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Power converting device, and control method therefor

A power conversion device and current control technology, applied in circuit devices, active power filtering, control/regulation systems, etc., can solve problems such as inability to eliminate high-order harmonic components and inability to obtain compensation effects.

Active Publication Date: 2009-04-29
HITACHI IND PROD LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Therefore, there is a problem that the high-order harmonic components flowing in the system cannot be eliminated, and a sufficient compensation effect cannot be obtained.

Method used

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  • Power converting device, and control method therefor
  • Power converting device, and control method therefor
  • Power converting device, and control method therefor

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0055] Embodiment 1 of the present invention will be described with reference to FIG. 1 .

[0056] The flicker suppression device 1 of the present invention is connected in parallel to a load 3 and connected to an AC power source 2 via a system impedance 7 . System impedance 7 refers to transmission line impedance or transformer impedance. At the connection point of the flicker suppressing device 1, if the load current fluctuates, the magnitude of the voltage drop caused by the system impedance 7 fluctuates, and voltage fluctuations, ie, flicker, occur. The flicker suppressing device of the present invention suppresses / reduces flicker caused by load current variation.

[0057] The flicker suppression device 1 is composed of a main circuit unit and a control calculation unit 100 . The main circuit is composed of a power converter 4 composed of an IGBT and a diode, a filter reactor (reactor) 5, and a DC capacitor 6. The AC output terminal of the power converter 4 is connected ...

Embodiment 2

[0112] Embodiment 2 of the present invention will be described with reference to FIG. 2 .

[0113] This embodiment differs from Embodiment 1 in that a filter for phase correction is provided in the output of the DFT calculator. By installing a filter for phase correction, the response delay to the fluctuation of the fundamental wave amplitude of the load current in the normal phase and reverse phase can be improved.

[0114] In the following, only the configurations different from the previous embodiment will be described. In addition, in FIG. 2 , the same function parts as those in FIG. 1 are denoted by the same reference numerals unless otherwise mentioned, and the description thereof will not be repeated.

[0115] The advantages of the forward-phase DFT calculator 107 and the reverse-phase DFT calculator 109 are that they extract the forward-phase fundamental component and the reverse-phase fundamental component respectively, and can remove high-order harmonic components, ...

Embodiment 3

[0133] Embodiment 3 of the present invention will be described with reference to FIG. 6 .

[0134] The difference between this embodiment and Embodiment 1 is that in addition to the fundamental wave, a second-order DFT is provided to calculate the amplitude and phase of the second-order higher harmonic component and add it to the current command value.

[0135] If it is a harmonic with a low order, the delay of current control is small. Therefore, not only the fundamental wave, but also the compensation current for specific higher harmonics can be output. For example, when the current control response is set to 1000rad / s, the cutoff frequency is 160Hz, so when the system frequency is 60Hz, the current control characteristics can be guaranteed to the level of the second harmonic. In this embodiment, the specific harmonic is assumed to be the second harmonic.

[0136]Hereinafter, only structures different from the previous embodiment will be described. In addition, in FIG. 5 ...

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PUM

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Abstract

In a flicker suppressing device for suppressing flickers by detecting a load current and outputting the current of the opposite phase, the load current may contain higher harmonics. In this case, the phase of the higher harmonic components to be outputted by the flicker suppressing device may be delayed by the current control delay, and the higher harmonic current of the load may be unable to be canceled, but the higher harmonics may be increased on the contrary. By the Fourier series expansion, therefore, the fundamental wave component amplitude of the load current is calculated to calculate the current command value of the flicker suppressing device on the basis of the calculated amplitude, so that the output current of the flicker suppressing device is controlled according to that current command value. By calculating the current command value from the Fourier series coefficient, the frequency component several times as high as the system frequency can be eliminated from the current command value, so that the flicker suppressing device can reduce the higher harmonics to flow out therefrom while suppressing the flickers.

Description

technical field [0001] The present invention relates to a power conversion device connected to an AC system, and more particularly to a power conversion device that suppresses voltage fluctuations (flicker) caused by load fluctuations. Background technique [0002] If the load connected to the system fluctuates, the voltage drop due to the impedance of the transmission line or the transformer fluctuates, and a voltage fluctuation (flicker) occurs at the connection point of the load. [0003] For example, Japanese Patent No. 2675206 proposes a flicker suppression device that suppresses flicker. [0004] The above-mentioned device calculates the effective current and the reactive current according to the load current, calculates the positive phase by implementing a low-pass filter, and calculates the reverse phase by implementing a high-pass filter. By outputting a current in reverse phase to the detected load current, fluctuations in the current flowing from the system are e...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G05F1/70H02J3/01H02J3/16
CPCH02J3/1842Y02E40/22Y02E40/20
Inventor 伊藤智道古关庄一郎清藤康弘相原孝志加藤修治
Owner HITACHI IND PROD LTD