Time filter

Source Type

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.


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.


Liang Z.,Guangxi University | Liang Z.,Guangxi Key Laboratory of Power System Optimization and Energy Technology | Li Y.,Guangxi University | Li Y.,Guangxi Key Laboratory of Power System Optimization and Energy Technology | And 2 more authors.
POWERCON 2014 - 2014 International Conference on Power System Technology: Towards Green, Efficient and Smart Power System, Proceedings | Year: 2014

Based on the hypothesis that pumped-hydro power storage (PHPS) station is available for multi-day optimization and adjustment, the paper has proposed a long-term operation optimization model of PHPS station based on approximate dynamic programming (ADP). In this multistage decision model, across the stages, value function approximation (VFA) of the reservoir energy storage was used to keep the overall optimization characteristics; During the stages, generated energy & generating periods, and electricity consumption for pumping & pumping periods are used as decision variables to conduct daily optimization operation. The paper got the approximate optimal solution through iteration solution decision variable and value function so as to avoid 'curse of dimensionality' in conventional multistage decision model. According to the experiment, the ADP-based model can accurately describe the long-term operation modes of PHPS station, and its calculation methods are more appropriate for this kind of large-scale optimized decision problem than dynamic programming (DP) and conventional mathematic planning methods. © 2014 IEEE.


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.


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.


Li C.,Guangxi University | Li C.,Guangxi Key Laboratory of Power System Optimization and Energy Technology | Hang N.-S.,Guangxi University | Hang N.-S.,Guangxi Key Laboratory of Power System Optimization and Energy Technology | And 4 more authors.
Gaoya Dianqi/High Voltage Apparatus | Year: 2012

For the increasing harmonics pollution effect caused by HVDC transmission system on power grids, this paper introduces a new type of filtering method which makes use of the commutation course of the converters in HVDC transmission system, increases the angle of commutation by series inductance to improve current waveform at power grid side of the converters, and adds series capacitor to compensate the voltage drop on the inductance. The method simplifies the filter of HVDC transmission system, and gains better filtering performance with lower cost. Taking six-impulse rectifier for example, the commutation course of the rectifiers is described, the factors affecting the angle of commutation and the impact of the angle on current waveform at AC-side are analyzed. Experiment of the 6-impulse rectifier demonstrates the feasibility of the present method.


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.


Liao R.,Chongqing University | Liu J.,Chongqing University | Yang L.,Chongqing University | Zhang Y.,Chongqing University | And 4 more authors.
Electric Power Components and Systems | Year: 2015

In modern power transmission and distribution systems, power transformers are critical components and their electrical properties together with service lives are determined by the insulation property of oil-paper insulation. To better apply the frequency domain spectroscopy technique to assess transformer insulation condition, a series of experiments were performed under controlled laboratory conditions. First, this article presents the frequency domain dielectric response measurement results of oil-paper insulation samples under different moisture contents and aging states, and then the extracted frequency dielectric characteristic parameters determined from the imaginary part of relative permittivity (εr′′) and dielectric dissipation factor (tanδ) curves are used to assess the moisture contents and aging states of oil-paper insulation. Finally, the quantitative relationships among dielectric characteristic parameters, moisture content, and degree of polymerization are also established. Results show that in the frequency range of 10-3-102 Hz, εr′′ and tanδ obviously increase as the moisture content of oil-paper insulation rises, while εr′′ and tanδ are very sensitive to aging only in 10-3-10-1 Hz. Consequently, εr′′ and tanδ in different frequency ranges can be used to distinguish the influences of moisture content and aging state on frequency domain spectroscopy measurement results. © 2015 Taylor & Francis Group, LLC.


Chen B.,Guangxi Key Laboratory of Power System Optimization and Energy Technology | Ouyang J.,Guangxi Key Laboratory of Power System Optimization and Energy Technology | Chen S.,Guangxi Key Laboratory of Power System Optimization and Energy Technology
Dianwang Jishu/Power System Technology | Year: 2015

In the reliability evaluation of practical large engineering system by the system reliability evaluation software, the time for the computation is too long, so it is hard to meet the demand on fast and accurate calculation. For this reason, The TRIZ theory is led into the improvement of power system reliability evaluation algorithm. Firstly, according to the TRIZ theory, the contradiction matrix is applied to find out the method to resolve the conflicts between the calculation speed and the obtained accuracy by sequential simulation algorithm; secondly, according to the principle of resolving conflicts the tower storage technology and Latin hypercube sampling (LHS) are screened out to improve the Monte Carlo simulation based traditional algorithm. The improved algorithm can shorten the time to search the fault state and completely cover the probabilistic distribution of state duration of system components. Simulation results of IEEE RTS-79 show that the improved algorithm is stable and it converges faster, besides, using the improved algorithm the solution with high accuracy can be obtained by shorter calculation time. ©, 2015, Power System Technology Press. All right reserved.

Loading Guangxi Key Laboratory of Power System Optimization and Energy Technology collaborators
Loading Guangxi Key Laboratory of Power System Optimization and Energy Technology collaborators