Design of a LCL filter for leakage current reduction in transformerless PV grid-connected three-level inverter

This paper presents a new methodology to design a passive damped LCL filter for a transformerless three-level photovoltaic grid-connected inverter. In addition to the conventional specifications, this paper also includes the leakage current limits in the filter design. An analysis of the passive damping scheme is presented aiming to define the LCL filter resonance damping which in turn affects directly the behavior of leakage current. It is shown also that grid inductance can modify the passive damping design parameters, once that leakage current and stability are affected. Experimental results are given to demonstrate the good performance of 10 kW PV inverter and to validate the proposed filter design methodology.