Analysis of impacts of SVC on voltage collapse mechanism and maximum loadability

Static var compensators (SVC) have been widely used to enhance voltage stability and power transfer. Dynamic control of large SVCs are able to maintain constant voltage over a wide range of operation. Allocation and size of SVCs are normally determined by off-line model analysis. However, under various operating conditions, e.g. change of system topology, redispatch of generation, load variation, etc, the SVC has different effects on maximum loadability and voltage stability. This can lead to voltage collapse at normal operating voltage when maximum loadability has been reached. Under this circumstance, classical undervoltage protection will fail to detect the problem. By addressing this issue, this paper scrutinizes the impact of SVC capacity on voltage collapse and the mechanism behind. The analysis results in a method to identify the maximum loadability in real time, which can be used as an indicator for online voltage stability monitoring. Finally, the methodology is validated by dynamic simulations in PSS/E.