Generalized Averaged Dynamic Modeling of Vector Switching AC Power Flow Controllers

Various devices based on thyristor phase control technology such as the SVC, TCSC and dc link technology such as HVDC, STATCOM, SSSC, and UPFC have been proposed and applied for ac power flow control. Alternatively, ac link power flow control devices based on pulse width modulation technology have been proposed in various forms including phase angle control, series reactance control, back-back interties, etc. The objective of this paper is to develop low frequency dynamic models for these converters that enable their application for power flow control. The analytical development follows generalized averaging techniques in the phasor domain to develop a state space model that captures the low frequency response of the system. Due to nature of the excitation functions being ac, the classical state space averaging techniques are refined further to accommodate the multiple frequency-cross product terms introduced due to the switching process. Detailed analytical development along with computer simulation results verifying the models are presented in the paper