Stoilkov, Vlatko

Preferred name

Stoilkov, Vlatko

Official Name

Stoilkov, Vlatko

Main Affiliation

stoilkov@feit.ukim.edu.mk

Now showing 1 - 8 of 8

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Modeling the arrangement of turbines for onshore wind power plants under varying wind conditions
(Wind Integration, 2018-10)
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Fickert, Lothar
Wind field layout optimization concerning various parameters is a major point in planning and will influence the revenue for the whole life of the installation. Besides the obvious impact of wind distribution also other parameters like connection costs and levelized costs of energy influence the optimum layout and have to be included in a realistic optimization algorithm. In this paper the sophisticated optimization of wind field layout with of two fundamentally different heuristic algorithms is investigated. To do so, detailed real-world data from an existing wind field in Bogdanci, Macedonia is utilized by employing real wind field data we are able to calibrate model adequacy and ascertain a model that will serve as a referent guidance in the planning of future onshore wind fields. Different layouts were designed using sophisticated algorithms for handling the resulting high-dimensional, highly nonlinear optimization problem. In particular, a nondominated sorting genetic algorithm (NSGA) and a mixed discrete particle swarm optimization algorithm (MD-PSO) were applied. Both optimization algorithms established bi-objective fitness functions, in particular- minimizing the levelized cost of energy and maximizing the capacity factor. By comparing the results obtained with the existing layout, it is established that both optimization algorithms are adequate in determination of wind power plant layouts. It is proven that the implementation of sophisticated optimization methods can results in essential savings during the whole lifetime of the wind field.
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Fault detection under operating wind turbine through yaw misalignment conditions
(MAKO CIGRE, 2019-10)
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In the past few years, the interest in controlling the wind turbine yaw misalignment has re emerged. The reason for this interest is the desire for maximum exploitation of wind turbines and elimination of any omission in the production of electrical energy. The operation of wind generator systems in conditions of inadequate control and compliance with direct wind direction is reflected in the reduction of electricity produced, as well as in reducing the exploitation period of the wind turbine. Accurate yaw angle measurement is a fundamental for efficient operation of the non-compliance angle control system. In wind turbines, which lack such a modern metering system, the occurrence of fatigue working conditions is becoming more and more frequent, and thus the problems and defects that occur with all mechanisms for controlling and adapting nacelle face the upcoming wind. Of particular importance to maintenance an operating wind field, is the adequate and real time detection of such an error. Frequent changes on the direction of the nacelle, or a rare adaptation of the pitch angle to a particular wind turbine have been recorded during the operation mode of one wind turbine from the Bogdanci wind field. The analysis of its operating modes, as well as the proposed solution for optimal operation, in absence of a modern measuring system to control yaw misalignment of the nacelle and the wind direction, are presented in this paper.
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Wind regimes representation modeling by using multivariable distributions
(MAKO CIGRE, 2019-10)
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The electricity produced from one wind turbine is almost entirely dependent on the intensity of the upcoming wind. On the other hand, while making analysis of electricity production of a single wind field, equal attention should be paid to wind direction, since it defines the overall wind flow in the wind field. Accordingly, when making estimations of the expected annual production of energy from one wind field, the correlations of wind speed and direction should be appropriately taken into account. The usual practice of using Weibull distributions by a number of sectors is not the most suitable for optimization processes for defining the layout of one wind filed. For this purpose, the paper proposes a method that is simple and easy to implement, which is based on a multivariable distribution function of the parameters of the wind. For the analysis of the proposed model the measured wind data used in this paper are from one existing wind field. In addition, three stage functional distributions are obtained, which satisfactorily match the measurement data. In order to determine the matching degree of the adapted multivariable distributions with the measurement data, the quantitative parameter for error estimation - R2 was used. Various sizes of data sampling intervals are also examined in order to reduce the generation time of multiple distributions, which will not affect the quality of matching between generated distributions and measured data.
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Trends in the development of wind generation systems
(MAKO CIGRE, 2019-10)
Ivanovski, Ilija
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The rapid technology development for utilization of wind energy, requires constant improvement of the mechanisms that make the conversion of this energy into electricity. For these reasons, it is necessary to continuously monitor the state and trends of the development of wind energy conversion systems. The paper provides an overview of the latest technological developments of multi megawatt wind generators. In addition, the technological and economic advantages and disadvantages of each wind energy conversion system are analyzed. At the same time, a comparative analysis of several types of wind generators has been made, based on: weight, material types, axial length of the generator, rotor diameter and energy yield. This comparison is appropriate for detecting and defining the adequate structure of a higher installed power generating system for both- onshore and offshore wind fields. In addition, the latest improvement and optimal techniques of wind generators, their operation in faulty conditions, the ways of networking, as well as their application to wind turbines with high installed power are shown. This review offers the opportunity to understand the procedures for future design of wind fields, consisting of multi-megawatt units for conversion of wind energy,
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Modeling an optimal wind turbine layout by application of evolutional algorithms
(MAKO CIGRE, 2019-10)
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Optimization of wind farm layout concerning various parameters is a major point in planning and will influence the revenue for the whole life of the installation. Besides the obvious impact of wind distribution also other parameters like connection costs and levelized costs of energy influence the optimum layout and have to be included in a realistic optimization algorithm. In this disertation the sophisticated optimization of wind farm layout with of two fundamentally different heuristic algorithms is investigated. To do so, detailed real-world data from an existing wind farm in Bogdanci, Macedonia is utilized by employing real wind farm data we are able to calibrate model adequacy and ascertain a model that will serve as a referent guidance in the planning of future onshore wind farms. The major unique feature of the research is the simultaneous optimization taking into account all major technical influence and cost factors, including: (i) detailed and advanced models for power modeling due to bivariate distribution of wind speed and direction; (ii) accurate estimation of levelized cost of energy (LCOE); (iii) analysis of the shortest electrical interconnections among wind turbines and (iv) correction of hub height on each wind turbine in the wind farm with taking also the wake effect into consideration. Different layouts were designed using sophisticated algorithms for handling the resulting high-dimensional, highly non-linear optimization problem. In particular, a non dominated sorting genetic algorithm (NSGA) and a mixed-discrete particle swarm optimization algorithm (MDPSO) were applied. Both optimization algorithms established bi-objective fitness functions, in particular- minimizing the levelized cost of energy and maximizing the capacity factor. By comparing the results obtained with the existing layout, it is established that both optimization algorithms are adequate in determination of wind power plant layouts. Results show also a remarkable improvement of 2.05% and 5.59% for levelized costs and capacity factor, respectively, compared to the as built wind farm layout.
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Viability and performance investigation of small wind turbines
(Faculty of Electrical Engineering and Information Technologies, “Ss. Cyril and Methodius” University in Skopje, 2023-12)
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In the past decades, extensive and exhaustive research has been done on the analysis of the operation of large wind turbines, but detailed analyses on small wind turbines are still rare. In addition, two current situations are considered: i) the exhaustion of the possibilities for designing new large wind fields, and ii) the energy crisis, which is particularly current in Europe, so it comes naturally to analyze the possibilities for exploitation of small wind turbines defined according IEC 61400-2 standard. The paper analyzes five potential locations in North Macedonia. Based on two-year measurement period at those locations, the probability distribution of wind speeds was obtained and integrated with the power curve for a specific turbine, the electricity production of four different, commercially available, small wind turbines was investigated. Three wind turbines are horizontal axes wind turbines, with installed power in the range of 3–50 kWp, and one is vertical axis wind turbine with installed power of 4 kWp. In accordance with the Rulebook for amending and supplementing the rulebook for renewable energy sources from June 2022, calculations have been made for the profitability of energy production from grid-connected small wind turbines. Finally, a graphical comparative analysis of different models of small wind turbines for all locations is presented, and conclusions and further directions and recommendations for optimal utilization of wind energy are given.
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Investigation of the sustainability and profitability of small wind turbines
(2023-09)
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In the past decades, extensive and exhaustive research has been done on the analysis of the operation of large wind turbines, but detailed analyses on small wind turbines are still rare. In addition, two current situations are considered: i) the exhaustion of the possibilities for designing new large wind fields, and ii) the energy crisis, which is particularly current in Europe, so it comes naturally to analyse the possibilities for exploitation of small wind turbines. The paper analyses five potential locations in North Macedonia. Based on three-year measurement period at those locations, the probability distribution of wind speeds was obtained and integrated with the power curve for a specific turbine, the electricity production of four different, commercially available, small wind turbines was investigated. Three wind turbines are horizontal axes wind turbines, with installed power in the range 3-50 kWp and one is vertical axis wind turbine with installed power of 4 kWp. In accordance with the Rulebook for amending and supplementing the rulebook for renewable energy sources from June 2022, calculations have been made for the profitability of energy production from grid-connected small wind turbines. Finally, a graphical comparative analysis of different models of small wind turbines for all locations is presented, and conclusions and further directions and recommendations for optimal utilization of wind energy are given.
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Simultaneous Optimization Of Electrical Interconnection Configuration In Onshore Wind Fields
(Faculty of Electrical Engineering and Information Technologies, “Ss. Cyril and Methodius” University in Skopje, 2019-01)
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The electrical interconnection cost of onshore wind fields (WF) is a part that should not be neglected in the design of WF. In order to minimize the investment and operational costs, this paper pro-poses an optimization formulation to find the optimal electrical interconnection configuration of wind turbines (WTs), simultaneously. This simultaneous minimization of total trenching length is done during а WF layout optimization by application of evolutional algorithm. In this paper, an algorithm is considered to comprehensively assess the optimal interconnection layout of the WTs. The interconnections are considerable fraction of the overall design cost of the WF. The optimal electrical interconnection design obtained by an algorithm with implemented Euclidean Minimum Spanning Tree method, corresponds to a lower cost and coupled with the technological developments can help policy makers and WF developers increase the use of onshore wind energy as a feasible unlimited renewable source of electrical energy.

Stoilkov, Vlatko

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