Robust Controller Design For A Multilevel Cascaded Statcom

In this paper, the controller robustness is studied for an indirect controlled cascaded-type based multi-level Static Synchronous Compensator (STATCOM) with 'square wave control'. The MATLAB based small-signal analytical model is used to perform eigenvalue analysis and to design controllers. Two different advanced control techniques are investigated and compared against the conventional method of proportional-integral (PI) feedback voltage control. The first strategy includes an additional current feedback, which shows minimal benefit. The second strategy considers a phase-lead compensation and indicates significantly shorter eigenvalue branches and improved robustness. The final results are confirmed with detailed non-linear PSCAD simulation.