Modular Cascaded H-Bridge Multilevel PV Inverter with Distributed MPPT for Grid-Connected Applications

This paper presents a modular cascaded H-bridge multilevel photovoltaic (PV) inverter for single- or three-phase gridconnected applications. The modular cascaded multilevel topology helps to improve the efficiency and flexibility of PV systems.To realize better utilization of PV modules and maximize the solar energy extraction, a distributed maximum power pointtracking control scheme is applied to both single- and three-phase multilevel inverters, which allows independent control of eachdc-link voltage. For three-phase grid-connected applications, PV mismatches may introduce unbalanced supplied power, leadingto unbalanced grid current. To solve this issue, a control scheme with modulation compensation is also proposed. Anexperimental three-phase seven-level cascaded H-bridge inverter has been built utilizing 9H-bridge modules (three modulesper phase).