Subharmonic detection method suitable for APF (Active Power Filter) under load unbalance system

A technology of unbalanced load and sub-harmonics, applied in measurement devices, spectrum analysis, measurement of electrical variables, etc., can solve the problems of unbalanced load active power filter compensation and inaccurate detection results, etc. Achieve the effects of advanced prediction, accurate detection results, and diverse detection data

Inactive Publication Date: 2014-09-03
哈尔滨同为电气股份有限公司
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Problems solved by technology

[0005] In order to solve the problem that the existing harmonic detection method detects the harmonic current without considering the load imbalance and the compensation of the active power filter, resulting in inaccurate detection results, a load imbalance is proposed. Sub-harmonic detection method suitable for APF under the system

Method used

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  • Subharmonic detection method suitable for APF (Active Power Filter) under load unbalance system
  • Subharmonic detection method suitable for APF (Active Power Filter) under load unbalance system
  • Subharmonic detection method suitable for APF (Active Power Filter) under load unbalance system

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specific Embodiment approach 1

[0023] Specific implementation mode 1. Combination figure 1 Describe this specific implementation mode, a sub-harmonic detection method applicable to APF under a load unbalanced system described in this specific implementation mode includes the following steps:

[0024] Step 1. The three-phase voltage e of the common points A, B and C of the APF output terminal a 、e b 、e c Phase-locked by the phase-locked loop PLL to obtain the fundamental phase ωt of the A-phase voltage, so as to obtain the unit sine signal sinωt and unit cosine signal cosωt in the same phase as the A-phase voltage of the three-phase AC grid voltage, and at the same time, form any h-order harmonic The reference phase hωt of the wave, and the sine signal sinhωt and cosine signal coshωt of any h harmonic;

[0025] Step 2. Input current i of phase A of the three-phase nonlinear load La , Phase B input current i Lb and C-phase input current i Lc The load three-phase current i in the αβ coordinates is obtain...

specific Embodiment approach 2

[0034] Embodiment 2. The difference between this embodiment and the sub-harmonic detection method applicable to APF under a load unbalanced system described in Embodiment 1 is that, among any h-th harmonics, for positive sequence harmonics wave, h=3k+1; for negative sequence harmonics, h=3k-1, where k is a natural number.

specific Embodiment approach 3

[0035] Specific Embodiment 3. The difference between this specific embodiment and the sub-harmonic detection method applicable to APF under a load unbalanced system described in specific embodiment 1 is that the A-phase input current i of the three-phase nonlinear load La , Phase B input current i Lb and C-phase input current i Lc The expressions are respectively:

[0036]

[0037] When h=3k+1, the sequence of the three-phase harmonic phase sequence is 120° lagging behind ABC in sequence, which is the positive sequence harmonic; when h=3k-1, the phase sequence sequence of the three-phase harmonics is 120° lagging behind ACB in sequence , which is the negative sequence harmonic; when h=3k, the amplitude and phase of the three-phase harmonic are equal, that is, the zero sequence harmonic, is the initial phase of the hth harmonic, I h is the current amplitude of the hth harmonic.

[0038] In a three-phase unbalanced system, the current can be expressed as the sum of the c...

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Abstract

The invention relates to a subharmonic detection method suitable for an APF (Active Power Filter) under a load unbalance system, relating to the field of subharmonic detection under the load unbalance system and solving the problem of inaccurate detection result because of leaving out of consideration of load unbalance and compensation condition of the active power filter when an existing harmonic detection method is used for detecting a harmonic current. The subharmonic detection method provided by the invention is capable of detecting a positive-sequence harmonic and a negative-sequence harmonic in the load unbalance system to simultaneously obtain a positive-sequence component and a negative-sequence component of the positive-sequence harmonic and the negative-sequence harmonic, and is capable of detecting any subharmonics; and meanwhile, in order to improve the compensation precision of the APF, any subharmonics are subjected to lead compensation to realize lead prediction of current instantaneous values of any subharmonics and compensate the phase delay caused by a control system, an APF output filter and the like, so that a detection result is more accurate. The subharmonic detection method is suitable for performing the subharmonic detection under the load unbalance system.

Description

technical field [0001] The invention relates to the field of subharmonic detection under load unbalanced system. Background technique [0002] Harmonic current detection is a very important link in the active power filter (APF), which determines the performance of the active filter to a certain extent. The harmonic full compensation strategy based on the instantaneous power theory has been very mature. However, in practical applications, this method has practical problems such as inability to limit and wide bandwidth, so the selective compensation strategy is more suitable. [0003] The selective compensation strategy is relative to the full compensation strategy. The compensation target of the full compensation strategy is that only the fundamental positive-sequence active current remains in the power grid after compensation, and all other components are compensated; while the selective compensation strategy can choose some components to be compensated arbitrarily. There ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R23/165
Inventor 武健徐殿国周维来何崇飞
Owner 哈尔滨同为电气股份有限公司
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