Shunt Active Power Filter Based on Cascaded Transformers Coupled With Three-Phase Bridge Converters

This paper proposes a multilevel shunt active power filter (SAPF) to deal with either harmonic current compensation or reactive power compensation. Such a device can reduce the harmonic distortion at the grid currents provided by nonlinear loads located in stiff systems. The proposed SAPF is based on three-phase bridge converters connected to cascaded single-phase transformers. The transformer arrangement permits the compensator to use a single dc-link unit, which simplifies the control strategy and the number of sensors. The multilevel waveforms are generated by using a suitable pulse-width modulation (PWM) strategy associated with the transformer turns ratio. Modularity and simple maintenance make the proposed SAPF an attractive solution compared with some conventional configurations. The model, the PWM technique, and the control strategy are presented, as well as studies considering harmonic distortion and semiconductor losses estimation. Simulation and experimental results are presented in order to validate theoretical approaches.