Analysis and modification of the single phase transformerless FB-DCB inverter modulation for injecting reactive power

Full Bridge Inverter with DC Bypass (FB-DCB) is among the attractive topologies used in the single phase photovoltaic systems due to its low leakage current and high efficiency. Grid standards have foreseen reactive power control for distributed generation resource such as wind turbines and photovoltaic arrays. In case of single phase photovoltaic generation, this capability contributes to power quality of the residential and smart grids. In this paper, the capability of the FB-DCB topology for operating in power factors other than unity is investigated in detail. Two modulation methods are evaluated according to the capability of reactive power generation, the leakage current reduction, and efficiency of the FB-DCB. Moreover, a novel modulation method is proposed enabling the reactive power injection. The switching losses are balanced, and switches´ stresses are reduced owing to the proposed modulation method. The advantages of the proposed method are validated using accurate MATLAB/SIMULINK simulations.