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Single-phase harmonic current detecting method

A technology of harmonic current and detection method, applied in the field of power system, can solve problems such as difficult to simulate circuit implementation

Active Publication Date: 2009-07-29
SHENZHEN SINEXCEL ELECTRIC
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  • Abstract
  • Description
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  • Application Information

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Problems solved by technology

But this scheme needs a pure hysteresis link to construct the three-phase current, which is difficult to realize with an analog circuit
Even if it is implemented with a digital circuit, the construction of a three-phase current circuit itself will cause a delay of at least 120 degrees

Method used

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Embodiment Construction

[0063] In view of the shortcomings of time delay caused by FFT (Fast Fourier Transform) harmonic detection and three-phase current construction technology based on instantaneous power theory in the prior art, the present invention proposes a new single-phase current harmonic detection method. Suppose the measured current is i s ,

[0064] (Formula 1)

[0065] Among them, ω is the grid frequency, θ is the fundamental phase of the grid current, and I m is the fundamental amplitude, I n is the nth harmonic amplitude, is the phase of the nth harmonic, n is a natural number, and n≥2.

[0066] By the following formula 2a

[0067] i a = x + i s i b = y ...

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Abstract

The invention relates to a single-phase harmonic current detection method, including the following steps: a. the detected current i(s) is sampled and three-phase current i(a), i(b), i(c) is constructed; b. the three-phase current is converted in a rotating coordinate system for obtaining a d-axis component i(d) and a q-axis component i(q); c. i'(d) and i'(q), the straight current components of i(d) and i(q), are obtained when i(d) and i(q) pass through a low-pass filter; d. by coordinate conversion of i'(d) and i'(q), i'(a), i'(b), and i'(c), three components of the three-phase coordinate system, are obtained; e. according to at least one component among i'(a), i'(b), and i'(c), i(sf), the fundamental component of i(s), is obtained; and f. i(sh), the harmonic component of i(s) is obtained by the subtraction of i(sf) and i(s). The single-phase harmonic current detection method provided by the invention does not need to do any delay treatment to the detected current i(s), can decompose the fundamental component and the harmonic component of the detected current in real time, and greatly reduces the cost of CPU and memory.

Description

technical field [0001] The invention relates to a power system, more specifically, to a detection method for harmonic current in the power system. Background technique [0002] With the development of modern industrial technology, there are more and more various power electronic switching devices in the power system. The switching action of these power electronic devices injects a large number of harmonic components into the grid, resulting in severe distortion of the voltage and current waveforms in the AC grid. The decline of power quality directly affects the safe operation of power supply and electrical equipment. Active power filter is an effective tool to suppress harmonics in power grid. [0003] figure 1 Shown is a schematic diagram of an active power filter. In the figure, i load represents the load current, i a is the supply current, U a is the supply voltage, i sf is the fundamental component of the load current, i sh is the harmonic component of the load...

Claims

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Application Information

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IPC IPC(8): G01R19/00
Inventor 冼成瑜
Owner SHENZHEN SINEXCEL ELECTRIC
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