Design Optimization of a fully GaN-based Buck-derived Active Power Decoupler for a Single-Phase Electrolytic Capacitor-less PV Microinverter

This work introduces, investigates, and explains the operation, control, and validation of an active energy storage system solution as an alternative replacement for conventional passive electrolytic capacitors in a single-phase photovoltaic (PV) microinverter. We propose a buck-derived architecture of Active Power Decoupler (APD) converter to replace the PV-side electrolytic storage elements in a single-stage isolated, single-phase 120V AC 60Hz grid-connected microinverter for a 400W rated system with 20-60VDC input range. Extensive system modeling for the APD circuit low and high frequency input/output voltages and inductor current is conducted as to develop a comprehensive understanding of the buck APD application, and further to establish a framework for multi-objective optimization of the converter volume and power loss through formation of their respective cost functions. The loss-volume Pareto optimization is explored to conduct the selection of optimum power components considering the decision space consisting of buck APD Gallium Nitride (GaN) power devices, capacitor, inductor, and switching frequency. The proposed design successfully reduces the energy storage system volume by at least 51.25% at the expense of 2.14 W additional power loss of and efficiency drop of 0.57% compared to the passive electrolytic capacitor solution. Further, experimental results are presented to validate the theoretical modelling and closed loop feedback controller design implementation under wide range of operating scenarios.