Analysis, modeling and control of an interleaved isolated boost series resonant converter for microinverter applications

The analysis, modeling and control of an interleaved boost series resonant converter (IBSRC) is presented in this paper. The converter consists of an interleaved boost stage, a high-frequency transformer (HF-XFMR) and a voltage doubler rectifier. The HF-XFMR's leakage inductance and the voltage doubler bridge rectifier's capacitors form a resonant tank that allows zero-voltage switching (ZVS) of the main semiconductor devices and zero-current switching (ZCS) of the rectifier's diodes. This capability enables the IBSRC to operate at high switching frequencies leading to a compact design while keeping efficiency high. This makes the IBSRC suitable for the dc-dc converter stage of a dual-stage microinverter. The IBSRC dynamics are extensively investigated using the extended describing functions (EDF) methodology, whereas the converter small-signal model is derived to design the closed-loop control strategy. Experimental results on a 350-W prototype are presented to demonstrate the feasibility of the proposed model and the performance of the controller during input and output variations.