Papers by Keyword: Fuzzy Set Theory

Abstract: In the last several decades, a couple of fuzzy power flow algorithms were presented to deal with the uncertainties in power grid. But there is no a functional simulation tool introduced to simplify the calculation. This paper presents a simulation tool, Matpower, under one of the algorithms to do the fuzzy power flow calculation. The algorithm gives the user the possibility to specify fuzzy numbers to represent the possible behavior of loads and generations and outputs fuzzy membership functions for voltage magnitudes and phases, active and reactive power flows and generations. Matpower, as a simulation tool, was modified to handle fuzzy numbers and show fuzzy results. In a final section, we present results obtained with a case study based on a real power system to illustrate and highlight details of the proposed algorithm. Suggestions for future implementation of the fuzzy Matpower are also summarized.

Abstract: Fault location method based on multi-source fault information in repair of distribution network is proposed to make the precision and speed of fault location higher. Firstly a topology description and storage method which is appropriate to distribution network fault location is proposed. Then, based on the topological structure of distribution network, fault information on the distribution network is integrated processed. Fault information grouped and priorities are identified using the association of distribution equipment. Low-voltage fault location is achieved by applying fuzzy set theory in fault message omissions and misstatements situations. Finally, an example demonstrates the effectiveness of this method.

Abstract: This study was performed to develop a fuzzy model for human health risk assessment of organic contamination of groundwater to quantify the uncertainties inherent in risk assessment processes. The fuzzy model was constructed based on the fuzzy set theory and traditional risk assessment approach. Triangular fuzzy number was used to describe the variability of parameters associated with traditional risk assessment and α-cut sets was taken to transform fuzzy numbers to intervals that can be fairly taken into arithmetic operation of lifetime cancer risk (ELCR) and hazard index (HI) which respectively denotes the carcinogenic and non-carcinogenic risks. Considering the exposure routes of drinking and showering, the developed fuzzy model yields risks at different memberships as well as the expectation of risks. The model was applied to a site in China with organics-contaminated groundwater. It was found that tetrachloroethylene (PCE) posed the most risks, followed by trichloroethylene (TCE), while carbon tetrachloride (CT) posed the smallest. Results also showed drinking, compared with showering, is the major exposure route and boiling is important for reducing health risks of groundwater.

Abstract: According to engineering fuzzy set theory and system coordination degree model proposed by professor Chen Shouyu and Yu Xuefeng, this paper established social economy-ecological environment-water resources comprehensive evaluation index system, combined with social and economic development situation, ecological environment and water resources utilization status in 9 areas of Jilin province, 2011. The paper made an evaluation of the existing water resources coordinated development of Jilin province, and analyses relative coordinated development level among regions.

Abstract: Remote sensing image analysis is an important aspect of remote sensing technology and application, but until now a comprehensive mathematical model is still missing for spatial analysis and reasoning. From the mathematical essence, the processing of remote sensing image analysis is to build a transform relationship between the premise and the conclusion of reasoning based on domain knowledge, and which is used to deal with the transformation reasoning. Based on fuzzy set and topology theory, this paper discussed how to build mathematical models of target identification, information extraction, and semantic extraction of remote sensing imagery. By a series of reasoning, a reasoning model based on the topological transformation is proposed, which is used to transform remote sensing image analysis into an uncertainty reasoning of mathematical sciences.

Abstract: In the real financial market, there are always other uncertain phenomena, such as fuzzy phenomenon, random phenomenon. Along with empirical study increasing investigator discovered that this kind of uncertainty affects policy-maker's behavior choice and the asset price change. Researcher pay more and more attention to the problems on the option pricing under in uncertain environments, Therefore, the paper shows that options can be valued successfully in uncertain environments, some option pricing models are established, the corresponding algorithm is designed to solve these models.

Abstract: The main requirement in designing a structure is to ensure the structure is reliable enough to withstand loading and the reliability study of structure. Classical and probability approach was introduced to analyse structural reliability. However, the approaches stated above are unable to take into account and counter the uncertainties arising from the natural of geometry, material properties and loading. This leads to the reduction in accuracy of the result. The goal of this study is to assess and determine the reliability of structures by taking into consideration of the epistemic uncertainties involved. Since it is crucial to develop an effective approach to model the epistemic uncertainties, the fuzzy set theory is proposed to deal with this problem. The fuzzy finite element method (FFEM) reliability analysis conducted has shown this method produces more conservative results compared to the deterministic and classical method espacially when dealing with problems which have uncertainties in input parameters. In conclusion, fuzzy reliability analysis is a more suitable and practical method when dealing with structural reliability with epistemic uncertainties in structural reliability analysis and FFEM plays a main role in determining the structural reliability in reality.

Abstract: The complex single-phase grounding fault is researched in neutral insulated or Peterson coil earthed power networks. Traditional single fault line detection method only using some parts of fault information has poor adaptability and reliability. In this paper fuzzy set theory is introduced and applied in fault line detection. By setting subordinate functions and intelligently fusing all kinds of the fault information and all fault detection methods the property of detection is improved..It has shown that this fusion strategy exhibits excellent property over the existing criteria by dynamic mould laboratory emulation.

Abstract: In order to realize energy-saving for marine power system, combining the fuzzy set theory with the traditional PID control technology, the marine power system energy-saving controller was designed, which control ship power grid frequency and voltage collaborative reduction within a certain scope and scale. As several prototypes testing, the application of the energy-saving controller, which control the ship power grid frequency from 60Hz dropping to 57Hz, and the voltage from 450V collaborative falling to 425.5V, and meet the Ship Building Standard, can save 9.85% of electric energy and 9.53% of fuel.

Abstract: Since working condition of reciprocating compressor is awfully bad and it has bigger risk in operation and higher fault rate，it is of importance to study reciprocating compressor fault. Fault tree has been established in this paper by analyzing factors leading reciprocating compressor fault based on the method of fault tree. 21 minimum cut sets leading to reciprocating compressor fault can be gotten through qualitative analyses on this fault tree，the happening probability of the top event can be calculated and the importance of the basic event s can be analyzed through quantitative analysis. The expert inquiry method combined with fuzzy sets theory is adopted to assess the happening probability of the basic events and top events.