發(fā)布時間：2018-06-21 11:16

  本文選題：微電網(wǎng) + 非計劃孤島　； 參考：《華北電力大學(北京)》2017年碩士論文

【摘要】：常規(guī)能源如煤炭、石油等的消耗所帶來的環(huán)境問題日益嚴峻,而當前社會對能源的需求日益增加。在此背景下,分布式能源如風能、太陽能的消耗越來越多,而且它們的特點是清潔可持續(xù),對環(huán)境危害很小,將分布式能源以及儲能和控制設(shè)備結(jié)合而構(gòu)成小容量的微電網(wǎng),在滿足本地負載的同時,與主電網(wǎng)連接進行功率交換,其應用場合越來越廣。并網(wǎng)時,微電網(wǎng)一般控制為電流源與主電網(wǎng)進行功率交換,如果非計劃孤島發(fā)生導致主電網(wǎng)斷電,此時微電網(wǎng)中的敏感負載可能會因為主電網(wǎng)斷電而導致供電質(zhì)量受損。因此有必要研究相應的控制策略實現(xiàn)PCC點的無縫切換,以完成并網(wǎng)到孤網(wǎng)切換過程中PCC點電壓的平滑過渡,保障敏感負載的良好供電質(zhì)量。首先,本文對現(xiàn)有的微電網(wǎng)并網(wǎng)、孤網(wǎng)和兩者間切換的控制策略做了充分研究。其次,通過對已有文獻的分析,提出一種基于PCC點電壓的無縫切換控制策略。并設(shè)計電壓、頻率限幅器和電感電流環(huán)、電壓外環(huán)、前饋電壓環(huán)的PI控制器參數(shù),通過開環(huán)Bode圖來說明參數(shù)選取的效果。在PISM中對不同阻值的負載進行并網(wǎng)到孤網(wǎng)的切換與孤網(wǎng)到并網(wǎng)重連仿真分析,在實驗室的微電網(wǎng)實驗平臺中,根據(jù)仿真內(nèi)容,完成并網(wǎng)到孤網(wǎng)的切換與孤網(wǎng)到并網(wǎng)重連物理實驗,仿真和物理實驗結(jié)果驗證了基于PCC點電壓的無縫切換控制策略的正確性。然后,提出一種基于電感參數(shù)設(shè)計的無縫切換控制策略。根據(jù)并網(wǎng)時輸出電流與電網(wǎng)電壓的夾角的不同,微電網(wǎng)變流器與主電網(wǎng)交換的功率以及流動方向也不同。通過查詢國際協(xié)會與各國出臺的PCC點電壓對電網(wǎng)異常響應時間的標準,給出本章所采用的切換時PCC點電壓允許波動的范圍,基于該標準,考慮到實際工程中電感紋波與基波壓降要求,根據(jù)微電網(wǎng)有功容量等參數(shù)給定變流器輸出電感參數(shù)值,在該電感參數(shù)值下不改變控制策略也可完成無縫切換過程。最后,微電網(wǎng)含有多個變流器時,可以采用下垂控制來完成并網(wǎng)到孤網(wǎng)的無縫切換。并網(wǎng)時微電網(wǎng)運行于PQ控制,限幅器不起作用;孤網(wǎng)發(fā)生時,由于給定功率可能會與負載功率不匹配,使得限幅器起作用,電壓和頻率的限制值根據(jù)下垂關(guān)系修改功率參考指令值,完成PCC電壓的無縫切換。孤島檢測到孤網(wǎng)后,狀態(tài)運行開關(guān)切換到下垂控制,根據(jù)微電網(wǎng)容量與負載大小關(guān)系,合理分配功率,優(yōu)化能源利用。并在PSIM軟件中驗證基于下垂控制的無縫切換控制策略。
[Abstract]:The environmental problems caused by the consumption of conventional energy, such as coal and oil, are becoming more and more serious, and the demand for energy is increasing day by day. In this context, distributed energy sources, such as wind and solar energy, are consuming more and more, and they are characterized by clean and sustainable, very little harm to the environment, the combination of distributed energy and energy storage and control equipment to form a micro-grid of small capacity. At the same time, the power exchange with the main power grid is more and more widely used. When the microgrid is connected to the grid, the power exchange between the current source and the main grid is usually used. If the unplanned isolated island occurs and the main grid is cut off, the sensitive load in the microgrid may damage the power supply quality due to the power failure of the main grid. Therefore, it is necessary to study the corresponding control strategy to realize seamless switching of PCC points, in order to complete the smooth transition of PCC point voltage in the process of grid-connected switching to isolated network switching, and to ensure the good power supply quality of sensitive load. Firstly, the existing control strategies of microgrid grid-connected, isolated network and switching between them are fully studied in this paper. Secondly, a seamless switching control strategy based on PCC point voltage is proposed. The Pi controller parameters of voltage, frequency limiter, inductor current loop, voltage outer loop and feedforward voltage loop are designed. The effect of parameter selection is illustrated by open-loop Bode diagram. In PISM, the load with different resistance values is switched from grid to grid and the reconnection of grid to grid is simulated. In the experiment platform of microgrid in laboratory, according to the content of simulation, The physical experiments of grid-to-solitary-network switching and reconnection are completed. The results of simulation and physical experiments verify the correctness of the seamless switching control strategy based on PCC voltage. Then, a seamless switching control strategy based on inductance parameter design is proposed. According to the difference of the angle between the output current and the voltage, the power and flow direction of the microgrid converter and the main grid are different. By querying the standard of PCC point voltage response time to power network, which is issued by the International Association and other countries, the paper gives the range of the PCC point voltage which is allowed to fluctuate when switching, based on this standard, Considering the requirements of inductance ripple and fundamental wave voltage drop in practical engineering, the seamless switching process can be completed without changing the control strategy according to the output inductance parameter value of the converter according to the parameters such as active power capacity of microgrid. Finally, when microgrid contains multiple converters, sagging control can be used to complete seamless switching from grid-connected to isolated grid. When the microgrid is connected to the grid, the limiter does not work because of PQ control. When the isolated network occurs, because the given power may not match the load power, the limiter works. The limiting value of voltage and frequency is modified according to the droop relation to change the power reference instruction value to complete the seamless switching of PCC voltage. After the isolated network is detected, the state operation switch is switched to droop control. According to the relationship between the capacity of the microgrid and the load, the power is allocated reasonably and the energy utilization is optimized. The seamless switching control strategy based on droop control is verified in PSIM software.
【學位授予單位】：華北電力大學(北京)
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM727

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本文編號：2048420