Grid tied DC to three phase AC dual active bridge based current source inverter with space vector based modulation and isolated high frequency transformer

Conventional line-frequency inverters operating with different topologies and modulation techniques have been widely used in various applications for decades. Photovoltaic (PV) systems produce dc voltage which essentially require an inverter for ac-grid interconnection. Analysis and design considerations for a wide power range of three-phase grid connected PV inverters have been a topic of research for a while.

Current source inverter is a new method for grid interconnected PV power plants that are being explore in literature. Many current source inverters models have been already implemented to convert dc to three phase ac in more efficient and effective way to reduce losses and total harmonic distortion, however there has been limited applications in PV. This thesis aims to present the direct dc to three phase ac converter that reduces the number of conversion stages from dc-ac and eliminates intermediate high capacitor DC link by using modified Dual Active bridge converter (DAB) and high frequency transformer topology. In addition, this thesis proposes a modified switching technique which uses conventional space vector modulation concept combined with phase-shift control of DAB to achieve line frequency output. The proposed inverter has advantages of high-switching frequency operation, high power density and direct dc to three phase that makes it a near-ideal match for PV inverter applications. High frequency transformer eliminates the need of high bulky transformer and provides isolation to the circuit. Design and validation have been performed using Saber sketch software tool and preliminary results show that this topology can be an alternative to conventional photovoltaic inverters.