Weighting least mean square (LMS) detection method for harmonic currents

A technology of harmonic current and detection method, applied in the direction of measuring current/voltage, measuring device, measuring electrical variable, etc., can solve problems such as increased calculation amount and poor load current tracking ability

Inactive Publication Date: 2013-09-18
SOUTHWEST JIAOTONG UNIV
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Problems solved by technology

Although the RLS algorithm improves the convergence speed compared with the LMS algorithm, it is at the cost of increasing the amount of calculation
Moreover, the RLS algorithm has poor tracking ability to the sudden change of load current, that is, after the RLS algorithm converges to the steady state, if the load current jumps, the RLS algorithm will take a long time to converge to the steady state again.

Method used

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  • Weighting least mean square (LMS) detection method for harmonic currents
  • Weighting least mean square (LMS) detection method for harmonic currents
  • Weighting least mean square (LMS) detection method for harmonic currents

Examples

Experimental program
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Embodiment

[0063] A weighted LMS harmonic current detection method, the steps are as follows:

[0064] A. Sampling

[0065] For periodic non-sinusoidal load current i L (t) Sampling to obtain the discrete value i of the load current L (n); Use the phase-locked loop (PLL) to get the reference input vector x(t)=[sin(2πft), cos(2πft)] of the filter T , and sample the discrete value of the reference signal vector x(n)=[sin(ωnT S ),cos(ωnT S )] T ; Among them, the superscript T means to seek the transpose of the vector or matrix, f=50Hz, and n is the discrete point of time t.

[0066] B. Filter the discrete value x(n) of the reference signal vector through an adaptive filter to obtain an estimated value of the fundamental current where w(n)=[w 1 (n),w 1 (n)] T It is the weight coefficient vector of the adaptive filter calculated at time n-1 at time n. If time n is the initial time, its value is zero.

[0067] C. The discrete value i of the load current in step A L (n) minus the fu...

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Abstract

The invention discloses a weighting LMS detection method for harmonic currents. The method comprises aspects that (1) cost functions are defined to be weighted square sums of posteriori errors, so that interference of harmonic currents on filter weight coefficients is eliminated; (2) updating increments of the filter weight coefficients are achieved through iteration, so that the calculation complexity is reduced; (3) conditions for guaranteeing stability are given. Compared with an LMS algorithm and a recursive least square (RLS) algorithm, the weighting LMS detection method has the advantages of being small in steady-state error and high in jump occasion tracking capacity to load currents. The calculation amount of the method is slightly larger than that of the LMS algorithm but smaller than that of the RLS algorithm, so that the method is applicable to detection of harmonic currents.

Description

technical field [0001] The invention belongs to the technical field of harmonic current detection of power systems. Background technique [0002] As nonlinear loads are widely used in industry, transportation and family life, a large number of harmonics are generated, which seriously reduces the power quality, and also affects the safe and stable operation of the power system and its user equipment. In order to effectively control harmonic pollution, active power filter (APF) is a good choice. Through the real-time detection of grid harmonics, it controls the inverter to generate a harmonic current with equal magnitude and opposite phase and injects it into the grid, so as to realize the compensation and suppression of harmonic pollution of the grid. However, the performance of APF harmonic suppression mainly depends on how to detect the harmonic current in real time and accurately, so the harmonic current detection method is very important. [0003] In recent years, harmo...

Claims

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Application Information

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IPC IPC(8): G01R19/00
Inventor 赵海全喻翌
Owner SOUTHWEST JIAOTONG UNIV
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