High Efficiency Hybrid Single-Phase Voltage-Source Inverter for PV Applications

Grid-connected low-power PV systems are becoming more and more popular inside the energy market. Such a systems, are commonly installed in residential and small commercial buildings, having as a main objective the reduction of the energy bill. Efficiency is a key word in the design of PV systems since this parameter contributes with economic benefits for the investors. Among low power systems, microinverters are designed to inject the generated energy from a single PV panel to the electrical grid. A single photovoltaic panel produces a voltage around 35 V, therefore microinverters are generally designed using two stages. First stage boost and regulate the output DC voltage while the second stage produces the injected AC current. Single-phase H-bridge inverter is the basic topology used in the second stage of the isolated microinverters. In this paper, a modified hybrid high-frequency H-bridge inverter is proposed using a combination between MOSFET's and IGBT's according with the low and high frequency pulse width modulated signals. The proposal is evaluated by means of numerical simulations and compared with transformerless topologies considering the total harmonic distortion and efficiency as the comparative parameters.