Research On Short-term Reliability Assessment Methods Of High-voltage Distribution Networks

As a bridge connecting the main network and the medium-voltage distribution network,the high-voltage distribution network reflects the safe operation level of the system.Existing high-voltage distribution network reliability research is limited to long-term reliability evaluation.The evaluation results are mainly used to guide grid planning,and are only a probability value,without giving a specific probability distribution.Therefore,in this paper,the short-term operational reliability of the highvoltage distribution network is taken as the research object,taking into account the impact of three random factors such as cascading failures,photovoltaic power output and load fluctuations,a related prediction model is established,and a probabilistic power flow calculation The short-term reliability assessment method obtains the probability distribution of reliability indicators,making the short-term reliability assessment results more in line with the actual situation.The main contents are summarized as follows:Firstly,aiming at the improvement of chain failure prediction and evaluation efficiency,a predictive failure risk index that takes into account the importance of component failure probability and structure importance is established,and the intermediate link of the accident chain is determined by the gray correlation algorithm that maximizes the deviation,and finally finds the cut-off occurrence Probabilistic system fault states,truncating the system state space,and achieving the screening of expected fault sets.The results of an example show the feasibility of the method,and can improve the calculation speed of the analytical method on the premise of ensuring the accuracy of the calculation.Secondly,photovoltaic power output and load forecasting,a particle swarm algorithm combined with a correlation vector machine algorithm prediction model was established.Using historical environmental data and state data,the prediction model was used to realize the short-term time-series probability distribution prediction of photovoltaic output and load considering environmental impact.The Monte Carlo method and semi-invariant combined with Gram-Charlier series expansion method were used to carry out the probabilistic power flow calculation.Combined with the example of high-voltage distribution network,the system was analyzed with or without photovoltaic power output and load fluctuations,with a certain confidence Time series of system power flow.Thirdly,based on the prediction of random factors,the short-term reliability model of the components is established,and the short-term changes of multiple random factors are comprehensively considered.The reliability evaluation of the high-voltage distribution network is based on the deterministic power flow and the probability power flow.Analyze and compare the effects of the three random factors of cascading failure,photovoltaic output and load fluctuation under conventional deterministic power flow calculation and probabilistic power flow calculation.The calculation example shows that the short-term reliability assessment based on probability power flow calculation can reflect the reliability level of the system more realistically and reasonably,and can better guide the dispatching operation of the high-voltage distribution network.