Small Signal Multi-Level Statcom Model

This paper presents analytical approach for modelling a multilevel STATCOM system. The small-signal dynamic STATCOM model has modular structure and consists of two separate subsystem models: an AC model and a DC model. The converter, controller and Phase-Locked-Loop (PLL) unit are included in the DC model. In order to represent the AC system together with the DC system the AC system variables are converted by using the dq-transformation. The use of an equivalent capacitance for representing a variable DC capacitance in a multilevel converter is discussed. The model is implemented in MATLAB and the validity and accuracy of the model is verified against non-linear digital simulation PSCAD/EMTDC.