大规模集中式光伏并网场景下电力系统失步振荡中心迁移特性

Migration Characteristics of Out-of-step Center in Power System Under Large-scale Centralized Photovoltaic Grid-connected Scene

针对大规模集中式光伏并网场景下电力系统失步振荡中心迁移机理研究不足的问题,以光伏并网的阻抗特性为切入点,对失步振荡中心迁移机理进行深入研究。根据光伏电源模型及其不同故障控制策略,运用动态变化的负阻抗对光伏电源的外特性进行等效,推导了多频振荡场景下光伏通过替换同容量同步发电机与直接并网2种方式下失步振荡中心位置分布的变化规律,并通过IEEE 9节点及IEEE 39节点系统的仿真对理论分析的正确性进行验证。结果表明:随着光伏出力的增加,振荡中心分布范围从线路一侧跃迁到另一侧,且在远离电源处分布范围逐渐增加,靠近电源处分布范围逐渐减小;失步振荡中心迁移方向为向远离光伏接入点处迁移。研究结果可为含大规模集中式光伏接入的电网失步解列提供参考。

Under the background of the large-scale centralized photovoltaic grid-connected scene,the research on the migration mechanism of out-of-step center is insufficient.Consequently,taking the impedance characteristics of photovoltaic as the entry point,we studied the migration mechanism of out-of-step center.According to the PV power model and its different failure control strategies,the external characteristics of the PV are equivalent to the dynamic changing negative impedance.Then the variation of the out-of-step center under two scenes are derived,PV replacement for one of the synchronous machines with the same capacity,and PV is directly grid-connected in equivalent three-machine system.The simulation of the IEEE 9-bus system and IEEE 39-bus system verifies the correctness of the theoretical analysis.The results show that,as the PV output increases,the oscillation center shifts from one side of the line to the opposite side,and the distribution range increases gradually when it is away from the power source,and decreases gradually when it is close to the power source.Out-of-step center migration direction is away from the PV access point.The research results can provide references for the out-of-step splitting of the grid with large-scale centralized PV access.