Study of Oscillatory Steady State Stability in the Cross-Section of Power System of Ukraine

Abstract

The task of increasing the stability of the United Energy System (UES) of Ukraine has a particular relevance in view of the prospect of joining the UES of Ukraine to the European energy association ENTSO-E. Modern software complexes of the analysis of modes of electric power systems (EPS), which use mathematical models of elements of the EPS, are required for the solution. The possibility of verification of models is complicated by the lack of naturally registered information on the violation of the stability of large energy connections due to the rarity of its cases. Therefore, for verification, calculations can be made using specially designed test schemes which reflect the properties of the researched EPS. Such scheme was used to study the oscillatory static stability at the intersection of the UES of Ukraine, depending on the setting of automatic excitation control (AEC) of synchronous generators. 

The excitation voltage, which applied to the winding of the rotor of the synchronous machine, is created by the excitation system. It consists of: an excitation (an electrical direct current (DC) machine; an electric alternating current (AC) machine a semiconductor rectifier; a converter with transformer power supply); automatic excitation controller (AEC); devices for forcing the excitation, excitation and extinguishing of the field; devices for protecting the rotor from over voltages and overloads; control and automation equipment. In practice, the types of excitation systems and AECs are characterized by a large variety. In the Software complex of stability analysis of complex EPSs of the IED of the National Academy of Sciences of Ukraine, two models are used for AEC modeling: RCA (regulator of continuous action) and RB (relay boost). In the continuous action controller (CAC) model, the input signal of the controller is assumed to be combined, which allows to take into account both the AEC of strong action, and the so-called "high-frequency" AEC (current controller of the rotor), and the simplest current compaction. The parameters of the RND model also specify the type of excitation system: independent excitation and self-excitation. The RND model is envisaged to take into account the limitation of the maximum current of a rotor, which is performed by modern AEC. It can be significant in checking static stability by a dynamic method (by calculating the transition process for small but finite perturbations). The rotor current (on the scale of the EMF) is calculated for this. 

The conducted research on the test model of the West-Vinnitsa crossing showed that the failure of the AEC setting could lead to a breakdown of stability in the form of self-oscillating power over the intersection lines; The software complex of the IED of the National Academy of Sciences of Ukraine AVR-74 can be used to study the oscillatory static stability of power associations.