联接弱交流电网MMC系统小信号稳定性分析

发布时间：2018-03-17 17:27

本文选题：模块化多电平换流器　切入点：弱交流系统　出处：《中国电机工程学报》2017年18期 　论文类型：期刊论文

【摘要】：模块化多电平换流器(modular multilevel converter,MMC)直流输电技术相比于传统直流输电更适用于向弱交流电网供电。该文建立MMC联接低短路比(short circuit ratio,SCR)交流电网系统小信号模型,重点研究联接弱交流电网MMC系统与电压源换流器(voltage source converter,VSC)系统之间的稳定性差异;该文同时首次建立MMC联接低转动惯量的发电机系统小信号模型,研究交流电网惯性对系统稳定性的影响。采用特征根分析法和参与因子分析法对小信号模型进行分析,得到影响联接弱交流电网MMC系统稳定性的关键因素。最后,在PSCAD/EMTDC中搭建201电平联接弱交流电网MMC系统仿真模型,仿真结果验证了小信号模型的准确性。通过理论分析与仿真验证共得到两个结论:1)当SCR极低、交流电网极弱时,锁相环(phase-locked loop,PLL)控制器参数与子模块电容相互影响导致联接弱交流电网MMC系统易发生高频失稳;2)较小的交流电网转动惯量与外环控制器会发生相互作用,导致联接弱交流电网MMC系统小信号失稳,而通过优化外环控制器参数能够提高系统稳定性。
[Abstract]:Compared with traditional DC transmission, modularized multilevel converter (Modular multilevel convertor) DC transmission technology is more suitable for supplying weak AC power grid. A small signal model of MMC connection with low short circuit ratio short circuit convertor is established in this paper. The stability difference between the MMC system connected with weak AC power grid and the voltage source converter (VSC) system is studied, and the small signal model of generator system with low moment of inertia connected by MMC is established for the first time in this paper. The influence of inertia of AC power grid on system stability is studied. The small signal model is analyzed by means of characteristic root analysis and participation factor analysis, and the key factors affecting the stability of interconnected weak AC power grid MMC system are obtained. The simulation model of 201 level connected weak AC power MMC system is built in PSCAD/EMTDC. The simulation results verify the accuracy of the small signal model. Through theoretical analysis and simulation verification, two conclusions: 1) when the SCR is extremely low and the AC network is extremely weak, two conclusions: 1) are obtained. The interaction between the parameters of the PLL controller and the capacitance of the submodule leads to the high frequency instability of the MMC system with weak AC power grid. (2) the rotational inertia of the AC power grid with a smaller moment of inertia will interact with the outer loop controller. It leads to small signal instability of MMC system connected with weak AC power network, and the stability of the system can be improved by optimizing the outer loop controller parameters.
【作者单位】：新能源电力系统国家重点实验室(华北电力大学);国网北京经济技术研究院;
【基金】：国家自然科学基金项目(51177042)~~
【分类号】：TM46;TM721.1

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