Topology Selection and Design Methodology for SiC based Solar Photovoltaic Medium Voltage Direct Grid Connect Inverters

Solar photovoltaics (PV) is rapidly expanding as the world’s leading renewable energy source by installed capacity, with utility-scale systems increasingly relying on medium voltage (MV) inverters. Recent advancements in MV silicon carbide (SiC) devices have enabled the development of direct grid-connect inverters, which offer improved efficiency over traditional central inverters. This paper provides a comprehensive design methodology for various MV inverter topologies, including three-level neutral point clamped (NPC) inverters, five-level active NPC inverters, three and five-level modular multilevel converters (MMCs), and cascaded H-bridge converter configurations. The methodology covers key design aspects such as SiC device selection, switching frequency optimization, filter design, and DC capacitor sizing. Furthermore, a refined loss model is introduced, derived from datasheet parameters and validated experimentally using 1700 V SiC MOSFETs to accurately assess converter performance. A comparative analysis of these topologies is conducted, considering component count, euro efficiency, device stress, harmonic distortion, and total volume. The results provide critical insights into the suitability of each topology for MV direct grid-connected PV applications.