Periodic Small-Signal Analysis as a Tool to Build Transient Stability Models of VSC-based Devices

The paper introduces a novel approach to derive a dynamic model of devices with inclusion of Voltage Source Converter (VSC) devices suitable for transient angle and voltage stability analysis of power systems. With this aim, we treat the VSC as a nonlinear switched set of equations and apply a time-domain shooting method to define the behaviour of such model at the fundamental frequency of the system. Then the time-varying small-signal model of the VSC is derived through periodic small-signal analysis. The resulting model is defined in terms of a transfer function from which we can define a lumped equivalent circuit of the original device. The proposed approach is discussed and tested through the study of the transient response of a Static VAR Compensator (STATCOM) device connected to the well-known IEEE 14-bus system.