Guilherme Hertz

A new non-isolated bidirectional converter is proposed on this work. This converter stage is suitable for applications of DC and AC motor drives. In this converter, for a given duty cycle, the output to input voltage ratio can be raised by adding transformer turns ratio. Another important feature of this converter is the lower blocking voltage across the controlled switches compared to similar circuits, which allows the utilization of MOSFETs switches with lower conduction resistances RDS(on). In order to verify the feasibility of this topology; principle of operation, theoretical analysis, and experimental waveforms are shown for a 500 W assembled prototype.

This project consists in a study of a voltage inverter applicable to photovoltaic energy generation. The studied inverter presents in the input, a voltage source characteristic, and a current source characteristic in the output, it is called VSI (Voltage Source Inverter) in
the literature and it should to be capable to transfer power to grid. The input receives a 400V continuous tension from the photovoltaic module and a classic boost converter with MPPT
(Maximum Power Point Tracker), which is studied in a parallel work. In this work contents, a
brief review of single-phase inverter topologies and control strategies is done, and then is presented the proposed work. Following, to the chosen inverter, a qualitative and quantitative analysis is done. Finally, a project example with 700VA output power is developed, with a 400VCC input und 220VAC output. The project example results are verified in the simulation.

This work proposes an double conversion three-phase uninterruptible power system (UPS) with power factor correction, high frequency (HF) transformer isolation, and suitable for operation with line-to-line input voltages equal to 220 V or 380 V. For both input voltages, the proposed converter has almost the same efficiency processing the same output power. The structure is composed by single-phase chopper modules, single-phase boost modules, and one three-phase inverter . The relevant features are soft commutation of the controlled switches in the chopper stage, simple control strategy that can be implemented with well-known integrated circuits (IC), and the use of few batteries in series due to the same reference of the step-up stages. Principle of operation of the proposed system, implemented control strategy and experimental results obtained for a 15 kVA prototype are presented.