Voltage stability assessment of isolated power systems with power electronic converters

This paper extends the concept of small signal models to the frequency domain and then presents a new method for isolated power system voltage stability analysis. An approximation for the voltage and reactive power relationship of the cycloconverter is proposed and verified by time domain simulation. Small signal models for various nonlinear, power system components including power electronic converters are derived, based upon which, the incremental network of the system is formed. The voltage stability indices of various buses, which are defined in the bus impedance matrix of the incremental network, can be calculated using the conventional factorisation method without the need to determine the matrix eigenvalues and eigenvectors. The model and algorithm can also be used to predict the stiffness of the system with respect to voltage fluctuations during operation