High gain high efficiency front end resonant dc-dc boost converter for PV microinverter

Interfacing a single PV module to the grid as in a PV microinverter requires a high step-up gain. This paper presents a voltage-stiff-output LLC tank based resonant boost dc/dc converter with inherent isolationas the input dc-dc stage of a PV microinverter. Characteristics of the tank network are derived and a novel control strategy is suggested which ensures MPPT. An additional loop is incorporated for excitation frequency control to ensure peak-gain operation under variation in tank parameters. Detailed design procedure for the tank are provided, starting from the analytical derivation of the basic design equations. Finally numerical simulation and experimental results are presented.