Power quality generally refers to high-quality power supply, including voltage quality, current quality, power supply quality and power consumption quality. It can be defined as the deviation of voltage, current or frequency that leads to electrical equipment failure or abnormal operation, including frequency deviation, voltage deviation, voltage fluctuation and flicker, three-phase imbalance, temporary or instantaneous overvoltage, waveform distortion (harmonics), voltage sag, interruption, sag and power supply continuity. In modern power system, voltage sag and interruption have become the most important power quality problems.
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H Laaksonen, P Saari, R Komulainen, "Microgrid with Power Quality Compensator.
Providing additional power ",in Proceedings of the 5th International Conference on Applied Simulation and Modeling, 2006, pp. 328-333.
Literature type: conference papers
2. Wanfang dissertation full-text database
Chen Xiangxun, "Several Methods of Measuring and Classifying Power Quality Disturbances by Wavelet Technology", Journal of China Electrical Engineering EIPKU- 10, 2002.
Literature type: periodical papers
3. Full-text database of China Journal Network.
Huang, "Application of Power Quality Monitoring System and Data Analysis Method", Guangdong Science and Technology, Guangdong Science &; Technology, 14, 2009
Literature type: periodical papers
4. IEE Electronic Library (IEL)
Kushare, Bansidhar E, Ghatol, Ashok Kara, Sumit; "Development of a network-based power quality monitoring system, which is used to handle customized power quality queries and automatic power quality monitoring report notifications via e-mail", in Information and Communication Technology in Electronic Science (ICTES 2007), 2007. ICTES。 IET- British International Conference, 20071February 20-22, page number:1–7.
Literature type: conference papers
5. Two in Ei Village (engineering index)
Zhao, Jianguo; Zhang, Da Hai, "Research on Power Communication Network and Power Quality Monitoring by OPNET", 2007: 2007 Second IEEE Conference on Industrial Electronics and Applications, P507-51,2007, 2007: 2007 Second IEEE Conference on Industrial Electronics and Applications.
Literature type: conference papers
The theme of "Power Quality" and its literature retrieval experience
XXX
(Guangzhou 5 10640, School of Electric Power, South China University of Technology)
In order to acquire more theories and knowledge about power quality and be familiar with the methods of scientific and technological literature retrieval, based on the analysis of the principles of scientific and technological literature retrieval, the research background and present situation of power quality are studied, and the scientific and technological literature retrieval around this topic is carried out by using domestic and foreign literature retrieval tools, and the research background and significance of this topic are deeply discussed. I have deepened my understanding of the subject of power quality and the basic principles of literature retrieval, and mastered how to retrieve scientific and technological literature, which provides convenience for future study and paper writing.
Keywords: power quality literature retrieval
1 Introduction:
With the development of science and technology and national economy, the demand for electric energy is increasing day by day, and the requirements for power quality are getting higher and higher. Power quality is becoming more and more important, and power departments and users pay more and more attention to power quality.
What is power quality? The related terms used in many documents and reports in this research field are as follows: ① Voltage quality refers to the deviation between the actual voltage and the ideal voltage, which should be understood as a generalized deviation, that is, it includes amplitude, waveform, phase and so on. , reflecting whether the power provided by power supply enterprises to users is qualified. Although this definition can include most power quality problems, it cannot or should not include quality problems caused by frequency, and does not include the influence of current on quality. (2) The current quality requires users to take the current with constant frequency and sine wave shape, and make the current waveform in phase with the power supply voltage to ensure the system to run with high power factor. This definition is helpful to improve the power quality of power grid and reduce line loss, but it can't summarize most quality problems caused by voltage, and the quality problems caused by voltage are often not always caused by electricity consumption. (3) Power supply quality should include technical meaning and non-technical meaning. The technical meaning includes voltage quality and power supply reliability. Non-technical meaning refers to service quality, including the response speed of power supply enterprises to users' complaints and complaints, the rationality and transparency of electricity prices. (4) the quality of electricity should include the current quality and non-technical meaning, such as whether the user pays the electricity bill in full and on time. , reflecting the responsibilities and obligations of power users in the interaction and influence between supply and demand. [ 1]
It can be seen that improving power quality is of great significance for the safe and economic operation of power grid and electrical equipment, ensuring product quality and scientific experiments, as well as people's normal life and production. Power quality is directly related to the overall benefits of the national economy.
The main way for me to study power quality is through scientific and technological literature retrieval. Document retrieval is the behavior, equation and procedure of finding the needed information quickly and accurately from a large number of documents. It plays a very important role for researchers, such as promoting the development of intellectual resources; Save scientific research time; Avoid repeated research and detours. A great deal of literature information about research topics can be obtained by consulting various databases, and a great number of excellent domestic periodical papers can be obtained by searching the full-text database of China Journal Network. Other Chinese literature databases include Wanfang Database. In addition, excellent foreign periodical papers can be retrieved by searching IEEE/IEE Electronic Library (IEL), EI, ISTP CD-ROM database, etc.
This paper shows the research results of literature retrieval on the subject of power quality, and makes a general discussion on the research status, achievements and development of power quality. The methods and development of literature retrieval are also discussed.
2. Basic principles of scientific and technological literature retrieval
2. 1 retrieval system
Tools for reporting, storing and finding documents are retrieval tools or retrieval systems. A computer retrieval system often contains several databases, and each database corresponds to a tool, which is equivalent to several tools that can be independently retrieved.
Search and answer all kinds of information questions of users. Different retrieval systems reveal different information from different angles, breadth, depth or levels, embody different functions and achieve different goals.
A computer retrieval system consists of a database and all the software and hardware needed to support retrieval, and the database is the core part of the retrieval system [2].
2.2 the development of retrieval
1. Due to the development of science and technology, the amount of information has increased rapidly. Take biomedical journals as an example. 10 in the 7th century, there were10 biological periodicals in the world, and by the 1990s, there were more than 2 100 biological periodicals. A large amount of information must be sorted out before it can be effectively used by people, so "document retrieval" appeared.
2. With the development of modern science and technology, literature retrieval has gone through the process from traditional literature retrieval (manual retrieval, offline retrieval and online retrieval) to network retrieval. With the appearance of the first computer, literature retrieval has entered the stage of computer retrieval (actually offline retrieval) since the 1950s. By the end of 1960s, large-capacity computers and time-sharing technology were born, and literature retrieval entered the stage of online retrieval. In the 1990s, the Internet rose all over the world, and literature retrieval entered the stage of network retrieval. [3]
2.3 the function of retrieval
Scientific literature is an indispensable raw material for all spiritual products. No matter what kind of scientific research you are engaged in, you must carry out literature research in order to grasp the relevant scientific trends and understand the achievements made by predecessors and the current research status. It has the following functions for researchers:
First, promote the development of intellectual resources. Literature retrieval is like a key to open a treasure house of knowledge. Mastering and using it effectively can open the door to the treasure house of knowledge, acquire, master and use all the spiritual wealth accumulated by mankind for thousands of years, transform it into social material wealth, create more spiritual wealth, and thus promote social development.
Second, save scientific research time. Contemporary scientific literature has to be huge, but it also has the characteristics of diverse types and forms, language expansion and concentration, overlapping content, scattered publication, accelerated invalidation and more and more unpublished literature, which seriously affects scientists' rapid and accurate possession of information. Therefore, mastering the function of literature retrieval can save researchers a lot of time to consult materials.
Third, avoid repeated research and detours. Literature retrieval can broaden the horizons of scientific workers and help them understand the new ideas and viewpoints emerging in various fields. In scientific research, some people use it because they don't understand the breakthroughs made by others; Some people even start from scratch and repeat the path that others have already taken. If researchers attach importance to academic research information, conduct literature research in a research room and make full use of literature retrieval means, they can find documents accurately, avoid unnecessary duplication of work and avoid detours.
Fourthly, through literature retrieval, people can understand the academic origins and find research methods. If you consult China's classical catalogue books, you can guide, coach and study. [4]
2.4 the use of retrieval
There are three methods of document retrieval: direct method, also known as common method, refers to the method of directly using retrieval system (tool) to retrieve document information. It is also divided into sequential investigation, reverse investigation and spot check. Traceability method refers to a method that is not conducive to the general retrieval system, but uses the references listed at the back of the literature to trace the original text (cited literature) one by one, and then expands the scope of literature information one by one from the bibliographies listed at the back of these original texts to trace the source one by one. It can snowball and get better retrieval results according to the citation relationship between documents. Circular method is also called subsection method or synthesis method. It uses direct method and backtracking method alternately in stages to learn from each other's strong points and cooperate with each other to obtain better retrieval results.
Document retrieval is a very practical activity, which requires us to be good at thinking and gradually master the law of document retrieval through regular practice, so as to obtain the required documents quickly and accurately. Generally speaking, literature retrieval can be divided into the following steps:
(1) Define the purpose and requirements of the search.
(2) Select a retrieval tool
(3) Determine the retrieval mode and method.
(4) According to the literature clues, consult the original literature.
3. Understand and recognize the power quality.
3. 1 power quality research background
In modern society, electric energy is one of the most widely used energy sources, and its application degree has become one of the main signs of a country's development level. With the development of science and technology and national economy, the demand for electric energy is increasing day by day, and the requirements for power quality are getting higher and higher.
Improving power quality is of great significance for the safe and economic operation of power grid and electrical equipment, ensuring product quality and scientific experiments, as well as people's normal life and production. Power quality is directly related to the overall benefits of the national economy. [5]
3.2 Research Status of "Power Quality" Project
The analysis and monitoring of power quality is a complex system engineering. It is designed in many aspects, such as power system, automatic control, modern communication and so on. At present and even in the future, its development will solve the following problems:
(1) Basic Theory Research
The basic theoretical research of power quality is the basis for in-depth study of its essence, including the meaning of unified distorted waveform line power quality, the definition of each power component, the research of generation mechanism, evaluation system, physical significance, scientific calculation method and so on. At present, people have put forward many definition methods to meet different needs. Each method has its own advantages in mathematical expression, physical meaning, modeling and implementation, but there is still a certain gap in the unified and acceptable expression in theory and practice, so it is impossible to make a comprehensive analysis and evaluation of power quality. The deficiency of this theory will undoubtedly hinder the further study of power quality.
(2) Development of new algorithm
With the rapid development of modern mathematics and artificial intelligence technology and the emergence of a large number of interdisciplinary and interdisciplinary theories, the models, methods and means of power quality analysis show strong diversity. How to use a more scientific and advanced model to analyze power quality and improve its impact on power grid is also the core of power quality research. As far as the current research status of power quality is concerned, wavelet analysis, fuzzy mathematics method, neural network method, genetic algorithm and crossover technology will become the mainstream research direction of new power quality algorithms in the future. Fuzzy mathematics method can be used to establish an accurate mathematical model, wavelet transform can be used to identify, classify and analyze the causes of disturbing data, and fuzzy-neural network method can be used to determine the transmission and storage of effective information. The introduction and maturity of these theories have a far-reaching impact on the research field of power quality from the algorithm itself to the application field of the algorithm and the improvement of the performance of the algorithm.
(3) Networking and intelligentization of power quality monitoring.
The scale of modern power grid is getting bigger and bigger, and there are more and more monitoring points. The monitoring of power quality in the future is not limited to a certain point, but to realize the monitoring of power quality in the same power supply system and different places, and even to realize the centralized monitoring of multiple different power supply systems. Functionally, it emphasizes intelligence. It not only has calculation and display functions, but also has certain judgment, analysis and decision-making functions, such as event prediction, fault identification, interference source identification and real-time control. It has an automatic, practical and advanced computing intelligent evaluation function.
Power quality analysis and monitoring is a complex problem. How to analyze and deal with all kinds of interference sources reasonably and comprehensively, and make full use of computer technology and network technology to analyze and monitor power quality are all issues that should be paid attention to. At the same time, the development trend of power quality monitoring puts forward higher requirements for the function of monitoring system, which also shows that the research in this application field needs the integration of various technologies and close cooperation in various fields. [6]
4. Conclusion
Through the elaboration of the course "Power Quality", I have learned some basic knowledge of power quality and a lot of knowledge about power in China and even the world, which is also of great significance to my future study and work. The process of retrieving documents and writing papers has deepened my understanding of the course of scientific and technological document retrieval, systematically understood the basic principles of scientific and technological document retrieval, and learned how to retrieve scientific and technological documents, which has far-reaching significance for my future graduation project and laid a solid foundation for my future study and work.
References:
[1] forest, basic problems of modern power quality, power grid technology,No. 10, 200 1
[2] Sun Ping Electrical and Electronic Engineering Information Retrieval and Utilization. 1999 10 Third Edition.
[3] Comprehensive, the development trend of literature retrieval-network retrieval, Youjiang Medical College for Nationalities, August 2002, No.4.
[4] Xu Yanfang on the role of literature retrieval. Journal of higher correspondence education (Philosophy and Social Sciences Edition), 19903.
Lin, Basic Problems of Modern Power Quality, Power Grid Technology, No.1 10, 200 1
[6] Zhang Jun, Status and Prospect of Power Quality Monitoring, China Electric Power Communication Network, 2009,4,2.