A T-STATCOM converter structure synergistically combining IGBTs and SiC-MOSFETs

The paper presents a new converter topology for a Transmission-type Static Synchronous Compensator (T-STATCOM), which is composed of two sections: a three-level, neutral-point clamped (3LC) converter using silicon based Insulated-Gate Bipolar Transistors (Si-IGBTs), and a two-level converter (2LC) using Silicon Carbide Metal-Oxide-Semiconductor Field-Effect Transistors (SiC-MOSFETs). These two converters are connected to each other using a coupling transformer featuring an open-end secondary winding. Taking advantage of the high switching frequency of SiC devices, the 2LC performs harmonic compensation and reactive power control, thus eliminating the need for bulky passive filters and enhancing the system overall efficiency. The proposed topology has been validated through the simulation of a 8 MVAr, 154 kV T-STATCOM system. Moreover, the consistence of the concept has been practically confirmed by a scaled-down experimental prototype rated at 6 kVAr. Up to 50% reduction in total losses and component costs is achieved by the proposed topology in comparison with state-of-the-art designs, as well as voltage Total Harmonic Distortion (THDv) compliance with IEEE Std. 519-2014.