A PWM Scheme to Realise Two Times Effective Switching Frequency with Constant Common Mode Voltage and Reactive Power Capability in 1-ϕ Grid-Tied Transformerless H6 PV Inverter

Abstract

A novel scheme consisting of the unipolar PWM scheme in conjunction with an H6 type transformerless topology is proposed for the grid-connected solar photovoltaic application. The high-frequency operation of the inverter is desirable, but it leads to higher switching loss. The proposed scheme requires the switches to be operated just at half the actual switching frequency thereby reducing the switching loss. The proposed single-phase transformerless inverter concept exhibits very low leakage current due to no variation in common mode voltage. This is done with controlled reactive power feeding capability, which makes the system capable of satisfying the futuristic demand expected from the grid connected PV sources. Voltage stress on the additional two switches is half of the DC link voltage. Therefore, their voltage rating goes down to half. Also, all the switches operate at half the effective switching frequency, which results in high efficiency. The working principle of the novel PWM scheme is discussed and analyzed in detail, and the simulation results are presented. The experimental results are also included to validate the concept.