Power converters for renewable energy applications

Abstract

The smart grid applications have a considerable development nowadays. Being complex systems they integrate relative simple and robust elements in order to be profitable and stable on long term. This work presents a research in the field of bidirectional DC-DC and DC-AC power converters, looking for topologies suitable for DC or AC busses interfaces. Two converters are presented in this thesis, a bidirectional DC-DC converter whose topology was found in literature but it was never studied in detail and novel topology of DC-AC Flyback inverter. A full analysis and simulation design for both the bidirectional DC-DC converter with large voltage conversion ratio and for the flyback inverter are presented. Stability studies are made for the two converters in order to verify their behaviour during perturbations, using the state-space average and the PWM switch model methods. Using the AC response, two compensation functions were developed in order to improve the systems stabilities. The new compensated systems are presented and analyzed. The stability analysis results are integrated in simulation models. The simulation results for voltages and currents through the circuit elements are given here. Their shapes and values highlights the well operation for the both DC-DC and DC-AC converters. A prototype for the bidirectional hybrid DC-DC converter with large conversion ratio was designed. The experimental results are compared with the simulation results highlighting that the BHDC operation is stable and it can be used in a microgrid application. A prototyping procedure is initiated for the flyback inverter.