Alternative Breed of Three-Phase Four-Wire Shunt Compensators Based on the Cascaded Transformer With Single DC Link

This paper discusses a variety of four-wire (4W) multilevel shunt compensators to deal with either harmonic or reactive power compensation. The converter configurations are generalized for K-stages and the main benefits of the proposed topologies lie on multilevel waveforms generation, single dc-link unit, and modular characteristic. The configurations are based on cascaded transformers along with three-phase-bridge converters. These converters are directly connected to the transformer primary side. A suitable pulse-width modulation strategy combined with an appropriate transformer turns ratio guarantees the desired multilevel output waveforms. The modularity feature provides simple maintenance and makes the proposed shunt active power filters an attractive solution in comparison with conventional configurations. The configuration model and overall control are addressed as well. Simulation and experimental results are presented for theoretical validation.