Because there are still some problems in the detection and management of electric energy, such as single function, poor real-time performance, lack of statistical analysis, and low efficiency, a method of detection and management is needed to improve the problems faced by the current power system.
1 Development of power harmonic detectionIn the power system, the most ideal current and voltage waveform is a sine wave at the power frequency, but in practice there will often be different distortions, especially in the distribution network in recent years, frequency conversion speed regulation, inverters, electronic equipment, etc. The continuous application causes the nonlinear load to increase, causing severe distortion of the current and voltage waveforms in the power system, resulting in a large number of harmonics in the power grid, resulting in many power accidents. Therefore, harmonic pollution is currently recognized as a major public hazard affecting the safety of the power grid. In the process of harmonic control, the method of harmonic monitoring is mainly used, which is also the basis for solving harmonic hazards and has a guiding role for one harmonic. According to the development history of harmonic detection, it can be divided into three stages: first, from the early 19th century to the 1940s, based on the Fourier transform, the harmonics were detected; second, the 20th century 50-80s The main use of frequency selective measurement technology; Third, from the 1980s to the present, with the development of computer technology, micro-processing technology and integrated circuits, the rapid Fourier transform spectrum analyzer and harmonic analyzer, through these detection instruments The use of the calculation results in greatly improved accuracy. In China, the use of this algorithm and phase-locked technology to measure harmonics began in the 1980s, and has now developed into a digital, electronic, intelligent harmonic test method.
2.1 Measurement using an analog band-stop or band-pass filter
This is the earliest method of harmonic measurement, which has the advantages of low circuit 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 result contains more fundamental components, resulting in relatively large operation losses.
2.2 Harmonic detection based on neural network
This is a kind of research result that can be obtained by improving the computing power and approximating any continuous function, and learning through the theory and analyzing the dynamic network, namely neural network. At this stage, the application of the network in power system harmonic detection is still in its infancy, and it is mainly used in power system harmonic prediction, harmonic source identification and harmonic measurement. The use of neural networks in harmonic measurement requires the consideration of network composition, algorithm selection, and sample determination.
2.3 Wavelet analysis method for measuring harmonics
This aspect of research has made significant progress at this stage, mainly to solve the Fourier transform in the time domain without local defects and frequency domain completely localized defects, that is, locality in both the time domain and the frequency domain. This method can be used to project high-order harmonic changes in power systems to different scales, thus reflecting the characteristics of singular, high-frequency harmonic signals, thus providing a basis for harmonic analysis.
2.4 FFT variation method
The method for detecting the harmonics of the power system is based on the measurement method based on the digital signal processing. The main operation step is to first sample the voltage or current of the signal under test, and then transform and then use the computer to perform the Fourier transform. The phase coefficients and amplitudes of the respective harmonics are obtained. This method is currently the most widely used harmonic detection method in power system, and its accuracy, function and operation are simple, and the accuracy of harmonic detection is realized.
3 Power Communication Technology ResearchIn today's society, the demand for electric energy is getting higher and higher, and the reliability requirements for power supply are also constantly increasing. The harmonics of the power grid bring many negative effects to the power system. Mainly manifested as: power generation equipment, transmission equipment, power supply equipment and electrical equipment all increase the loss to varying degrees, reducing the utilization rate and efficiency of the equipment; reducing the reliability of the automatic device and relay protection; causing the measurement instrument to indicate no Accurate, harmonics affect the growth of instrumentation; cause interference to the communication system, affect the safety of communication equipment and personnel; cause an impression on the electrical equipment, use electrical equipment to malfunction, reduce the service life of the equipment. Therefore, the power system should strictly test the harmonics and improve the power environment.
With the development of the electric power industry, the power communication industry has also been developing at a high speed, which greatly enhances the communication capability. Focusing on the research and research on power quality, ensuring the quality of power has become the consensus of power companies, and establishing a systematic and efficient electric energy Xiliang online monitoring network to monitor and manage the power grid becomes inevitable, so that the power quality level can be carried out at any time. Monitoring, in order to find the reasons that affect the safe operation of the power grid, take effective measures to solve in time, improve the power quality of the power system, ensure the safe operation of the power grid, and achieve its economic benefits. The influence of power harmonics has never stopped, and the power harmonic detection instruments are complex and diverse, but the compatibility of different instruments has become a difficult point. For this problem, the PQDIF data format has become the standard of unified format, realizing effective data management. The resources are shared, and a practical universal platform is established to introduce power quality detection into the development stage of standardization. Regardless of the economical and efficient perspective, the situation that the data processing effect is not ideal due to the difference in data format is avoided. The use of the Internet-based PQDIF format for storage and transmission in power harmonic detection systems has also led to the development of power communication technologies.
4 ConclusionWith the development of information technology and communication technology, power quality detection technology is developing in the direction of informationization, networking and standardization, and it is more suitable for the operation of power systems. In the harmonic detection of power systems, it is better integrated into computer technology. Communication technology and electronic technology are the development trend of harmonic detection.
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