| With the rapid expansion of the scale of the power system,how to ensure the stable operation of the power grid and improve the anti-interference ability of the power grid has become a research hotspot in this field.Furthermore,the irregular global climate change caused by environmental pollution leads to the frequent occurrence of various kinds of extreme natural disasters in recent years.They can directly damage or indirectly cause adverse effects on the power grid,leading to the rising risk probability of power grid operation,and the external factors leading to the failure of single power grid equipment are becoming more and more complex.Therefore,it is of great practical significance and research value to study the evaluation and analysis technology of disaster response capability of the power grid in the extreme natural disaster environment and the nonlinear fault estimation of single equipment in the power grid.Given the above problems,this paper mainly carried out the following three aspects of research work.Firstly,because of the shortcomings of the current assessment methods of power grid’s predisaster and post-disaster response capability under extreme natural disasters,by analyzing the comprehensive data of power grid system and the related indicators of disaster response capability,an index system for the assessment of power grid’s pre-disaster tolerance and post-disaster resilience is established from the time dimension.Then,the main and secondary indexes of the relevant indicators are obtained by using the analytic hierarchy process and entropy weight method The objective weight is combined into comprehensive weight according to the weight proportion,and then the fuzzy comprehensive evaluation is used to quantitatively evaluate the disaster response capability of the power grid,which can better overcome the shortcomings of existing evaluation methods.Secondly,a transmission line operation risk assessment method under extreme natural disasters is proposed.By calculating a total load of transmission lines and towers,and using the strength and stress interference model to determine the failure rate of transmission lines and towers,combined with the principle of series reliability to determine the comprehensive probability of line failure.Using the nonsequential Monte Carlo method and the comprehensive probability of line failure to set the expected fault set,combined with the DC power flow optimization model to calculate the loss of a load of each line.Then,the economic value of line loss load is determined and defined as fault consequence by considering load level and emergency repair recovery time.On this basis,the judgment index of transmission line risk assessment is constructed by considering fault consequence and the comprehensive probability of line fault.Finally,a new robust fault estimation method for discrete-time fuzzy systems is proposed to meet the higher requirements of nonlinear fault estimation theory for the increasingly complex and diverse single equipment faults.Based on the design of a new on-line real-time switching mechanism of depth subdivision,an on-line real-time switching fault observer is constructed.By introducing the enhancement factor and attenuation factor of the normalized fuzzy weighting function,the depth of the whole fuzzy control system space is subdivided into six subspaces according to the real-time value of the normalized fuzzy weighting function.For each subspace,a set of fault observer gain matrices are designed by considering the dynamic characteristics of the subspace.Simulation results show that the proposed robust fault estimation method for discrete-time fuzzy systems has less conservatism and better robust performance than the existing methods. |
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