Study on Power Harmonic Detector and Its Communication Technology

At present, there are some problems in the detection and management of power such as single function, poor real-time performance, lack of statistical analysis and inefficiency. Therefore, a detection and management method is needed to improve the problems faced by the current power system.

1 power harmonic detection of the development

In the power system, the most ideal current and voltage waveforms are sine waves under power frequency, but in practice there are often different distortions, especially in the distribution network in recent years, such as frequency control, inverter, electronic equipment The continuous application leads to the increase of non-linear load, causing serious distortion of the current and voltage waveform in the power system, resulting in a large number of harmonics in the power grid, resulting in the appearance of many power accidents. Therefore, harmonic pollution is currently recognized as a major public hazard affecting the safety of power grids. Harmonic control in the process, the main method of harmonic monitoring, which is the basis for solving the hazards of harmonics, a harmonic has an instructive role. According to the development of harmonic detection, it can be divided into three stages: first, the detection of harmonics is based on the Fourier transform from the early 19th century to the 1940s; secondly, from the 1950s to the 1980s , Mainly using frequency-selective measurement technology; Third, since the 1980s, with the development of computer technology, micro-processing technology and integrated circuits, there has been a spectrum analyzer and a harmonic analyzer of Fast Fourier Transform. Through these detection instruments The use of the calculation results greatly improve the accuracy. In our country, using this algorithm and phase-locking technique to measure the harmonic wave began in the 1980s and has now developed into a digital, electronic and intelligent harmonic testing method.

2 harmonic detector principle and method

2.1 using analog band-stop filter or band-pass filter for measurement

This is the earliest harmonic measurement method, which has the advantage of low cost, simple structure, easy control and low output impedance. The disadvantage is that it is greatly affected by the environment, the detection accuracy is not high, and the detection results contain more fundamental components, resulting in relatively large operating losses.

2.2 Neural Network based on the harmonic detection

This is a kind of neural network that can improve the computing power and approximate any continuous function, and obtain the research results obtained by studying and analyzing the dynamic network through theory. At this stage, the network in the power system harmonic detection is still in its infancy, which is mainly used in power system harmonic prediction, harmonic source identification and harmonic measurement and so on. In the harmonic measurement using neural network, the main thing to consider is the composition of the network, the choice of algorithms and sample identification and other issues.

2.3 Wavelet Analysis Method Harmonic Measurement

The research in this area has made significant progress at this stage. The main work is to solve the problem that the Fourier transform has no local defects in the time domain and complete localized defects in the frequency domain, that is, both in the time domain and the frequency domain. Using this method, the harmonic changes in the power system can be projected onto different scales to reflect the characteristics of the singular and high frequency harmonics signals and provide the basis for harmonic analysis.

2.4 FFT method of change

Using this method to detect power system harmonics is a measurement method based on digital signal processing. The main operation steps are to first sample the voltage or current of the signal under test, and then transform the Fourier transform of the measured signal to make the Fourier transform Get the harmonic coefficient of each phase and amplitude. The method is the most widely used harmonic detection method in power system at present, and has the advantages of high precision, multiple functions and simple operation, and realizes the accuracy of harmonic detection.

3 Power Communication Technology Research

In today's society, the demand for electric energy is getting higher and higher, and the requirements on the reliability of power supply are also increasing. The harmonic of the power grid brings about many negative effects on the power system. Mainly as follows: power generation equipment, transmission equipment, power supply equipment and electrical equipment have increased the loss of varying degrees, reducing the utilization and efficiency of the equipment; to reduce the reliability of automatic devices and relay protection; caused by the instrumentation is not Accurate, harmonic affect the growth of instrumentation ; interfere with the communication system, affecting the safety of communications equipment and personnel; impose on the electrical equipment, the use of electrical equipment malfunction, reduce equipment life. Therefore, the power system should be strictly detected harmonics to improve the electricity environment. With the development of power industry, the power communication industry has also been constantly developing rapidly, which has greatly enhanced the communication ability. In the face of the importance of power quality and research to ensure that power quality has become the consensus of power companies to establish a systematic and efficient power quality online monitoring network monitoring and management of the power grid become inevitable, so that you can always monitor the level of power quality So as to find out the reasons that affect the safe operation of power grids, take prompt and effective measures to solve them, improve the power supply quality of the power system, ensure the safe operation of the power grid and realize its economic benefits. It has always been the power harmonics has never stopped, the power harmonic detection equipment is complex and diverse, but the compatibility of different instruments becomes a difficult point. For this problem, PQDIF data format into a unified format standards to achieve effective data management, Make the resource share, set up a practical common platform, the power quality testing into the standardization of the development stage. No matter from the perspective of economy and efficiency, the data processing effect that is caused by the difference of data formats is avoided. The application of PQDIF format storage and transmission based on internet in power harmonic detection system also makes power communication technology developed.

4 Conclusion

With the development of information technology and communication technology, the power quality detection technology is developing in the direction of informationization, networking and standardization, and more adapts to the operation of power system. In power system harmonic detection, it better incorporates computer technology , Communication technology and electronic technology, is the development trend of harmonic detection.

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