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随着特高压交直流工程迅速发展,系统受到大扰动后面临多群失稳问题,多频失步振荡场景下的失步中心迁移规律亟待研究.推导了三机等值系统振荡中心位置表达式,分析了振荡中心的迁移规律,进而得到多频振荡下失步振荡中心出现的充要条件,并将其描绘成等值三机电压相角轨迹在相角平面中所满足的约束条件,提出一种失步中心预警策略.该策略依据电压相角轨迹接近约束条件时等值机的电压相角与频率,预判失步中心出现的地点与时刻,提前激活解列装置,使其在失步周期的最佳时刻动作.最后,PSS/E中三机九节点与IEEE 118节点算例验证了所提方法的有效性.“,”With the rapid development of UHV AC/DC projects,the power system is vulnerable to instability of multi-group modes.As a result,it is urgent to research the migration rule of the out-of-step center in multiple-frequency conditions.Based on theoretical derivation of the swing center location in the three machines system,the migration rule of the swing center in multi-frequency conditions was analyzed.Accordingly,the necessary and sufficient condition for the out-of-step center was obtained,which was depicted in a voltage phase angle plane where the phase angle of three machines should satisfy the constraints.Based on this,a pre-waming strategy of the out-of-step center was proposed.According to the voltage angle and frequency as the phase angle trajectory approaches to the constraints,the appearance time and location of the out-of-step center can be calculated.So the splitting device is activated in advance,which guarantees it works in time.Finally,IEEE 9 and IEEE 118 system in PSS/E verify the effectiveness of the forecasting method.