含风电的混合直流输电并网系统暂态特性分析

为了提高直流输电并网系统的暂态稳定运行特性,文中基于送端采用双馈风电机组(DFIG),建立LCC-二极管-MMC混合直流输电并网系统,研究该系统的并网暂态运行特性,其整流侧采用电网换相换流器(line commutated converter,LCC),逆变侧采用模块化多电平换流器(modular multilevel converter,MMC)。为解决MMC无法清除直流故障的问题,在逆变侧的直流出口处加装大功率二极管以阻断故障电流通路。在MATLAB/Simulink平台搭建LCC-二极管-MMC风电并网仿真模型,通过设置直流及并网点接地故障,仿真分析LCC及MMC的各种优越性。研究结果表明:该系统不存在逆变侧换相失败的问题且发生直流故障时系统中大功率二极管能够阻断故障电流通路,在故障期间逆变侧直流电压也无突增现象且有功功率波动极小,从而增强了系统的暂态稳定特性。

Analysis on Transient Characteristics of Hybrid DC Transmission Connected-grid System with Wind Power

In order to improve the transient stability of the HVDC system, in this paper uses the DFIG based on sending, to establish the LCC-diode-MMC hybrid DC transmission network system, and study the grid-connected tran - sient operation characteristics of the system, the rectifier side using the line commutated converter (line commutated converter, LCC), inverter side using modular multilevel converter (modular multilevel converter, MMC). In order to solve the problems of the MMC can't remove the DC fault, install the high power diode at the DC outlet of the inverter side to block the fault current path. In the MATLAB/Simulink platform, LCC-diode-MMC wind power grid simulation model is established. The superiority of LCC and MMC is analyzed by setting the DC and grounding fault. The results show that the system does not have the problem of inverter phase commutation failure and the high-power diode in the system can block the fault current path when the DC fault occurs, during the fault, the DC voltage of the inverter side does not increase and the active power fluctuates very small, thus enhancing the system's transient stability characteristics.