模块化多电平级联变换器及其在城市电网中的应用研究

发布时间：2018-02-26 20:08

本文关键词： 模块化多电平级联变换器城市电网电能质量输电能力通用实验平台　出处：《华北电力大学(北京)》2017年博士论文　论文类型：学位论文

【摘要】：城市电网是现代化城市建设中的重要基础设施,提高城市电网的供电质量与输电能力是城市电网发展的基本目标。模块化多电平级联变换器(modular multilevel cascaded converter,MMCC)是一类基于全控型电力电子器件、由功率模块级联构成的高压大容量电能变换装置的统称。MMCC可根据应用场合灵活组合成多种拓扑结构,直挂于中压母线处,具有占地面积小、损耗低、支持四象限运行等优点。本文围绕MMCC内特性及其在城市电网中的应用开展了如下研究:本文总结了MMCC内特性中的基本共性问题,即内部功率波动与环流。本文将MMCC拓扑结构等效为连通图形式,利用图论基本理论分析了MMCC共性问题的产生机理。在此基础上,提出了一种MMCC内特性通用分析方法,该方法可准确求得MMCC内部功率波动与环流的幅频特性,适用于不同拓扑结构、功率模块类型、输入/输出特性的各类MMCC。进而,针对MMCC环流问题,提出了一种通用环流抑制策略,该方法具有明确的物理意义,实现简单,并可以与支路能量均衡控制相结合。MMCC共性问题研究为其在城市电网中的应用提供了理论基础。敏感、非线性负荷的电能质量问题集中、综合治理可最大程度降低治理成本,是提高城市电网供电质量的关键技术手段之一。统一电能质量控制器(unified power quality conditioner,UPQC)为电能质量问题综合治理装置,本文提出了一种串并联混合型MMCC-UPQC拓扑结构,直挂于中高压母线处综合治理电能质量问题。本文提出的串并联混合型MMCC-UPQC将串联补偿电压作为并联补偿输出电压的一部分,因此所使用的模块数与开关器件数较传统高压大容量UPQC大大减小,进而增加了装置的功率密度,并具有较高的经济性。针对电压暂降问题,本文提出了一种协同无功注入式UPQC电压暂降补偿策略,最大程度的利用了装置电流容量,延长电压暂降补偿的持续时间。并且在考虑载流受限的前提下,确定了零有功功率注入补偿域及相应的换流器限流方式。最后,通过仿真对本文提出的串并联混合型MMCC-UPQC及电压暂降补偿策略进行了验证。在现有城市电网输电走廊的基础上,采用先进输配电技术提高输电线路容量为提高城市电网输电能力的关键技术手段。本文针对城市电网电缆输电系统,提出了一种基于三星型全桥(triple star bridge cell,TSBC)MMCC的低频输电系统。该系统在电缆线路的两端分别加装TSBC-MMCC实现工频-低频的电能变换,降低了电缆的工作频率,既可以减小电缆充电功率,提高线路输电能力,也可以较好的与现有交流设备兼容互联。本文着重分析了TSBC-MMCC的低频工作特性,推导了功率波动与内部环流的幅值、频率特性。在此基础上,定义了TSBC-MMCC低频工作下的特征环流,分析了相关参数对特征环流幅值特性的影响,推导得到了换流器受环流影响较小的工作区间。进而,本文建立了TSBC-MMCC数学模型,并设计了基于TSBC-MMCC的双端低频输电的四种运行模式,实现了灵活的潮流控制。最后,对基于TSBC-MMCC的低频输电系统进行了相关仿真验证。为实现对各类MMCC及其应用的全面、深入研究,本文研制了MMCC通用实验平台,主要包括三个组成部分,即主电路部分、系统级控制器及通用软件部分。平台的主电路部分以MMCC功率桥臂为基本单元,详细阐述了其参数计算方法、器件选型、桥臂主控制器构架设计等,并搭建了功率桥臂测试回路,以保证MMCC整体装配的可靠性。与此同时,本文以统一设计、分层运行的方式研制了MMCC系统级控制器,该控制器支持MMCC功率模块数大量扩展的需求。通用软件部分中,本文重点研究了MMCC通用实验平台的底层调制算法,提出了一种混合调制算法,实现了电平数较少下精准、高效的电压输出。最后,应用MMCC通用实验平台搭建了TSBC-MMCC物理样机,实现了灵活的四象限运行,并验证了通用实验平台的正确性及先进性。
[Abstract]:City power grid is an important infrastructure of modern city construction, improve the quality of power supply and transmission capacity of city power grid is the basic goal of the development of city power grid. The modular multilevel cascade converter (modular multilevel cascaded converter, MMCC) is a kind of full controlled power electronic devices based on high voltage and large capacity power conversion device is composed of the power module cascaded collectively.MMCC according to application of flexible combination topology, hanging in medium voltage bus, has a small footprint, low loss, support four quadrant operation and other advantages. In this paper, and its application in the city grid is carried out as follows: around the MMCC characteristic in this paper summarizes the basic common problems MMCC Nate in, namely the internal power fluctuation and circulation. The MMCC topology is equivalent to the graph form, using the basic theory of graph theory analysis of MMCC common problems The mechanism. On this basis, a method is proposed for analyzing MMCC characteristics of general, amplitude frequency characteristics of the method can accurately calculate the MMCC internal power fluctuation and circulation, suitable for different types of topology, power module, input / output characteristics of various types of MMCC. and MMCC, according to the circulation problem, put forward a control strategy general circulation, has clear physical meaning, this method is simple, and can be combined on the common problems of.MMCC provides a theoretical basis for its application in the city grid and branch energy balance control. Sensitive, non line load power quality problem, comprehensive management can minimize the cost of governance is. One of the key techniques to improve the quality of power supply of the city grid. Unified power quality controller (unified power quality conditioner, UPQC) for comprehensive power quality control device is presented in this paper. A series parallel hybrid MMCC-UPQC topology, straight hanging point comprehensive control in high voltage electric bus qualityproblems. Series parallel hybrid MMCC-UPQC method is put forward in this paper as part of a series compensation voltage shunt compensation of output voltage, so that the number of module number and switching devices used by the traditional high voltage and large capacity UPQC greatly reduced then, increase the power density of the device, and has high economic. In order to solve the problem of voltage sag, this paper presents a co reactive power injection UPQC voltage sag compensation strategy to maximize the use of the device's current capacity, the duration of voltage sag compensation. And considering the current limited under the zero active power compensation into the domain and the corresponding converter current limiting mode. Finally, through the series parallel hybrid MMCC-UPQC and Simulation of the proposed voltage sag compensation strategy Verified. Based on the existing city power grid transmission corridor, the use of advanced technology to improve the transmission capacity of transmission lines is the key technique to improve the transmission capacity of city power grid. Based on the cable transmission system of city power grid, based on Samsung FB (triple star bridge cell, TSBC) low frequency transmission system MMCC at both ends of the system in the cable lines were added TSBC-MMCC - low frequency realizes the frequency conversion of electrical energy, reduce the working frequency of the cable, the cable can reduce charging power, improve the ability of transmission, can be compatible with the existing communication equipment interconnection. This paper analyzes the characteristics of low frequency TSBC-MMCC, derived amplitude. The power fluctuation and internal circulation frequency characteristics. On this basis, the definition of TSBC-MMCC work under the low frequency circulation characteristics, analysis of the related parameters on the characteristics of current amplitude The value of properties, derived work interval converter by circulation is less affected. Then, this paper establishes the TSBC-MMCC mathematical model, and design four kinds of double end TSBC-MMCC low frequency power transmission operation mode based on achieving flexible flow control. Finally, the low frequency transmission system based on TSBC-MMCC simulated in order to verify. All kinds of MMCC and its application to comprehensive, in-depth research, this paper developed a general MMCC experimental platform mainly consists of three parts, namely the main circuit, system level controller and general software. Main circuit based on MMCC power bridge as the basic unit, elaborated its parameter calculation method the device selection, the main controller, arm architecture, and built a power arm test loop, in order to ensure the reliability of MMCC assembly. At the same time, based on the unified design, hierarchical operation The development of the MMCC system level controller, the controller supports MMCC power module the number of expansion needs. The general software part, this paper focuses on the general experimental platform MMCC modulation algorithm, we propose a hybrid modulation algorithm, the level number is less accurate, high voltage output. Finally, the general laboratory the application of MMCC platform TSBC-MMCC physical prototype was built up, the four quadrant operation is flexible, and verify the validity and superiority of general experiment platform.

【学位授予单位】：华北电力大学(北京)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM46

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