When solar power was in its infancy, inverters tended towards centralization with capacities in excess of 100 kW. In more modern times this trend has changed with operators preferring to use strings of sub-100 kW inverters. In all cases, the architecture is similar to a DC/DC boost converter to increase the voltage from the PV panel and a DC/AC inverter that generates an AC voltage at the correct frequency for the local grid (50 Hz / 60 Hz). The system also adds protection circuitry and sophisticated monitoring/control to ensure maximum efficiency.
While the topology chosen for the inverter will have an impact on the efficiency, the primary semiconductor switching devices (WBG and Si MOSFETs, IGBTs and diodes) are critical in achieving the efficiency needed for today’s solar power applications. In the early days, silicon (Si) had been the primary material used and, through years of incremental innovation, this technology has reached a point where very little further enhancement is possible.
Semiconductor manufacturers have been exploring other materials to build future switching devices from. Wide bandgap (WBG) materials including gallium nitride (GaN) and silicon carbide (SiC) have risen because of their properties which are ideally suited for developing efficient semiconductor devices.
WBG materials have inherently lower on-resistance than Si-based devices, reducing static losses when conducting continuously. As switching frequencies rise to reduce the size of magnetic components, WBG technology further improves efficiency as the gate charge is reduced compared to silicon, reducing dynamic losses as well.