Single-Phase AC-DC-AC Multilevel Converter with Transformers Applied to Grid Voltage Compensation

Abstract

This paper presents a single-phase ac-dc-ac multilevel converter composed of two three-leg converters series-connected throughout two transformers (one on the grid side and one on the load side), sharing the same dc-link, The proposed converter can mitigate grid fundamental overvoltage and can be applied to systems with equal or different voltage levels at the input and output. Besides, the converter allows to feed the load with sinusoidal voltages (with constant amplitude and frequency) and to operate with sinusoidal grid current with high power factor. Circuit model equations, PWM technique based on space vector approaches and a control system are presented. The proposed topology is compared with the conventional one in terms of harmonic distortions and semiconductor power losses. Simulation and experimental results under same conditions are provided for validation purposes.