MMC型换流器电容电压平衡策略的仿真与设计

发布时间：2018-12-21 14:36

【摘要】：MMC(Modular Multi-level Converter)是一种新型的柔性直流输电拓扑结构。柔性直流输电的拓扑结构从原始的两电平、三电平变换器,发展到近些年流行起来的模块化多电平变换器,它具有良好的输出电能质量、适应高电压应用、冗余特性等优点成为柔性直流输电的研究热点。本文以MMC在逆变方面应用为主要研究方向,围绕模块化多电平逆变器的控制技术中涉及的调制技术、电容电压平衡策略等展开研究,分析了它的拓扑结构、工作方式、数学模型、调制算法以及控制算法,并进行了仿真和实验验证。首先介绍了模块化多电平换流器组成结构和基本工作原理,对模块化多电平换流器创建了数学模型,适当地将电路等效变化,给出了三相等效电路图和单相等效图,建立了以开关函数为基础的公式,更加清晰地阐述了 MMC多电平换流器的工作机理。其次,针对MMC的结构特点,以MATLAB/Simulink为数学工具对基于载波移相调制技术的电容电压平衡算法建立了仿真模型。对载波移相技术进行了详细分析,通过采用桥臂电压均衡控制和子模块均衡控制完成了对电容电压的平衡控制,仿真结果表明等效开关频率与子模块数成正比关系,采取基于载波移相调制技术的电容电压平衡算法,使电容电压保持稳定,波动系数和输出电压谐波成分减小。最后,根据仿真数据和现有条件搭建了一个基于DSP的仿真控制平台,包括主电路、驱动电路、电压电流采样调理电路等电路。通过对硬软件的设计和调试,最后给出了上桥臂电容电压波形,实验波形表明电压的波动系数在合理范围以内,证明了控制策略能够对电容稳压同时保证了系统正常工作。
[Abstract]:MMC (Modular Multi-level Converter) is a new type of flexible DC transmission topology. The topology of flexible DC transmission has developed from the original two-level and three-level converters to the popular modular multilevel converters in recent years. It has good output power quality and is suitable for high voltage applications. The advantages of redundancy have become the research focus of flexible DC transmission. In this paper, the application of MMC in inverter is the main research direction. The modulation technology and capacitive voltage balance strategy involved in the control technology of modularized multilevel inverter are studied, and its topology and working mode are analyzed. The mathematical model, modulation algorithm and control algorithm are verified by simulation and experiment. Firstly, the structure and basic working principle of modularized multilevel converter are introduced. The mathematical model of modularized multilevel converter is established, and the equivalent circuit diagram of three-phase and single-phase equivalent circuit is given. The formula based on switch function is established, and the working mechanism of MMC multilevel converter is explained more clearly. Secondly, according to the structural characteristics of MMC, the simulation model of capacitor voltage balance algorithm based on carrier phase shift modulation is established with MATLAB/Simulink as a mathematical tool. The carrier phase shift technology is analyzed in detail. The capacitor voltage balance control is accomplished by using the bridge arm voltage equalization control and the sub-module equalization control. The simulation results show that the equivalent switching frequency is proportional to the number of sub-modules. The capacitive voltage balance algorithm based on carrier phase shift modulation technique is adopted to stabilize the capacitance voltage and reduce the fluctuation coefficient and the harmonic components of the output voltage. Finally, according to the simulation data and existing conditions, a simulation control platform based on DSP is built, including main circuit, driving circuit, voltage and current sampling conditioning circuit and so on. Through the design and debugging of hardware and software, the voltage waveform of the upper arm capacitor is given. The experimental waveform shows that the fluctuation coefficient of the voltage is within a reasonable range. It is proved that the control strategy can stabilize the capacitor voltage and ensure the normal operation of the system.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM46

【参考文献】