A Novel Four Switch Transformerless Inverter with Step Up/Down Capability for PV Fed Grid Connected Systems

This paper presents a novel four-switch transformerless inverter (FSTI) topology for 1-ø grid-connected solar photovoltaic applications with reactive power capability. This proposed FSTI steps up/down the output voltage while completely suppressing the leakage/parasitic currents. Further, this inverter topology supports the on/off-grid application where active/reactive power requirement is essential. In addition, the FSTI comprises of least active power devices, lower voltage and current stresses of power devices, appropriate THD in grid current and better efficiency. The FSTI performance is evaluated for the 1-ø grid connected system. The FSTI is modeled using small signal analysis for the grid-connected inverter's stable operation and fast response. The FSTI is validated on a 500VA laboratory prototype for input PV voltages of 100V, 180V and grid voltage of 110Vrms. The experimental results are in good agreement with the theoretical analysis, which verifies the practicality of the proposed inverter. The FSTI demonstrates the DC to AC power transfer while stepping up/down the inverter’s output voltage with maximum efficiencies of 97% and 96% for the input voltages of 180V and 100V, respectively.