Three-leg inverter-based distribution static compensator topology for compensating unbalanced and non-linear loads

This study proposes a new three-leg voltage source inverter (VSI)-based distribution static compensator (DSTATCOM) topology to compensate unbalanced and non-linear loads in low-voltage three-phase four-wire distribution systems. The proposed topology uses a three-leg VSI with a single DC storage capacitor. This scheme has an additional small AC capacitor which is connected between negative DC bus to the system neutral. As the proposed topology uses a single DC-link capacitor, the DC voltage balancing issues associated with the popular split capacitor neutral clamped VSI topology is avoided. Moreover, the topology is able to compensate neutral current without using four-leg inverter topology. Analysis and modelling of the proposed topology is explained in detail. Simulation studies are carried out to verify the performance of the proposed scheme and results are presented. The performance of the new topology has been compared with conventional three-leg two level split capacitor VSI-based DSTATCOM topology. Results are also experimentally verified on a laboratory prototype of DSTATCOM.