高比例水电送出系统超低频频率振荡风险及影响因素分析

2016年云南电网与南方电网主网异步互联前期,开展了孤岛试验,实验过程中发生了频率低于0.1Hz的超低频频率振荡事件。2018年,渝鄂背靠背工程即将投运,工程投运后西南电网将与华北-华中主网实现异步互联。西南电网与云南电网都具有水电资源丰富、水电机组占比较高的外送型电网结构。为防御西南电网与华北-华中电网异步互联后可能引发的超低频频率振荡现象,针对故障扰动形式、调速器参数、旋转备用、开机方式和参与调频机组容量研究了超低频频率振荡的影响因素,通过仿真分析了低周减载、高周切机和直流频率控制器(frequency controller,FC)、优化水电机组比例-积分-微分(proportional integral differential,PID)参数对超低频频率振荡的抑制效果。综合对比后得出退出部分水电机组调速器或优化水电机组PID参数可抑制和解决超低频频率振荡问题。

Research on Ultra-Low Frequency Oscillation Risk and Influencing Factors of High-Ratio Hydroelectric Transmission System

In 2016,an islanding experiment was conducted in early stage of asynchronous interconnection between Yunnan power grid and South China power grid.During the experiment,ultra-low frequency oscillations below 0.1 Hz happened.In 2018,Chongqing-Hubei back-to-back project is about to be put into operation,and Southwest power grid will be asynchronously interconnected with North China power grid and Central China power grid.Both Southwest power grid and Yunnan power grid have the feature of exporting electricity,with abundant hydro resources and high penetration level of hydropower generating units.In this paper,in order to prevent possible ultra-low frequency oscillations caused by asynchronous interconnection between Southwest grid and North-Central China Grid,influencing factors of ultra-low frequency oscillations are studied,including fault disturbance types,parameters of power governor,spinning reserve,start-up modes,and power capacity of frequency regulation.Methods of suppressing ultra-low frequency oscillations were analyzed,such as low-cycle load shedding,high-frequency tripping and direct current frequency controller(FC),and optimization of proportional integral differential(PID)parameters for hydropower units.After comparison,it is concluded thatparameters of power governor and optimization of PID parameters for hydro generators are useful for solving the problem of ultra-low frequency oscillation.