Transient states and island mode operation of industrial electricity networks

In the paper, there is presented an analysis of the operation of an industrial plant medium voltage power network. The plant has several production halls with induction motors installed in them. Two generating units, with an asynchronous and a synchronous generator, are installed in this network. There was investigated the behavior of the generating units in the following transient states: step changes in the generated power and transition of the network to island mode operation. Such transient states may result in the loss of angular stability of the power network. Due to the lack of reliable data, the uncertainty of the mathematical model parameters of the plant power network elements was taken into account in calculations. Based on the analyses performed, it was found that in certain transient states there can appear non-decaying electromechanical swings resulting in emergency shutdown of generating units and, in consequence, the loss of the plant supply. To limit the unfavorable phenomena, there was proposed the use of stabilizer systems installed in the turbine governor and the synchronous generator excitation system. There was performed an optimization of settings of the both proposed stabilizers when taking into account the transient state caused by the emergency shutdown of the synchronous unit. A genetic algorithm was used for the parameter optimization of the stabilizers. In addition, there was carried out a comparative study when modeling loads as induction motors or constant admittances.