Modelling and dynamic systems analysis of instability in a capacitor-coupled substation supplying an induction motor

A capacitor-coupled substation (CCS) is a relatively inexpensive way of supplying power to communities living near high voltage power lines. However, when a CCS is used to supply a large induction motor (IM), self-excitation can occur, resulting in significant sub-synchronous voltage, current and speed oscillations. Useful insight can be obtained by analysing a CCS-induction motor (CCS-IM) system using analysis methods from control systems theory. In this paper, a dynamic model of self-excitation is formed and compensation techniques are analysed using Root Locus. The model is validated by comparing it with experimental results from a laboratory installation.