Energies

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315 KiB

Open AccessArticle

Entropy-Based Bagging for Fault Prediction of Transformers Using Oil-Dissolved Gas Data

by Yuanbing Zheng, Caixin Sun, Jian Li, Qing Yang and Weigen Chen

Energies 2011, 4(8), 1138-1147; https://doi.org/10.3390/en4081138 - 4 Aug 2011

Cited by 18 | Viewed by 6361

The development of the smart grid has resulted in new requirements for fault prediction of power transformers. This paper presents an entropy-based Bagging (E-Bagging) method for prediction of characteristic parameters related to power transformers faults. A parameter of comprehensive information entropy of sample [...] Read more.

The development of the smart grid has resulted in new requirements for fault prediction of power transformers. This paper presents an entropy-based Bagging (E-Bagging) method for prediction of characteristic parameters related to power transformers faults. A parameter of comprehensive information entropy of sample data is brought forward to improve the resampling process of the E-Bagging method. The generalization ability of the E-Bagging is enhanced significantly by the comprehensive information entropy. A total of sets of 1200 oil-dissolved gas data of transformers are used as examples of fault prediction. The comparisons between the E-Bagging and the traditional Bagging and individual prediction approaches are presented. The results show that the E-Bagging possesses higher accuracy and greater stability of prediction than the traditional Bagging and individual prediction approaches. Full article

(This article belongs to the Special Issue Future Grid)

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169 KiB

Open AccessArticle

Discussions on the Architecture and Operation Mode of Future Power Grids

by Liye Xiao, Liangzhen Lin and Yi Liu

Energies 2011, 4(7), 1025-1035; https://doi.org/10.3390/en4071025 - 4 Jul 2011

Cited by 21 | Viewed by 6956

Abstract

The new energy revolution, of which the primary energy will be based on renewable energy sources and the terminal energy will be based on electric power, will have a revolutionary impact on the future power grids. In order to develop the corresponding power [...] Read more.

The new energy revolution, of which the primary energy will be based on renewable energy sources and the terminal energy will be based on electric power, will have a revolutionary impact on the future power grids. In order to develop the corresponding power grid for the future energy system, first of all, the architecture and mode of operation of the future power grid must be investigated. In this paper, we suggest that the DC—dominant operation mode for transmission system, distribution network and distributed power system should be developed, and a MP-MC dominated transmission architecture (multiple powers to multiple consumers) and the two-way power exchange control (TPEC) should be employed to build “wide-area super virtual power plants” (WASVPPs) which cover all the major power plants in a wide range, allowing the consumers to obtain a stable and reliable supply of electricity from the “cloud powering” created by WASVPP and the distributed power system which is connected to the grid. Full article

(This article belongs to the Special Issue Future Grid)

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605 KiB

Open AccessArticle

AC Power Routing System in Home Based on Demand and Supply Utilizing Distributed Power Sources

by Tsuguhiro Takuno, Yutaro Kitamori, Ryo Takahashi and Takashi Hikihara

Energies 2011, 4(5), 717-726; https://doi.org/10.3390/en4050717 - 26 Apr 2011

Cited by 41 | Viewed by 9289

Abstract

To help reduce consumption of fossil fuels, renewable, natural and distributed power sources are being adopted. These alternative energy sources inevitably show fluctuations in the amount of output power, frequency, and voltage. The suppression of such fluctuations is a key issue to avoid [...] Read more.

To help reduce consumption of fossil fuels, renewable, natural and distributed power sources are being adopted. These alternative energy sources inevitably show fluctuations in the amount of output power, frequency, and voltage. The suppression of such fluctuations is a key issue to avoid disturbances in power grids. A similar situation arises as far as the regulation of in-home power flow is concerned. We focus on the quality of supplied and demanded power in particular. In this paper, an in-home power distribution system based on information of power is proposed. The system is developed in order to integrate power dispatch and communication. The experimental results show the feasibility of new flexible and efficient power management approaches. Full article

(This article belongs to the Special Issue Future Grid)

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304 KiB

Open AccessArticle

Multiple Objective Compromised Method for Power Management in Virtual Power Plants

by Jinxia Gong, Da Xie, Chuanwen Jiang and Yanchi Zhang

Energies 2011, 4(4), 700-716; https://doi.org/10.3390/en4040700 - 21 Apr 2011

Cited by 31 | Viewed by 7502

Abstract

In practical optimization, a priority requirement for different objectives of multiple objective optimization problems should be considered. In this paper, the distributed power management of a Virtual Power Plant (VPP) with priority requirement is optimized by the compromised method. The operation optimization model [...] Read more.

In practical optimization, a priority requirement for different objectives of multiple objective optimization problems should be considered. In this paper, the distributed power management of a Virtual Power Plant (VPP) with priority requirement is optimized by the compromised method. The operation optimization model of VPP is formulated as a fuzzy multiple objective optimization problem considering the satisfaction of customers and suppliers, the system stability, the power quality, and costs with operation limitations. The multiple objective optimization algorithm with the compromise of the satisfactory degree and the priority of objectives is studied based on the principle of two-step interactive satisfactory optimization. This method is also applied in a test system. Full article

(This article belongs to the Special Issue Future Grid)

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301 KiB

Open AccessArticle

Model for Predicting DC Flashover Voltage of Pre-Contaminated and Ice-Covered Long Insulator Strings under Low Air Pressure

by Jianlin Hu, Caixin Sun, Xingliang Jiang, Qing Yang, Zhijin Zhang and Lichun Shu

Energies 2011, 4(4), 628-643; https://doi.org/10.3390/en4040628 - 19 Apr 2011

Cited by 11 | Viewed by 7572

Abstract

In the current study, a multi-arc predicting model for DC critical flashover voltage of iced and pre-contaminated long insulator strings under low atmospheric pressure is developed. The model is composed of a series of different polarity surface arcs, icicle-icicle air gap arcs, and [...] Read more.

In the current study, a multi-arc predicting model for DC critical flashover voltage of iced and pre-contaminated long insulator strings under low atmospheric pressure is developed. The model is composed of a series of different polarity surface arcs, icicle-icicle air gap arcs, and residual layer resistance. The calculation method of the residual resistance of the ice layer under DC multi-arc condition is established. To validate the model, 7-unit and 15-unit insulator strings were tested in a multi-function artificial climate chamber under the coexistent conditions of low air pressure, pollution, and icing. The test results showed that the values calculated by the model satisfactorily agreed with those experimentally measured, with the errors within the range of 10%, validating the rationality of the model. Full article

(This article belongs to the Special Issue Future Grid)

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381 KiB

Open AccessArticle

A Smart Online Over-Voltage Monitoring and Identification System

by Jing Wang, Qing Yang, Wenxia Sima, Tao Yuan and Markus Zahn

Energies 2011, 4(4), 599-615; https://doi.org/10.3390/en4040599 - 18 Apr 2011

Cited by 46 | Viewed by 8498

Abstract

This paper proposes a complete and effective smart over-voltage monitoring and identification system. In recent years, smart grids are of the greatest interest in power system research. One of the main features of smart grid is their self-healing, which can continuously carry out [...] Read more.

This paper proposes a complete and effective smart over-voltage monitoring and identification system. In recent years, smart grids are of the greatest interest in power system research. One of the main features of smart grid is their self-healing, which can continuously carry out online self-evaluation, discover existing faults, and correct them immediately. The over-voltage smart monitoring-identification-suppression systems play a key role in the construction of self-healing grids. In this paper, eight kinds of common over-voltage are discussed and analyzed. The S-transform algorithm is used to extract features of over-voltage. Aiming at the main features of each kind of over-voltage, six different characteristic quantities are proposed. A well designed fuzzy expert system and a support vector machine are employed as the classifiers to build a two-step identification model. The accuracy of the identification system is verified by field records. Results show that this system is feasible and promising for real applications. Full article

(This article belongs to the Special Issue Future Grid)

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604 KiB

Open AccessArticle

A Multiagent System for Autonomous Operation of Islanded Microgrids Based on a Power Market Environment

by Hak-Man Kim, Tetsuo Kinoshita and Myong-Chul Shin

Energies 2010, 3(12), 1972-1990; https://doi.org/10.3390/en3121972 - 20 Dec 2010

Cited by 61 | Viewed by 12484

Abstract

One of the most important requirements of microgrid operation is to maintain a constant frequency such as 50 Hz or 60 Hz, which is closely related to a power balance between supply and demand. In general, microgrids are connected to power grids and [...] Read more.

One of the most important requirements of microgrid operation is to maintain a constant frequency such as 50 Hz or 60 Hz, which is closely related to a power balance between supply and demand. In general, microgrids are connected to power grids and surplus/shortage power of microgrids is traded with power grids. Since islanded microgrids are isolated from any power grids, the decrease in generation or load-shedding can be used to maintain the frequency when a power imbalance between supply and demand occurs. The power imbalance restricts the electricity use of consumers in the case of supply shortage and the power supply of suppliers in the case of supply surplus. Therefore, the islanded microgrid should be operated to reduce power imbalance conditions. Meanwhile, the microgrid is a small-scale power system and the employment of skillful operators for effective operation of its components requires high costs. Therefore, automatic operation of the components is effective realistically. In addition, the components are distributed in the microgrid and their operation should consider their owners’ profits. For these reasons, a multiagent system application can be a good alternative for microgrid operation. In this paper, we present a multiagent system for autonomous operation of the islanded microgrid on a power market environment. The proposed multiagent system is designed based on a cooperative operation scheme. We show the functionality and the feasibility of the proposed multiagent system through several tests. Full article

(This article belongs to the Special Issue Future Grid)

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801 KiB

Open AccessArticle

Hierarchical MAS Based Control Strategy for Microgrid

by Zhe Xiao, Tinghua Li, Ming Huang, Jihong Shi, Jingjing Yang, Jiang Yu and Wei Wu

Energies 2010, 3(9), 1622-1638; https://doi.org/10.3390/en3091622 - 10 Sep 2010

Cited by 57 | Viewed by 12299

Abstract

Microgrids have become a hot topic driven by the dual pressures of environmental protection concerns and the energy crisis. In this paper, a challenge for the distributed control of a modern electric grid incorporating clusters of residential microgrids is elaborated and a hierarchical [...] Read more.

Microgrids have become a hot topic driven by the dual pressures of environmental protection concerns and the energy crisis. In this paper, a challenge for the distributed control of a modern electric grid incorporating clusters of residential microgrids is elaborated and a hierarchical multi-agent system (MAS) is proposed as a solution. The issues of how to realize the hierarchical MAS and how to improve coordination and control strategies are discussed. Based on MATLAB and ZEUS platforms, bilateral switching between grid-connected mode and island mode is performed under control of the proposed MAS to enhance and support its effectiveness. Full article

(This article belongs to the Special Issue Future Grid)

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