A Mega-Hertz Micro Converter with Extended Soft Switching Operation for Photovoltaic (PV) Application

The increasing greenhouse effect and relative environmental pollution, along with limited fossil fuel has made it urgent to a transition towards renewable energy sources. The combined global capacity of Photovoltaic (PV) energy has increased considerably from 6.01 gigawatts (GW) to 505 GW from 2006 to 2018. A typical power configuration of a PV energy conversion system consists of a front-end DC/DC micro converter that is used to provide maximum power point tracking (MPPT), as well as to provide some step-up voltage conversion from the output of the PV solar panel. Different DC/DC PV power converters have been reported in literature. The existing DC/DC converters either require a high number of switches and magnetic components, suffer from high voltage stress over some circuit elements, or have low circuit efficiency and restricted switching frequency due to hard switching (hence large size passive components are required). In this thesis, a very high frequency DC/DC micro converter with inherent extended soft-switching operation is proposed for PV energy conversion systems. In the proposed topology, a boost-based MPPT circuit is integrated with a CL (capacitor-inductor) parallel resonant converter to form a single stage DC/DC PV micro converter. While the proposed converter has an auxiliary circuit to assist extended soft- switching operation, the inductor in the auxiliary circuit is coupled with the boost inductor so that the size and space of the overall circuit can be further reduced. A modified enhanced maximum power point tracking algorithm is also developed to work with the proposed step-up DC/DC micro converter. The theoretical analysis and the operating principles of the proposed converter will be discussed in this thesis. Simulation and experimental results on a MHz (Mega-Hertz) proof-of-concept hardware prototype are provided to highlight the performance of the proposed circuit.