Contribution of Photovoltaic Power Generation Systems to AC Short Circuits - a Survey of Current Modeling Practices and Challenges

As an important part of evaluating the transmission and distribution system impacts of interconnecting new generation sources, network operators must assess the impact of these sources on fault interrupting capabilities of automatic switching devices and protective relay coordination for balanced and unbalanced faults on the network. A growing component of these new generation sources is solar photovoltaic-based systems. Modeling of these sources for short circuit studies is complicated by the non-linear control characteristics of their associated inverters. These characteristics preclude the use of linear circuit analysis techniques based on Thevenin equivalents that are the prevalent methodologies relied upon in most commercial short circuit analysis tools. This paper contrasts the physical characteristics of well-understood synchronous generator technology with that of modern-day PV inverter technology. Limitations of commercial short circuit analysis tools for addressing solar PV generation systems, and recommendations for development of industry consensus standard analysis methods, are presented.