| The extensive use of power electronics equipment has greatly improve the level of social productivity,but it has stricter requirements on power quality,and is more sensitive to power quality disturbances.The power quality problems represent by various disturbance phenomena have also become increasingly prominent,due to the input and use of a large number of sensitive equipment and non-linear loads in the power grid.Voltage oscillation is one of transient disturbances of power quality,which affects the normal operation of electrical equipment,brings potential safety hazards or property damage,and its occurrence has many characteristics,such as unpredictability and contingency.So it is especially important to correctly understand voltage oscillation and accurately evaluate voltage oscillation events.This thesis introduces the related concepts and classifications of power quality,describes the current research status of voltage oscillations,as well as the hazards and governance measures,and focuses on the mathematical processes of the most common oscillations.In order to make a reasonable evaluation of voltage oscillations,this thesis elaborates on the parameter selection and model establishment process in the comprehensive assessment of voltage oscillations,and presents a comprehensive evaluation method of voltage oscillation based on interval analytic hierarchy process.The main research contents are as follows:(1)Firstly,the method establish an index system for voltage oscillation evaluation,chooses five characteristic variables as evaluation index,namely,oscillation amplitude,duration,oscillation frequency,energy and voltage levels,the each index is classified,and a comprehensive and universal evaluation index system is structured;Secondly,the interval number is introduced on the basis of the analytic hierarchy process in this method,and the indicators are compared according to the expert experience to construct the interval judgment matrix and calculate the interval weight of each indicator,at the same time,cite the possibility ranking method to convert the interval weights of each index into comprehensive weights;Finally,a reasonable index score classification method is proposed,and the semantic evaluation corresponding to the comprehensive score of oscillation severity is determined by the health value.In the verification of voltage oscillation evaluation examples,the evaluation index system proposed in this thesis is universal,and the proposed evaluation method can reflect the objectivity and ambiguity of the evaluation results.(2)On the basis of the voltage oscillation evaluation method mentioned in this thesis,a Linux-based voltage oscillation evaluation system is developed,and QT is used to implement evaluation program design and interface design.The system mainly designed these functions,namely,reading files,waveform display,evaluation of voltage oscillation.By accessing the oscilloscope file which generated by the power quality analyzer,the system displays and evaluates the voltage oscillation waveform in the file,and transforms the voltage oscillation evaluation method from theory to practical application,this system brings some practical application value in engineering. |
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