【摘要】：隨著化石能源的枯竭、環(huán)境污染的加重以及傳統(tǒng)電網(wǎng)安全性的降低,各國紛紛加快對分布式發(fā)電技術(shù)的研究。分布式發(fā)電技術(shù)具有運行方式靈活、環(huán)境友好性強等優(yōu)點,但對大電網(wǎng)干擾較大,制約了其的大規(guī)模使用。微電網(wǎng)概念的提出,解決了分布式發(fā)電和大電網(wǎng)之間矛盾的局面。微電源多通過電力電子變換器接入微電網(wǎng),具有靈活的控制和運行方式。但由于其慣性較小,在當受到擾動時,系統(tǒng)會發(fā)生振蕩失穩(wěn)。所以與傳統(tǒng)電網(wǎng)相比,微電網(wǎng)的穩(wěn)定性分析有較大不同。圍繞這一問題,本文對采用下垂控制的微電網(wǎng)進行小信號穩(wěn)定性建模和分析。首先,對微電源的輸出功率傳輸特性、逆變器的控制方法,進行了分析、介紹。對采用下垂控制的逆變器進行設計,并在控制環(huán)中加入虛擬阻抗,減小線路參數(shù)對輸出阻抗的影響,保持為感性。然后,對逆變器、負荷和大電網(wǎng)的表達式進行線性化,得到各自的小信號模型,并得出戴維南等效電路。在此基礎上,選定一個d-q坐標系為公共坐標系D-Q,將各元件模型轉(zhuǎn)換到公共坐標系下,得到整個微電網(wǎng)的功率閉環(huán)特征方程。根據(jù)方程求出閉環(huán)特征根,繪制根軌跡圖。最后,利用Matlab/Simulink軟件搭建微電網(wǎng)仿真并驗證所搭模型的正確性;對有、無虛擬阻抗兩種情況進行仿真對比,驗證了加入虛擬阻抗的有效性和必要性;利用根軌跡圖,分析負載電抗和虛擬電感對系統(tǒng)穩(wěn)定性的影響:負載電抗的增大和虛擬電感的減小使系統(tǒng)的穩(wěn)定性降低,并通過仿真驗證了所得結(jié)論的正確性。
[Abstract]:With the depletion of fossil energy, the aggravation of environmental pollution and the decrease of the security of traditional power grid, many countries have accelerated the research of distributed power generation technology. Distributed generation technology has many advantages, such as flexible operation mode and strong environmental friendliness, but it interferes with large power grid and restricts its large-scale application. The concept of microgrid resolves the contradiction between distributed generation and large power grid. Micro power supply is connected to microgrid through power electronic converter, and has flexible control and operation mode. However, because of its small inertia, oscillation instability will occur when the system is disturbed. Therefore, compared with the traditional grid, the stability analysis of microgrid is quite different. Aiming at this problem, the small signal stability modeling and analysis of microgrid with droop control is carried out in this paper. Firstly, the transmission characteristics of output power and the control method of inverter are analyzed and introduced. The inverter with droop control is designed and virtual impedance is added to the control loop to reduce the influence of line parameters on the output impedance and to maintain inductance. Then, the expressions of inverter, load and large power grid are linearized, and their small signal models are obtained, and the Thevenin equivalent circuit is obtained. On the basis of this, a d-q coordinate system is selected as the common coordinate system D-Q. each element model is converted to the common coordinate system, and the power closed-loop characteristic equation of the whole microgrid is obtained. The closed-loop characteristic root is obtained according to the equation and the root locus is drawn. Finally, the Matlab/Simulink software is used to build the simulation of microgrid and verify the correctness of the proposed model. The validity and necessity of adding virtual impedance are verified by comparing the two cases of virtual impedance with or without virtual impedance, and the root locus diagram is used to verify the validity and necessity of adding virtual impedance. The influence of load reactance and virtual inductor on the stability of the system is analyzed. The stability of the system is reduced by the increase of load reactance and the decrease of virtual inductance, and the correctness of the conclusions is verified by simulation.
【學位授予單位】：安徽理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM727

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