基于三线双极结构的扩展式多端直流系统建模与特性分析

摘要

为更大程度地提升电网输电能力，缓解潮流拥塞问题，提出了将现有交流线路改造成多端直流系统的想法。通过对三极直流系统的分析，指出了其对多端直流系统的不适用性，进而提出了一种采用三线双极结构的扩展式多端直流系统。首先对扩展式多端直流系统的结构进行了描述，然后针对三线双极结构的运行原理、扩容机理和其核心设备---电流调节控制器的运行特性和可行拓扑结构进行了阐述和分析。最后，通过PSCAD/EMTDC下的仿真分析，验证了三线双极结构在多端直流系统应用中的可行性及相应控制策略的有效性。同时，仿真结果还确立了全桥模块化多电平换流器作为电流调节控制器的可行性。%In order to improve the transmission capability of power grids and mitigate the congestion of power flow,an idea about conversion of existing alternating current (AC) lines to multi-terminal direct current (MTDC)system is proposed. According to an analysis of the tripole high voltage direct current(HVDC)system,it is indicated that the tripole HVDC is not suitable for the MTDC system.Then,the three-wire bipole structure based extended MTDC system is proposed.Firstly,the structure of the extended MTDC system is described.Secondly,the operating principle and mechanism of power expansion of the three-wire bipole structure are analyzed in particular,as is its key equipment,the current regulation controller,whose operating characteristics and feasible topologies are elaborated.Finally,by use of the PSCAD/EMTDC simulation software, the designed model is simulated.The simulation results verify the feasibility of the application of three-wire bipole structure in the MTDC system,and the effectiveness of the corresponding control strategies.Meanwhile,the feasibility of the full-bridge modular multilevel converter acting as the current regulation controller is established.