Design of a Photovoltaic Grid-Tied Inverter Employing a Dual-Stage Boost Converter and a Transformer-Less Step-Down Circuit

This paper proposes a topology for a transformer-less, pure sine wave grid-tie inverter (GTI) for photovoltaic (PV) application. The proposed GTI employs a dual-stage boost converter, a transformer-less step down circuit, an H-bridge inverter and a T-LCL Immittance conversion circuit. The switching technique of the proposed inverter consists of a combination of sinusoidal pulse width modulation (SPWM) and a square wave along with grid synchronizing conditions. As the suggested method is entirely transformer-less, it significantly reduces the total harmonic distortion (THD) of the output voltage (less than 0.1%), minimizes its size and swells the inverter efficiency up to 97%. The T-LCL Immittance conversion circuit not only reduces the harmonics of the inverter output but also provides a nearly constant output current thereby stabilizing the system rapidly. The overall performance of the proposed inverter is simulated using PSIM using the designed values of circuit components. The simulation results show that the proposed inverter is capable of not only eliminating harmonics but is also highly efficient, compact and cost effective.