本文選題：孤島電網(wǎng)　切入點：頻率穩(wěn)定　出處：《沈陽工業(yè)大學》2017年碩士論文

【摘要】：微電網(wǎng)是一種將分布式電源、負荷、儲能裝置、變流器以及監(jiān)控保護裝置有機整合在一起的小型發(fā)配電系統(tǒng)。微電網(wǎng)解決了分散式并網(wǎng)難的問題,提升了風電的利用率。隨著風電滲透率的增加,微網(wǎng)頻率波動進一步加劇,孤網(wǎng)模式下頻率波動尤為嚴重。本文針對孤網(wǎng)中負荷增加與風速波動引起頻率跌落及小幅度振蕩問題展開研究,通過改進變流器的控制策略解決孤島電網(wǎng)低頻震蕩問題。首先,建立永磁發(fā)電機和變流器的數(shù)學模型,分析永磁風電機組有功功率控制特點,采用矢量控制策略實現(xiàn)風電機組有功、無功解耦控制,為后續(xù)研究提供理論基礎。其次,分析孤網(wǎng)功率平衡特性,針對孤網(wǎng)中轉動慣量控制策略出現(xiàn)頻率二次跌落問題提出降載荷控制策略。在低風速區(qū),風電機組追蹤次優(yōu)功率曲線超速減載運行,保留有功備用余量為風電機組參與孤島電網(wǎng)調頻做準備。在高風速區(qū),協(xié)調變槳距角控制策略與降載荷控制策略,在確保風電機組穩(wěn)定運行的前提下,保留充足的有功功率備用余量支撐孤島電網(wǎng)頻率的穩(wěn)定性。所提降載荷控制策略,在高、低風速區(qū)均解決頻率二次跌落問題。再次,針對單一降載荷控制策略不能有效解決低頻震蕩問題,本文提出協(xié)調機側分段減載與網(wǎng)側模糊下垂的聯(lián)合控制策略。分段減載控制策略在分析不同降載荷系數(shù)功頻特性的基礎,對全風速范圍進行劃分,在不同風速區(qū)間確定合適的降載系數(shù),解決單一降載荷控制策略下有功功率備用余量不足的問題,增強風電機組對孤島電網(wǎng)頻率穩(wěn)定性的支撐作用。網(wǎng)側模糊下垂控制策略,通過設計模糊控制器和模糊規(guī)則,建立了孤島電網(wǎng)頻率偏差、頻率變化率與風電機組補償功率間的聯(lián)系,優(yōu)化了變流器的輸入輸出功率,有效抑制孤網(wǎng)頻率驟降,解決低頻震蕩問題。最后,在Matlab/Simulink仿真環(huán)境中,搭建不同控制策略下風電機組參與孤島電網(wǎng)調頻時的仿真模型,進行仿真驗證。結果表明聯(lián)合控制策略下,永磁風電機組的運行狀態(tài)最穩(wěn)定,孤島電網(wǎng)頻率波動最小。在仿真的基礎上,通過實驗進一步驗證聯(lián)合控制策略可行性和有效性。
[Abstract]:Microgrid is a small power generation and distribution system that integrates distributed power sources, loads, energy storage devices, converters, and monitoring and protection devices.Microgrid solves the difficult problem of decentralized grid connection and improves the utilization rate of wind power.With the increase of wind power permeability, the frequency fluctuation of microgrid is further aggravated, especially in the isolated grid mode.In this paper, the problem of frequency drop and small amplitude oscillation caused by load increase and wind speed fluctuation in isolated network is studied, and the problem of low frequency oscillation in isolated island power network is solved by improving the control strategy of converter.Firstly, the mathematical model of permanent magnet generator and converter is established, and the characteristics of active power control of permanent magnet wind turbine are analyzed. The vector control strategy is used to realize the decoupling control of active power and reactive power of wind turbine, which provides a theoretical basis for further research.Secondly, the power balance characteristics of the isolated network are analyzed, and a load reduction control strategy is proposed for the frequency secondary drop of the moment of inertia control strategy in the isolated network.In the low wind speed area, wind turbines track the sub-optimal power curve to overspeed and reduce the load, and reserve the active power reserve for the wind turbine to participate in the frequency modulation of the isolated island power network.In the high wind speed region, the variable pitch angle control strategy and the load reduction control strategy are coordinated. Under the premise of ensuring the stable operation of the wind turbine, sufficient active power reserve is reserved to support the stability of the isolated island power network frequency.The proposed load control strategy solves the problem of frequency secondary drop in high and low wind speed regions.Thirdly, since a single load reduction control strategy can not effectively solve the problem of low frequency oscillation, this paper proposes a joint control strategy of coordinating segment load reduction on the side of the machine and fuzzy droop on the grid side.The piecewise load reduction control strategy is based on analyzing the power and frequency characteristics of different load reduction coefficients, dividing the whole wind speed range, and determining the appropriate load reduction coefficients in different wind speed ranges.To solve the problem of insufficient spare allowance of active power under a single load reduction control strategy, and to enhance the support function of wind turbine to the frequency stability of isolated island power network.By designing fuzzy controller and fuzzy rules, the relationship among frequency deviation, frequency change rate and compensation power of wind turbine is established, and the input and output power of converter is optimized.Effectively restrain the frequency drop of the isolated network and solve the problem of low frequency oscillation.Finally, in the Matlab/Simulink simulation environment, the simulation model of wind turbine participating in frequency modulation of isolated island power network is built under different control strategies, and the simulation results are verified.The results show that the operation state of permanent magnet wind turbine is the most stable and the frequency fluctuation of isolated island power network is minimum under the joint control strategy.On the basis of simulation, the feasibility and effectiveness of the joint control strategy are further verified by experiments.
【學位授予單位】：沈陽工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM712;TM614

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