Generic dynamic load models in long-term voltage stability studies

The aim of this paper is to examine up to what extent the so-called generic non-linear dynamic (GNLD) loadmodels can replace a more detailed representation of aggregate load, including induction motors, thermostatically controlled and static loads, in long-termvoltagestability simulations. In the first part of the paper the main characteristics of the GNLD models are compared with those of more detailed models considered as ‘reference’. It is concluded that the long-term instability phenomena are closely reproduced, in most cases, by using the GNLD model. The accuracy of the GNLD reproduction depends on the load characteristics, the type of phenomena that have to be reproduced and the position of the load in the network. Short-term instability phenomena solely due to induction motor dynamics might not be reproduced with adequate accuracy by GNLD models that are characterised by an inherent de-coupling of active and reactive power. Further, the possibility of including on load tap changer transformer into GNLD models is investigated and accomplished. These considerations are illustrated by adopting as case study a network often used in the literature.