A dual-active-bridge-based high-frequency isolated inverter for interfacing multiple PV modules with distributed MPPT

This paper presents a multiport converter structure, based on a modified low-device-count DC-AC dual-active-bridge (DAB) converter, for interfacing multiple PV modules, while ensuring module-level maximum power point tracking. One of the major advantages of the proposed topology is that unlike conventional cascaded H-bridge solutions, both line-module and intermodule leakage current flows are prevented due to the presence of galvanic isolation between the grid and the modules and lack of direct connection between the modules on the dc side. The topological structure used to interface the different dc inputs is based on intermediate coupling at a common high-frequency ac bus and the use of a shared PWM inverter cell to generate the 50 Hz ac output. This reduces the overall device count as compared to the simple solution of using individual microinverters paralleled on the 50 Hz ac bus. The topology also retains the advantages of its core building block viz. zero-voltage-switching operation of the devices and the possibility of realizing power decoupling using film capacitors. PLECS simulation results on a 800 W peak system and preliminary experimental results are presented to verify operation of the circuit.