本文選題：光伏發(fā)電 + 低電壓穿越��； 參考：《西安理工大學》2017年碩士論文

【摘要】：近年來隨著光伏發(fā)電系統(tǒng)并入電網(wǎng)的容量逐步上升,其并入電網(wǎng)所產(chǎn)生的問題日益突顯,當電網(wǎng)側(cè)發(fā)生故障時要求光伏電站需要具有低壓穿越的能力,并且在故障期間向電網(wǎng)發(fā)送一定的無功功率幫助電網(wǎng)進行恢復(fù)。由于傳統(tǒng)逆變器慣性不足、抗擾動能力差,針對這一問題,本文將虛擬同步發(fā)電機(Virtual synchronous generator,VSG)技術(shù)引入,使光伏發(fā)電系統(tǒng)具有同步發(fā)電機的外特性,讓逆變器具有調(diào)頻調(diào)壓的功能,這樣勢必會提高光伏發(fā)電系統(tǒng)的運行特性。本文將基于虛擬同步發(fā)電機的光伏發(fā)電系統(tǒng)作為研究對象,在電網(wǎng)電壓跌落之后改進傳統(tǒng)虛擬同步發(fā)電機控制策略實現(xiàn)低壓穿越。首先介紹了光伏發(fā)電并網(wǎng)系統(tǒng)幾年來的發(fā)展,并且分析了光伏發(fā)電系統(tǒng)低壓穿越技術(shù)和虛擬同步機技術(shù)的研究現(xiàn)狀并對光伏發(fā)電系統(tǒng)低壓穿越技術(shù)標準做了簡要的介紹。其次,對光伏發(fā)電系統(tǒng)的結(jié)構(gòu)進行了對比分析并建立了光伏發(fā)電系統(tǒng)的詳細數(shù)學模型,在光照強度和溫度變化情況下對其進行了仿真驗證。對虛擬同步發(fā)電機和并網(wǎng)逆變器的等效機理進行了分析和研究,建立了虛擬同步發(fā)電機的數(shù)學模型,并提出了并網(wǎng)逆變器的虛擬同步發(fā)電機控制策略,對工頻控制器和勵磁控制器進行了詳細的設(shè)計和分析,并且對其進行了仿真研究。最后,給出了對稱故障情況和不對稱故障情況下的改進型虛擬同步發(fā)電機的低電壓穿越控制框圖以及正常情況和故障情況下有功功率以及無功功率參考生成方法,對正負序提取的工作原理和實現(xiàn)方式進行了詳細分析,采用超級電容儲能系統(tǒng)吸收故障期間的過剩功率,給出了超級電容儲能系統(tǒng)控制框圖以及切換方法,通過Matlab/Simulink仿真軟件搭建了光伏發(fā)電系統(tǒng)的仿真模型,分別在對稱故障和不對稱故障兩種情況對傳統(tǒng)和改進虛擬同步發(fā)電機控制策略進行了仿真研究,仿真結(jié)果表明所提出的控制策略能夠在對稱故障下避免過電流和過電壓發(fā)生,并且向電網(wǎng)發(fā)出大量無功功率實現(xiàn)無功支撐,在不對稱故障下保證并網(wǎng)電流對稱無畸變,同時對直流電壓波動進行了有效的抑制。
[Abstract]:In recent years, with the gradual increase of the capacity of photovoltaic power system into the grid, the problems caused by the integration of photovoltaic power system into the grid have become increasingly prominent. When the fault occurs on the power grid side, photovoltaic power stations are required to have the ability of low-voltage traversing. And send a certain reactive power to the power grid during the fault to help the grid to recover. Because the inertia of the traditional inverter is insufficient and the anti-disturbance ability is poor, the virtual synchronous generator (VSG) technology is introduced in this paper, which makes the photovoltaic power generation system have the external characteristics of synchronous generator and the inverter has the function of frequency modulation and voltage regulation. This is bound to improve the performance of photovoltaic power system. In this paper, the photovoltaic generation system based on virtual synchronous generator is taken as the research object, and the traditional control strategy of virtual synchronous generator is improved to realize low voltage traversing after the voltage drop of power grid. This paper first introduces the development of photovoltaic grid-connected system in recent years, and analyzes the research status of low-voltage traversing technology and virtual synchronous machine technology in photovoltaic power generation system, and briefly introduces the technical standard of low-voltage traversing in photovoltaic power generation system. Secondly, the structure of photovoltaic power generation system is compared and analyzed, and the detailed mathematical model of photovoltaic power system is established, and the simulation results are verified under the condition of light intensity and temperature change. The equivalent mechanism of virtual synchronous generator and grid-connected inverter is analyzed and studied, the mathematical model of virtual synchronous generator is established, and the control strategy of virtual synchronous generator of grid-connected inverter is proposed. The power frequency controller and excitation controller are designed and analyzed in detail. Finally, the low voltage traversing control block diagram of the improved virtual synchronous generator under symmetric and asymmetric fault conditions and the reference generation method of active and reactive power under normal and fault conditions are given. The principle and realization of positive and negative sequence extraction are analyzed in detail. The control block diagram and switching method of super capacitor energy storage system are given by using super capacitor energy storage system to absorb excess power during failure. The simulation model of photovoltaic power generation system is built by Matlab / Simulink software. The traditional and improved control strategies of virtual synchronous generator are simulated and studied in the case of symmetric fault and asymmetric fault respectively. The simulation results show that the proposed control strategy can avoid overcurrent and overvoltage under symmetric fault, and send a large amount of reactive power to the power network to achieve reactive power support, and ensure symmetrical and no distortion of grid-connected current under asymmetric fault. At the same time, the DC voltage fluctuation is effectively suppressed.
【學位授予單位】：西安理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM615

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