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This paper presents a load shedding scheme for a distribution network connected to mini hydro generations. The proposed scheme uses the rate of change of frequency ( ROCOF) to estimate the power imbalance and voltage stability ( VS) to prioritize the load that is to be shed. The load with the most critical voltage stability (which is based on a special index) is given the first priority to be disconnected from the network in order to avoid voltage collapse. By performing load shedding based on the combination of the ROCOF and VS techniques, a better system frequency and enhanced voltage magnitudes can be achieved. The performance of the proposed scheme is validated on existing Malaysian network interconnected with a mini hydro generator. Simulation results show that the proposed scheme not only successfully stabilizes system frequency, but also simultaneously stabilizes the voltage magnitude of the buses within an acceptable limit. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Under-voltage load shedding (UVLS) is an important technique to maintain the voltage stability and frequency of a power system network. UVLS has been applied widely in transmission systems to avoid system blackouts. However, with increasing penetration of distributed generation such as photovoltaic (PV) systems, the application of UVLS becomes important for islanded distribution systems. Under this condition, the network does not have a frequency reference as when it is connected to the grid. In this condition, when the load demand exceeds the PV capacity, UVLS is the only option to stabilize the system by shedding the load based on the changes of the voltage magnitude. In this work, a new UVLS scheme based on voltage stability indices is proposed. Four voltage stability indices are used as indicators for load shedding. Based on the stability indices, the loads that have the highest tendency of voltage collapse shall be the first ones to be shed. The proposed scheme is tested on a practical distribution network energized by a grid, a mini hydro generator, and a PV system. The test results on various scenarios prove that the proposed method is able to restore the system stability. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]