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Liu L.,Huazhong University of Science and Technology | Zhou J.,Hunan Electric Power Company | An X.,Tsinghua University | Zhang Y.,Hunan Electric Power Company | Yang L.,Hunan Electric Power Company
Expert Systems with Applications | Year: 2010

Considering that the water quality assessment is a fuzzy concept with multiple indicators and classes, and there are still some limits of fuzzy comprehensive evaluation method, the fuzzy mathematics method and the information entropy theory are combined to establish an improved fuzzy comprehensive evaluation method for water quality assessment. In this method, the exponential membership function has been adopted to solve the zero-weight problem, and the information entropy has been used to modify the coefficients of weight in order to exploit the useful information of data to a maximum extent. In addition, the weighted average principle has been taken to replace the maximum membership principle for reserving the information in the assessment coefficients as much as possible. The water quality of Three Gorges region is taken as an example and the results show that the improved fuzzy comprehensive evaluation method is superior to the traditional model and worth to be recommended. © 2009.

Sun Q.,Hunan University | Yao J.,Hunan University | Zhao J.,Hunan Electric Power Company | Jin M.,Hunan University | And 2 more authors.
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2013

An accurate short-term bus load forecasting is the basis of realizing energy saving, consumption reducing and meticulous management of dispatching. The integrated forecasting method presented was based on the selection of optimal similar days, using improved clustering analysis algorithm to obtain characteristic curves and sets of historical per-unit curves with similar shape. Identifying bad data and making adjustments by constructing vertical and horizontal eigenvectors reflecting the properties of the sample points. In order to obtain a set of curves whose load level is similar to the target date, the effects of daily characteristics factors on the load level was calculated, and fuzzy object function is weighted over each factor importance degree. Establishing discriminant function of all sets with similar shape, and target date was classified. Taking the intersection of load level set and curve shape set as the result of similar day selection. Sample with minimum date interval to target date was selected as virtual predict object, and then the weight of each algorithm in integrated forecasting was calculated. Case study shows that the proposed method can be effective in improving the quality of raw data, as well as the bus load forecasting accuracy. © 2013 Chinese Society for Electrical Engineering.

Peng J.-C.,Hunan University | He Y.-Q.,Hunan University | Zhou Z.-M.,Hunan Electric Power Company | Jiang H.,Hunan University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2010

A fast evaluating method on distribution system reliability is proposed, aiming at the distribution system with the main supply and an alternative supply. In this method, the distribution system is divided into main and branch networks. At first, the up-stream reliability indices of each point in branch networks are determined by up-stream delivering of each comoponent's reliability indices. Each branch network is replaced by an equivalent component in the main network. Then the failure-mode-effect-analysis (FMEA) method is employed to calculate the reliability indices of each point in the main-network, and the down-stream reliability indices of each point in the branch-network. Then the down-stream reliability indices of each point is determined by down-stream merging of reliability indices of the up-stream-network. Synthesizing the up-and down-stream reliability indices yielded the reliability indices of each point in branch-neworks. The proposed method takes into account the difference in operation time of breakers and section switches. It is not only as accurate as the FMEA method, but faster than the existing algorithms. Simulation results have verified the effectiveness of the proposed novel algorithm. © 2010 Chin. Soc. for Elec. Eng.

Ma F.,Hunan University | Luo A.,Hunan University | Xu X.,Hunan Electric Power Company | Xiao H.,Hunan University | And 2 more authors.
IEEE Transactions on Industrial Electronics | Year: 2013

With the rapid development of high-speed and high-power railway system in China, power quality such as the negative sequence current and harmonic current caused by electric locomotives becomes more and more critical. This paper proposes a half-bridge-converter-based railway static power conditioner (RPC) (HBRPC) which consists of two half-bridge converters connected by two capacitors in series. Compared with the traditional RPC, the HBRPC requires only a pair of power switch legs and two capacitors. Under the premise of accomplishing the same function of RPC, the proposed conditioner can reduce half of the power switches, which can make it with lower cost and hardware complexity. A double-loop control is proposed for HBRPC to keep the dc-link voltage stable and achieve the dynamic tracking of the current reference signals, while a balanced voltage control is proposed to eliminate the error of two capacitor voltages and maintain the normal operation of HBRPC. Finally, simulation and experiment results have verified the proposed structure and its control method effectively. © 2012 IEEE.

Lu Z.,Huazhong University of Science and Technology | Zhao M.,Huazhong University of Science and Technology | Xie P.,Hunan Electric Power Company | Wu L.,Huazhong University of Science and Technology | And 3 more authors.
Journal of Lightwave Technology | Year: 2012

In the last few years, much attention has been paid to the researches of metallic helical metamaterials due to their giant circular dichroism for transmitted lights. However, so far as we know, there is little work concerning the study of their reflection properties, which are also significant questions for the helical metamaterials. In this work, we study the reflection properties of the helical metamaterials by using the Finite-Difference Time-Domain (FDTD) method. The circular dichroism and the reflected polarization states of left-handed single-, double-, triple-, and quadruple-helical structures are investigated, respectively. It's found that both the single-and the double-helical structures perform giant circular dichroism, and their reflected polarization states are related to the handedness of helical structure; while triple-and quadruple-helical structures exhibit no circular dichroism at all, and their reflected polarization states are irrelevant to the handedness of helical structure. © 2012 IEEE.

Shi H.,Hunan Electric Power Company | Zhang S.,Hunan Electric Power Company
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2015

A static security online decision support optimization model is proposed based on the smart grid dispatching and control system platform. In view of the inadequacy of the current online system decision support application, problems are analyzed and the characteristics of the provincial power grid are referred to prior to adoption of new modeling principles and frameworks. A static security decision support model based on multiple control measures and constraints is developed and parameter optimization methods are discussed. Not only optimization objectives and control methods are enriched, but also control constraints are refined by the model. Higher feasibility and better optimization of decision support based on the model is achieved by simulation. © 2015 Automation of Electric Power Systems Press.

Wang Z.,Nanchang Institute of Technology | Su H.,Hunan Electric Power Company
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2014

In order to improve the adaptability and reliability for evaluation of the investment value of power plant carbon capture systems, a decision-making mathematical model for carbon-capture system optimal investment timing is proposed based on the real option theory by referring to the real option characteristics of venture capital investment for carbon capture systems. By taking into account the irreversibility and delay ability of investment decisions, and the uncertainties of carbon price and carbon mitigation cost, the investment critical value and the optimal investment strategy for power plant carbon capture systems are obtained. The results of numerical example reveal that the model can make a rational assessment for the opportunity cost of venture capital investment, and the potential value of the project can be exploited as much as possible. Compared with the traditional net present value assessment method, the proposed model can overcome the defects of the net present value method, and effectively guide the timing of carbon capture system risk investment, rather than make the simple decision on immediate investment or nondevelopment. The model has provided a quantitatively analytic mathematical tool for the investment carbon capture system in a power plant that can be used as scientific reference for decision-makers. © 2014 State Grid Electric Power Research Institute Press

Li C.,Huazhong University of Science and Technology | Li H.,Zhongnan University of Economics and Law | Kou P.,Hunan Electric Power Company
Neurocomputing | Year: 2014

Heuristic optimization has shown its superiority in handling identification problem of complicated system, for methods based on heuristic optimization do not have special requirements on model structures of the target system. In this paper, a piecewise function based gravitational search algorithm (PFGSA) is proposed and applied in parameter identification of automatic voltage regulator (AVR) system. In the proposed algorithm, a piecewise function is designed as the gravitational constant function to replace the traditional exponential equation. The piecewise function provides more rational gravitational constant to control the convergence of algorithm, and thus excellent searching ability is likely to be achieved. Moreover a new weighted objective function is proposed in the identification frame. Comparative experimental studies are conducted to test the searching ability of PFGSA and to verify the performance of proposed identification strategy, while genetic algorithm, particle swarm optimization and GSA are employed for comparison. The experimental results show that PFGSA performs the best on term of accuracy and stability in the parameter identification of AVR system, and the proposed identification strategy is effective. © 2013 Elsevier B.V.

Wen Y.,Zhejiang University | Cui J.,Zhejiang University | Zhang J.,Zhejiang University | Guo C.,Zhejiang University | And 2 more authors.
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2013

In view of the challenges faced by the electric power dispatching center that cannot fully monitor and control risks affecting the safety of power system, a design scheme of security risk management system (SRMS) is proposed based on risk management method. The flow chart and multi-time scale paradigm mechanism of security risk management are explained for power system dispatching and operation. The software architecture and key functions of SRMS are then designed. Preliminary application of SRMS in Hunan Electric Power Dispatching Center is finally described. © 2013 State Grid Electric Power Research Institute Press.

Pei W.,CAS Institute of Electrical Engineering | Deng W.,CAS Institute of Electrical Engineering | Zhang X.,CAS Institute of Electrical Engineering | Qu H.,CAS Institute of Electrical Engineering | Sheng K.,Hunan Electric Power Company
IEEE Transactions on Industrial Electronics | Year: 2015

The integration of plug-in electric vehicles (PEVs) to a power system leads to significant impacts on the electricity distribution infrastructure, and coping with the charging demand of high PEV penetration in an existing distribution network is an important concern. This paper provides a comprehensive study on using multiterminal low-voltage direct current (MT-LVDC) to connect multiple feeders or transformers, which can solve network constraints efficiently to improve the ability of the power supply for more PEV integration. This paper proposes an adaptive droop control for the MT-LVDC distribution system and presents a probabilistic evaluation method to analyze the PEV integration capacity. To illustrate the potential of using MT-LVDC to improve PEV integration in an existing distribution network, a case study is performed, and the results show that MT-LVDC based on the proposed adaptive droop control can share the charging power demand during steady-state and dynamic conditions between multiple feeders or transformers. The ability of MT-LVDC to improve the PEV integration capacity and cost can be evaluated effectively. © 1982-2012 IEEE.

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