For transformerless photovoltaic（PV）grid-connected inverters，the leakage current needs to be suppressed to a specified range.According to the common leakage current analytical model for full-bridge and half-bridge structure inverters，the mechanism of leakage current elimination for commonly used inverters is systematically analyzed.Then the optimized topologies of H5，Heric and an H6-type configuration and their optimized modulation strategies are studied.By adopting a new scheme for leakage current suppression，the leakage current of these optimized inverters can be better eliminated;and with the proposed modulation strategies，the inverters will be able to operate in any power factors.Finally，the correctness of theoretical analysis is verified by the experimental results on a 5 kW optimized H5 prototype.