The IEC 61400-25 standard has defined mapping of power plant information model to Web services. How to ensure the security of Web services-based communication for wind power plants is a unsolved problem. WS-Security i...
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The IEC 61400-25 standard has defined mapping of power plant information model to Web services. How to ensure the security of Web services-based communication for wind power plants is a unsolved problem. WS-Security is a standard used to deal with the security requirement in application of Web services, while username/password and X.509 certificates are security tokens most commonly used in electric power utility. We propose a security mechanism that deal with the requirements of authentication, integrity, non-reputation, and confidentiality across the communication process based on WS-Security and the two security token. The security mechanism is implemented by extension of SOAP message, design of security agent, and the related security message processing algorithm. An instance is modeling based on IEC 61400-25 to demonstrate the security enhanced remote control of wind power plants. The result support the usefulness of the security mechanism for Web Services-based wind power plants communication.
With the start of trial operation of direct purchasing electricity for large consumers in China, the method on how to price electricity is of vital theoretical and practical significance. Hedonic electricity pricing m...
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The character of the voltage at the end of the opened phase conductor was studied and an improved voltage criterion was proposed to distinguish between transient and permanent faults. The performance of the improved c...
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The character of the voltage at the end of the opened phase conductor was studied and an improved voltage criterion was proposed to distinguish between transient and permanent faults. The performance of the improved criterion is hardly influenced by the load currents of healthy phases, transmission line length, fault distance and fault earth resistance. For EHV/UHV lines with shunt reactors, the improved method is also effective when a calculated capacitive coupling voltage is employed. Simulation tests show that the conclusions drawn in this paper are correct.
Distributed generation in microgrid is mainly composed of new energy and renewable energy resources. The maximum power point of the PV cell array is various from time to time with the change of circumstance and load. ...
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Distributed generation in microgrid is mainly composed of new energy and renewable energy resources. The maximum power point of the PV cell array is various from time to time with the change of circumstance and load. The fuzzy control can react to the environment change quickly and keep the photovoltaic system work on its maximum power point all the time. However, the limitation in the fuzzy control itself and the characteristic of self-optimization lead to serious concussion of the system around the maximum power point. Whereas the PID control method is effective in the elimination of concussion and is easy to be realized. To tackle the problem, the fuzzy parameter self-tuning PID control method is adopted in the paper to achieve the MPPT control of PV system. The method can effectively eliminate the concussion around the maximum power point and improve the stability of the whole microgrid; and achieve grid-connected operation with a high power factor in combination with the harmonic elimination PWM control of inverter. Simulation results show that the scheme has merits of simple structure, high power factor and reliable operation, etc. and is worthwhile to be popularized.
Distributed generation (DG), which is interlinked with distribution system, will inevitably have an impact to system. In the paper, a reliability evaluation method is proposed, which is based on the analysis to the st...
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Distributed generation (DG), which is interlinked with distribution system, will inevitably have an impact to system. In the paper, a reliability evaluation method is proposed, which is based on the analysis to the structure and power flow of distribution system with distributed generation. First, a new concept, the smallest unit, is put forward for improving the fault traversal networks times. The authors use the depth-first search in data structure to divide distribution system into several the smallest units, and propose the islanding operation mode to increase the reliability of the system. Distribution system will be automatically turned into the islanding operation mode once faults occur. To evaluate quantitatively the reliability of distribution system, Monte Carlo simulation method is used by simulating the running status of distribution system. At last, the calculation results of actual case show that the proposed method is available to evaluate the reliability of distribution system with distributed generation.
With the start of trial operation of direct purchasing electricity for large consumers in China, the method on how to allocate the wheeling charges of large consumers is of vital theoretical and practical significance...
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With the start of trial operation of direct purchasing electricity for large consumers in China, the method on how to allocate the wheeling charges of large consumers is of vital theoretical and practical significance. An integrated method for allocating the congestion management cost of larger consumers is presented in this paper considering time-of-use (TOU) pricing in congestion period, power supply reliability and the use capacity of the line. Modeling the TOU index, power supply reliability index and use capacity of the line index is proposed. The weights of three indices are determined by interacting between the transmission utility and large consumers based on multilevel models to get comprehensive evaluation indices for all consumers. The integrated indices are used to allocate the cost. Test results show that the method can allocate the congestion cost more reasonably.
The occurrence cause and negative effects of the islanding are presented in the paper, and a new method is presented based on chaos system. This paper applies certain chaos system of its sensitivity to periodical volt...
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The occurrence cause and negative effects of the islanding are presented in the paper, and a new method is presented based on chaos system. This paper applies certain chaos system of its sensitivity to periodical voltage signal to make its periodical solution yield a dramatic change to detect islanding, existence of the islanding can be identified by discriminating operation status of chaos system. The proposed method is showed to have fast acting and little influence on power quality. The simulations of the proposed method are carried out according to IEEE Std 1547-2003, the simulation results verify its effectiveness.
powersystem is approaching its limits due to the deregulation of power industry and unavailability of new transmission corridor. However powersystem security assessment is carried out and the operating limits are se...
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powersystem is approaching its limits due to the deregulation of power industry and unavailability of new transmission corridor. However powersystem security assessment is carried out and the operating limits are set according to the given contingency list which might happen in very rare frequency. In other words, the frequency of fault occurrence and the risk of blackout is varied when the operating condition (load level, status of power equipment, and weather) changes. How can we do the security assessment based on the operating condition to get the best equilibrium between the security and the profit is the focus of this paper. The idea of risk based on-line powersystem security assessment is suggested. A precise calculation method of average failure rates of components is presented. Besides, operating condition based failure rates of components are also analyzed systematically in the paper. The Monte-Carlo simulation demonstrates the viewpoint of the paper.
With increasingly proportion of distributed generation (DG) in the powersystem, traditional powersystem planning has new challenges and demands. The necessity for flexible electric system, changing regulatory, energ...
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With increasingly proportion of distributed generation (DG) in the powersystem, traditional powersystem planning has new challenges and demands. The necessity for flexible electric system, changing regulatory, energy savings and environmental impact are providing impetus to the development of DG. Itpsilas critical that the powersystem impacts be assessed accurately so that DG can be applied in a manner that avoid degradation of power quality, assure reliability and control of the utility system. In recent years, wind energy has become an important part of DG in many countries and its importance is continuing to increase. This paper focuses on the capacity planning of wind power stations, considering technical constrains, like feeder voltage profile, harmonic distortion etc, and establishes a model based on improved genetic algorithm to solve, which produces chaotic initial population to start iteration to raise algorithm for the speed and accuracy. Through simulation and calculation, the two sets of results are compared, and the feasibility of the above model and algorithm is demonstrated.
Frequency spectrum leakage caused by synchronous error in nonsynchronous sampling system reduces the accuracy of frequency spectrum analysis and harmonic measurement. A sampling frequency self-adapting software algori...
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Frequency spectrum leakage caused by synchronous error in nonsynchronous sampling system reduces the accuracy of frequency spectrum analysis and harmonic measurement. A sampling frequency self-adapting software algorithm in protection relay measure and controlsystem is presented in this paper. The sampling frequency self-adapting software algorithm obtained the actual signal frequency fairly accurately by calculating the sampling data from protection relay measure and controlsystem, and adjusted the sampling time interval according to the frequency which was calculated by the self- adapting software algorithm. The process of the software algorithm design is introduced, simulation and analysis are discussed. The results of simulation and analysis show that this software algorithm can improve the accuracy of frequency spectrum analysis and harmonic measurement for powersystem signal, and the algorithm can be realized easily.
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