模块化多电平换流器主回路参数设计  

Design of Main Circuit Parameters of Modular Multilevel Converters

作　　者：徐政[1] 肖晃庆 张哲任[1] 

机构地区：[1]浙江大学电气工程学院,杭州310027

出　　处：《高电压技术》2015年第8期2514-2527,共14页High Voltage Engineering

基　　金：国家电网公司科技项目(SGCC-HRP031-2015)~~

摘　　要：模块化多电平换流器（MMC）将在电力系统中得到越来越广泛的应用，其主回路参数的设计直接影响系统的投资和运行性能。因此研究了MMC主回路中几种重要元件的参数设计问题，包括连接变压器、桥臂电抗器、子模块电容器、IGBT模块等。基于MMC的基本等值电路，提出了连接变压器阀侧空载额定电压的确定方法，论证了阀侧空载额定线电压的取值范围为直流侧电压的（1．00～1．05）／2倍；引入等容量放电时间常数的概念，发现电容电压波动率与等容量放电时间常数之间的关系基本不随具体工程而变，即具有跨工程的普遍适用性，因而可以一般性地给出子模块的电容参数，还分析了以往工程的对应参数，给出了等容量放电时间常数为40ms的推荐值；基于MMC的解析数学模型考察了4种极端工况下子模块功率器件所承受的电压和电流水平，发现子模块功率器件的负载水平会随运行工况的改变而发生巨大变化；引入二倍频环流谐振角频率和相单元串联谐振角频率的概念，提出了桥臂电抗器参数的取值原则，并分析了以往工程的对应参数，给出了桥臂电抗器参数普遍适用的推荐值为相单元串联谐振角频率取电网工频角频率。Modular multilevel converters （MMCs） have been increasingly used in power systems. Their main circuit pa- rameter design determines the initial cost and performance of the systems using them. We have studied the parameter design of several important components of the main circuit of MMC, such as link transformers, arm reactors, sub-module capacitors, and IGBT modules. Firstly, based on the fimdamental equivalent circuit of MMC, a method is proposed for the determining the rated no-load voltage of link transformer at valve side, which further confirms that the range of （1.00-1.05）/2 times of the voltage should be selected at DC side. Secondly, by introducing the concept of equivalent ca- pacity discharging time constant, it is found that the fluctuation ratio of sub-module capacitor voltage varies with the time constant in a relationship that rarely changes for different projects, therefore, the time constant is universally applicable and the general parameters of sub-module capacitors can be obtained accordingly. Analyzing several practical projects, we have obtained a recommended value of the equivalent capacity discharging time constant, which is 40 ms. Thirdly, the voltage and current load of sub-module power electronic devices under four extreme operating conditions are investigated using analytical formulae of the MMC. It is discovered that the current load changes greatly according to the operating condition. Finally, by introducing the concepts of phase unit series resonance angle frequency and circulating current re- sonance angle frequency, we have established a principle for determining the parameters of ann reactor, and through analyzing some corresponding parameters of existing projects, the recommended value of phase unit series resonance an- gle frequency is given as the rated angle frequency of connected power system.

关 键 词：模块化多电平换流器 主回路参数 连接变压器 桥臂电抗器 子模块电容器 电容电压波动率 等容 量放电时间常数 相单元串联谐振角频率 环流谐振角频率 

分 类 号：TM721.1[电气工程—电力系统及自动化]