Stability of complex electrical power systems (EPS) is an important technical property, indicator of reliable and efficient operation of the EPS. The concept of stability can be divided into three types: the static, dynamic and resulting one. Static stability is the ability of the system to restore normal operation after minor perturbations, in its turn, dynamic and resulting stability is the ability of the system to restore normal operation after large disturbances. The most dangerous system condition is asynchronous operation, when the system loses resulting stability. This paper is devoted to the evaluation issues of static stability of operation mode on the example of the Latvian power system 330 kV. It is separately described the principle of operation of the elimination automatic device of asynchronous operation (AGNA, out of step protection), as a modern reliable means of emergency automation to preserve resulting stability.

The current stage of world energy development is characterized by the creation of powerful, territorially unified energy systems under free market conditions as well as renewable energy integration. Such transactions challenge networks’ configurations and their operating modes. Electric power system (EPS) static stability could be considered one of the primary targets in this regard. The aim of this study was to evaluate the undergoing and expected modernization of the Latvian EPS in terms of static stability in a regional scale-based case study. In order to define static stability, a method based on a bus admittance matrix was proposed. A simplified Latvian EPS model was developed and assessed for the following three modes: past (2017), current (2020), and planned (2025), taking into account the Baltic States’ planned development scenarios including large wind farm integration. The evaluation of computation results provided an opportunity to visually inspect changes in the EPS’ sensitive elements such as lines and nodes. As a result, positive changes were observed (decrease of several weak points) for the planned mode (2025) as compared to the past mode (2017) under the considered modernization scenario. The detailed analysis and results are presented in the article.

This paper presents a new technique for the reduction of large power system. It is based on Jordan elimination of nodes represented with their static or dynamic load characteristics dependent on voltage. Thus the reduced network models preserve their past behavior with the same final outcomes in problems of steady states, static and dynamic electromechanical transient processes. We report an example of solving a nonlinear problem in Eurostag software.

This paper examines the potential benefits smart and quickly controllable load can provide for transmission network congestion management if end-users give the transmission network operator or an independent aggregator service access to disconnect their devices in case of contingencies. The necessary amount of available quickly controllable load for the fulfilment of N-1 criteria is found for the case study of the Latvian power system. Of particular interest is the possibility to increase the maximum available transfer capacity between the Latvian and Estonian bidding areas by removing the N-1 provision from the calculation of the cross-border trading capacity if it can be supplied by the controllable load instead. For this purpose, a steady-state power flow model of the 330 kV transmission network and its interconnections with neighboring countries is used for simulations.

The market economy dictates the terms of unification of the energy systems of the countries that leads to a change in number of interconnections, the increase of the transmitted power, and therefore, it is necessary to reconfigure the networks and, consequently, the recalculation of their normal modes, as well as the project assessment of static stability is required. Stability is an important constraint in power system operation and control. Power system stability is understood as the ability to regain an equilibrium state after being subjected to a physical disturbance. Principal among methods of static stability analysis is the determination of system stability on the consideration of eigenvalues in steady state condition. This provides appropriate strategy to have a quick decision on the system's steady state behavior. The configuration of the electrical systems should be often changed in terms of market relations. The research is aimed to overcome the difficulties while dealing with the characteristic polynomial of a higher degree. Latvian power systems static stability is evaluated applying the methods of localization of the roots of the CP and isolines.

In most countries, electricity is bought and sold at regulated and non-regulated prices. Non-regulated prices are mainly set on the wholesale electricity market and can significantly increase during peak periods due to input of more expensive generation. Another problem, which leads to an increase in prices on the market, is to achieve the carrying capacity of certain sections that does not allow transferring the necessary amount of electricity in the deficit area. At that, overloaded network elements are more prone to emergency shutdown that is not allowable in the peak periods, because it can cause serious system failures. One of the problem solutions may be a load regulation, which, in its turn, may provide both long-term and short-term perspectives. Long-term perspective is aimed to improve energy efficiency carrying out the modernization and reconstruction of the main equipment or the construction of generation sources, etc. Short-term perspective is focused directly on demand management. This article discusses the possible scenarios of the impact of regulated load on the stability of the Latvian power system, based on the power system model circuit created in the software ETAP POWER STATION.