Comparative study of the current and voltage controllers applied to the STATCOM

The aim of this paper is to present a comparative study, from the point of view of the stability, for the current and voltage controllers applied to the STATCOM. It is well known that the STATCOM is considered as a controllable AC voltage source behind a leakage reactance. But due to its shunt connection, the STATCOM can he also regarded as a controllable AC current source. Considering these characteristics, two kinds of control strategies can he utilized. The first one, acting on the current injected by the STATCOM and the second one acting on the voltage supplied by it. In the last one, there is only one manner to measure the feedback signal, whereas in the current control there are two ones. Additionally, either a typical PI (proportional integral) or a PR (proportional resonant) controller can be used for the purpose of enhancing the steady state response of the controller. A comparative study of these alternatives is presented, as well as computer simulations on PSCAD, so as to verify the performance of the controllers.