Engin Karatepe | Ege University (original) (raw)

Papers by Engin Karatepe

Energy, 2015

To ensure the optimization of the energy generated by grid connected PV (photovoltaic) systems is... more To ensure the optimization of the energy generated by grid connected PV (photovoltaic) systems is necessary to plan a strategy of automatic fault detection. The analysis of current and voltage indicators have demonstrated effectiveness in the detection of permanent faults in the PV array in real time as short-circuits or open circuits present in the system. In this paper, the analysis of the evolution of these indicators is focused on the detection of temporary faults due to partial shade on the PV array or disconnection of the inverter in case of grid fluctuations of voltage or frequency to prevent islanding. These situations can be identified by observation of the evolution of both indicators and power losses due to these effects can be evaluated from them. The analysis and experimental validation were carried out in two grid connected PV systems in Spain and Algeria.

Renewable and Sustainable Energy Reviews, 2015

The level of uncertainty increases with growing distributed generation (DG) penetration in the po... more The level of uncertainty increases with growing distributed generation (DG) penetration in the power systems, thus convincing and user-friendly planning tools and strategies should be developed. We investigate the comparison between single- and multiple-DG concepts in terms of power loss, voltage profile, and line flows. A new procedure is presented based on grading the restructuring priorities by using a simple power flow analysis based probabilistic assessment including the output power uncertainties in DG resources. This procedure can facilitate the choice of which infrastructure of an existing network has precedence in the modernization of a network when DG units are integrated. Note that there is a threshold penetration level in terms of line losses, and trade-off between single- and multiple-DG concepts in respect of the capacity of existing lines and voltage profiles.

IEEE Transactions on Power Systems, 2016

Integration of wind turbines introduces new challenges in terms of planning criteria. In this stu... more Integration of wind turbines introduces new challenges in terms of planning criteria. In this study, a new transmission expansion planning methodology considering N-1 contingency conditions is proposed to minimize investment cost and curtailed wind energy over planning period. To deal with the uncertainty of load and output power of wind turbines, probabilistic method based on clustering is used for determination of load and wind model. To incorporate the wind power curtailment into the proposed methodology, optimal power flow which uses DC-power flow equations is utilized by including cost functions of generators and overall optimization is carried out by using an integer genetic algorithm. Finally, the proposed methodology is applied to the modified IEEE RTS 24-bus test system by considering different case studies in order to show the effects of including cost functions.

IEEE Transactions on Power Systems, 2017

In this study, two important planning problems in power systems that are transmission expansion ... more In this study, two important planning problems in power systems that are transmission expansion and reactive power are formulated as a mixed-integer linear programming taking into account the bilevel structure due to the consideration of market clearing under several load-wind scenarios. The objective of the proposed method is to minimize the installation cost of transmission lines, reactive power sources, and the annual operation costs of conventional generators corresponding to the curtailed wind energy while maintaining the reliable system operation. Lower level problems of the bilevel structure are designated for the market clearing which is formulated by using the linearized optimal power flow equations. In order to obtain mixed-integer linear programming formulation, the so-called lower level problems are represented by using primal-dual formulation. By using the proposed method, power system planners will be able to find economical investment plans by considering the balance between wind power curtailment and the installation of transmission lines and reactive power sources.

Electrical Engineering, 2016

This paper presents genetic algorithm optimization method with a suitable objective function to d... more This paper presents genetic algorithm optimization method with a suitable objective function to determine optimum location and rated values of FACTS devices by taking into account changes in the power system load over time. In this study, annual daily load profile is considered as a whole instead of an instant load profile while looking for optimum size and location of FACTS devices. For this reason, to simplify the optimization procedure, a graph-based panelized objective function is developed, which can be used in a mixed integer search heuristic optimization technique. This paper focuses on the evaluation of the simultaneous use of thyristor controlled series capacitor and static VAR compensator. The proposed method allows including, in a simple way, the long term load profile in the planning stage to improve the power system performance using FACTS devices. After the optimization process, the performance of the proposed method has been tested on the IEEE-30 bus system with several annual test load profiles. The planning horizon is included in the optimization framework and the impact of planning horizon result is presented to compare with that of single load profile. The optimization strategy is shown to lead a significant reduction in the voltage and line violations under the long term test load profiles.

Electrical Power and Energy Systems, 2017

Harmonic distortion caused by increasing size of inverter-based distributed generation (DG) can g... more Harmonic distortion caused by increasing size of inverter-based distributed generation (DG) can give rise to power quality problems in distribution power networks. Therefore, it is very important to determine allowable DG penetration level by considering the harmonic related problems. In this study, an optimization methodology is proposed for maximizing the penetration level of DG while minimizing harmonic distortions considering different load profiles. The methodology is based on updating the voltage magnitude and angle at point of common coupling depending on the size of DG to be utilized in the harmonic power flow modeling. The harmonic parameters are determined by using decoupled harmonic power flow method, in which the harmonic source modeling with harmonic current spectrum angle adjustment is embedded, while the nonlinear loads and inverter-based DGs are connected to the distribution power network. The allowable penetration level of DGs is determined based on power quality constraints including total harmonic voltage distortion, individual harmonic voltage distortion, and RMS bus voltage limits in the optimization framework. Fuzzy-c means clustering method is also applied to decrease the computational effort of the optimization process in the long-term load profile. The effectiveness of the proposed method is illustrated on the IEEE 33-bus radial distribution network for different scenarios.

IEEE Transactions on Sustainable Energy, 2017

Integration of wind power plants into power systems requires special attention on network plannin... more Integration of wind power plants into power systems requires special attention on network planning to reduce curtailed wind energy as well as investment costs and generation costs. To this aim, in this study, transmission expansion planning, reactive power planning, and the allocation of TCSC devices are coordinated in order to minimize investment costs of transmission lines, reactive power sources, and TCSC devices along with the sum of generation costs and penalty for load curtailment. Installed wind power plants are modeled by using load-wind scenarios, which are obtained by clustering procedure. They are integrated into the constraints of the proposed method via linearized ac power flow equations. This assures keeping the proposed method as mixed-integer linear programming problem. The proposed method is applied to the Garver 6-bus and IEEE 24-bus RTS test systems under different case studies. Results prove the contributions of the coordinated network planning.

Electrical Power and Energy Systems, 2020

Photovoltaic (PV) system is one of the most important technologies among the renewable energy res... more Photovoltaic (PV) system is one of the most important technologies among the renewable energy resources. With the increasing penetration of PV systems in distribution networks, harmonic distortions also rise due to the inevitable effects of PV inverters. Therefore, determination of the optimal PV penetration level is a vital issue in terms of preventing power quality problems. In this paper, probabilistic and deterministic approaches are proposed to determine the optimal penetration levels of PV systems in unbalanced distorted distribution networks by taking into account the uncertainty of load profile and the intermittent characteristic of PV system output power due to changes in solar irradiance. The Interior Point (IP) method is applied to solve the optimization problem in conjunction with the Monte Carlo Simulation (MCS) and K – means clustering, respectively. The methodology is based on the dependence of the harmonic spectrum of PV injected current on solar irradiance. The harmonic power quality parameters are calculated by using loop frame of reference based three phase harmonic power flow method in the unbalanced distribution network, where the nonlinear loads and PV systems are interfaced. The allowable PV penetration levels are determined based on power quality parameters comprising of total harmonic voltage and individual harmonic voltage distortions, and RMS bus voltage limits.

Solar Energy, 2021

Research on monitoring and fault detection systems for photovoltaic plants is significantly incre... more Research on monitoring and fault detection systems for photovoltaic plants is significantly increasing with the continual development in technologies and the availability of qualified data. Nevertheless, many gaps still exist that need to be addressed. The electrical output of PV plants in various weather conditions is very close to those obtained under fault conditions. For a large scale PV plant, it is very crucial to utilize the data in the decision-making process without using external sensors or performing simulation studies that require detailed parameters of the plant. The main challenge here is to automatically rationalize the collected data in order to make a decision on distinguishing between faulty and natural outputs. This paper proposes a method for distinguishing faults and inherent changes in the PV plant’s output to help O&M crews identify and fix system issues. The proposed method has the ability to map the inherent characteristics of the PV plant by using only the data received from inverters without using additional equipment or detailed models. It has been developed by analyzing the working mechanisms of several large scale PV plants installed in Turkey. The proposed method can easily be implemented in a newly installed or existing PV plant. The novelty of this study is detecting abnormal operations in a PV plant even under low irradiance and cloudy-sky conditions without using any irradiance and temperature sensors. The effectiveness of the proposed method is shown in rooftop and ground-mounted PV plants.

The aim of this study is to investigate the effects of non-uniform solar irradiation distribution... more The aim of this study is to investigate the effects of non-uniform solar irradiation distribution on energy output of different interconnected configurations in photovoltaic (PV) arrays. In order to find which configuration is less susceptible to mismatch effects, a PV module model is developed. This model can take into consideration the effects of bypass diodes and the variation of the equivalent circuit parameters with respect to operating conditions.

Partially shaded photovoltaic (PV) modules typically exhibit additional difficulties in tracking ... more Partially shaded photovoltaic (PV) modules typically exhibit additional difficulties in tracking the maximum power point since their power–voltage characteristics are complex and may have multiple local maxima. For this reason, conventional techniques fail to track the maximum power point effectively if the PV array is partially shaded or some of its cells are damaged. This paper presents a novel power compensation system for PV arrays for complicated non-uniform insolation conditions.

Abstract This paper presents a detailed characterization of the performance and dynamic behaviour... more Abstract This paper presents a detailed characterization of the performance and dynamic behaviour of photovoltaic systems by using LabVIEW real-time interface system. The developed software tool integrates several types of instruments into a single system which is able to offer online measurements all data sources and comparison simulation results with monitored data in real-time. Comprehensive monitoring and analyzing of PV systems play a very important role.

ÖZET Güç akış analizi güç sistemleri açısından vazgeçilmez bir araç olarak karşımıza çıkmaktadır ... more ÖZET Güç akış analizi güç sistemleri açısından vazgeçilmez bir araç olarak karşımıza çıkmaktadır Bu amaçla bir çok güç akış analizi metodu ve programı literatürde ve piyasada geliştirilmiştir. Bu çalışmada ise gerçek bir sistemin güç akış analizleri ele alınmıştır. İzmir ili ve çevresine ait enerji iletim ve dağıtım hatlarının güç akış analizleri farklı senaryolar altında incelenmiş ve olası durumlar için alternatif çözüm önerileri üretilmiştir.

The emerging non-crystalline silicon (c-Si) solar cell technologies are starting to make signific... more The emerging non-crystalline silicon (c-Si) solar cell technologies are starting to make significant inroads into solar cell markets. Most of the researchers have focused on c-Si solar cell in maximum power points tracking applications of photovoltaic (PV) systems. However, the characteristics of non-c-Si solar cell technologies at maximum power point (MPP) have different trends in current–voltage characteristics.

ÖZET Güç sistemlerine entegre edilen dağıtılmış enerji üretim sistemlerinin hızla artması nedeniy... more ÖZET Güç sistemlerine entegre edilen dağıtılmış enerji üretim sistemlerinin hızla artması nedeniyle gerilim kontrolü önem kazanmıştır. Elektrik şebekeleri daha dinamik ve daha karmaşık bir yapıya bürünmektedir ve bu koşullarda artık klasik kontrol metodları yerini akıllı sistemlere bırakmaktadır. Bu çalışmada dağıtılmış enerji üretim sistemleri ve tap ayarlı transformatör eklenmiş IEEE-30 bara test sistemi modifiye edilerek kullanılmıştır.

Abstract-In this paper we present a Matlab-Simulink model for performance evaluation of Bluetooth... more Abstract-In this paper we present a Matlab-Simulink model for performance evaluation of Bluetooth DHx data packets. The simulation model developed takes into account channel quality, distance and interference in the Bluetooth frequency band. We propose a new adaptive algorithm for packet selection based on the number of retransmissions until successful packet reception under current environment conditions.

Mismatching losses reduction of photovoltaic (PV) array has been intensively discussed through th... more Mismatching losses reduction of photovoltaic (PV) array has been intensively discussed through the increasing penetration of residential and commercial PV systems. Many causes of mismatching losses have been identified and plenty of proposed methods to solve this problem have been recently proposed. This paper deals with reducing method of mismatching losses due to the non-uniform irradiance conditions.

Abstract: the article presents a Semi-Markov Chain based model and the related lifetime analysis ... more Abstract: the article presents a Semi-Markov Chain based model and the related lifetime analysis of a wireless module operating in an event-triggered application scenario. In this context, the related operating pattern is modeled mathematically and equations are derived to provide a lifetime prediction using MATLAB. The lifetime is examined as a function of the channel noise and the arrival rate with defined hardware and software parameters.

Abstract Partially shaded photovoltaic (PV) modules typically exhibit additional difficulties in ... more Abstract Partially shaded photovoltaic (PV) modules typically exhibit additional difficulties in tracking maximum power point (MPP), since their power-voltage (PV) characteristics are complex and may have multiple local maxima. For this reason, conventional techniques fail to track MPP effectively, if the PV array is partially shaded. This paper presents a novel power compensation and control system for PV arrays under complicated non-uniform insolation conditions.

ÖZET Son yıllarda güç sistemleri açısından önem kazanan olgulardan biri dağıtılmış enerji üretim ... more ÖZET Son yıllarda güç sistemleri açısından önem kazanan olgulardan biri dağıtılmış enerji üretim sistemleridir. Her ne kadar yeni bir kavram olmasa da, gerek yenilenebilir enerji kaynaklarında gerekse düşük güçteki üretim birimlerinde gerçekleşen gelişmelerle birlikte günümüzde önemini oldukça artırmıştır.