Mathematical Model of STATCOM Based on Switched System

With respect to the deficiency of the output modeling, topology modeling and switching function modeling of the STATCOM, this paper states the voltage regulating principle of the STATCOM and analyzes the switch characteristics of the voltage source converter controlled by the SPWM, then deduces the duty ratio of each switches based on the switching function. Then, introduces the switching system concept in the modeling of the STATCOM, the mathematical model of STATCOM, which includes four sub-system in one switching period, each one corresponding to the specified switching duty ratio, each duty ratio corresponds with the concept of switching function, is deduced. This model can describe the physics concept of the STATCOM in detail and can deliver the static and dynamic characteristics exactly.