A Novel Low Device Count Four-Port Converter Based Solar-Fed Off-Grid System for Catering Household Hybrid AC/DC Loads

Hybrid ac/dc off-grid topologies offer the combined advantage of higher energy efficient dc loads, and existing low-cost ac loads. Such budding topologies tender a promising solution for rural electrification when supplied from solar power along with battery backup. The desirable features of such a scheme for catering household appliances are: low semiconductor count, continuous current ports for PV, battery and dc load, low-voltage levels for PV and battery, dc and ac load voltage regulation, maximum power point tracking, battery overcharge and deep-discharge protection, high-voltage boosting sans low-frequency transformer, and reduced power converter stages. The schemes reported in the literature lack one or more of these features. To address this concern, a hybrid ac/dc scheme is proffered. The first stage is formed by a novel three-switch four-port converter, which facilitates most of the aforesaid features required in a hybrid system. The remaining features are obtained using a conventional dc-ac converter, which forms the second stage of the proposed solution. The overall solution is substantiated through comprehensive analysis and experimental demonstrations using a 400 W experimental prototype.