电网故障时模块化多电平换流器型高压直流输电系统的分析与控制  

Analysis and Control of Modular Multilevel Converter Based HVDC Transmission Systems During Grid Faults

作　　者：管敏渊[1] 徐政[1] 潘武略[2] 张静[2] 郑翔[2] 

机构地区：[1]浙江大学电气工程学院,杭州310027 [2]浙江省电力公司,杭州310007

出　　处：《高电压技术》2013年第5期1238-1245,共8页High Voltage Engineering

基　　金：国家高技术研究发展计划(863计划)(2012AA050205;2012AA051704)~~

摘　　要：电网故障条件下模块化多电平换流器型高压直流输电系统的控制策略是目前亟需进行的一个研究课题。为此,基于Kirchhoff定律,给出了描述模块化多电平换流器(MMC)交流侧和直流侧动态特性的通用动态数学模型。该模型不仅适用于交流电网对称状态,而且适用于交流电网不对称故障状态,并考虑了换流变压器漏感的影响。根据对称分量法将换流器的通用动态数学模型分解为包含正序和负序分量的2个子系统,引入了换流器的正序和负序电流矢量解耦控制器以及外环功率控制器,可以实现在交流电网正常以及故障状态下对模块化多电平换流器型高压直流(MMC-HVDC)输电系统的有效控制。设计了电网故障期间MMC输送功率的动态限幅控制,可以根据故障的种类和程度调节输送功率的限幅值,防止开关器件过载。指出了总直流电流在3个相单元之间的分配在交流系统对称状态下是基本均匀的,而在交流系统不对称故障状态下是不均匀的。仿真结果验证了所设计的电网故障时MMC-HVDC控制器的有效性和正确性。The control strategies of modular multilevel converter based high voltage direct current（MMC-HVDC） transmission systems under grid fault conditions are urgently needed.A generalized mathematical model describing the AC-side and DC-side dynamics of modular multilevel converter（MMC） is introduced based on the Kirchhoff’s laws.This model takes into account the leakage inductance of the converter transformer,and it applies not only to normal conditions,but also to fault conditions of power grid.According to a symmetrical component method,the general mathematical MMC model is decomposed into two subsystems,including positive-sequence and negative-sequence components,respectively.Then,inner vector current controllers and outer power controllers are designed,which provide effective control on MMC-based high-voltage direct current（MMC-HVDC） transmission system under both normal and fault grid conditions.Moreover,a dynamic power-limiting control is proposed to regulate power limitations and protect power semiconductors under different grid fault conditions for preventing overloads of switching gears.The distribution of DC current to units of three phases is equal only in balanced grid conditions,but not equal in unbalanced grid conditions.Time-domain simulation results illustrate the feasibility and validity of the proposed controllers for MMC-HVDC system in grid fault conditions.

关 键 词：电压源换流器 VSC 基于电压源换流器的高压直流输电 柔性直流输电 模块化多电平换流器 MMC 电网故障 功率限幅 故障穿越能力 

分 类 号：TM721.1[电气工程—电力系统及自动化]