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Research On Power Quality Control Technology Of Photovoltaic Microgrid

Posted on:2017-01-01Degree:MasterType:Thesis
Country:ChinaCandidate:X H LvFull Text:PDF
GTID:2272330488973431Subject:Electrical engineering
Abstract/Summary:PDF Full Text Request
In a situation with non-renewable energy depletion and more and more serious environmental pollution, in order to optimize the energy structure, solve the problem of energy crisis, all the countries in the world is in the way developing the renewable energy. It is typical of clean and renewable energy, with many advantages as its widely distribution, short cycle, easy on-site construction, which has gradually become dominant. This method becomes the main way in the future development of intelligent power grid. Micro-grid technology has gradually become the focus of scholars at home and abroad. Different from the traditional energy, micro sources such as solar, wind and other renewable energy sources are connected to the micro-grid. The intermittency and uncertainty of output power, a large number of power electronic devices, a complex control strategy of grid connected, will bring micro-grid new electric energy quality problems, such as micro net voltage fluctuation and voltage waveform distortion, three-phase voltage unbalance. Therefore, in order to ensure the efficiency, safe and stable operation of photovoltaic micro-grid, it is necessary to start corresponding research, and put forward the effective way, to meet the needs of the users. Based on the characteristics of photovoltaic micro-grid power quality, this paper mainly talks about the photovoltaic properties and control, hybrid energy storage and active power filter (APF) to launch the research.Combining the renewable energy grid technology with power quality, this paper mainly talks about the PV grid connected inverter technology, hybrid energy storage and the active power filter in micro grid power quality control. The main research contents of this paper are as follows:(1) On the basis of summarizing a large number of Chinese and foreign literature, analysis and describe the photovoltaic micro network harmonic, voltage fluctuation and voltage flash variable power quality and the status quo of the research. Also this paper summarizes the energy storage technology and the role of in improving the micro grid.(2) First mathematical model of photovoltaic micro-sources is elaborated and validated. And according to the five parameters of photovoltaic micro-source, which PV array vendors gives, the accuracy of the mathematical model is verified modeling and simulation. In order to make the PV micro source operating at the maximum power point in certain natural conditions, this paper discussed three kinds of algorithms of MPPT. And through building simulation model and a boost circuit, the effectiveness of MPPT algorithm of disturbance observation method is verified. In order to achieve effective grid connection with photovoltaic grid, the subject of photovoltaic micro source uses a grid voltage oriented scheme. And the scheme is based on power grid voltage as a benchmark the three-phase current in DQ rotating coordinate control, which not only can achieve without static error, but also can complete the active and reactive power decoupling control. This paper completed with the design of photovoltaic micro underlying source control scheme, the grid connected operation of micro photovoltaic network can maximum controllable active power output energy, and the power factor can also be adjusted flexibly.(3) Exposition and analysis of the mathematical model in the system are conducted for the energy storage, a storage battery and supercapacitor hybrid energy storage. By means of theory it is proved that hybrid energy storage system can overcome the shortcomings of the traditional battery energy storage system, to improve the energy storage system, peak clipping fill valley, stabilize power fluctuations, and increase the life span of the battery capacity. Then the main circuit topology of hybrid energy storage system is established, analyzing the working principle and control strategy of bipolar DC-DC converter. Finally use Matlab/ Simulink software to build a light storing model. The simulation results show that the super capacitor and battery hybrid energy storage system can greatly improve the ability to stabilize the system output power fluctuations and realize the voltage stability of photovoltaic micro grid system in high voltage DC side, which is conducive to improve the photovoltaic micro grid power output of quality.(4) In order to solve the micro-grid harmonic power quality problems, this study proposed the passive control method, through laying out APF in the important point to improve the power quality. The main principle of APF control is to inject the current in PCC which is opposite to the current in the micro-grid, to improve the quality of electric energy. In the choice of APF control method, taking into account the repetitive controller with steady state can completely eliminating the static error of the kernel, so in this section from the research of repetitive controller kernel transfer function to set out, design a repetitive control and proportional integral hybrid control strategy, combining both the advantages. In order to validate the correctness and feasibility of the repetitive control algorithm applied in APF, simulation model based on MATLAB/Simulink is built to simplify the model, omitting micro-grid intermittent power generation equipment The simulation results show that the repetitive control method is effective in suppressing the harmonic current.The main results of this paper are as follows:(1) This chapter completes the bottom design of photovoltaic micro source control scheme, making the grid connected operation micro network of photovoltaic micro source act in maximum or controllable active power (in the capacity range) foreign output energy condition. Also power factor can also be adjusted flexibly.(2) Optical storage model and control algorithm are studied in this paper using Matlab/Simulink. By using super capacitor and battery hybrid energy storage system can greatly improve the ability to stabilize the system output power fluctuations and improve the photovoltaic micro grid power quality.(3) Design a control strategy integrated with repetitive control and proportional control, combining the advantages of both, the new control strategy has a good steady-state control accuracy, which also has a good tracking performance. At last this paper designs correctness of repetitive control and APF control strategy based on the verified simulation on MATLAB/Simulink.
Keywords/Search Tags:Photovoltaic power generation system, Microgrid, Power quality, Maximum power point tracking, Hybrid energy storage
PDF Full Text Request
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