SINGLE SWITCH HIGH STEP-UP DC-DC CONVERTERS FOR PHOTOVOLTAIC SYSTEMS.
high step-up DC–DC converters; zero current switching; magnetic coupling.
The growing interest in distributed generation systems, especially for renewable energy sources, encourages further research works on DC-DC converters. In photovoltaic applications, it is necessary to increase the voltage to connect the PV module to the grid. Thus, this thesis proposes a family of high step-up DC-DC converters with single switch. The variation of topologies is obtained by modifying the positions of the capacitors and the high gain is achieved through magnetic coupling. The passive clamp circuit reduces the voltage stress across the switch, allowing the use of low RDSon MOSFET. This leads to low conduction loss of the switch. In addition, the diodes operate with zero-current switching at their turn-off transition, eliminating the reverse recovery losses. The operation principle, steady-state analysis, the main waveforms and the voltage stresses across components are presented. A prototype with rated power of 140W is built to evaluate the performance of the proposed topologies. The highest efficiency obtained is 93.77% at 51.27 W, while at full load, the efficiency is 91.84%.