Apparatus and method for detecting harmonic current

Abstract

The invention discloses an apparatus and a method for detecting harmonic current. Voltage and current signals measured by a sensor enters a sampling maintaining A / D converting circuit through an anti-aliasing filtering circuit; a lock phase loop synchronization pulse generating circuit provides a conversion signal for the sampling maintaining A / D converting circuit; a digital signal processor uses an LMS / LMF self-adaptive harmonic current detection algorithm to detect a harmonic current value in load current; a keyboard circuit and a colorful liquid crystal display realize a man-machine conversation; and a ferroelectric storage stores data. The invention uses the improved LMS / LMF algorithm to update weight and uses the self-correlation estimation of the normalized prior error signal and the last error signal during a step-size iteration, thereby effectively avoiding the influence caused by a lower signal-to-noise ratio and obtaining the better stable effect. The invention uses a TMS320F2812 chip to realize on the specific algorithm; a DSP program is easy to operate to continuously detect signals to be detected for a long time; and the hardware circuit of the whole apparatus is simple, small and convenient to carry and store data.

Description

technical field [0001] The invention relates to an accurate and fast detection instrument and detection method for harmonic and reactive current components, specifically a harmonic detection method using an adaptive algorithm of LMS / LMF (least mean square algorithm / minimum fourth-order moment algorithm, the same below) A current detector and a DSP (Digital Signal Processor, the same below) detection method thereof belong to the technical processing field of current signal detection. Background technique [0002] With the wide application of power electronic devices, the harmonics generated by them have become one of the serious public hazards that pollute the power system. Many countries and regions have formulated their own harmonic standards. my country also passed the "Power Quality Public Grid Harmonics" (GB / T-14594-93) standard in 1993 to limit the harmonics of power supply systems and electrical equipment. Pollution. The effect of effectively suppressing harmonics dep...

AI Technical Summary

Problems solved by technology

[0003] Conventional harmonic current detection methods include: (1) method of extracting fundamental wave components, which has large errors, poor real-time performance, and is very sensitive to circuit component parameters

(2) The Fourier analysis method based on FFT, which has a large amount of calculation, poor real-time performance, and spectrum leakage and fence phenomenon for non-integer harmonics

(3) The harmonic current detection method based on the instantaneous reactive power theory is one of the most widely used detection methods at present, and the p-q method is only suitable for the detection of harmonics and reactive currents under the condition of no grid voltage distortion, i p -i q The method is also effective when the grid voltage is distorted, and has good detection speed and accuracy, but the detection circuit is relatively complicated

On the basis of this basic algorithm, many new algorithms have been proposed, such as normalized solution correlation LMS algorithm (NDLMS algorithm), affine projection algorithm (APA algorithm), etc. Although these algorithms can obtain better steady-state effects, However, the calculation is cumbersome. The NDLMS algorithm needs to introduce relevant principles and use the orthogonal components of the input vector to update the weight coefficients. Although it can improve the convergence accuracy, the algorithm is complicated, and the APA algorithm is a normalized minimum mean square error algorithm (NLMS algorithm ) multidimensional generalization, its computational complexity is much higher than that of the general LMS algorithm

More importantly, the general adaptive algorithm generally has the problem of compromise between detection speed and steady-state error, and cannot well solve the contradiction between dynamic response speed and steady-state performance.

[0005] In recent years, compared with traditional analog implementation, harmonic detection based on DSP, microcontroller (MCU) and programmable logic device (PLD) is easy to realize advanced control, and reduces circuit cost, and is easy to realize large-scale products Production, however, the nonlinear load current contains high frequency components, which will cause delay and distortion of the load current sampling signal, which poses a challenge to the real-time detection of digital harmonics. In order to improve the time delay caused by digital control, generally Adopt DSP design scheme to weaken the impact of delay by enhancing data sampling and processing rate

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