AN IMPROVED GAN-BASED SINGLE-PHASE TRANSFORMER-LESS PV GRID-TIED INVERTER WITH REACTIVE POWER CAPABILITY

摘要

Photovoltaic (PV) grid-tied transformer-less inverters gained a lot of attention in recent years because of their higher efficiency, reduced volume and lower cost compared to conventional inverters. This paper presents a single-phase transformer-less inverter with advanced functions that can lead to a next-generation high-performance grid-connected inverter. The topology under investigation provides new current paths to reduce the leakage current and increase the efficiency of the system. Furthermore, this paper investigates the impact of emerging GaN-based power devices on a single-phase transformer-less inverter in terms of efficiency and high switching frequency capability. Moreover, GaN power devices reverse conduction capability is studied to provide the proposed inverter with reactive power control. Existing pulse width modulation (PWM) techniques cannot provides a freewheeling path in the negative power region to generate reactive power in a single-phase transformer-less inverter. So, a new PWM technique is proposed to provide new modes of operation to achieve reactive power generation capability in the proposed inverter. The simulation results verify that the proposed topology reduces the conduction losses of the system. GaN HEMTs can be operated at high switching frequencies, and the simulation results show that GaN HEMTs operating at high switching frequency provide lower losses and superior performance when compared to their Si counterparts. Moreover, the simulation results validated the improvement of the proposed transformer-less inverter with the new PWM technique to generate reactive power. Thus, these results prove the effectiveness of the proposed inverter for grid-tied PV applications.