本文選題：多電平　切入點(diǎn)：級聯(lián)三相橋　出處：《重慶大學(xué)》2014年碩士論文

【摘要】：級聯(lián)多電平逆變器已成為電力電子技術(shù)領(lǐng)域的研究熱點(diǎn)之一，它廣泛應(yīng)用于新能源發(fā)電并網(wǎng)系統(tǒng)、高壓直流輸電、大容量電機(jī)驅(qū)動(dòng)等場合。目前應(yīng)用較為廣泛的是以單個(gè)H橋逆變器為基本單元構(gòu)成的級聯(lián)H橋(Cascaded H-Bridge, CHB)多電平逆變器，其調(diào)制策略及控制方法的研究已經(jīng)比較成熟。近年來，有學(xué)者提出了一種以三相橋?yàn)榛締卧獦?gòu)成的級聯(lián)三相橋多電平逆變器，與級聯(lián)H橋逆變器相比，它更加適合三相大功率場合以及新能源發(fā)電并網(wǎng)系統(tǒng)。本文以級聯(lián)三相橋多電平逆變器為研究對象，對其調(diào)制策略、控制方法及并網(wǎng)技術(shù)等方面進(jìn)行了研究。 首先建立了級聯(lián)三相橋多電平逆變器的數(shù)學(xué)模型，從數(shù)學(xué)角度分析了其級聯(lián)關(guān)系及控制方式，并分析了二級級聯(lián)結(jié)構(gòu)的電壓、電流及功率等電量關(guān)系，，同時(shí)分別研究了逆變器二級級聯(lián)結(jié)構(gòu)和耦合變壓器結(jié)構(gòu)的電壓、電流矢量圖及電壓空間矢量描述，并且對后者更多級的擴(kuò)展方式進(jìn)行了分析研究。本文在載波相移PWM(Carrier Phase-shifted PWM, CPS-PWM)調(diào)制策略的基礎(chǔ)上，提出一種新的調(diào)制方法——載波相移分配PWM （Carrier Phase-shifted-distributed PWM,CPSD-PWM）調(diào)制策略，并推導(dǎo)出不同調(diào)制策略下逆變器交流側(cè)輸出的線電壓諧波數(shù)學(xué)表達(dá)式。研究表明，CPSD-PWM的本質(zhì)是在線電壓的各次諧波分量表達(dá)式中加入了數(shù)學(xué)因子ejm。 然后，研究了基于LCL濾波器結(jié)構(gòu)的級聯(lián)三相橋逆變器的并網(wǎng)控制策略，給出了連接逆變器模塊的抑流電感的折算方法，并建立了并網(wǎng)逆變器等效電路模型。通過仿真驗(yàn)證了級聯(lián)三相橋多電平逆變器二級級聯(lián)結(jié)構(gòu)和耦合變壓器結(jié)構(gòu)的并網(wǎng)控制策略，表明了新調(diào)制策略的正確性。同時(shí)，通過對比兩者的仿真結(jié)果，得出各模塊交流側(cè)輸出電流的負(fù)序分量是影響其直流母線電壓波動(dòng)的原因之一。 最后，搭建了級聯(lián)三相橋逆變器實(shí)驗(yàn)平臺，通過升壓模塊構(gòu)造了三組獨(dú)立的直流母線，采用DSP和FPGA數(shù)字控制器實(shí)現(xiàn)了CPSD-PWM調(diào)制策略，實(shí)驗(yàn)結(jié)果證實(shí)了新調(diào)制策略的正確性。 綜上，本文對級聯(lián)三相橋多電平逆變器的數(shù)學(xué)模型、拓?fù)鋽U(kuò)展、調(diào)制策略及并網(wǎng)控制方法等方面進(jìn)行了詳細(xì)的分析和研究，并通過仿真和實(shí)驗(yàn)驗(yàn)證了理論分析的正確性。
[Abstract]:Cascaded multilevel inverter has become one of the research hotspots in the field of power electronics. It is widely used in new energy generation grid connection system, high voltage direct current transmission, large capacity motor drive and so on.At present, the cascade H-bridge Cascaded H-Bridge( CHB) multilevel inverter, which is composed of a single H-bridge inverter as its basic unit, has been widely used. Its modulation strategy and control methods have been well studied.In recent years, some scholars have proposed a cascaded three-phase bridge multilevel inverter with three-phase bridge as the basic unit. Compared with the cascaded H-bridge inverter, it is more suitable for three-phase high-power occasions and new energy generation grid-connected system.In this paper, the modulation strategy, control method and grid-connected technology of cascaded three-phase bridge multilevel inverter are studied.Firstly, the mathematical model of cascaded three-phase bridge multilevel inverter is established, the cascade relation and control mode are analyzed from the point of view of mathematics, and the relationship between voltage, current and power of two-stage cascade structure is analyzed.At the same time, the voltage, current vector diagram and voltage space vector description of the two-stage cascade structure and the coupling transformer structure of the inverter are studied respectively, and the more multistage expansion mode of the latter is analyzed and studied.Based on the carrier phase shift PWM(Carrier Phase-shifted PWM (CPS-PWM) modulation strategy, a new modulation method, the carrier phase shift assignment (PWM) carrier Phase-shifted-distributed PWM (CPSD-PWM) modulation strategy, is proposed in this paper.The mathematical expressions of linear voltage harmonics of AC side output of inverter with different modulation strategies are derived.It is shown that the essence of CPSD-PWM is to add the mathematical factor ejm. into the expressions of each harmonic component of the on-line voltage.Then, the grid-connected control strategy of cascaded three-phase bridge inverter based on LCL filter structure is studied, the conversion method of current suppression inductance connected with inverter module is given, and the equivalent circuit model of grid-connected inverter is established.The grid-connected control strategy of cascaded three-phase bridge multilevel inverter with two-stage cascade structure and coupled transformer structure is verified by simulation, and the correctness of the new modulation strategy is demonstrated.At the same time, by comparing the simulation results, it is concluded that the negative sequence component of the output current of the AC side of each module is one of the reasons that affect the voltage fluctuation of the DC bus.Finally, the experimental platform of cascaded three-phase bridge inverter is set up, three groups of independent DC bus are constructed through the boost module, and the CPSD-PWM modulation strategy is realized by using DSP and FPGA digital controller. The experimental results prove the correctness of the new modulation strategy.In summary, the mathematical model, topology extension, modulation strategy and grid-connected control method of cascaded three-phase bridge multilevel inverter are analyzed and studied in detail, and the correctness of the theoretical analysis is verified by simulation and experiment.
【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TM464

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