A universal STATCOM with delta-connected cascade multilevel inverter

It is believed that cascade multilevel converter will be the major circuit to be used in static synchronous compensator (STATCOM). Recently, all the researches about STATCOM have been focused on the wye-connected cascade multilevel converters. But STATCOM with this kind of circuit structure can only compensate the reactive power and harmonics. This paper proposes a universal STATCOM based on delta-connected cascade multilevel inverter. Other than reactive power compensation, the proposed STATCOM can also be used to compensate negative sequence current caused by unbalanced loads. The compensation theory is illustrated. The operation principle and control scheme are verified by simulation results.