Analysis of the most common methods for determining the stability of energy systems

Problem. There are many methods for determining the stability of the energy system. In normal operating condition (normal rated mode), the power system must reliably ensure the consumption of electricity of normalized quality. However, in addition to the normal state, there are emergency and transient states caused by various transients. This is due to the fact that the energy system is constantly changing its parameters. Such changes are determined by variations in the amount of power produced and consumed, as well as the changes in system configuration. Goal. The goal is studying the possibilities of various methods of determining the power systems stability and drawing up the general algorithm of actions for maintenance of their stability. Methodology. When determining the stability of energy systems by the Lyapunov method, two methods can be used: the direct method and the first approximation method. Lyapunov direct method refers to differential methods. To conclude about the stability of the system we do not find a general or particular solution of differential equations, but with their help we find a mathematical function, the complete derivative of which over time allows to obtain a conclusion about the stability of the system. Results. Many methods can be used to determine whether a sustainable energy system is stable or not. The most common are the Lyapunov methods and the Moiseev method. It is determined that the direct Lyapunov method refers to differential methods. The application of the direct Lyapunov method for energy problems is limited. Currently, it can be used only for some individual cases. The method of the first approximation (Lyapunov first method) has received wider application in the solution of power problems. When applying this method, which belongs to the group of methods of full integration, the right-hand sides of the equations are decomposed into power series. Originality. It is determined that one of the perspective directions of increasing the efficiency of the mathematical device work is using the methods of the second order in modeling and optimization of operating modes of electric power systems. This allows you to increase the speed and reliability of the convergence of iterative processes. Practical value. Based on the analysis of various existing methods for solving the problems of stability of energy systems, an algorithm of actions is proposed and developed, which will help to solve the problem of stability in practice.

RESEARCH ON THE INFLUENCE OF MIXED OWNERSHIP REFORM ON FINANCIAL FLEXIBILITY OF STATE-OWNED ENTERPRISES

This paper selects the data of A-share manufacturing enterprises in 2010-2019 as the sample, and the impact of mixed ownership reforms on the financial flexibility of the state-owned enterprises was studied by double differential methods. The results showed that there were differences in the effects of mixed ownership reform on different types of flexible reserves of enterprises. In the reform, the state-owned enterprises have significantly improved the flexibility in the debt, but the flexibility in cash is significantly reduced. Finally, the article puts forward relevant recommendations for state-owned enterprises based on the above conclusions.

On the issue of surgical intervention for hydronephrosis

Despite the fact that the clinical history and operative treatment of hydronephrosis belong to the so-called brilliant period of abdominal surgery, which came from the time of the introduction of antiseptics and asepsis, however, no indication or differential methods of diagnostics in perfection, which we see, for example, with the treatment of brushes and other tumors of the genital area.

The differential method of detecting coil circuitsfaults in three-phase transformer

Idle voltages proportional to corresponding magnetic flows of three-phase transformer of general purpose are measured using differential methods aimed at detection of inter turn faultin windings of three-leg transformers.The standard method of determining the inter turn fault in the transformer windings is based on measuring idling current and measuring loss power. In addition, differential methods well known in relay protection are proposed to determine the presence of inter turn faultin three-phase linear transformers. The methods are based on the fact that the inter turn fault increases the magnetic resistance of the phase rod of the transformer core, in the phase winding of which there is a inter turn fault. When one-phase voltage is applied to the winding of phase B in the windings of side phases A and C of the linear three-phase transformer, the same voltage phase and amplitude shall be induced. When phase A and C windings are connected in opposition and differential signal is measured, voltage difference of phases A and C is as follows. If, in the original, intact state, the differential signal was close to zero, the inter turn faultin one of the side phases A or C introduces an imbalance and the differential signal increases. The differential signal is easily measured against the background of the near zero differential signal in the intact state of the transformer, which causes a high sensitivity of the differential method to the presence of inter turn fault. In case of a inter turn faulton the winding of the central phase B, it is necessary to take into account the differential signal in the intact state of the transformer.

Assessing the competitiveness of the resort area

Subject. This article discusses the issues of development of the Krasnaya Polyana resort area. Objectives. The article aims to assess the competitive ability and attractiveness of this resort area through developing indicators. Methods. For the study, we used a comparative analysis, and factor and ranking score techniques. Results. The article offers original methods to assess the competitiveness of the ski resort area and describes possible directions to increase and improve the competitiveness and attractiveness of ski resorts. Conclusions. Comprehensive development indicators help assess the competitive ability of the ski resort area. Modified expert, sociological, rating, and differential methods contribute to the effective management of the resort area's advantages.

Radiation Impacts on Free Convection Circulation of a Power-Law Fluid past Vertical Plate Filled Along With Darcy Porous Medium

The fluid is actually thought about to be grey, absorbing, and producing yet non-scattering channel. In this study, our team recommend to study the natural convection warmth as well as mass move coming from an upright level embedded in a power-law liquid saturated Darcy permeable resource together with domino effect and radiation effects. The managing partial differential methods are transformed in to ordinary differential formulations using correlation improvements and after that took care of numerically making use of Shooting strategy. It was discovered that speed circulation boosted with improving buoyancy specifications; temp reduced along with enhancing Prandtl amount, and focus minimized along with raising the Schmidt amount.