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电流型多电平变流器拓扑和控制策略的研究

Research on the Topologies and Control Strategies of Current Source Multilevel Converters

【作者】 熊宇

【导师】 张仲超;

【作者基本信息】 浙江大学 , 电力电子与电力传动, 2005, 博士

【摘要】 随着超导储能技术(SMES)的发展,电流型逆变器(CSI)的储能效率问题必将得到解决。电流型多电平逆变器具有控制电流更直接方便、动态响应更快、易于再生以及内在的短路保护能力等优点,因而在大功率应用场合将具有广泛的应用前景。本文着重研究了几种新型的电流型多电平拓扑及其控制策略,主要包括以下几方面的内容。 基于开关函数,建立了三电平电流型逆变器和组合式电流型多电平逆变器在三相静止坐标系和两相旋转坐标系的低频数学模型,为电流型多电平变流器的系统设计提供了理论基础。文中还研究了对偶定理在研究电流型多电平逆变器拓扑中的应用问题。 论文提出了一类新型单相直接式电流型多电平变流器拓扑。该类拓扑由直流母线电流分配电路和单相逆变器组成,其结构非常简单,所用开关器件和均流电感的数目比同类拓扑更少。文中分析了由该类拓扑组成的单相5电平、7电平变流器的工作原理,建立了它们的低频数学模型,并研究了它们在感性负载和容性负载时的变流器输出波形。为保证新拓扑各支路电流平衡,文中给出了相应的开关控制策略。针对该类拓扑,参照于电压型逆变器,文中还给出了一种通过调节输出电平宽度消除低次电流谐波的方法。仿真和实验结果验证了新拓扑的正确性和谐波消除法的可行性。 论文研究了一类新型三相直接式电流型多电平变流器拓扑。该类拓扑通过合成均流电感的电流而获得阶梯形的多电平电流。该类拓扑的结构非常简单,在开环控制下就能实现各共享电感电流的平衡控制。论文分析了由该类拓扑组成的三相6电平、12电平逆变器的工作原理,研究了对各支路电流进行平衡控制的开关控制策略,研究了在感性负载和容性负载时的两种逆变器的输出电流波形、均流电感电流波形。仿真和实验验证了新拓扑的正确性。与传统的通过变压器并联叠加和直接并联叠加型拓扑相比,新拓扑无论在拓扑结构、控制方法上都有显著的优点。 论文提出了一类新的三相分相控制式电流型多电平逆变器拓扑。这类拓扑通过三相星形负载的中性线进行解耦,逆变器的每相都可以独立控制,因此可以将多电平PWM技术应用到该类逆变器以减小输出电流谐波。文中给出了一种多载波PWM技术的数字化实现方案,并以单相5电平逆变器单元为例介绍了三相5电平逆变器的工作原理。最后建立了一个三相分相式5电平CSI的实验系统,验证了文中的结论。 论文还研究了几种适用于组合式电流型多电平变流器的PWM控制方法,介绍了载波相移SPWM技术,研究了多载波PWM技术在新型单相5电平电流型

【Abstract】 With the development of the superconducting magnetic energy storage (SMES) technology, superconducting inductors can be used as higher efficiency energy storage elements, the multilevel current source inverters (CSI’s) will be very attractive in high power applications due to their advantages such as controlling the output current more directly and conveniently, faster dynamic response, easy regeneration capability, and implicit short-circuit protection. This dissertation presents some new topologies and control strategies of multilevel CSI’s, including following aspects.Based on switching function, mathematical models of three-level CSI and the combinational multilevel CSI have been analyzed in abc stationary coordinate and dq rotated coordinate, which are the basis of control system design. The application of the duality principle in deriving multilevel CSI topologies are discussed.A new kind of direct type single-phase multilevel current source inverter topology is proposed in this paper. The topology is made up of a DC-bus current changing circuit and a single-phase inverter. Including very few switching valves and current sharing inductors, the structure of this type of inverter is very simple. A 5-level CSI and a 7-level CSI using the new topology are discussed in detail. The switching strategy that can ensure equal current division among the branches is presented. The waveforms of output current of the two inverters under capacitive load and inductive load are provided. The method of low-order harmonic reduction by varying the output level widths is proposed. This inverter is verified by the simulation and experimental results.A new type of three-phase direct type multilevel CSI topology is presented. The new multilevel CSI’s synthesize the staircase current wave from several levels of balance inductor currents. The structure of the new inverter is very simple. The current balance of sharing inductors can be achieved without close-loop control. A three-phase 6-level inverter and a three-phase 12-level inverter using the new topology are discussed in detail. The waveforms of output current and current-sharing inductors current of the two inverters under capacitive load and inductive load are provided. The proposition is verified by the simulation results and experimental results. Compared with traditional multiple CSI’s, the new topologies have many advantages.A new type of split-control three-phase 5-level CSI is proposed in this dissertation. The inverter is decoupled by the neutral line of the loads. Each phase of the inverter operates separately so that multilevel PWM technique can be applied. The digital current source multicarrier phase opposition disposition (POD) PWM signal generating technique is developed. The operation principle of the three-phase 5-levelCSI using the new topology is introduced by analyzing one phase cell. An experimental prototype of a three-phase 5-level CSI has been built to practise the proposition in the paper.Several PWM techniques applicable to combinational multilevel CSI are studied in this dissertation. Carrier Phase-shifted SPWM technique is introduced. Multicarrier PWM method is discussed and applied to the new single-phse 5-level CSI. Some basic points about SVPWM method applied to a three-phase combinational 5-level are proposed.

  • 【网络出版投稿人】 浙江大学
  • 【网络出版年期】2005年 05期
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