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Variable-step LMS (Least Mean Square) adaptive harmonic detection method applied to APF (Active Power Filter)

A harmonic detection and self-adaptive technology, applied in the field of variable-step minimum mean square self-adaptive harmonic detection, can solve the problems of sensitivity to changes in component parameters and grid frequency, open-loop detection system, and reduced tracking accuracy. The effect of tracking speed and detection accuracy, reducing steady-state offset, and enhancing robustness

Inactive Publication Date: 2015-12-09
NANJING UNIV OF SCI & TECH
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Problems solved by technology

These detection algorithms have their own characteristics, but there are some common problems: the detection system is open-loop, and the frequency is fixed, so it is sensitive to changes in component parameters and grid frequency
However, when applied to APF, due to the low signal-to-noise ratio, the tracking waveform of the above algorithm will produce a certain steady-state offset error, and when the load changes suddenly, the tracking accuracy will decrease accordingly

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  • Variable-step LMS (Least Mean Square) adaptive harmonic detection method applied to APF (Active Power Filter)
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  • Variable-step LMS (Least Mean Square) adaptive harmonic detection method applied to APF (Active Power Filter)

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Embodiment Construction

[0031] In conjunction with the accompanying drawings, the variable step size LMS adaptive harmonic detection method applied to APF of the present invention comprises the following steps:

[0032] Step 1. Install voltage sensors or current sensors on each phase of the grid system to monitor the load current i of each phase L (t) and system voltage u S (t), subscript L stands for Load, S stands for System, variable t is time;

[0033] Step 2. The load current i of each phase monitored in step 1 L (t) Sampling to obtain the current value i after sampling L (n) As an input signal, n is a discrete time scale (dimensionless); at the same time according to the system voltage u S (t) The sampling value is obtained by the phase-locked loop (PLL) and the reference input signal vector composed of sine and cosine signals:

[0034] X(n)=[sin(ωnT s )cos(ωnT s )] T =[x 1 (n)x 2 (n)] T ;

[0035] In the formula, n is the discrete time scale (dimensionless), T s is the sampling per...

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Abstract

The invention discloses a variable-step LMS (Least Mean Square) adaptive harmonic detection method applied to an APF (Active Power Filter). According to the method, on the basis of the existing MVSS-LMS algorithm, forgetting weight and estimation of a historical error are added, step updating is controlled, a step updating range is controlled dynamically, and gliding window forgetting weight is adopted to reduce computation complexity. Compared with the traditional adaptive harmonic detection algorithm, the method of the invention is simple in computation, the dynamic response speed is fast, steady-state errors are reduced in an APF low signal-to-noise ratio environment, the anti-interference ability is high, and harmonic current detection effects are good. The method can be effective in application situations of a single-phase system and a three-phase system.

Description

technical field [0001] The invention belongs to the technical field of power system measurement, in particular to a variable-step least mean square (LMS) adaptive harmonic detection method applied to an active power filter (APF). Background technique [0002] With the development of the power industry, the input of a large number of nonlinear loads has brought a series of harmonic and imbalance problems. It is an effective method to install an active power filter at the harmonic source. The active power filter can quickly and dynamically track and compensate harmonics and reactive power, and the detection accuracy and speed of its harmonic detection link directly affect the filtering performance of the APF. The existing harmonic detection algorithms include fast Fourier transform, instantaneous reactive power theory, wavelet transform and so on. These detection algorithms have their own characteristics, but there are some common problems: the detection system is open-loop ...

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Application Information

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IPC IPC(8): G01R23/16
Inventor 吕广强刘娱段海军耿严岩
Owner NANJING UNIV OF SCI & TECH
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