JP2000092848A - Operating method for large number of power conversion devices - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce noise on the part of an alternating-current power supply, by controlling switching of main circuit elements through a carrier wave generator which shifts the phase or frequency of carrier waves used for PWM control for each of power conversion devices, thereby operating the power conversion devices. SOLUTION: A large number of power conversion devices 1, 5 and 6 are connected with an alternating-current power supply 4, and switching of the main circuit elements of each of the power conversion devices 1, 5 and 6 is controlled through a carrier wave generator 3 which shifts the phase or frequency of carrier waves used for sine-wave PWM control. The power conversion devices 1, 5 and 6 are operated by controlling switching of these main circuit elements. As a result, the timing of switching can be averaged to one period, and thus noises having a high peak can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a plurality of power converters connected to an AC power supply and switching main circuit elements by sine wave PWM control.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing an example of the operation of a number of power converters. In FIG. 3, a number of power converters 1, 5, and 6 are connected in parallel with an AC power supply 4, and P
A carrier generator 3 of the WM control amplifier 2 is provided.
FIG. 4 is a waveform diagram of each part of the circuit in FIG. 3, and compares the signal wave (sine wave of the AC power supply) 21 with the carrier wave 22 or 23 that is not synchronized in the power converter, and switches the main circuit element. Waveform 24 or 25 occurs. Waveform 2 as switching noise at that time
6 or 27 appears, and a waveform 28 is obtained by combining the two.

[0003]

However, such a method of operating a power converter under PWM control has the following problems. In recent years, since the main circuit element can perform high-speed switching, a high surge voltage is generated at the rising and falling edges of the switching as shown by the waveform 24 or 25 in FIG. This surge voltage is generated as noise such as the waveform 26 or 27,
The power converters 1, 5, and 6 are carriers 2 having the same phase and frequency.
When a large number of units are operated at 2 and 23, the switching timings are likely to overlap, and a surge voltage is superimposed, and a high peak noise 28 proportional to the number of units is generated. Such a high peak noise 28 appears on the AC power supply side, and adversely affects other devices. The present invention has been made in view of the above points, and an object of the present invention is to provide a method of operating a multi-unit of a power converter that reduces these effects.

[0004]

Means for achieving the object are as described in claim 1, wherein the main circuit element is connected to an AC power supply, and the main circuit element is switched with a high carrier wave by sine wave PWM control. A method of operating a plurality of power converters for generating an alternating current, wherein switching of the main circuit element is controlled by a carrier generator that changes a phase or a frequency of a carrier used for PWM control for each power converter. And a method for operating multiple power converters, wherein each power converter is operated. With such an operation method, switching timing is averaged in one cycle, and noise having a high peak is reduced. Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a system diagram showing the configuration of a main part of an embodiment in which a plurality of power converters 1, 5, and 6 according to the present invention are operated. FIG. In FIG. 1, reference numeral 2 denotes a PWM control amplifier for switching a main circuit element of the power conversion device 1, and reference numeral 3 denotes a device for distributing carrier waves having different phases and frequencies to each PWM control amplifier 2, as shown in FIG. It generates the carrier waves 22 and 23 described above.

In FIG. 2, reference numeral 21 denotes a signal wave;
Is a carrier wave for the first machine, and 23 is a carrier wave for the second machine. 24 is a main circuit output waveform switched by the signal wave 21 and the carrier wave 22, and 25 is a main circuit output waveform switched by the signal wave 21 and the carrier wave 23. 26 is a waveform of only the surge generated by the switching of the waveform 24, and 27 is a waveform of only the surge generated by the switching of the waveform 25. Also,
28 is a combined waveform of the waveforms 26 and 27. The peak of the noise waveform as one cycle on the AC power supply side is suppressed by the peak of the surge when one unit is operating.

[0007]

As described above, according to the present invention, by changing the phase or frequency of the carrier used for the PWM control of each power converter, the noise peak can be suppressed low and the noise can be actively reduced. Since a part can be canceled, noise can be reduced, and there is no need to add a main circuit component, which is extremely useful in practical use.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one example to which the present invention is applied.

FIG. 2 is a waveform showing an example to which the present invention is applied.

FIG. 3 is a configuration diagram showing one example of the related art.

FIG. 4 shows waveforms shown for explanation of the conventional art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power converter 1st unit 2 PWM control amplifier 3 Carrier generator 4 AC power supply 5 Power converter 2nd unit 6 Power converter 3rd unit 21 Signal wave 22 Carrier wave of 1st machine 23 Carrier wave of 2nd machine 24 Main unit of 1st machine Circuit waveform 25 Main circuit waveform of Unit 2 26 Noise waveform of Unit 1 27 Noise waveform of Unit 2 28 Noise waveform generated in AC power supply (Revised 98-02)

Claims (1)

[Claims] 1. A main circuit element which is connected to an AC power supply and is switched by a sine wave PWM control with a high carrier wave;
In a method of operating a large number of power converters for generating direct current or alternating current, switching of the main circuit element by a carrier generator for changing the phase or frequency of a carrier used for PWM control for each power converter. And a method for operating a plurality of power converters, wherein each power converter is operated.