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新型多频率三端口模块化多电平换流器拓扑及其控制策略

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未来电网中将会存在的工频、直流与低频等多种频率,而传统换流器仅能实现交-交、交-直两种频率电气量间的能量交换.为此,提出一种新的多频率三端口模块化多电平换流器(multi-frequency triple-port modular multilevel converter,MFTP-MMC)拓扑,该拓扑结构简单对称,能够直接实现工频-低频-直流的功率变换和频率控制,不存在无功约束问题,可以输出2倍直流电压,具有直流故障自清除功能.针对MFTP-MMC拓扑建立其dq坐标下的动态数学模型,实现了系统 2 种交流频率分量同直流分量的解耦,在此基础上给出相应的控制策略,包括内环电流控制、环流控制、子模块均压控制以及外环功率控制,其物理概念清晰、控制性能良好.进一步,给出了桥臂无功分配系数的优化方法.同时针对其拓扑提出直流侧故障时闭锁以及故障后软起动策略.MATLAB/Simulink平台下的一系列仿真结果验证了所提MFTP-MMC拓扑和数学模型的正确性及其控制策略的有效性.
Novel Multi-frequency Triple-port Modular Multilevel Converter Topology and Its Control Strategy
There will be industrial frequency,low frequency and DC frequency in the future power grid;however,tradi-tional converter only realize the energy exchange between AC-AC and AC-DC.In this paper,a new multi-frequency triple-port modular multilevel converter(MFTP-MMC)topology is proposed.The MFTP-MMC topology has simple and symmetrical structure,can directly realize power conversion and frequency control among industrial frequency grid,low frequency grid and DC grid,has no reactive power constraint problem,can output twice the DC voltage,and has the func-tion of DC fault self-blocking.The dynamic mathematical model in dq coordinates is established for MFTP-MMC,and the decoupling of two AC frequency components with DC component of the system is realized.On this basis,the corre-sponding control strategies are proposed,including inner loop current control,circulating current control,submodule voltage balancing control,and outer loop power control.The strategies have clear physical meaning and good control performance.Furthermore,the optimization method of reactive power distribution method between main arm and assis-tant arm is given.According to the topology,the blocking strategy in case of DC-side fault and the soft start strategy are proposed.The validity of MFTP-MMC topology,mathematical model and its control strategies proposed in this paper have been verified on MATLAB/Simulink platform.

multi-frequency triple-port converterflexible low frequency transmission systemDC fault blockingmathematical modelcontrol strategyarm reactive power distribution

闫书豪、孟永庆、段子越、王天一、王秀丽、王锡凡

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西安交通大学电气工程学院,西安 710049

西安交通大学陕西省智能电网重点实验室,西安 710049

多频率三端口换流器 柔性低频输电系统 直流故障阻断 数学模型 控制策略 桥臂无功分配

国家重点研发计划国家电网有限公司科技项目

2021YFB24011005211DS22002C

2024

10.13336/j.1003-6520.hve.20230036

高电压技术
中国电力科学研究院　中国电机工程学会

高电压技术

CSTPCD北大核心
影响因子：2.32
ISSN：1003-6520
年,卷(期)：2024.50(8)