Comparison of the performance of sensitivity-based voltage control algorithms in DG-integrated distribution systems

Conference ProceedingsThe integration of renewable energy generators in distribution grids has increased the complexity of the voltage control problem. Reactive power control (RPC) algorithms based on sensitivity analysis have been proposed in the literature for the management of the voltage problem. Sensitivity methods are computationally complex for practical real-time analysis and this has led to use of de-coupled and other simplified load flow models. However, algorithms based on decoupled models have been shown to be inefficient for analysis of distribution systems with low X/R ratio. This paper uses a simplified line modelling approach recently proposed in the literature to facilitate the development of computationally simple distributed, non-decoupled, load flow equations that completely capture the characteristics of the radial distribution feeder, removing the need to use the decoupled models. Results show that the simple algorithm based on this new line modelling approach gives better voltage control performance compared to the decoupled models

Novel Optimization-Based Algorithms for a Substation Voltage Controller Using Local PMU Measurements

This paper presents an improved version of a local voltage controller for a transmission substation. The controller uses available phasor measurement units (PMUs) at the substation, for optimal management of its local reactive (VAr) control resources, such as shunt reactive devices and transformer taps. Two optimization formulations with different objectives are introduced based on various operating criteria in electric utilities. The first approach aims to minimize the required reactive power injection such that it corrects the substation bus voltages to be within pre-specified limits so as to be close as possible to the optimal values. The second one minimizes the number of switching actions that are needed to correct the voltages to be within limits. Genetic algorithm (GA) is used for solving these discrete optimization problems. Performance of the proposed formulations is tested and analyzed through simulations for a typical substation in Southern California transmission network. Finally, the results from the two approaches are compared and discussed

Results of multi-agent system and ontology to manage ideas and represent knowledge in a challenge of creativity

This article is about an intelligent system to support ideas management as a result of a multi-agent system used in a distributed system with heterogeneous information as ideas and knowledge, after the results about an ontology to describe the meaning of these ideas. The intelligent system assists participants of the creativity workshop to manage their ideas and consequently proposing an ontology dedicated to ideas. During the creative workshop many creative activities and collaborative creative methods are used by roles immersed in this creativity workshop event where they share knowledge. The collaboration of these roles is physically distant, their interactions might be synchrony or asynchrony, and the information of the ideas are heterogeneous, so we can say that the process is distributed. Those ideas are writing in natural language by participants which have a role and the ideas are heterogeneous since some of them are described by schema, text or scenario of use. This paper presents first, our MAS and second our Ontology design

Results of multi-agent system and ontology to manage ideas and represent knowledge in a challenge of creativity

International audienceThis article is about an intelligent system to support ideas management as a result of a multi-agent system used in a distributed system with heterogeneous information as ideas and knowledge, after the results about an ontology to describe the meaning of these ideas. The intelligent system assists participants of the creativity workshop to manage their ideas and consequently proposing an ontology dedicated to ideas. During the creative workshop many creative activities and collaborative creative methods are used by roles immersed in this creativity workshop event where they share knowledge. The collaboration of these roles is physically distant, their interactions might be synchrony or asynchrony, and the information of the ideas are heterogeneous, so we can say that the process is distributed. Those ideas are writing in natural language by participants which have a role and the ideas are heterogeneous since some of them are described by schema, text or scenario of use. This paper presents first, our MAS and second our Ontology design

The proposed fuzzy logic system for voltage regulation, power factor improvement and power losses reduction in power systems with high infiltration of distributed generation

Abstract: Recently, the awareness of the severe consequences of greenhouse gases on the environment has escalated. This has encouraged the world to reduce the usage of fossil fuels for power generation and increase the use of cleaner sources such as solar energy and wind energy. However, the conventional power system itself was designed as a passive power system in which power generation is centralized, and power flows from substations towards the loads. The introduction of these renewable energy sources also called distributed generators create an active power system in which power generation is decentralized, and generation of power can occur anywhere on the power system. Decentralized power generation creates challenges for the conventional power system such as voltage fluctuations, high voltage magnitudes, reverse power flow and low power factor. On this paper, an adaptive control system that coordinates different distributed generators for voltage regulation and power factor correction is introduced and designed. The control system will decrease the total reactive power that flows on the transmission network through a reactive power exchange between distributed generators. Therefore, power factor will improve, power system losses will reduce, and the total apparent power on lines will reduce giving more room to active power to flow. The results obtained showed that the control system is effective in regulating voltage and improving the power factor when multiple distributed generators are connected

Voltage Stability Assessment and Control Based on Synchrophasor Measurements in Ambient Condition

Voltage stability assessment and control are among the top priority tasks for electric utilities and power system operators. Failure in performing these correctly, has resulted in some of the major blackouts over the past few decades. Continuous loading increase on system infrastructure, higher reliability and security requirements, as well as progressive renewable resource integration, incapable of guaranteeing sustained reactive support, have all made this function more complex, and yet more crucial.Traditionally, developed algorithms for calculating voltage stability margin and recommending the necessary control action, rely on complete and accurate system models, as well as extensive offline studies. Investigating previous incidents has proved this to be a challenging goal to achieve. At the same time, integration of high-sampling measurement devices such as synchrophasors, powerful processors, and fast communication have resulted in increased situational awareness and monitoring quality of the system behavior. As a result, there is high interest today, to develop measurement-based real-time tools for determining system status from stability point of view and deduce the optimal control actions in critical conditions.In this dissertation, accurate modeling of the power system ambient data, corresponding to its operation at quasi steady-state condition is discussed, and the difference between system's steady-state response and power flow solutions is investigated. Based on this clarification, a new distributed model-free algorithm is proposed for voltage stability assessment and control of a power system, based on steady-state Q-V sensitivity of system buses. This is realized through subspace system identification from input-output response based on ambient measurements. Once the sensitivities are known, system proximity to voltage instability can be determined using the minimum sensitivity, rank system buses according to their stability margin and the need for corrective control actions, and determine the optimal set of actions needed to bring system operation point back to a secure state. To pursue the latter, two optimization approaches with different objectives based on various operating policies are introduced towards finding the best local control action within a substation. Finally, an index is introduced to determine vulnerability of the system to voltage instability caused by limitation on a generator's reactive power

Dağıtık üretimli elektrik enerji sistemlerinde gerilim azaltım yöntemi ile enerji optimizasyonu

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Dağıtım sistemlerinde akıllı şebeke teknolojilerinin kurulmasıyla, dağıtım şirketleri (operatörler ve planlayıcılar) için birçok olanak sağlanmaktadır. Böylelikle, dağıtım şirketleri, şebekenin verimini, güvenilirliğini artırmak, bazı teknik ve ekonomik sorunları çözmek için haberleşme ve ileri ölçüm altyapısı gibi akıllı şebeke teknolojilerine önem vermektedir. Dağıtık üretimin (DÜ) olumsuz etkilerini yok etmek gibi zorlukların üstesinden gelmek için geleneksel kontrol yöntemlerinin geliştirilmesi gerekmektedir. Bu yüzden problemlerin üstesinden gelmek, tüketiciye kaliteli elektrik enerjisi sağlamak ve şebekenin verimini artırmak gibi akıllı şebeke işlemleri için yeni kontrol yöntemleri geliştirilmelidir. Bu tez Volt/VAr Optimizasyonu (VVO) olarak adlandırılan dağıtım şebeke gerilim ve reaktif güç optimizasyonu için yeni yaklaşımlar önermeyi amaçlamıştır. Önerilen yaklaşımlar VVO'nun önemli bir özelliği olan kullanıcıların cihazlarına zarar vermeden ve performansını etkilemeden limitler içinde gerilimi azaltarak talep gücü azaltmaya ve enerji tasarrufuna olanak sağlayan Tasarruflu Gerilim Azaltımı (CVR - gerilim azaltımı ile enerji optimizasyonu) için uygulanmıştır. İlk olarak, gerilim ve reaktif güç kontrolü ayrı ayrı ele alınarak dağıtık reaktif güç kontrol algoritması VVO için uygulanmıştır. Önerilen bu VVO/CVR'nin amacı dağıtık reaktif güç kontrol algoritması ile kayıplar minimize edilirken dağıtım trafo merkezinde bulunan gerilim regülatörü (VR) ile gerilimi olabildiğince alt limite yaklaştırmaktır. Tezde ikinci olarak gerilim ile reaktif güç birlikte ele alınarak merkezi ve merkezi olmayan birleşik VVO/CVR uygulanmıştır. Ele alınan problem karışık tam sayılı doğrusal olmayan programlama (KTDOP) problemi olarak modellenmiştir. KTDOP olarak modellenen VVO/CVR problemi genetik algoritma (GA) kullanılarak çözülmüştür. İki farklı VVO/CVR yaklaşımının uygulanmasıyla sadece gerilim profili iyileştirilmemiş ayrıca çekilen güç ile kayıplar azalarak günlük enerji tüketimi de azaltılmış ve enerji tasarrufu elde edilmiştir. VVO/CVR'a Model Öngörülü Kontrolün (MÖK) uygulanmasıyla sistemin gelecek durumları dikkate alınmış ve gereksiz kontrolden kaçınılarak kullanılan aygıtların işlem/anahtarlama sayısının azaldığı görülmüştür. Önerilen yöntemler sürekli durumda kontrol merkezi ve kullanıcılar arasında iki yönlü haberleşme yapısına sahip olduğu varsayılan DÜ ve DSTATCOM içeren dengesiz yüklenme ve hat yapısına sahip olan IEEE 13-34 baralı test sistemine uygulanmıştır. Benzetimler günlük değişken yük talebi, farklı tip tüketici, üç fazlı güç akışı ile üç fazlı dengesiz hat modeli ve gerilime bağlı yük modeli kullanılarak gerçekleştirilmiştir.Deployment of smart grid technologies in distribution systems provides many opportunities for utilities. Thus, a large number of utilities intend to explore the capabilites of smart grid technologies to imrove the efficiency, reliability of grid and overcome technical-economical issues of the grid. Conventional control methods need to be improved to address the challenges associated with negative influence of distributed generation (DG). Hence, new control techniques need to be developed for smart grid operations to overcome the problems, provide high quality power for the customers and increase the grid efficiency. This thesis aims to introduce novel approaches for one of the useful techniques employed for distribution network voltage and reactive power optimization called as Volt-VAR Optimization (VVO). The proposed approaches are applied for Conservation Voltage Reduction (CVR) as a part of VVO which provides energy saving by decreasing the voltage magnitudes to the minimum allowable limits without affecting the performance of the end user's devices. The first part of the study introduces distributed reactive power control based VVO/CVR approach in a decoupled way. The objective of the novel VVO/CVR approach is to minimize system power losses by distributed reactive power control while reducing the voltage down to the lower acceptable limits. The second part of the study introduces centralized and decentralized integrated VVO/CVR approach. The control problem is formulated as a mixed integer non-linear programming (MINLP) problem. The foregoing problem is solved through Genetic Algorithm (GA). Applying two different VVO/CVR approaches not only improves the voltage profile along the feeder but also reduces the daily energy demand. Model Predictive Control (MPC) technique is applied to second VVO/CVR problem and it has been seen that the operation/switching times of equipment are reduced by avoiding unnecessary control. The proposed approaches in this thesis are validated on IEEE 13-34 test feeder system with DG and DSTATCOMs assuming steady-state operating conditions and two-way communication network. The formulation is based on a three-phase power flow with variable load demand, different customer types, voltage dependent loads, unbalanced line configurations