Multi-PV inverter utility interconnection evaluations

Utility-interconnected Photovoltaic (PV) systems are quickly becoming a mainstay in today´s energy portfolio and will conceivably achieve a level of penetration where operation and performance of these devices is likely to influence the operation of area electric power systems (EPS). To achieve this, PV systems need to harvest all available energy from the solar resource, channel this energy and convert it to usable power, and provide a high level of performance and interoperability all while maintaining a level of confidence and reliability that fulfill the vested interest in PV technology. High penetration of PV systems is realized through two distinctly different approaches; a high number of small residential PV systems at a given locality, or the more influential approach of a centralized PV power station, where a multi-megawatt PV installation is comprised by numerous commercial-sized inverters. This report is focused on the interaction of multiple residential utility-interconnected PV systems connected to a single distribution transformer. Four residential inverters have been connected to a point of common coupling (PCC) along with a single RLC load that will absorb the real power and provide a resonant tank circuit tuned to 60 Hz to be used for evaluating loss of utility. Determination of the interoperability in a high penetration configuration will be evaluated in a laboratory setting at Sandia National Laboratories´ Distributed Energy Technologies Laboratory. The evaluations will focus on power quality, start up/shutdown routines, utility compatibility, and loss of utility functions. The direct current (dc) source will be provided by a Programmable Photovoltaic simulator that is designed to provide dc power with settable irradiance and module temperature conditions. An alternating current (ac) utility simulator will provide the necessary anomalies on the ac line to investigate the responses of the inverters under test.