Effect of Sudden Increase of Dynamic Loads on Voltage Stability

With more and more dynamic loads, mainly induction motors, the associated voltage stability has become a growing concern in modern power system. This paper focuses on induction motor starting up. Firstly, a failure starting-up example of a 12 MW induction motor in China SINOPEC Yanshan chemical is given and analyzed through Lyapunov´s first method and time-domain simulation. Then, from the viewpoint of static voltage stability, small-signal stability and acceptable voltage level, this paper classifies the starting-up situations into 6 categories. This classification can be used to analyze the above example. Furthermore, this paper points out that load rate and node voltage sensitivity should be considered in order to prevent cascaded voltage collapse in multi-motor situation. Finally, an index is proposed to forecast voltage stability during the starting up process.