Fault Ride Through ??Overview

Electricity networks around the world are evolving rapidly with the large scale integration of power electronic interfaced distributed renewable energy resources DRERs. With this rapid deployment of power electronic interfaced renewables, requirements set evolved to maintain grid security & reliability.

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Fault Ride Through FRT, referred to as under voltage ride through UVRT, or low voltage ride through LVRT, is the capability of electric generators to stay connected in short periods of lower electric network voltage. This is particularly important during voltage sags or swells. One of the important requirements in the grid codes is the low voltage ride through LVRT capability which demands to stay on grid and supply the expected reactive current to support the utility during grid faults.

FRT is an essential requirement which should be adhered by DRERs, which will ensure security and reliability of the power system during grid faults. Increase of low inertia systems connected to the grid known as Distributed Energy Resources?DERs such as Solar, Wind, Fuel Cell and Battery System among the most common. This trend make the Power System susceptible to a catastrophic chain reaction in case of a grid fault.

FRT capability is mostly expressed with the voltage time or frequency time diagram that shows the desired capabilities for a generation unit to ride through a voltage or frequency disturbance in order to ensure the systems' security. The purpose of using FRT is to prevent the generation lost as much as technically and economically is reasonable.

FRT capability can be applied to the power generation units, power parks modules, and DC converters. The FRT’s diagram is different among the countries. At the normal and short circuit condition, generation units must stay connected to the grid in a specific voltage and frequency range.

WORLD PRACTICES ASPER GRID CODE ??

FRT regulations in Great Britain are so specific and pay more attention to some delicate points such as division of WTs into onshore and offshore, different operative fault clearance time, two-ended or three-ended circuits, and is divided into different kinds of retained voltage including 30%, 50%, and 85%. FRT regulation in Canada and America have different standards related to their countries classification.

Europe grid code has a harmonized proposal, a specific regulation for power park modules, and finally, a wide range of FRT instead of a specific FRT which is because of a wide range of countries which should follow these rules. Because of protection issues, HVRT capability is less noted in the grid codes. For another category of grid codes like France and India, FRT requirements depend on the level of voltage which the fault occurs. LVRT requirements of South Africa’s grid code consists of four categories which are based on the generating units rated capacity.

Different potential method, technologies are used to have the improvement in the FRT capability