Design and characterization of a three-phase current source inverter using 1.7kV SiC power devices for photovoltaic applications

Classically, the energy conversion architecture found in photovoltaic (PV) power plants comprises a multitude of solar arrays delivering a maximum voltage of 1kV followed by a step-up chopper connected to a three-phase voltage source inverter. This two-stage conversion system (DC/DC + DC/AC) is then connected to the MV grid through a LV/MV transformer. In order to simplify the PV systems, this research work focuses on the study and implementation of a DC/AC topology employing a single conversion stage: the three-phase current source inverter (CSI). Although relatively simple, the CSI presents as major drawback the conduction losses. To deal with this problem, wide-bandgap silicon carbide (SiC) semiconductors are used, which allows to efficiently convert energy (η> 98.5%) while keeping a relatively high switching frequency (several tens of kHz). Nonetheless, since the available power semiconductor modules on the market are not compatible with the CSI, a novel 1.7kV SiC-based module is developed in the context of the thesis. Thus, the dynamic characterization of the new SiC device is carried out and serves as a basis for the design of a 60kW Current Source Inverter prototype. Finally, the inverter’s semiconductor efficiency is evaluated through a calorimetric method, confirming the ability of the topology to operate at higher switching frequencies. At the present time, little research has been conducted on the CSI implementation with SiC devices. The originality of this work lies mainly in the design, characterization and implementation of the new SiC power module adapted to this well-known inverter topology.