Current harmonic detection system and working method

Abstract

The invention relates to a current harmonic detection system and a working method. A load current and a power grid current respectively pass through two current transformers and then are connected with a pre-filter circuit through two signal lines, and the pre-filter circuit is connected with an input port of an AD (Analog to Digital) data acquisition module through a monobus. The A phase voltage of a power grid passes through a voltage sensor and is connected with an over-zero comparing circuit through a one-channel signal line, and the AD data acquisition module and the output of the over-zero comparing circuit are connected an input port of a digital signal processing (DSP) chip. The DSP chip outputs a sampling frequency signal to the AD data acquisition module. According to the current harmonic detection system and the working method, the problems of long detection delay, current spike interference and the like of the traditional current harmonic method are solved; an active power filter can quickly and accurately detect power grid harmonics and carry out harmonic management and reactive compensation; and the power supply quality of the power grid for a non-linear load is greatly increased.

Description

technical field [0001] The invention relates to a current signal detection technology, in particular to a current harmonic detection system and working method based on improved FBD algorithm and DSP technology. Background technique [0002] The number of power electronic devices working in switch mode in the distribution network is increasing continuously. The characteristics of these loads, such as nonlinearity, conflict and unbalance, will distort the voltage and current of the power system and seriously affect the quality of power supply. Active Power Filter (APF) is an effective power electronic device that compensates real-time changing harmonics and reactive power and improves the quality of power grid power supply. In order to better realize the function of APF, the detection link of harmonic and reactive current is very important. [0003] Currently the most widely used current detection methods are detection methods based on instantaneous reactive power theory, det...

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Problems solved by technology

However, due to the existence of the low-pass filter (LPF) in these detection methods, the detection delay reaches 1 to 2 power cycles, resulting in hysteresis error, which affects the compensation performance of APF

Kuang Naixing of Zhejiang University published a paper "A High-performance Harmonic Detection Digital Low-pass Filter" in the 30th issue of "Power System Automation" in 2006. They designed a new type of low-pass filter to replace the traditional low-pass filter, but increased the complexity of the system

Ding Zujun from Southeast University and others published the paper "Modeling of Hysteresis Error of FBD Algorithm Current Detection" in the 2nd issue of "Journal of Electrotechnical Society" in 2008, which established a hysteresis model of FBD current detection method and introduced a linear transformation compensation algorithm, but the improved method remains A low-pass filter is added, which increases the amount of calculation and increases the computational burden of the microprocessor

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