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The number of grid-connected rooftop solar photovoltaic (PV) systems is expected to increase significantly in the next few years. Many studies have been conducted on analyzing transmission level voltage stability with high PV penetration, and recent efforts have also analyzed voltage stability at the medium- and low-voltage distribution levels. However, those studies have not considered detailed distribution secondary modeling extending from the primary feeder to the service transformer and all the way through the distribution secondary connections and service drops. This study investigates how variable rooftop solar PV generation impacts voltages at customers sharing a service transformer. Several different types of secondary system topologies are taken into account. A set of rules is presented that can be used to ascertain the level of voltage volatility expected as the solar PV generation varies. [ABSTRACT FROM AUTHOR]

This paper presents a new method for studying electromechanical transients in power systems using three phase, combined transmission and distribution models (hybrid models). The methodology models individual phases of an electric network and associated unbalance in load and generation. Therefore, the impacts of load unbalance, single phase distributed generation and line impedance unbalance on electromechanical transients can be studied without using electromagnetic transient simulation (EMTP) programs. The implementation of this methodology in software is called the Three Phase Dynamics Analyzer (TPDA). Case studies included in the paper demonstrate the accuracy of TPDA and its ability to simulate electromechanical transients in hybrid models. TPDA has the potential for providing electric utilities and power system planners with more accurate assessment of system stability than traditional dynamic simulation software that assume balanced network topology. [ABSTRACT FROM PUBLISHER]