New technique for adaptive-frequency load shedding suitable for industry with private generation

Abstract

A new principle for adaptive load shedding schemes is investigated. The method requires the instant collection of data that can be utilised in analytical formulae for the frequency and its rate of change. The correctness of the method requires some sensitivity analyses towards the effectiveness of the parameters of every element of the industrial power system. Dynamic loads are represented with a new combined D-factor to account for both frequency and voltage changes. The turbine speed regulator and the generator automatic voltage regulator with a full-phase coordinate model is analysed and compared with the performance of the transient energy function and its analytical formulae. The new adaptive technique, which utilises the principle of adaptive timing setting triggered by a ROCOF relaying and, with an estimate of the lowest frequency at df/dt = 0, is compared with a modern scheme utilising ROCOF and two linear-type relays. The proposed adaptive method proved to reduce the amount of load shed, and it is inherently accurate.