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With the growth of distributed generators in the power grid, replacing the fossil‐fuel‐based conventional generation sources with renewable power resources, namely photovoltaics (PVs) or wind turbines, is inevitable. However, when rotating‐kind synchronous machines that usually possess high inertia are replaced by PVs that have an inherent static nature, grid stability issues such as reduced system inertia, lack of reactive power, and decreased system damping may arise. This study investigates the stability impacts with high‐PV penetration in the Texas 2000‐bus network. From the impact analysis conducted under transient conditions, it is observed that high‐PV penetration could negatively adversely affect the voltage and frequency stability of the system which is mainly due to the replacement of conventional generators that results in reduced network inertia and lack of reactive power support. Hence, to alleviate the adverse stability implications of PVs on power systems with reduced inertia, a long‐term generator scheduling strategy is proposed considering the criticality of synchronous generators for optimally decommitting and scheduling the generators. Extensive case studies are conducted to determine the ideal dispatch strategy for the test system based on transient stability criterions. [ABSTRACT FROM AUTHOR]

Distribution networks are evolving into active meshed networks with bidirectional power flow as the penetration of distributed generation (DG) sources is increasing. This necessitates the use of directional relaying schemes in these emerging active distribution networks. However, conventional directional overcurrent (OC) protection will not be adequate to protect these networks against the stochastic nature of renewable DGs and the changing network architectures. Hence, this study proposes an adaptive directional OC relay algorithm that determines optimal protection settings according to varying fault currents and paths induced by the DGs in active meshed distribution networks. The proposed algorithm consists of a two‐phase approach that deduces: (i) optimal floating current settings through a fuzzy decision‐making module, and (ii) optimal floating time settings through an optimisation algorithm. Extensive case studies are implemented on the modified power distribution networks of IEEE 14‐bus and IEEE 30‐bus by varying the type, location, and size of DGs. The results validate the ability of the proposed protection scheme to capture the uncertainties of the DGs and determine optimal protection settings, while ensuring minimal operating time. [ABSTRACT FROM AUTHOR]

The increasing penetration of distributed generators (DGs) in modern day power grids results in varying fault current levels and network scenarios which may affect the conventional overcurrent protection relays. This necessitates a protection scheme with efficient fault signal estimations and smart decision-making capabilities in case of unexpected events. In this paper, a novel, fast, and adaptive relay mechanism has been proposed for complete protection of radial distribution systems with DG penetration. A fast recursive discrete Fourier transform (FRDFT) algorithm is used here for efficient fundamental tracking of varying power system signals. The numerical relay design using the FRDFT algorithm is embedded with a fuzzy-logic decision-making module for obtaining optimal protection settings in case of changing system conditions. The proposed adaptive scheme is tested on a standard IEEE 34-bus distribution system equipped with DGs by simulating various case studies. Simulation results verify that the adaptive relay is able to capture the changing system scenarios and select the protection settings accordingly. [ABSTRACT FROM PUBLISHER]

Abstract: In order to reduce the green house gas emissions all over the world the investment on renewable energy infrastructure is increasing particularly in the distribution network. The penetration of generating sources in the distribution network changes the characteristics of distribution system and will have impact on various technical parameters based on its size and location in the network. This paper modeled the IEEE 34 Node distribution test feeder using the commercial software package DIgSILENT power factory version 14. Solar photovoltaic generators are introduced as Distributed Generators (DGs) at various nodes and the impacts that DG produces on real and reactive power losses, voltage profile, phase imbalance and fault level of distribution system is studied. Simulated results obtained using load flow and short circuit studies are presented and discussed. [Copyright &y& Elsevier]