AC Coupling in Utility-Interactive and Stand-Alone Applications: Page 16 of 16
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In residential systems, ac coupling is one approach that can be used to increase PV system voltages (up to 600 Vdc) to minimize wire costs when PV arrays are located a significant distance from the power-conditioning and -storage equipment. It can be a great solution in the retrofit market when customers want to add battery backup to existing grid-direct systems. Finally, ac-coupled systems can achieve higher dc-to-ac conversion efficiencies, especially when the generation matches periods of high-electricity demand.
In spite of the benefits ac coupling has to offer, it may also have some downsides when compared to more standard dc-coupled system designs. Again, depending on the application and equipment used, system regulation and optimized battery charging can be a challenge, especially when equipment from different manufacturers is installed. The introduction of higher voltage charge controllers has offset one of the perceived advantages of ac coupling when long-distance array-to-battery power transmission is required. In general, ac-coupled systems can be more complex in design and installation, and this is compounded by the fact that the knowledge base in the industry to support inexperienced integrators is still underdeveloped compared to what is available for the more common grid-direct and dc-coupled systems.
In spite of the benefits and drawbacks of ac-coupled system architectures, they are an important and viable approach for integrators to have in their design toolkit. AC coupling can provide solutions for systems that would otherwise have been undevelopable. As interest in ac-coupled systems continues to grow, installers will continue to learn valuable lessons from the field. Correspondingly, manufacturers will continue to develop both products and more-robust support services to aid integrators in the design and installation of this modular and scalable system platform.
Joe Schwartz / SolarPro magazine / Ashland, OR / solarprofessional.com
Inverter Manufacturers with AC-Coupled Solutions
Magnum Energy / 425.353.8833 / magnumenergy.com
OutBack Power Technologies / 360.435.6030 / outbackpower.com
Schneider Electric / 847.397.2600 / schneider-electric.com
SMA America / 916.625.0870 / sma-america.com