基于局部网络电压相量的等值模型及其电压稳定性指标

基于输电系统中任意非PV节点及其邻近节点所组成的局部网络电压相量，建立一种新的系统等值模型。同时，在该模型的基础上提出节点电压稳定性裕度指标--节点等效负荷极限裕度(margin to node equivalent load limit，MNELL)。仿真结果表明，MNELL能准确识别系统的电压稳定薄弱节点，并且当系统某一节点的MNELL将达到0时，即该节点达到等效负荷极限时，系统将发生电压崩溃。这样，根据该指标就可方便地设置判断系统电压崩溃的门槛值，进而采取恰当的措施防止电压崩溃的发生。

An Equivalent Model and Voltage Stability Index Based on Local Network Voltage Phasors

An equivalent system model (ESM) based on a local network is presented in this paper, which is defined as any node, excluding PV node, in a transmission system and other nodes directly connected to this node. The ESM includes effects of both local network and grid system outside of the local network. A new node voltage stability index called the margin to node equivalent load limit (MNELL), which is based on ESM and uses only local voltage phasors, is presented. Simulation results show that the MNELL can identify not only the weakest nodes (buses) causing system instability but also the margin of a system state to its voltage collapse point. This feature enables us to set an index threshold to monitor and predict system stability in a real time or on-line environment so that a proper action can be taken to prevent the system from collapse.