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Islanding detection is one of the most dominant challenges for distributed generation systems connected to the main power grid. Rudimentary islanding detection methods (frequency relays, voltage relays), have considerable non-detection zones (NDZ). Nod-detection zone which defines as the area that the method fails to detect the islanding, is the primary criterion to evaluate the detection method performance...
Microgrids can be defined as distribution systems with distributed generation (DG) units, energy storages and controllable loads. Microgrids are expected to form an essential part of future Smart Grids with self-healing feature. Most of the time microgrids will be operated normally parallel with utility grid. In addition to this microgrids have a special self-healing capability, because they can continue...
This paper presents three models for dynamic analysis of inverter-based distributed generators equipped with voltage positive-feedback anti-islanding protection. The models analyzed are: the switched model, where the switches are represented in details, the average model, where the switches and signal generators are replaced by controlled voltage sources, and the small-signal model, where the average...
Most existing power flow calculation methods use a swing bus as a reference node for the whole system. Increasingly, new distributed generation resources (DGRs) are being added to the grid. Sometimes, local demand or failure of the grid can result in independent micro-grids forming, which are known as `islanding' systems. However, current DGRs are often limited such that there is no single DGR which...
This paper assesses the transient operation of a 33 kV distribution network in islanded operation consisting of different type and size of loads and distributed (mainly renewable) generators. The generators considered include synchronous generator representing the combined heat and power unit, fixed speed induction generator, doubly fed induction generator and power electronic connected photovoltaic...
Conventional methods of load shedding are too slow, do not effectively calculate the correct amount of load to shed and lack in operating in a coordinated way. This results in either unnecessary or insufficient load reduction. A new technique should be applied that will be fast and optimal relying on slow communication in order for the distribution network to maintain stability and to improve the...
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