本文選題：三電平半橋LLC諧振變換器 + 混合控制策略��； 參考：《山東大學(xué)》2017年碩士論文

【摘要】：LLC諧振變換器相對于PWM變換器具有開關(guān)頻率高,開關(guān)損耗小,功率密度大,體積小,效率高等優(yōu)點,因此在DC-DC電源、電動汽車充電等應(yīng)用領(lǐng)域得到廣泛關(guān)注和研究。與傳統(tǒng)的諧振變換器相比,三電平LLC諧振變換器的開關(guān)管電壓應(yīng)力降為輸入電壓的一半,適合于電壓輸入較高的情況。且能夠使原邊開關(guān)管零電壓開通(zero voltage switching,ZVS)和副邊二極管零電流關(guān)斷(zero current switching,ZCS),因此具有較高的變換效率。本文以三電平半橋LLC諧振變換器為拓撲,分析了傳統(tǒng)的變頻控制策略,給出了變頻調(diào)制的工作過程和等效電路,通過基波近似法分析了輸出電壓增益與開關(guān)頻率的關(guān)系,并指出了變頻調(diào)節(jié)在輸出電壓調(diào)節(jié)范圍上的不足。為了能夠提高電壓調(diào)節(jié)范圍,本文在三電平半橋拓撲上引入了移相調(diào)制,分析了其工作過程、電壓調(diào)節(jié)范圍及軟開關(guān)條件,導(dǎo)出了實現(xiàn)軟開關(guān)的工作狀態(tài)分界點,由此提出一種三電平半橋LLC諧振變換器移相和變頻相結(jié)合的混合式調(diào)制策略,該策略根據(jù)軟開關(guān)工作狀態(tài),切換移相調(diào)制和變頻調(diào)制,以實現(xiàn)全程軟開關(guān)和寬范圍輸出電壓控制。小信號分析是閉環(huán)控制的必要環(huán)節(jié)。移相模式下由于開關(guān)頻率保持恒定,利用狀態(tài)空間平均法對LLC諧振變換器進行了小信號建模,推導(dǎo)出了其穩(wěn)態(tài)模型和小信號模型,并設(shè)計了控制器;傳統(tǒng)的狀態(tài)空間法不適用于變頻模式,本文采用了等效電路法對LLC諧振變換器進行小信號建模,并設(shè)計控制器。兩種控制策略均通過閉環(huán)仿真進行了驗證。最后,本文對三電平半橋LLC諧振變換器的硬件電路進行了設(shè)計,包括驅(qū)動電路,保護電路和采樣調(diào)理電路等,利用數(shù)字化控制方案,采用TMS320F28335作為控制芯片,對混合式調(diào)制策略實現(xiàn)閉環(huán)控制。實驗結(jié)果驗證了理論分析的正確性和所提出的控制策略的可行性和有效性。
[Abstract]:Compared with PWM converters, LLC resonant converters have many advantages such as high switching frequency, low switching loss, large power density, small volume and high efficiency. Therefore, LLC resonant converters have been widely studied in the fields of DC-DC power supply, electric vehicle charging and so on. Compared with the conventional resonant converter, the switching voltage stress drop of the three-level LLC resonant converter is half of the input voltage, which is suitable for higher voltage input. The ZVS) and the ZVS (ZVS) can be switched off by the zero voltage of the primary side switch and the zero current of the auxiliary side diode (ZVS), so it has high conversion efficiency. In this paper, a three-level half-bridge LLC resonant converter is used as the topology, the traditional frequency conversion control strategy is analyzed, the working process and equivalent circuit of the frequency conversion modulation are given, and the relationship between the output voltage gain and the switching frequency is analyzed by the fundamental approximation method. And pointed out the frequency conversion regulation in the range of output voltage regulation. In order to improve the voltage regulation range, phase shift modulation is introduced into the three-level half-bridge topology. The working process, voltage regulation range and soft switching conditions are analyzed, and the working state dividing point is derived. A hybrid modulation strategy based on phase shift and frequency conversion for three-level half-bridge LLC resonant converter is proposed. The strategy switches phase shift modulation and frequency conversion modulation according to the soft switching state. In order to achieve the whole process of soft switching and wide range output voltage control. Small signal analysis is a necessary part of closed-loop control. Due to the constant switching frequency in phase-shifting mode, the small-signal model of LLC resonant converter is built by the state-space averaging method, the steady and small signal models are derived, and the controller is designed. The traditional state space method is not suitable for the frequency conversion mode. In this paper, the equivalent circuit method is used to model the LLC resonant converter with small signal, and the controller is designed. The two control strategies are verified by closed loop simulation. Finally, the hardware circuit of three-level half-bridge LLC resonant converter is designed, including drive circuit, protection circuit and sampling conditioning circuit. Using digital control scheme, TMS320F28335 is used as control chip. Closed loop control is realized for hybrid modulation strategy. The experimental results verify the correctness of the theoretical analysis and the feasibility and effectiveness of the proposed control strategy.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM46

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本文編號：2106901