Modes Of Power Supply Systems Research Articles

Identification of the sharing contribution of the power supply system power sources to the electricity losses and their cost

THE PURPOSE. Consider the problems of estimating the cost of services for the transmission of electricity through the electric networks of territorial grid organizations (TGOs), including large industrial enterprises with the status of TGOs and their own generation. Develop a methodology for calculating the cost of electricity losses in the elements of the power supply system of such enterprises, taking into account the technical and economic characteristics of the sources. Develop a methodology for determining the share contribution of individual sources and consumers to electricity losses and their cost. Calculate the cost of electricity losses and the structure of the contribution to it of power sources of an industrial TGO enterprise and draw conclusions. METHODS. When solving the tasks set, methods for calculating steady-state modes of power supply systems were used. RESULTS. The article describes the relevance of the topic, created calculation methods, in the conditions of a large industrial power center, the system of payment by sub-subscribers of an industrial enterprise for services for the transmission of electricity and its relationship with the flow distribution is considered. The structure of the contribution of power sources to the losses of electricity in the power supply system is analyzed. An approach has been formulated to adjust the individual tariff for the purchase of electricity losses, taking into account the placement of power sources in the power supply system. Recommendations are given to reduce the degree of undercompensation of the cost of electricity transmission services by third-party consumers. It is proposed to use for these purposes the norms of technological losses of electricity (NTLE), determined by the cost of losses. CONCLUSION. Under the current regulatory framework, it is in the interests of TGO enterprises to distribute sub-subscribers in the scheme in such a way that their actual NTLE, determined taking into account the targeting of losses, does not exceed the calculated NTLE. In this case, there is no transfer of the cost of losses from sub-subscribers to the own consumption of the TGO enterprise. At the same time, sub-subscribers do not incur additional costs, since they pay off with the guaranteeing supplier at the boiler tariff. NTLE for these purposes must be determined by the cost of losses, taking into account the characteristics of the sources. The share of payment for losses in the networks of an TGO enterprise, which goes to its own consumption and is not compensated by sub-subscribers, is reduced. Consequently, the amount of costs for electricity and their share in the cost of finished products of the TGO enterprise is reduced.

Equivalent Transformations of Complex Circuits in Calculations of Power Supply Systems of Agrocomplex

he tasks at the stage of planning and operation of power supply systems are related to the calculation of the parameters of their operation modes. With the massive nature of such complex calculations, their execution is possible only with the help of appropriate software and computing tools, that is, using an electronic computer. (Research purpose) The research purpose is to substantiate the algorithm of equivalence of power supply systems or their individual sections as an integral part of the algorithms complex for calculating electrical systems. (Materials and methods) It has been shown that at present there are many agricultural consumers, interruptions in the power supply of which lead to significant damage, in this regard, closed power supply systems are becoming increasingly used, as the requirements for reliability, uninterrupted power supply and the quality of electricity supplied to the consumer are increasing. It was determined that the calculation of closed systems is more complicated than open ones. It was revealed that when solving a wide range of tasks related to the creation and modernization of power supply systems, there is a need to simplify the systems or their individual sections. (Results and discussion) The equivalence rule was formed and methods for calculating equivalent resistances and electromotive force of the converted sections of the replacement circuits were given, which simplifies the circuit and accelerates the process of calculating and analyzing the modes of power supply systems. (Conclusions) It was established that the proposed equivalence algorithm is based on universal formulas for calculating intrinsic and mutual resistances, which were previously obtained by the authors for use in problems of calculating steady-state modes of power supply systems. It was stated that the calculation algorithm is also applicable for the equivalence of forward and reverse sequence circuits in the calculation of currents of asymmetric short circuits and in the analysis of the dynamic stability of electric power systems

ИНФОРМАЦИОННОЕ ОБЕСПЕЧЕНИЕ СИСТЕМЫ ОПТИМАЛЬНОГО УПРАВЛЕНИЯ КОНФИГУРАЦИЕЙ РАСПРЕДЕЛИТЕЛЬНОЙ СЕТИ

Relevance In the context of growing demand for electricity and expensive energy resources, the requirements for the efficiency of power grid organizations in terms of reducing the level of electricity losses in electric networks are increasing. The solution of this problem is possible by optimizing the operating modes of power supply systems. Modern automation tools used in the power grid complex make it possible to calculate, analyze and control the operating modes of electric networks in real time, relying on the actual values of mode parameters, which increases the control efficiency and adaptability of the network to changing external factors. Analysis of the current level of automation of electric networks was carried out in the work and a variant of the system for optimal control of the configuration of the distribution network was proposed and substantiated. Aim of research Determination of the sources of information necessary for correct operation of the system of optimal configuration management of the distribution network. Research methods To achieve the main aim of research the method of the simulation mathematical modeling in MATLAB/SIMULINK was used. Results As a result of the study, it has been found that the modern level of automation of power supply networks makes it possible to implement an optimal control system for the configuration of the distribution network without installing additional power, measuring and network equipment. It is proposed to use 110/10 kV remote control systems, monitoring and diagnostics systems for 110/10 kV power transformers and automated commercial electricity metering systems as sources of measuring information. The practical significance of the obtained results is manifested in increasing the efficiency of the power transmission process through medium voltage distribution networks by optimizing the modes of their operation in real time.

Improving the efficiency of emergency control systems for future-oriented connection of sources of distributed generation

Improvement of energy-intensive technological processes of industrial enterprises requires increasing the reliability and efficiency of power supply of consumers. In this regard, one of the priority areas associated with introduction of the sources of distributed generation is mainstreamed in energy industry. This trend has both beneficial and negative impacts. It makes difficult to control normal, emergency, and post-emergency modes of power supply systems of enterprises of ferrous metallurgy. When new sources of distributed generation are introduced under the conditions of complex closed-loop power supply system, it is necessary to assess the level of short-circuit currents to check the electrical equipment and residual voltages across the busbars of the consumers of ferrous metallurgy. Also, it is necessary to determine the critical time of generators dropping and evaluate the stability in case of isolated operation. An algorithm has been developed for automated search of a dividing point in case of an emergency and isolated operation depending on the power balance to maintain stability. It is based on a combination of the method of successive network reduction and step-by-step method. To improve the reliability of essential consumers, the authors have developed an algorithm for automatic search for the dividing point during operation of emergency control system depending on the power balance to maintain stability. The authors have developed proprietary software to assess the effectiveness of emergency automation equipment of multi-level complex closed-loop power supply system of metallurgical enterprise. Performed calculations and analysis of emergency and post-emergency modes are designed to develop a comprehensive approach of a set of measures to ensure the reliability and stability of essential consumers in the mode of automatic search.

Improving the quality of electricity supply systems in stationary objects of railway transport

THE PURPOSE. Development of a methodology for modeling the modes of power supply systems for railways equipped with devices to improve the quality of electricity in the networks supplying stationary objects of railway transport. Two design solutions were considered that ensure the reduction of unbalance and voltage deviations on the 0,4 kV buses of substations supplying these objects. The first of them was based on the use of suction transformers, and the second - on the use of lines with a grounded phase.METHODS. The studies were carried out using the Fazonord software package, which provides complex modeling in phase coordinates of the modes of power supply systems.RESULTS. The results obtained made it possible to draw the following conclusions: when using suction transformers, which were included in the rail cut, the average value of the unbalance coefficient in negative sequence on the 0.4 kV buses of the object's substation decreased by 2,5% compared to the absence of such devices; in the presence of transformers, which were included in the return wire, this indicator decreased by 19%. The use of lines with a grounded phase instead of a two-wire-rail line made it possible to improve the quality of electricity on 0.4 kV buses, while the maximum of the unbalance coefficient in the negative sequence was reduced by 40%.CONCLUSION. On the basis of computer modeling, it is shown that the use of suction transformers with a return wire and 25 kV lines with a grounded phase makes it possible to improve the quality of the electric power industry in the power supply systems of stationary objects of railway transport.

COMPLEX-CLOSED POWER SUPPLY SYSTEMS AND CALCULATION OF THEIR ELECTRICAL MODES

When creating and improving power supply systems, steady-state calculations are the most common, they contain nonlinear elements in the form of generators and loads, therefore their steady-state mode is described by nonlinear equations. The solution of such equations is possible only by iterative methods, which is associated with the problem of convergence of the iterative process. Due to some features of electrical systems, which are inherent, including power supply systems of the agro- and forestry complex, the convergence of the iterative process may be slow and not even secured. (Research purpose) The research purpose is developing a method for calculating the steady-state modes of power supply systems that meets the condition of convenience of implementation on an electronic computer and removes the problem of convergence of the iterative counting process. (Materials and methods) Proposed a direct calculation method with cyclic correction of the initial information for each cycle in order to take into account the nonlinearity of elements of power supply systems. (Results and discussion) The calculation formulas for determining the intrinsic and mutual resistances that underlie the proposed method are given, their main feature is that they are distributed with elements included in the nodes corresponding to sources and loads, and obtained by the authors as a result of the transformation and solution of nodal equations. It was established that the method is implemented through the operation of the following algorithms: calculation of intrinsic and mutual resistances; calculation of current distribution, that is, determination of currents in the branches of the network; calculation of voltages in all nodes of the power supply system; calculation of power flow distribution in order to subsequently identify power losses and electric energy consumption. (Conclusions) It was shown that the derived universal calculation expressions can also be used for equivalence purposes. It was revealed that the proposed method and the algorithms implementing it are relatively easy to program and provide the necessary speed and accuracy of calculations; they are designed to solve practical problems related to the design and operation of complex closed power supply systems, increasing their reliability and efficiency.

Joint voltage and frequency predictive controllers for distributed generation plants

The paper determines the effect of proposed joint voltage and frequency predictive controllers for distributed generation (DG) plants on quality indicators characterizing the control process in different operating modes of power supply systems. The studies are conducted in the MatLab environment (Simulink and SimPowerSystems simulation packages) employing control engineering methods. It is proposed to design and adjust joint predictive controllers by determining the resonant frequency of oscillations for the master generator rotor. This approach provides better quality indicators of voltage and frequency control in power supply systems while maintaining the same settings for the controllers of DG plants. With an additional load in an isolated power supply system, the maximum voltage sag is found to be 1.75 times lower than for local predictive control and 3.5 times lower as compared to the use of conventional controllers. For the specified mode, predictive controllers enable a threefold reduction in the transient time between rotor rotational speeds in a synchronous generator. In the start mode of a powerful electric motor, the predictive controllers of synchronous generators in the power supply system enable a 1.5 times reduction in voltage sag, with a 1.4 times reduction in overvoltage following its start. In the case of a short-term three phase short-circuit, joint predictive controllers allow a 1.5 times decrease in transient time and a 2.3 times decrease in the overshoot of power line frequency as compared to local control. In addition, frequency oscillation in the power system is also reduced. Similar effects are observed in other operating modes of the considered power supply systems equipped with DG plants. The performed dynamic simulation confirms the effectiveness of using joint voltage and frequency predictive controllers for DG plants, which consists in a positive impact on the quality of processes involved in controlling the parameters of power supply systems in various operating modes.

Developing methods for taking into account the radiation coming from Earth in simulations of incoming electric power on the Russian Segment of the International Space Station in experiment Albedo

The paper describes the implementation of space experiment Albedo, which provided a framework for developing methods of taking into account the radiation emitted by the system «atmosphere–underlying terrain» in simulations of the operation of the power supply system of the Russian Segment of the International Space Station. As a result of the implementation of the space experiment a procedure was developed for determining and using characteristics of radiation coming from Earth in the simulation of a space station power supply system, including procedures and special software for determining solar array performance and simulating power input coming from solar arrays taking into account Earth albedo, as well as recommendations are given for the control modes of power supply systems of orbital spacecraft. As a result of testing computational schemes for evaluating the solar array performance and simulating electric power output that takes into account the Earth albedo, substantiated values were obtained for the proposed reference parameter for evaluating the performance of solar arrays of the Service Module of the International Space Station. Key words: Russian Segment of the International Space Station, solar arrays, electric power input, solar array performance estimate, radiation coming from Earth, albedo.

Control of quality and modes of power supply systems using contactless devices

The article discusses the issues of creating contactless switching devices for automatic quality control and operation modes of power supply systems, using the developed contactless thyristor voltage relays, characterized by high reliability and speed, combining a sensitive system and a powerful final controlling element. Schemes with operating principles and experimental characteristics are given. It is proposed to use it to automatically turn on or off the booster transformer winding when the input voltage changes to maintain the rated voltage of electricity consumers, as well as to create a power regulator for capacitor banks of reactive energy compensating devices.

Simulation of dynamic modes of power supply systems equipped with diesel generators, at inferior power quality

The article provides results of studies aimed at implementation of power supply systems (PSS) computer-based models in conditions of inferior power quality, where the PSS include backup diesel generators. The main aim of the study was to research these generators synchronization with the PSS network. The simulation was performed in the MATLAB environment using the Simulink and SimPowerSystems software packages. Based on the results obtained, it can be concluded that the self-synchronization method can be used for turning on diesel generators for parallel operation with PSS. After the synchronization processes completion, an improvement in the quality indicators of electricity in the PSS network and at the interfaces with the power supply system in terms of asymmetry and harmonic distortions.

МОДЕЛИРОВАНИЕ РЕЖИМОВ СИСТЕМ ЭЛЕКТРОСНАБЖЕНИЯ НЕТЯГОВЫХ ПОТРЕБИТЕЛЕЙ

The results of computer studies of the modes of power supply systems of nontraction consumers of railways are presented. It is shown that the greatest asymmetry in the reverse sequence and voltage deviations are observed at the substation connected to the two-wire-rail line.

Higher harmonics and limiting thereof in power supply systems of different voltages

The simulation of the modes of power supply systems of different voltages, with a transformer carrying linear and non-linear loads and a capacitor bank, has been implemented. The dependences of the capacitors overload by current and the coefficient of harmonic voltage components on the capacitor bank capacity within the operating range of the transformer total load by linear and non-linear loads have been obtained. For the systems under consideration, upon a daily variation in the capacitor bank linear load and capacity, it is virtually impossible to eliminate the capacitors overload by higher harmonic currents and observe regulatory voltage quality requirements. Anti-resonant chokes installation in the capacitor bank circuits reduces the overload of capacitors to a permissible value, and brings up the coefficient of harmonic voltage components to values that took place in the absence of the capacitor bank.

ORGANIZATION OF POWER SUPPLY OF THE FIRST CATEGORY RECEIVERS FOR PERSPECTIVE CIVIL AVIATION AIRCRAFT

The article deals with the issue of providing electric power to the first category receivers in the emergency mode of the power supply systems operation of perspective and modernized aircraft. The analysis of the published scientific works performed both in Russia and abroad, and aimed at solving problems of analyzing abnormal operations mode, synthesizing power supply systems and controlling them in order to prevent dangerous consequences is carried out. The authors considered the ingenious technical solutions aimed at providing the necessary quality power supply for the first category receivers in the emergency operation modes of the aircraft power supply systems for the safe completion of flight and landing. The research analysis and generalization of data on the technical characteristics of units and devices developed by the world's leading manufacturers of aviation equipment and used as emergency sources of electrical power on board modern civil aviation aircraft has been completed. The advantages and disadvantages of each technical solution are determined, as well as limitations to the area of their application are formed. The analysis of perspective emergency sources of the electric power including those, which previously were not applied in aviation because of their insufficient technical perfection, for example, hydrogen electrochemical generators is carried out. Based on the performed analysis, a solution which allows improving the operating modes of the electrical batteries is proposed. The offered solution makes it possible to increase the reliability and durability of electrical batteries, as well as the power supply duration of the first category receivers from them.

Differential Mathematical Models of Computer Research of the Abnormal and Transient Modes of Power Supply Systems of Railways

Differential Mathematical Models of Computer Research of the Abnormal and Transient Modes of Power Supply Systems of Railways