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Variable PWM carrier frequency-based power grid impedance measuring method

A technology of carrier frequency and grid impedance, applied in the direction of measuring resistance/reactance/impedance, measuring devices, measuring electrical variables, etc., can solve problems such as attenuation of injected harmonic amplitude

Active Publication Date: 2018-03-09
STATE GRID JIANGSU ELECTRIC POWER CO LTD NANTONG POWER SUPPLY BRANCH +1
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  • Application Information

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Problems solved by technology

[0011] The purpose of the present invention is to provide a grid impedance measurement method based on variable PWM carrier frequency, which can effectively solve the problem that the amplitude of injected harmonics attenuates with the increase of frequency in the existing broadband harmonic injection method

Method used

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  • Variable PWM carrier frequency-based power grid impedance measuring method
  • Variable PWM carrier frequency-based power grid impedance measuring method
  • Variable PWM carrier frequency-based power grid impedance measuring method

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Embodiment Construction

[0023] A grid impedance measurement method based on variable PWM carrier frequency. In inverter PWM modulation, the carrier frequency is changed around the set frequency. By setting the change law of the carrier frequency, the harmonic amplitude is obtained from low frequency to the set frequency Carrier frequency spectrum with increasing frequency at a fixed frequency;

[0024] The frequency-changing carrier signal is used as the carrier wave of PWM modulation, and is modulated with the modulation wave generated by the inverter controller to generate a PWM signal to control the inverter switching tube. The inverter AC power thus controlled also contains multiple Carrier frequency, and the closer the frequency is to the set frequency, the greater the amplitude;

[0025] Then the inverter output voltage and current signals are sampled and analyzed to obtain grid impedance at various frequencies.

[0026] Practical application systems such as figure 1 , the dotted box is part ...

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Abstract

The invention discloses a variable PWM carrier frequency-based power grid impedance measuring method. During the PWM (pulse width modulation) of an inverter, the frequency of carriers is changed to change near a preset frequency. Through setting the change rule of the carrier frequency, a carrier frequency spectrum with gradually increased harmonic amplitude from a low frequency to a preset frequency is obtained. The carrier signals with the frequency change are used as carriers for PWM modulation, and modulated waves generated by an inverter controller are subjected to modulation together with the carrier signals so as to generate PWM signals. The PWM signals are used for controlling the switch tube of the inverter. Therefore, a plurality of carrier frequencies are included in a controlled inverter alternating-current power supply. The closer the frequency to the preset frequency, the larger the amplitude value. After that, voltage and current signals outputted by the inverter are subjected to sampling and analyzing, so that the impedance of the power grid at various frequencies can be obtained. According to the invention, the problem in the prior art that the amplitude of the injected harmonic is attenuated along with the increase of the frequency during the existing wide-frequency harmonic wave injection method is effectively solved.

Description

technical field [0001] The invention relates to a grid impedance measurement method based on variable PWM carrier frequency. Background technique [0002] Due to the extensive use of power electronic equipment in the power grid, especially the access of new energy grid-connected power generation, the grid impedance is more complex than ever. In order to maintain the stability of the power system, some grid-connected devices need to adjust control parameters based on grid impedance, for which online measurement of grid impedance is required. The harmonic injection method based on the inverter is the main way to measure the grid impedance at present. [0003] The inverter is a converter device that converts DC power into AC power. It is widely used in new energy power generation and other fields. The basic principle of the inverter is to first chop the DC power into high-frequency pulse power with different widths. These pulse widths The unequal power waveform includes low-f...

Claims

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Application Information

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IPC IPC(8): G01R27/08
CPCG01R27/08
Inventor 季晨宇张炜吉宇
Owner STATE GRID JIANGSU ELECTRIC POWER CO LTD NANTONG POWER SUPPLY BRANCH
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