Author: Matt Feinstein, Lux Research

Inverters that avoid the use of transformers as part of their voltage-modifying topologies often boast light weight (for easier mounting during installation) and high efficiency – as evidenced by those marketed by SMA America and the recent IG TL 4.6 release from Fronius, two leading players in the space. The selling point against transformerless inverters is that transformers provide galvanic isolation, which prevents the transmission of harmful faults onto the grid. Without that component, the system would be at risk to such faults – a risk cited by the Department of Energy (DOE) High-tech Inverter Workshop in 2005.

While SMA has partnered with the Underwriters Laboratories (UL) safety certification organization to develop testing procedures and incorporate multiple fault detection mechanisms – allowing for a relatively sizeable pickup and specific standards put in place in Europe – electrical standards in the U.S. surrounding grid connection and the associated liability are particularly tangled and unclear. Not only must National Electric Code (NEC) standards evolve to accompany new inverter technologies, but state authorities have taken to developing their own requirements amidst the breakthrough of new technologies – and they are obliged to accommodate utilities, which are cautious by nature due to the possible safety and performance risks associated with grid-tied power supplies.

Still, installers are the gatekeepers when it comes to power electronics used in solar projects, and they will use whatever products have short lead times, high reliability, and high performance – assuming that all regulatory standards are met. It is that assumption which may come into question soon, as the inverter industry continues its evolution. However, if large inverter players like SMA, Fronius, and Power-One can pull through the necessary changes in U.S. regulations by using their influence and girth, they also provide a new appeal to mute that of recently-debuted micro-inverters and power optimizers. Novel technologies – like transformerless inverters or plug-and-play circuit protectors – must seize the opportunity to pioneer the next wave of grid-connected products that will accommodate the grid and the utilities that run them.

SEMI PV Group, The Grid – December 2010