Harmonic current detection and filtration method and device of active power filter

Abstract

The invention relates to a harmonic current detection and filtration device of an active power filter, which comprises an output reactor, a power unit, a drive circuit, a two-phase coordinate system conversion module, a low pass filter module, a three-phase coordinate system conversion module and a subtracter. The two-phase coordinate system conversion module is used for converting a three-phase load current into a two-phase load current in a two-phase coordinate system, namely a d-q coordinate system. The two-phase coordinate system is in synchronous rotation with a voltage vector in a circuit, wherein the rotation angular frequency is omega s. The low pass filter module is used for filtering the harmonic component currents of the components d and q in the two-phase load current output by the two-phase coordinate system conversion module, so as to obtain the fundamental component current. The three-phase coordinate system conversion module is used for converting the fundamental component current processed by the low pass filter module into a fundamental component current of a three-phase load current in a three-phase coordinate system. The subtracter is used for subtracting the fundamental component current output by the three-phase coordinate system conversion module from the three-phase load current, so as to obtain a harmonic signal current. The method and the device have the advantages of accurate detection and can filter the harmonic current in the active power filter.

Description

technical field [0001] The invention relates to a harmonic current detection filter device of an active power filter, which belongs to the field of power quality control. Background technique [0002] In recent years, the widespread use of power electronic devices and nonlinear loads has caused a large amount of harmonic current and reactive current to be injected into the grid, which seriously threatens the safe operation and normal use of the grid and electrical equipment. Filtering and compensation of harmonic reactive power has been People pay more and more attention to it. [0003] There are a number of disadvantages to using passive filtering devices to solve reactive and harmonic problems. For example, passive filters are mostly designed for harmonics of specific frequencies, and can only filter out specific sub-harmonics, which may cause resonance with the power grid; and are very sensitive to grid impedance and frequency changes; large volume, large loss, etc. Wai...

AI Technical Summary

Problems solved by technology

figure 1 It is a block diagram of the existing active power filter load current detection and processing principle. Since the load current is designed according to the maximum load, the detected load current may be small due to the change of the load during the actual commissioning process, which will inevitably cause A / D sampling signal is small

Although the harmonic current generated by some loads is relatively large, it still accounts for a small proportion compared with the fundamental current of the load. The resolution of the wave current signal will be relatively low, so the sampled harmonic current will be too small compared with the sensor range, causing distortion and thus affecting the compensation effect of the active power filter

At present, signal amplification is used to solve this problem, but the input range of the A / D converter is only about 5V, so the signal amplification factor cannot be increased too much

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