Local Electric System Research Articles

Developing an electrical power system of a mobile electron beam accelerator to treat wastewater and industrial effluents / Desenvolvimento de um sistema de energia elétrica de um acelerador móvel de feixe de elétrons para tratar águas residuais e efluentes industriais

The treatment of wastewater and industrial effluents by electron beam irradiation is a promising technique, however, not very widespread in Brazilian territory. The design and construction of a mobile unit by the Nuclear and Energy Research Institute, containing an electron beam accelerator of 700 keV and 20 kW is innovative to demonstrate the effects and positive results of this technology. The aim is to transfer the mobile unit to several companies with interest in liquid waste treatment, connect to the industry electrical system and start the ionization treatment process through electron beam. The mobile unit connection to the local electrical system may be a challenge due to the great diversity of voltages and distances involved, as well as the large injections of harmonic content generated by the electron beam accelerator that can affect sensitive loads in the industrial system. In this work, an analysis of the electrical power system of the mobile unit was made, regarding the interruption capacity, selectivity protection and adequate short circuit levels, in order to assure a greater reliability in the operation. At the end, the control panel of the mobile unit, simulations and measurements were carried out at the 1.5 MeV and 37.5 kW electron beam accelerator, installed in the Radiation Technology Center, demonstrating the necessity of applying a filter to reduce the measured harmonic distortion. The analysis of the mobile unit electrical power system was made, in order to assure a greater reliability in the operation.

Activating the potential of decentralized flexibility and energy resources to increase the EV hosting capacity: A case study of a multi-stakeholder local electricity system in Norway

The increasing amount of flexible load in the energy system represents both a challenge and an opportunity. One primary source of load growth is the electrification of the transport sector and the subsequent charging of electric vehicles, which is a load type that can potentially adjust their load profiles. However, to activate the full potential of end-user flexibility, it is necessary to develop pricing mechanisms that can promote efficient load responses on a larger scale. In this paper, a trading mechanism is proposed and analysed within a capacity-based grid tariff scheme by formulating a game-theoretic framework that includes decentralized decision-making by self-interest pursuing end-users. The model is applied to a real-world case in Norway, and it is demonstrated how electrification of vehicles can be achieved with the existing infrastructure. It is found that capacity-based grid tariffs have a limited ability to reduce the coincident peak load in the system since they mainly incentivize individual peak load reductions. However, by including a capacity trading mechanism within the capacity-based tariff structure, we demonstrate that it is possible to increase the value of flexibility since the flexible end-users are incentivized to coordinate their flexibility dispatch with other stakeholders.

Calculation of the Capacity for the Operation of a Mini-Energy Complex Based on an Inde-pendently Operating Asynchronous Generator

The article present the analysis of the operation of the mini-energy complex (MEC) based on alternative energy sources. An asynchronous generator (AG) was taken as energy source. The IEC operates independently with standard power parameters without the use of a frequency converter. To operate independently, AG needs a source of reactive excitation current. Based on the calculations carried out and the results obtained with the use of the experimental facility,the operating conditions of the MEC with standard parameters of electricity under varying load have been analyzed. A characteristic feature of the autonomous MEC is the commensurate capacity of the generating device and consumers. Therefore, any power consumer on/off leads both to significant changes of local electric system parameters and affects the operation of the generator itself. In this article, the main attention is paid to the influence of three-phase motor load on stable AG operation. When the MEC operates independently, reliable self-excitation of the asynchronous generator and the start-up of consumers whose power is commensurate with the generating unit must be ensured. It is also necessary to ensure the maintenance of voltage stability, the possibility of automatic operation of the generating unit, and the preservation of its integrity in emergency modes. Thus, for stable MEC-based AG operation the nature of the load should be taken take into account, the parameters of the of the local grid should be known as well as the exact availability of consumers and their characteristics, and also equivalent circuit parameters of asynchronous motors. In addition, it is necessary to accurately calculate the capacity when changing the parameters of the electrical system, so as not to lose the self-excitation of the asynchronous generator, which is equivalent to disconnecting the entire load of the generator and causes a sharp increase in speed. To solve these problems, it is necessary to create a high-speed MEC control system.

Cyber-physical modelling operator and multimodal vibration in the integrated local vehicle-grid electrical system

The interaction of the individual user and the electrical are deeply strengthened with wireless communication and internet of things development. In the region of urban, the growing penetration of electric vehicles and the corresponding fast charging techniques not only emerge an effective interface for the virtual power plant, but also emerge the vulnerable points for the cyber attack. Facing the complexity of the physical vehicle-grid system and the uncertainty of the communication network, the unified modelling with a cyber-physical operator is established in this work. By the implicit Runge-Kutta method, the cyber-physical dynamics of the vehicle-grid electrical system is narrowed in the finite-dimensional space, which mimics the latency and denial-of-service attacks with a discretized matrix. After that, the techniques of space transformation and the subspace mapping are introduced to further approximate the hybrid system by a reduced cyber-physical operator. The resulting operator simultaneously preserves the system structure and reduces the dimensions, which provides the opportunity for the extraction of dynamic indexes and the participation factor. The proposed cyber-physical operator has experimentally verified in the case studies as well as the disclosure of the multimodal vibration. It is found that the interface of open cyber network and the lower-inertia batteries inside the electric vehicles might become the potential attacking points for the integrated local energy system. By the malicious cyber attacks, the stability feature of the cyber-physical system could be reshaped to a multimodal shape, which injects inharmonious energy from the cyber network into the physical system.

Optimal midterm peak shaving cost in an electricity management system using behind customers’ smart meter configuration

This paper analyses a local electricity system (LES) comprising photovoltaic production (PV), a connection to the distribution network, local loads and an energy storage system (ESS). Given the flexibility of the ESS, the LES can provide a peak shaving service (PSS) to the grid operator based on the actual monthly power tariff. This paper proposes a stochastic mixed-integer linear programming problem that maximises the expected operating profit of the LES midterm. Assuming a behind customers’ smart meter configuration, income is derived from selling the energy of prosumers to other external electrical areas. If the costs are higher than the income, the net profit will be negative, i.e. a net loss. The cost component of the objective function can be reduced through the management of local resources and by providing PSS to the distribution network operator to minimise the power cost of the monthly power tariff. The model is tested for 720 h (considering a month of 30 days) in three cases: (i) without PV and ESS; (ii) with PV and ESS, where losses are 0%; (iii) with PV and ESS, where losses are 18%. Due to the monthly power tariff, the net loss of the LES is reduced through the optimal management of local resources when the ESS losses are lower than 18%. To assess seasonal implications about the LES, the 12 months of the year are also tested. The month of October indicated the highest peak shaving, while the lowest peak shaving depended on the ESS losses.

MODES EVALUATION FEATURES IN LOCAL POWER SYSTEMS WITH DISTRIBUTED GENERATION AND STORAGE

The structure of local electric power systems with sources of Dispersed Generation is considered. The main models of these systems are presented. A detailed classification of the generation unit of local power systems with sources of scattered generation is presented, which contains the main characteristics of generators. Different types of means of electricity storage and features of their application are analyzed. The main types of storage devices that contain devices for storing electricity using capacitors and supercapacitors, devices for mechanical energy storage, devices for storing chemical energy, storage devices for thermal energy are identified. Energy processes in electric power systems with distributed generation sources and electric energy storage devices are carefully analyzed by estimating the values and signs of exchange capacities in the intersections of these systems. Among the above processes: non-sinusoidal modes in the intersections of local power systems and frequency deviations in sinusoidal and non-sinusoidal modes of operation. To optimize energy processes in these systems, a method of visual display of technical and economic indicators is proposed, which allows a comprehensive assessment of systems with distributed generation sources and different types of electrical energy storage and processes in them. Taking into account the peculiarities of the structure and functioning of systems with sources of dispersed generation, such criteria as the economic component of the cost of system elements, its availability in the specified region, environmental friendliness and service life are selected. To combine technical and economic criteria, it is proposed to use their graphical representation.

Impact of the configuration and condition of the power system on the damping of low-frequency oscillations

ABSTRACT The current stage of power system development is characterised by the transformation from local electric power systems to global interconnections. It provides economic benefits, improves the reliability of power system operation and increases the quality level. However, such large interconnected systems have some technical and economical limitations, for instance, long distance transmission, and almost have a weak tie between the electric power systems. One of the main problems of the reliability of such large interconnected systems is low-frequency oscillations, which significantly reduces network capacity and leads to dynamic instability. Therefore, the analysis of the influence of various topologies and regime modes of electric power system to the low-frequency oscillations for the development of control actions and recommendations for their effective damping and reduction is relevant. In this paper, simulation and analysis was done by using of two-area electric power systems and using «EUROSTAG» software. The factors, such as the previous steady-state condition and the structure of the electric power system, affecting the damping properties of electric power system and the impact of the Back-to-Back High-Voltage Direct Current link based on voltage source converters to the damping of low-frequency oscillations were considered.

GSM Based Generator Fuel and Temperature Monitoring System

Pakistan is facing energy crisis since last many years, that’s why frequent power outages have become an unavoidable routine of our life. In order to reduce such disturbances of power outages, various industrial and domestic sectors including academic institutions and several other departments are moving towards the use of generators during power outages. No doubt, the use of generators is much more expensive as compared to the country’s local electricity system but it gets extreme expensive if it includes the misuse and theft of the fuel. The aim of designing this project is to develop a complete fuel and temperature monitoring system and the main objective is to control the misuse or theft of fuel.

Synchrophasors Determination Based on Interpolated FFT Algorithm

Within the standard IEEE C37.118 applications and proposed hardware structure of a phasor measurement unit (PMU) are described. This paper presents the concept of the system for measuring and transferring synchrophasors from a theoretical aspect. Synchrophasor algorithms are developed in MATLAB/Simulink for the purpose of easier verification and hardware deployment on today’s market available and affordable real time development kits. Analysis of the synchrophasor measurement process is performed gradually. Firstly, by defining the synchrophasor based on three-phase to αβ-transformation and then introducing a discrete Fourier transform (DFT) based on synchrophasor estimation algorithm. Later, accompanying adverse effects resulting from its application are analyzed by means of simulation. To increase accuracy and improve estimation algorithm interpolated discrete Fourier transform (IpDFT) with and without windowing technique is used. To further optimize algorithm performance convolution sum in recursive form has been implemented instead of classical DFT approach. This study was carried out in order to validate described measurement system for the monitoring of transients during island operation of a local power electric system. Finally, simulation and experimental results including error analysis are also presented.

Вдосконалення способів виконання захистів ліній зв’язку з підстанціями розосереджених джерел генерації

The article deals with the problems of using relay protection of power lines. Attention is paid to the peculiarities of the operation of protection under different modes of operation of these lines, namely: normal, post-accident and scheduled repair. The protection of two-sided power lines that connect individual local power plants to powerful electrical systems, including dispersed generation sources, local systems, and dispersed generation sources, must meet the general requirements of providing the required sensitivity, selectivity for various types of damage. Difficulties in providing the required sensitivity when using maximum current protections on such lines are associated with low levels of short-circuit currents from dispersed generation sources and local electrical systems. The features of the relay protection performance in redundant power supply of consumers using dispersed generation sources are given. The maximum operating current of the line consumed from the electrical system is 2 - 3 times the rated current, which is determined by the power of the generators of the dispersed sources of generation. In this case, the short-circuit currents from the low-power generators of the dispersed sources of generation are proportional to the maximum operating currents of the line. On double-sided power lines that connect local systems and dispersed power sources to a high-power electrical system, maximum current directional protection provides selectivity and are the main types of protection for such lines. Key words: power supply, relay protection, reclosers, sectionalizers, distributed sources of generation, short circuit, sectioning, selectivity

Evaluation of Functioning Quality of Local Electrical Systems by the Criterion Method Based on Markov Processes

The article proposes to use of a combination of the criterion method and Markov processes to evaluate the quality of functioning of renewable energy sources (RES) in the form of integrated readiness characteristic of the electricity network with RES or a local electrical system (LES). This is possible throughthe analysis of the problems of ensuring the quality of electricity supply in the conditions of intensive development of RES and defined by the qualimetric characteristics of the electricity networks, which are important for the provision of quality electricity. This contribute the development of generalizedsolutions and network development strategies, especially when it comes to building RES. The components of the integral index are determined as the probability of matching the actual regime to the "ideal". The "ideal" mode is determined on the basis of the principle of least action and corresponds to the circuit diagram of the network formed by the r-scheme. The basis thus determined in this way reduces the subjectivity of both evaluations and decisions taken on the basis of it.

Opportunities for Local Energy Supply in Norway: A Case Study of a University Campus Site

Neighbourhoods can contribute to climate change mitigation by supplying and/or facilitating renewable energy sources (RES). In this context, we evaluate opportunities related to the energy system of a Norwegian university campus, Campus Evenstad, by quantifying monetary value of local energy resources like solar photovoltaics (PV) and a bio-based combined heat and power (CHP) plant in a cost analysis. Environmental value is discussed regarding operational control of energy units to minimize emissions. Using mixed integer linear programming (MILP), we also present results from an investment analysis for local thermal and electric energy system to achieve different levels of emission compensation. Results show that local electricity supply generates most monetary value through saved costs related to reduced power grid import, and that solar PV is the most cost-efficient resource to achieve compensation of GHG emissions.

Selfoptimization local electric systems modes with renewable energy sources

Selfoptimization local electric systems modes with renewable energy sources

LOCAL ELECTRICAL ENERGY SYSTEMS WITH ACTIVE CONSUMER: METHODS OF CONSTRUCTION AND ALGORITHM OF THEIR FUNCTIONING

On the basis of the analysis of foreign literary sources, their classification according to the main tasks of modernization of local power systems according to the provisions of the concept of Smart Grid has been performed. A brief description of the development of local power systems with the presence of dispersed generation and active consumers as well as the consequences of their interaction with the central grid system is given. The role of the active consumer as an entity of the electric power system, which is capable by its actions to significantly affect its state, is considered. The methods of construction of local electric power systems and features of their functioning are investigated. The possibilities of introduction of the results of development of local electric power systems from the point of view of their management, circuit decisions, optimization of energy processes and mutual influence of elements of electric networks in the conditions of Ukraine are analyzed. The models of market processes in the local liberalized electricity markets and the mechanism of auctioning in the electricity market are presented. The role of the aggregator as the subject of the local energy market and its possibilities in managing the demand for energy resources is disclosed, and optimal solutions are proposed for the modernization of energy processes at various hierarchical levels of the electric system. From the point of view of end user management, the four-layer structure of interaction of electricity consumers with elements of the power grid at social, information and technological levels is considered. The principle of reactive power compensation is presented in order to increase the reliability of the network and indicators of electric power quality. The principles of construction of multi-agent control systems, its advantages in comparison with other systems of intellectual control of power processes, possibilities and architecture of construction are considered.

Фотоелектричні станції як елемент енергоефективного електропостачання

This paper considers the problem of the integration of a photovoltaic power plant into the local electrical system. An option of the power flows control for the reduction of the power losses in the transmission systems with power plants with photovoltaic power plants (PVP) is considered.

Li- and Na-ion Storage Performance of Natural Graphite via Simple Flotation Process

Natural graphite is obtained from an abandoned open-cast mine and purified by a simple, eco-friendly and affordable beneficiation process including ball milling and flotation process. Both raw graphite (55 wt %) and its concentrate (85 wt %) were electrochemically tested in order to evaluate these materials as anode materials for Li-ion and Na-ion batteries. It was found that both raw and purified graphites exhibit good electrochemical activities with respect to lithium and sodium ions through completely different reaction mechanisms. The encouraging results demonstrated in this work suggest that both raw and graphite concentrates after flotation could be used respectively for stationary and embedded applications. This strategy would help in developing local electrical storage systems with a significantly low environmental footprint. Keywords: Natural graphite, Na-ion batteries, Li-ion batteries, Energy storage, Stationary application, Froth flotation

Influence of dispersed generation on reliability of electrical networks

Greater part of renewable sources of energy is represented by solar power plants (SPP). Their operation mode depends on natural conditions of the region, where they are located. That is why the problem of SPP stability estimation is important in the problem of covering the daily schedule of energy consumption. The system operator, in his study, emphasizes that photovoltaic and wind power plants are unreliable in terms of electrical power stability. Deviations from scheduled charts over the course of the day amount to more than 450 MW at a set power of 1217 MW. One more specific feature of the installation of renewable energy sources is their uneven distribution throughout Ukraine. Thus, the presence of one powerful source of up to 3 MW, or several less powerful ones up to 0.5 MW, connected to one substation of the distribution network (REM), makes it possible to consider REM as a local electrical system (LES). And for the local electric system, there are not yet clear legislative acts according to which renewable energy sources will function. Particularly acute for distributive electrical networks is the question of reliability and uninterrupted power supply. The article analyzes the pace of increase in the generation of photovoltaic stations in the context of the combined electricity system of Ukraine and the energy supply company of "Vinnytsyaoblenergo". The analysis of existing normative documents regulating the work of photovoltaic stations is carried out. Within the framework of the considered documents, the criteria for assessing the reliability of the operation of electric networks, namely SAIDI, are the length of long interruptions in the electricity supply of electricity consumers. The interconnection of changes in the reliability indices of electrical networks with the increase in the number and installed capacity of renewable energy sources, in particular photovoltaic stations, is shown. To increase the technical and economic efficiency of joint operation of distributed power sources and distribution electric networks, it is necessary to solve a number of tasks, which will allow to increase electricity generation of RES, reduce electricity losses in distribution electric networks, improve the quality and reliability of electricity supply to consumers.In order to efficiently exploit distributed energy sources and their integrated use in power grids, especially in the sense of improving the reliability of power supply, it is necessary to develop a method for restoring electricity supply to forest users, with a loss of centralized power supply

From interconnections of local electric power systems to Global Energy Interconnection

The interconnections of electric power systems are developed for the economic benefits and in order to increase the overall power supply reliability and quality level. Development of power industry shows the positive effects in operation of the country-wide electric power systems and international interconnections. Creation of World Energy System or, by the other words, Global Energy Interconnection is objective trend on the way of expansion of international and intercontinental electric power interconnections. Several important aspects of above mentioned problems are discussed in this paper.

Variable Switching Frequency Control of Distributed Resources for Improved System Efficiency

This contribution explores the possibility of improving the global efficiency of three-phase inverter-based distributed resources (DR) embedded in low-voltage distribution feeders, by the adaptation of their switching frequency (SF) to the operation point of both the converter and local loads. The core of this proposal lies on the fact that in a good number of applications, in both service and residential sectors, the owner of the DR is also in charge of the losses caused in the local electric power system. This fact leaves room for a global optimization of the power losses, i.e., converter losses will be considered together with those losses caused by the current harmonics injected into the local grid. A dynamic adaptive SF frame of the DR is considered in this proposal to allow its operation beyond its rated frequency at light loads, subjected to the thermal constraints of the device. Simulation results obtained using PLECS software as well as an experimental validation of the method are included.

A compact nanogrid for home applications with a behaviour-tree-based central controller

This paper proposes a nanogrid for home applications. Compactness, rapid installation and minor changes to the existing equipment are among the basic concepts behind the proposed nanogrid. With this in mind, the authors designed the proposed nanogrid as a compact object. To this aim, the power electronic converters of a typical nanogrid are no longer distributed and placed close to peripherals; they now are grouped together. The electric wires of the local power distribution system connect the grouped converters to the distributed peripherals (e.g. photovoltaic panels, batteries storage systems, loads). As a benefit, when the proposed nanogrid is installed between the meter and the switchboard of an existing dwelling, no significant changes to local equipment, devices and electrical system are required.A central controller governs the proposed nanogrid. Such a controller ensures the power balancing, implementing the continuous controllers of all the power converters belonging to the proposed nanogrid. In addition, such a controller optimizes generation and demand, implementing a decisional process based on behavioural rules.In this paper, a behaviour tree models the behavioural rules. The behaviour tree serves the discrete controller to decide the operation point of the nanogrid. The behaviour tree drives the central controller to pursue strategic targets so as to ensure power supply continuity to critical loads, maximize the exploitation of renewable energy sources and minimize power flow at the point of delivery.This paper also illustrates a single-phase 1 kW prototype of the proposed nanogrid; the prototype is subject to four tests and conditions: black start, utility failure, utility restore and over generation. Besides the capability to pursue the strategic targets mentioned above, the experimental results also demonstrate the proposed nanogrid’s capability to adjust the current imported from the utility grid, to change from grid-connected mode to stand-alone mode and vice versa, to compensate for a surge of the DC bus voltage.