Mid- And Long-term Risk Assessment Of New Energy Integrated Power System Based On Multiple Time Scale Decomposition Of Wind And Solar Irradiance Characteristics

The essential causes of the impact of large-scale new energy integration on the power system operational risk are the randomness,intermittentity,and time-varying characteristics of meteorological elements such as wind speed and solar irradiance which are directly related to new energy generation.Therefore,this thesis starts with studying the changing rules of wind speed and solar irradiance,then sums up the time-period characteristics of wind and solar irradiance.Furthermore,the time-period characteristics model of meteorological elements and new energy output is built.From both adequacy and static safety aspects,the time-varying risk assessment of new energy integrated power system in medium and long term is achieved through the proposed models.The risk evaluation results can provide reference for planning,mid-and long-term scheduling and maintenance decisions,provide basis for system operators to take measures to reduce system risk.The main content of the thesis is as follows:(1)The probability distribution models of wind speed and solar irradiance that is difficult to reflect the randomness and time-variation of meteorological elements at the same time,are commonly used in risk assessment of new energy integrated power system.This thesis analyzes the time-period characteristics of meteorological elements including wind speed and solar irradiance in various time scales such as year,month and day.The periodicity of annual changes are reflected by annual mean value of meteorological elements,and the time-period characteristic model is built through superimposing monthly changing trend simulated by fitted function and daily fluctuation components simulated by random variable.Futhermore,a case analysis is used to verify the validity and universality of proposed model.Finally,according to the relationship between wind power output and wind speed,photovoltaic output and solar irradiance,a time-period characteristic model of new energy output has been established.(2)At present,using probability distribution of meteorological elements to establish new energy output model is a common way for adequacy assessment in new energy integrated power system,and usually focuses on annual adequacy,which is difficult to reflect the time-varying characteristics of meteorological elements as well as system adequacy.The thesis combines the time-period characteristics model of new energy output with sequential Monte Carlo simulation method,mid-and long-term adequacy assessment for new energy integrated power system is achieved by monthly and annual adequacy indices.Finally,through a case analysis,it is verified that the proposed method can reflect the time variation of system adequacy more accurately than traditional adequacy assessment methods that use probability distribution model of meteorological elements.(3)At present,the static safety assessment of new energy integrated power system mostly uses probabilistic power flow result such as node voltage over-limit probability,branch overload probability and lacks of researches on the time-varying static security.The thesis proposes a static safety probability assessment method and an index system for new energy integrated power system by combining new energy output model based on the time-period characteristics of meteorological elements with probabilistic power flow methods based on Monte Carlo simulations.The proposed method and index system can evaluate the static safety level and its trend of the system and weak part during normal operation and N-1 fault conditions under the disturbance of new energy sources.Finally,the validity of proposed methods and indices is verified through a case analysis.