Transformer-based single-phase AC-DC-AC topology for grid issues mitigation

This paper proposes a single-phase ac-dc-ac converter composed of a transformer and two three-leg converters connected in series. The proposed converter allows to feed the load voltage with sinusoidal voltages with constant amplitude and frequency and to operate with sinusoidal grid current with high power factor. Besides, the converter can be used to mitigate fundamental over-voltage and voltage harmonics at the grid. The system model, regions of operation, two pulse width modulation (PWM) techniques (including space-vector PWM), a power flux analysis, and a method to regulate the dc-link voltages using the voltage vector redundancies are given. Finally, a complete control system is provided. The proposed topology is compared with two conventional systems in terms of operation range, harmonic distortions and semiconductor losses. Simulation and experimental results are provided to validate the feasibility of the system.