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Zhu Y.,Guangxi University | Zhu Y.,Guangxi Key Laboratory of Power System Optimization and Energy Technology | Jian J.,Yulin Normal University | Wu J.,Guangxi University | And 2 more authors.
IEEE Transactions on Power Systems | Year: 2013

In order to reduce the fuel cost of thermal units, a semidefinite programming (SDP) method is used to solve a hydrothermal coordination (HTC) optimization problem. By manipulating the structure of decision variable matrix, the original nonconvex problem is reformulated into a convex SDP relaxation model without sacrificing the nonlinear relation among hydropower generation, reservoir storage volume, and discharge water. A global minimum is therefore guaranteed and well-developed convex optimization theories can thus be employed to solve the problem. Both sparse matrix techniques and a simplified SDP model are discussed to reduce computational cost. One mostly used HTC case is employed to test the performance of the proposed method. Detailed comparisons between the proposed and other methods show that the final result of SDP model is by far the best result ever. In addition, a large-sized HTC case shows the potential of SDP in practical use. Finally, we prove that as a relaxation technique, the SDP solution, which satisfies all the constraints, is indeed the optimal solution of the original nonconvex problem. © 2013 IEEE. Source


Xia X.,Guangxi University | Wei H.,Guangxi University | Wei H.,Guangxi Key Laboratory of Power System Optimization and Energy Technology
Procedia Engineering | Year: 2012

This paper directly uses the second-order differential equations to denote the swing equations of generators and adopts numerov method to convert the differential equations to a series of algebraic equations. Considering the truncation error of specific numerical integration algorithm, the transient differential equations are dispersed to inequality constraints instead of equality constraints. The proposed method can reduce the dimension of correction equation by reducing the number of the equality constraints and variables, so as to improve the computational efficiency and reduce the memory usage. Numerical simulations on the four test systems, from 9 to118 buses, show that the proposed method is robust and efficient. © 2011 Published by Elsevier Ltd. Source


Xia X.,Guangxi University | Wei H.,Guangxi University | Wei H.,Guangxi Key Laboratory of Power System Optimization and Energy Technology | Yang Y.,Guangxi University | Yang Y.,Guangxi Key Laboratory of Power System Optimization and Energy Technology
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2012

An improved reduced-dimension interior point method is proposed for transient stability constrained optimal power flow (TSCOPF) in this paper. The two groups of differentiated implicit recursive equations of motion of the rotor are eliminated to be one set of equations through recursive features. Considering the truncation error of specific numerical integration algorithm, the transient differential equations are dispersed to inequality constraints instead of equality constraints. The method can reduce the number of the equality constraints and variables and the dimensions of the correction equation, improve the computational efficiency and reduce the memory usage. Numerical simulations on the three test systems, from 22 to118 buses, show that the proposed method is robust and efficient. Source


Wei Y.-Q.,Guangxi University | Li B.,Guangxi University | Li B.,Guangxi Key Laboratory of Power System Optimization and Energy Technology | Wei H.,Guangxi University | Wei H.,Guangxi Key Laboratory of Power System Optimization and Energy Technology
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2012

How to deal with the discrete variables accurately and efficiently is the key issue and difficulty for solving the reactive power optimization of large-scale power systems. This paper presents a continuous model for solving reactive power optimization of power systems with discrete variables. The new model is solved by the modern interior point method. The proposed method includes two steps. Firstly, the reactive power optimization is calculated for obtaining the activation points of the discrete variables, when discrete variables treated as continuous variables. And then, treat the discrete variables continuously by introducing Sigmoid function. Therefore the reactive power optimization with discrete variables can be calculated accurately and efficiently based on the results of the last step. Extensive numerical simulations result show that the proposed algorithm possesses good convergence and high computational efficiency, and is available to solve reactive power optimization of large-scale power systems. Source


Li B.,Guangxi Key Laboratory of Power System Optimization and Energy Technology | Wang Y.-L.,Guangxi Key Laboratory of Power System Optimization and Energy Technology | Tan T.-T.,Guangxi Lvneng Electrical Power investigation Design Co.
Advanced Materials Research | Year: 2014

This paper established a multi-level extension model for function effects post-evaluation of substation construction project, the model not only reduces the influence of subjective factors on the evaluation results, but also can determines the key factors which affect the quality of the evaluation results and overall developing trend of the project and provides some suggestions for the project late operation. Taking into account the fact that the element of the judgment matrix formed by traditional AHP is a certain value and may lead to a big difference from the judgment matrix formed by the different group of experts, thus reduces the credibility of the evaluation results; In order to overcome the problem, this paper introduces the concept of interval number, the maximum and minimum of judgment matrix elements relative importance comparison are used as the upper and lower limits of interval number respectively. Interval number are used as the elements of judgment matrix to make the evaluation result more rational. At the end, a practical 220kV substation construction project is taken as an example to verify the validity and rationality of the established model. © (2014) Trans Tech Publications, Switzerland. Source

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