【摘要】：LLC諧振變換拓?fù)渚哂熊涢_關(guān)、效率高、功率密度高、EMI較低、可使用磁集成技術(shù)等優(yōu)點(diǎn)。在千瓦功率等級的應(yīng)用中,LLC諧振變換器的最大效率值可以達(dá)到97%。因此在中功率DC-DC變換中得到廣泛的應(yīng)用。在工業(yè)電源應(yīng)用中,功率變換器的負(fù)載狀態(tài)具有多變性。對于通信基站的燃料電池備用電源,它的輸入電壓波動較大,負(fù)載范圍也較寬,因此對功率變換器的寬負(fù)載特性提出了較高的要求。傳統(tǒng)的LLC諧振變換器在輕載下會有增益失真等問題,傳統(tǒng)的解決方法是增加假負(fù)載,但是這樣又會帶來額外的損耗,增加成本。本文針對近年來頗受研究者關(guān)注的LLC諧振變換器的輕載增益失真以及輕載效率問題進(jìn)行了研究。首先,本文從拓?fù)浞治龅慕嵌?提出傳統(tǒng)的穩(wěn)態(tài)分析模型不適合用于對輕載狀態(tài)的分析。因為寄生電容的存在,改變了輕載狀態(tài)下諧振電路的諧振工作過程。在全負(fù)載范圍的分析中,不能忽略電路中寄生電容的影響。在考慮寄生電容的前提下,本文利用基波分析法建立了LLC諧振變換器的穩(wěn)態(tài)模型,分析了其輕載工作過程和直流電壓增益。并建立了LLC諧振變換器在輕載時的損耗模型,用來有針對性地提高變換器的效率。其次,通過分析LLC的諧振參數(shù)對于變換器增益特性以及變換器效率的影響,本文設(shè)計了輕載增益失真和效率問題的解決方法。改進(jìn)了LLC諧振參數(shù)的設(shè)計方法,以幾個關(guān)鍵參數(shù)為變量,以滿足增益需求、滿足軟開關(guān)條件、對效率的影響盡量小等作為邊界條件,得到可以避免輕載增益失真的LLC諧振參數(shù)。優(yōu)化了變換器的控制策略,輕載時加入改進(jìn)了的間歇控制模式,提高變換器在輕載時的轉(zhuǎn)換效率。最后,本文依托燃料電池功率轉(zhuǎn)換系統(tǒng)的DC-DC功率變換模塊的具體應(yīng)用,對改進(jìn)后的方法進(jìn)行了SABER仿真和實驗驗證。設(shè)計了一臺滿載輸出功率為5kW的全橋LLC諧振變換器樣機(jī),對優(yōu)化方法進(jìn)行了驗證。實驗結(jié)果證明,采用的優(yōu)化方法可以避免輕載時的增益失真問題,并能有效提高輕載時的效率。
[Abstract]:LLC resonant topology has the advantages of soft switching, high efficiency, high power density, low EMI and magnetic integration technology. In the application of kilowatt power level, the maximum efficiency of LLC resonant converter can reach 97. So it is widely used in medium power DC-DC transform. In the application of industrial power supply, the load state of power converter is variable. For the fuel cell reserve power supply of the communication base station, its input voltage fluctuates greatly and the load range is also wide, so the wide load characteristic of the power converter is required. The traditional LLC resonant converter will have gain distortion under light load. The traditional solution is to increase the false load, but this will bring extra loss and increase the cost. In this paper, the light load gain distortion and light load efficiency of LLC resonant converters which have attracted much attention in recent years are studied. Firstly, from the point of view of topological analysis, this paper proposes that the traditional steady-state analysis model is not suitable for the analysis of light load state. Because of the existence of parasitic capacitance, the resonant process of resonant circuit under light load is changed. In the analysis of full load range, the influence of parasitic capacitance in the circuit can not be ignored. On the premise of considering parasitic capacitance, the steady state model of LLC resonant converter is established by using fundamental wave analysis method, and its light-load operation process and DC voltage gain are analyzed. The loss model of LLC resonant converter under light load is established to improve the efficiency of the converter. Secondly, by analyzing the influence of resonant parameters of LLC on gain characteristics and efficiency of converter, a method to solve the problem of gain distortion and efficiency under light load is designed in this paper. This paper improves the design method of LLC resonant parameters, takes several key parameters as variables to satisfy the gain requirements, meet the soft switching conditions, and minimize the influence on efficiency as the boundary conditions, to obtain the LLC resonant parameters which can avoid light load gain distortion. The control strategy of the converter is optimized, the improved intermittent control mode is added to the light load control mode, and the conversion efficiency of the converter under light load is improved. Finally, based on the specific application of the DC-DC power conversion module of the fuel cell power conversion system, the improved method is simulated by SABER and verified by experiments. A full-bridge LLC resonant converter with full load output power of 5kW is designed and the optimization method is verified. The experimental results show that the proposed optimization method can avoid the gain distortion and improve the efficiency of light load effectively.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TM46

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本文編號：2325983