By virtue of its remarkably low voltage stress，low harmonics and low power loss，the three-level inverter is increasingly applied in renewable energy systems such as the solar and wind power system.Anyway，the manifest feature of the new energy generating system is power fluctuation.Proceeding from the stochastic power fluctuation，the conventional three-level inverter is evaluated in terms of its topological power loss first.Then，some new schemes of hardware and control strategies are proposed for a three-level inverter applied in a solar inverter.Finally，a prototype is built to verify the improvement.Test results show the proposed schemes can improve the efficiency of the three-level inverter，especially the efficiency in the low and medium power range.