LCC-MMC混合高压直流输电系统

A LCC-MMC Hybrid HVDC Transmission System

提出并建立了一种新型混合直流输电系统,其整流侧由电网换相换流器(LCC)构成,逆变侧则采用模块化多电平换流器(MMC);该系统结合了LCC及MMC的优点。在所推导的输电系统准稳态数学模型的基础上设计了系统稳态控制策略及启动策略。为了弥补MMC无法清除直流故障的缺陷,在逆变侧的直流出口处装设大功率二极管阀组以阻断故障电流通路。用PSCAD/EMTDC仿真软件搭建所设计的混合输电系统,并证明了所设计的控制器和启动策略的有效性、逆变侧MMC不存在换相失败的技术优势以及在逆变侧的直流出口处装设大功率二极管阀组以阻断故障电流通路的可行性。

This paper proposes and builds a novel hybrid high voltage direct current system, in which the rectifier side is made up of the line commutated converter（LCC） and the inverter side is composed of the modular multilevel converter（MMC）. This system combines the merits of both LCC and MMC. The steady-state control stratedy and start-up stratedy are proposed based on the deduced quasi-steady state mathematic model. High power diode is installed in the DC outlet of the inverter side to block the fault current paths which could remedy the defect that the MMC are unable to clear up DC faults. A hybrid HVDC simulation system is built in PSCAD/EMTDC, and the effectiveness of the proposed steady-state control strategy and start-up strategy are illustrated. And meanwhile the technical advantage that MMC does not exist commutation failure is proved. Moreover, simulation results confirm the feasibility that the high power diode installed in the dc outlet of the inverter side could block the fault current paths.