voltage is PWM-controlled according to the output voltage command to output any AC and DC voltage. P to output
In the controller of the WM cycloconverter, the PW
An input current detection device that detects one or more input currents of the M cycloconverter and a current command of the PWM converter device are created from the input current signal obtained by the input current detection device, and arbitrary input current waveform control is performed. And a control means for performing the control. In addition, the P
One or more correction currents of the WM converter device are detected, a current command of the PWM converter device is created from the correction current obtained by the correction current detection device and the input current signal, and arbitrary input current waveform control is performed. And a control means for performing the control. INDUSTRIAL APPLICABILITY The present invention makes it possible to regenerate the surge energy generated at the time of switching to the power system, and also to shape the waveform of the input current.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to specific examples. FIG. 1 shows a PW for implementing the present invention.
1 shows a system configuration using a PWM converter using an M cyclo converter and a DC voltage source. FIG. 2 shows a system configuration of a PWM cycloconverter and a PWM converter using a diode rectifier circuit for implementing the present invention. FIG. 3 shows a system configuration of a PWM converter using a DC voltage source made up of a PWM cycloconverter and a snubber circuit for carrying out the present invention. FIG. 4 shows an example of a snubber circuit configuration diagram for implementing the present invention. FIG. 5 shows an example of a snubber circuit configuration diagram for implementing the present invention.

First, referring to FIG. 1, the PWM cycloconverter is directly connected between the three-phase AC power source 1 and the three-phase output which is the input current of the motor 5 by using a total of nine bidirectional semiconductor switch groups 4, and the AC An arbitrary frequency and voltage can be output without converting the power supply voltage to DC. However, a pulsed current flows through the input stage of the bidirectional semiconductor switch group 4. Therefore, a filter is created using the three-phase AC reactor 2 and the three-phase AC capacitor 3. According to the present invention, the DC power supply 8 which is a DC voltage system power supply is provided separately from the AC power supply 1, the small PWM converter 7 is provided therein, and the current is supplied to the input portion of the PWM cycloconverter. The resonance current due to the filter can be suppressed. As the current suppressing means, the input current signal 9 detected by using the current detecting CT 10 is input to the control unit of the PWM converter 7, and compared with an arbitrary current waveform desired to be realized by the PWM cycloconverter. An ideal input current waveform is realized by supplying it.

By detecting the correction current signal 12, the control performance can be improved. As an example of the correction method, when the controlled object is only the resonance current in the harmonic components of the input current, the resonance current can be suppressed by comparing the input current signal 9 with the ideal sine wave and applying the correction current from the PWM converter 7. realizable. In this case, the resonance current depends on the design of the filter, but the current value is sufficiently smaller than the total input current. Therefore, the PWM converter 7
Therefore, the current capacity can be small, and the cost is low.

In FIG. 2, instead of the DC power supply 8 in FIG. 1, a three-phase full-wave rectification is performed using a diode rectifier 13 and a smoothing capacitor 14 is used to drive the PWM converter 7 using a smoothed DC power supply. Is. First, when the PWM output is performed by the bidirectional switch group 4, the three-phase AC reactor 2
And a resonance phenomenon occurs due to the three-phase AC capacitor 3, and the voltage of the three-phase AC capacitor 3 is greatly disturbed. Next, this resonance voltage is rectified by the diode rectifier 13 and stored in the smoothing capacitor 14. And PWM by the energy
The converter 7 is used to suppress the resonance current of the three-phase AC capacitor 3. That is, the resonance energy of the input filter can be absorbed, the resonance current can be suppressed by the energy, and the distortion of the input current can be improved.

FIG. 3 shows a DC clamp type snubber circuit 1 in place of the DC power source 8 shown in FIG. 1 and the diode rectifier 13 shown in FIG.
5 is used. A DC clamp type snubber circuit may be used as a protection device for a bidirectional semiconductor switch in a PWM cycloconverter. The circuit configuration of the snubber circuit 15 in FIG. 3 is shown in FIGS. 4 and 5, and configurations such as the snubber diode group 16 and the snubber diode group 17 are conceivable. By using this snubber circuit 14 as the DC power supply voltage of the PWM converter 7 of the present patent, the energy due to the surge generated at the time of switching can be used as a correction current without wasting, and higher efficiency can be realized in the entire system. . By using this patent, higher performance input current control can be realized without causing a loss in such resistance.

[0010]

As described above, according to the present invention, each phase of the AC power supply and each phase on the output side are directly connected by a bidirectional switch having a self-extinguishing capability, and the AC power supply voltage is changed according to the output voltage command. In a PWM cycloconverter that PWM-controls and outputs arbitrary AC and DC voltages, the PWM cycloconverter has a PWM converter device connected to a DC voltage system, and the output unit of the PWM converter device is connected to the input power source side of the PWM cycloconverter. Since the connection is made, it is possible to suppress the resonance current of the PWM cycloconverter and easily improve the input current waveform. Moreover, the surge energy generated at the time of switching of the bidirectional semiconductor switching element forming the main circuit of the PWM cycloconverter can be regenerated to the power system. Originally, the PWM cycloconverter can control the input current waveform in principle.
However, since the output section is directly connected by the bidirectional semiconductor switch, the output current must be controlled at the same time. Therefore, the input current control performance is restricted. This patent relates to an auxiliary device for enhancing the control performance of such a PWM cycloconverter, and input current control can be easily realized by diverting a general PWM converter.

[Brief description of drawings]

FIG. 1 shows a system configuration using a PWM cycloconverter and a PWM converter using a DC voltage source for implementing the present invention.

FIG. 2 shows a system configuration of a PWM cycloconverter and a PWM converter using a diode rectifier circuit for implementing the present invention.

FIG. 3 shows a system configuration of a PWM converter using a DC voltage source formed by a PWM cycloconverter and a snubber circuit for implementing the present invention.

FIG. 4 shows an example of a snubber circuit configuration diagram for implementing the present invention.

FIG. 5 shows an example of a snubber circuit configuration diagram for implementing the present invention.

FIG. 6 shows an example of a conventional PWM cycloconverter system configuration and suppression of filter resonance.

[Explanation of symbols]

1 3-Phase AC Power Supply 2 3-Phase AC Reactor 3 3-Phase AC Capacitor 4 Bidirectional Switch Group 5 Motor 6 3-Phase AC Reactor 7 PWM Converter 8 DC Voltage Source 9 ₁ , 9 ₂ , 9 ₃ Input Current Signal 10 CT for Current Detection 11 CT for Current Detection 12 _{1 to} 12 ₃ Correction Current Signal 13 Diode Rectifier 14 Smoothing Capacitor 15 ₁ to 15 ₉ Snubber Circuit 16 Snubber Diode Group 17 Snubber Diode Group 18 Damping Resistance

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Eiji Watanabe             2-1, Kurosaki Shiroishi, Hachiman Nishi-ku, Kitakyushu City, Fukuoka Prefecture               Yasukawa Electric Co., Ltd. (72) Inventor Jun Koyama             1-14 Bunkyo-cho, Nagasaki-shi, Nagasaki Nagasaki University             Undergraduate F-term (reference) 5H750 AA02 AA03 AA09 BA01 BA06                       BB12 CC08 CC14 CC16 DD07                       FF02 GG02

Claims (5)

[Claims] 1. Each phase of an AC power supply and each phase on the output side are directly connected by a bidirectional switch having a self-extinguishing capability, and the AC power supply voltage is PWM-controlled in accordance with an output voltage command so that any AC and A PWM cycloconverter for outputting a DC voltage, comprising a PWM converter device connected to a DC voltage system, wherein an output part of the PWM converter device is connected to an input power source side of the PWM cycloconverter. converter. 2. A diode rectifying device for full-wave rectifying an input voltage of the PWM cycloconverter, a smoothing capacitor for smoothing a DC voltage created by the diode rectifying device, and a smoothing voltage for detecting a smoothing voltage of the smoothing capacitor. The PWM according to claim 1, further comprising a detection device.
Cyclo converter. 3. One or more snubber devices connected to the input / output terminals of a power semiconductor element of the PWM cycloconverter, each including a diode and a capacitor, and a snubber voltage detection device for detecting a voltage across the snubber capacitor. The PWM cycloconverter according to claim 1, further comprising: 4. Each phase of the AC power supply and each phase on the output side are directly connected by a bidirectional switch having a self-extinguishing capability, and the AC power supply voltage is PWM-controlled in accordance with the output voltage command so that any AC and A PWM cycloconverter control device that outputs a DC voltage, comprising: an input current detection device that detects one or more input currents of the PWM cycloconverter; and an input current signal obtained by the input current detection device. And a control means for performing arbitrary input current waveform control. 5. A current command for the PWM converter device is created from one or more correction currents of the PWM converter device and the correction current obtained by the correction current detection device and the input current signal. 5. A control means for performing arbitrary input current waveform control is provided.
The described PWM cycloconverter.