| With the increasing proportion of wind power and photovoltaic power generation in the power supply structure,the randomness and intermittence of the new energy power generation also pose a potential threat to the safe and reliable operation of the power grid.With the rapid development and its engineering application of smart grid and UHV transmission technology,the transmission network structure has undergone tremendous changes.System static adequacy and dynamic security issues caused by random failure of UHV transmission line increasingly arouse widespread concern.At the same time,with the rapid development of electric vehicles and the implementation of the retail side open,electric vehicle charging and discharging and the stochastic behavior of the market operation in the electricity market result in spatial and temporal uncertainty of load demand and also also bring the uncertainty and reliability of power grid operation.Taking into account the power generation,transmission and load uncertainty,the reliability evaluation of large-scale complex power grid and identification of weak links can provide important reference information for the Power Grid Corp to reduce the risk of grid operation.But in the practical engineering application of reliability evaluation and analysis of large power grid,the existing theories and models of reliability assessment still have high computational complexity which limits the application of reliability technology in practical engineering.Therefore,the problems about the computation efficiency and the calculation speed of the reliability evaluation of the large power network are urgently need to be solved.Accordingly,the research on acceleration method for reliability assessment of power grid is carried out in the paper,which is improved from the three aspects:network topology analysis,load flow calculation and optimal load reduction model.A fast algorithm for reliability evaluation based on adequacy is proposed,a fast evaluation method for dynamic risk of power grid from the perspective of rapid screening of fault sets is proposed and finally the reliability of the new energy sources in the powear grid is modeled and the power grid is evaluated.The main research contents are as follows:1)In order to improve the efficiency of power system adequacy assessment,a new method is proposed to evaluate the adequacy of power grid based on power flow sensitivity and network topology.The current sensitivity is used in power system adequacy evaluation,the power flow sensitivity matrix is derived to describe the relationship between the variation of branch power and node injection power,the improved model of linear programming is gived,which can quickly obtain the optimal load reduction strategy of powder system after fault.A minimal cut set algorithm based on minimal path is presented to tranform the complex topological structure of the system into a simple series parallel connection to obtain the adequacy of the system quickly over part of the network with only the network topology information instead of the power flow calculation information.In addition,a factor table addition chain technique with a reduced computational burden and less storage space is applied to meet the calculation needs of the new uncommon components,dynamic network topology analysis is used to establish the topological main table and auxiliary table based on base-case power flow to analyze the changed part of the power system after fault separately,an adequacy assessment method based on factor table addition chain and dynamic network topology analysis is proposed to guarantee the rapidity of the adequacy evaluation and greatly improve the speed of topology analysis.The calculation results show that the proposed method can effectively improve the speed of power grid adequacy assessment,and can be used for the adequacy evaluation of real power grid.2)As the curse of dimensionality appears easily in analytic method of power system security risk assessment due to the larger system scale,a fast algorithm for power grid risk assessment based on fault set selection is proposed.In this method,the searching range of the component is defined firstly,and the range of all the independent N-2 components is determined by setting the maximum order of the breadth first search;It is assumed that the system can be stable in the light of the fault condition if the system can be kept stable under the condition of serious fault.Based on the assumption,all the random variables and failure mdes are taken into comprehensive consideration to design and realize the fault set automatic generation technology.The priority of the fault set is sorted,the more serious faults are calculated,which can effectively reduce the number of faults to be calculated and speed up the security evaluation.Through the dynamic risk assessment of Heilongjiang and Liaoning power grid,the algorithm is proved to be fast and accurate,which can meet the actual needs of the power grid.3)Based on the outage model of loop,large power grid with complex structures and multiple devices is divided into loop and power grid to calculate,a reliability sensitivity algorithm based on grid circuit is proposed.First of all,loop outage model is analyzed and calculated to get the sensitivity indicator between loop and equipment parameters,and then calculate the sensitivity indicator between the network and the loop,and combine the two sensitivity indicators to obtain the sensitivity indicator between the load point reliability and component parameters.By using this algorithm,the complexity of the original one-time calculation is simplified,and the sensitivity of the system to the component parameters can be calculated quickly.At the same time,the minimum cut set method is used to calculate the reliability of the circuit in the sensitivity analysis,and the original nonlinear and high dimensional problem is transformed into a simple linear relation which can improve the efficiency of sensitivity analysis.The reliability and sensitivity of the method is verified by calculating the reliability sensitivity of the actual 750kV substation and the CEPRI-36 test system in Baiyin City.4)Due to the randomness and intermittence of the new energy power generation,the uncertainty of the new energy grid connection is greatly increased.In order to solve this problem,the point estimation method is applied into the reliability evaluation of large power grid with new energy sources,three point estimation method is proposed to evaluate the reliability of the new energy power grid,the problem of uncertainty in the output of new energy is solved by the point estimation method,which can effectively meet the needs of practical calculation and improve the evaluation speed.The application of the point estimation method and its preliminary application in the simulation of power system probabilistic uncertainty provides a good way to solve the problem.The reliability of the IEEE-RTS 79 test system is calculated.The results show that the proposed method can not only effectively realize the reliability evaluation of power grid with new energy sources,but also has high computational efficiency.5)The operation risk of power grid is discussed,combined with the existing resources of online dynamic security assessment system,the framework and construction scheme of integrated defense system for power grid adequacy and security is proposed,which contains the data interface,the probability of risk analysis,risk assessment,parallel computing,the integration of risk prevention and control,man-machine interface and historical data storage subsystem.Through the analysis of the software and hardware requirements of the prevention and control decision-making framework,the hardware architecture composed of various kinds of server,node computer group and network communication switch and the four layer software structure including data,platform,application and presentation layer are obtained,the data integration of power system analysis program PSASP software is realized,which can realize the power grid risk index calculation,fault analysis and the weak links searching and other functions based on the calculation of the original grid and provide an effective technical method for the construction of strong smart grid in the new energy environment. |
