Papers by Aleksandar Janjic
Applied Sciences, 2020
The increasing electric vehicle fleet requires an upgrade and expansion of the available charging... more The increasing electric vehicle fleet requires an upgrade and expansion of the available charging infrastructure. The uncontrolled charging cycles greatly affect the electric grid, and for this reason, renewable energy sources and battery storage are getting incorporated into a hybrid charging station solution. Adding a renewable source and a battery to the charging station can help to “buffer” the power required from the grid, thus avoiding peaks and related grid constraints. To date, the origin of the energy coming from the battery has not been traced. In this paper, a solution of the hybrid electric vehicle charging station coupled with the small-scale photovoltaic system and battery energy storage is proposed to eliminate the adverse effects of uncontrolled electric vehicle charging, with the exact calculation of renewable energy share coming from energy stored in the battery. The methodology for the multicriteria optimization of the charging/discharging schedule of a battery an...
The application domain of Smart Grid is a matter of a great interest of scientific and industrial... more The application domain of Smart Grid is a matter of a great interest of scientific and industrial communities. A comprehensive model and systematic assessment is necessary to select the most suitable Enterprise Architecture (EA) development or integration project from many alternatives. In this paper, a Fuzzy Influence Diagrams with linguistic probabilities is proposed for the Smart Grid EA conceptual model and risk analysis. The proposal relies on a methodology devoted to decisionmaking perspectives related to EA and risk assessment on Smart Grid initiatives based on fuzzy reasoning and influence diagrams (FID).
Symmetry, 2021
One way to optimize wastewater treatment system infrastructure, its operations, monitoring, maint... more One way to optimize wastewater treatment system infrastructure, its operations, monitoring, maintenance and management is through development of smart forecasting, monitoring and failure prediction systems using machine learning modeling. The aim of this paper was to develop a model that was able to predict a water pump failure based on the asymmetrical type of data obtained from sensors such as water levels, capacity, current and flow values. Several machine learning classification algorithms were used for predicting water pump failure. Using the classification algorithms, it was possible to make predictions of future values with a simple input of current values, as well as predicting probabilities of each sample belonging to each class. In order to build a prediction model, an asymmetrical type dataset containing the aforementioned variables was used.
Symmetry
This paper deals with uncertainty, asymmetric information, and risk modelling in a complex power ... more This paper deals with uncertainty, asymmetric information, and risk modelling in a complex power system. The uncertainty is managed by using probability and decision theory methods. More specifically, influence diagrams—as extended Bayesian network functions with interval probabilities represented through credal sets—were chosen for the predictive modelling scenario of replacing the most critical circuit breakers in optimal time. Namely, based on the available data on circuit breakers and other variables that affect the considered model of a complex power system, a group of experts was able to assess the situation using interval probabilities instead of crisp probabilities. Furthermore, the paper examines how the confidence interval width affects decision-making in this context and eliminates the information asymmetry of different experts. Based on the obtained results for each considered interval width separately on the action to be taken over the considered model in order to minim...
Mathematical Problems in Engineering
Due to the large number of power transformers (ETs) in the distribution system, there is a need f... more Due to the large number of power transformers (ETs) in the distribution system, there is a need for a relatively simple representation of the status of each unit in order to more easily determine where and how to allocate the budget for preventive and corrective maintenance. In recent years, the concept of the transformer health index (HI) as an integral part of resource management was adopted for the condition assessment and ranking of ETs. HI algorithms take different forms and can be determined based on a large number of specific parameters. However, the main problem in HI methodology or any modern diagnostic technique is the existence of regular measurements and inspections and accurate test results. The paper proposes a solution in the form of the upgraded HI and the novel methodology for ET ranking including the value of available information to describe ET current state. The confidence to the measurement results is calculated using evidential reasoning (ER) algorithm based on...
Advances in Fuzzy Systems
Risk assessment of distribution assets is one of the most important factors in the process of net... more Risk assessment of distribution assets is one of the most important factors in the process of network development or maintenance planning decision-making. The process of decision-making is faced with uncertainties, involving technical, financial, safety, environmental, and other operational issues that make standard risk assessment techniques insufficient. Probabilistic uncertainties require appropriate mathematical modeling and quantification when predicting future state of the nature or the value of certain parameters. The paper is proposing a new methodology for the multicriteria risk assessment of the distribution network assets, based on influence diagrams and fuzzy probabilities. Influence diagram has been used to determine all relevant factors concerning risks and their interdependencies are depicted. Fuzzy probabilities are represented by triangular fuzzy numbers with constraints on feasibility of elicited probabilities. This methodology enables the decision process in uncer...
Electric Power Systems Research
Facta universitatis - series: Electronics and Energetics
The successful automation of a smart home relies on the ability of the smart home control system ... more The successful automation of a smart home relies on the ability of the smart home control system to organize, process, and analyze different sources of information, according to several criteria. Because of variety of key design criteria that every smart home of the future should meet, the main challenge is the trade-off between them in uncertain environment. In this paper, a problem of smart home design has been solved using the methodology based on multiplicative form of multi-attribute utility theory. Aggregated functions describing different smart home alternatives are compared using stochastic dominance principle. The aggregation of different criteria has been performed through their numerical convolution, unlike usual approach of pairwise comparison, allowing only the additive form of aggregation of individual criteria. The methodology is illustrated on the smart home controller parameter setting.
Facta universitatis - series: Electronics and Energetics
35/10 kV substation. Substation reliability calculation is carried out for 5 different scenarios ... more 35/10 kV substation. Substation reliability calculation is carried out for 5 different scenarios of CB removal with their expenses. At the end, discounted investment costs for each action and period of 5 years are calculated and are shown in table. For this substation final results are showing best scenario with removal CB's on power transformers.
Facta universitatis - series: Electronics and Energetics
This paper represents an approach for the estimation and forecast of losses in a distribution pow... more This paper represents an approach for the estimation and forecast of losses in a distribution power grid from data which are normally collected by the grid operator. The proposed approach utilizes the least squares optimization method in order to calculate the coefficients needed for estimation of losses. Besides optimization, a machine learning technique is introduced for clustering of coefficients into several seasons. The amount of data used in calculations is very large due to the fact that electrical energy injected in distribution grid is measured every fifteen minutes. Therefore, this approach is classified as the big data analysis. The used data sets are available in the Serbian distribution grid operator's report for the year 2017. Obtained results are fairly accurate and can be used for losses classification as well as future losses estimation.
TURKISH JOURNAL OF ELECTRICAL ENGINEERING & COMPUTER SCIENCES, 2015
Unlike the traditional way of efficiency assessment of renewable energy sources integration, the ... more Unlike the traditional way of efficiency assessment of renewable energy sources integration, the smart grid concept is introducing new goals and objectives regarding increased use of renewable electricity sources, grid security, energy conservation, energy efficiency, and deregulated energy market. Possible benefits brought by renewable sources integration are evaluated by the degree of the approach to the ideal smart grid. In this paper, fuzzy analytical hierarchy process methodology for the integration efficiency has been proposed, taking into account the presence of multiple criteria of both qualitative and quantitative nature, different performance indicators, and the uncertain environment of the smart grid. The methodology has been illustrated on the choice of the size and location of a distributed generator in the radial distribution feeder.
This paper presents how the problems of power quality and electrical energy losses in distributio... more This paper presents how the problems of power quality and electrical energy losses in distribution systems led to the development of an interoperable smart grid platform being implemented in several electrical utilities in Serbia through various pilot projects. With practical examples of solving the problem of power quality and of locating the source of electrical losses in distribution network, using different types of Measuring Information Systems, evolution of smart grid development in Serbia is shown. Through the demands raised in the exploitation of these systems, it is presented how a flexible smart grid platform, enabling the use of all available information and communication technologies and interoperability with intelligent electronic devices and systems of different manufacturers, is developed. Beside the platform description, which allows the inclusion of all smart grid stakeholders, few examples of its practical use by different users are given. At the end, appropriate c...
Risk became the crucial decision making criteria in evaluation of some control actions in power s... more Risk became the crucial decision making criteria in evaluation of some control actions in power systems, but very often, these decisions are made in a highly uncertain environment. In this paper, a new graphical tool for risk assessment and decision making under uncertainty – hybrid influence diagram with fuzzy probability values and fuzzy random variables is proposed. Influence diagram is a generalization of a Bayesian network, in which not only probabilistic inference problems but also decision making problems can be modeled and solved. Unlike classical Bayesian networks, which are using conditional probability tables, that are often difficult or impossible to obtain, a verbal expression of probabilistic uncertainty, represented by fuzzy sets is used in this approach. Besides discrete random variables, this hybrid model allows the use of continuous variables through the process of fuzzification. Through this integrated method, both type of inference support: bottom-up and top-down...
The paper discusses power and especially voltage quality issues in the smart grid environment. Ne... more The paper discusses power and especially voltage quality issues in the smart grid environment. New demands that are facing the distribution network, by introducing the concept of intelligent networks (Smart Grids), are presented. Some examples of non-compliance of laws and practices in Serbia are presented as well, as the illustration of lack of strategic planning in the field. Through several case studies, a few typical problems regarding power quality, occurring in the electrical utilities in Serbia, which have to be solved in a new environment are presented. In the end, the conclusion and specific suggestions in regard with the importance of strategic planning and preparation for the customization to the expected changes are given.
International Journal of Electrical Power & Energy Systems, 2015
The work of an electricity distribution company is impossible without the extensive use of differ... more The work of an electricity distribution company is impossible without the extensive use of different types of vehicles (including conventional and electric vehicles) for various purposes. New imperatives set by the market-related economy dictate the rational use of all resources, including the vehicle fleet, subject to constraints on the acquisition, deployment and operation of the fleet in a very uncertain environment. In this paper, a two-step multi-criteria algorithm for the optimization of distribution companies vehicle fleets under uncertainty is proposed. In the first step, fuzzy sets for the preferred vehicle fleet size using queuing theory are composed. In the second step, a multi-criteria fuzzy decision making technique is proposed for the determination of the optimal combination of different types of vehicles. Optimization is carried out for several divisions of one distribution company with different terrain properties. Thanks to the flexible approach of the proposed model, a fair and balanced distribution of vehicles has been achieved between the company's divisions.
2012 2nd International Symposium On Environment Friendly Energies And Applications, 2012
The problem of optimal dispatch of distributed generation (DG) differs from the classical problem... more The problem of optimal dispatch of distributed generation (DG) differs from the classical problem of generation dispatch in the power system, because of the specific criteria related to the DG interconnection. Most important goals are to maximize the renewable production and to minimize the total cost, while satisfying additional constraints related to the operation of a distribution network. When there are many DGs in a distribution network, it is very complicated to decide the optimal DG outputs to satisfy all the criteria and constraints imposed by the distribution network. Another problem is the lack of the dispatcher control over DGs, and very often, the only available action is to switch on or off the generator. Finally, network operator and DG owner perspective is often opposed regarding appropriate control action in the network. In this paper, a multi-criteria decision support based on AHP method is proposed for the choice of the dispatching action. The method is illustrated on the choice of the DG to be switched off in the case or reverse power flow.
2014 IEEE International Energy Conference (ENERGYCON), 2014
In this paper, the optimal vehicle fleet mix composed of both electric and gasoline powered cars ... more In this paper, the optimal vehicle fleet mix composed of both electric and gasoline powered cars for the electricity distribution company has been determined. The optimization is performed based on multi-criteria analysis and OWA operators. The criteria for the proper choice of vehicles encompass the service quality, CO 2 emission, the overall fleet costs and the possibility to use storage capabilities of electric vehicles. The methodology is illustrated on the vehicle fleet determination for the medium size distribution company with 50 000 consumers.
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Papers by Aleksandar Janjic