AC/DC Distribution Network Operation Optimization Considering The Uncertainty Of Distributed Generation And Load

With the development of DC distributed generations,DC loads and power electronics technology,as well as the advantages of dc distribution network over ac distribution network in terms of transmission capacity and power quality,dc distribution network has gradually become a research hotspot.As a transitional phase from AC to DC,the research of AC/DC distribution network operation optimization is an important premise to ensure the safe and economical operation of the system.First,the structure of AC/DC distribution network is introduced,the probability distribution of wind power and photovoltaic output are obtained by simulating the wind speed and illumination intensity with two-parameter Weibull distribution and Beta distribution,the probability distribution of the load is obtained by simulating the load with the determined value adds the error following the normal distribution.Second,in order to solve the problem that the forecast data of distributed generation and load is inaccurate and the solving speed is slow,the fuzzy theory and the second-order cone programming are introduced into the distribution network operation optimization,the AC/DC distribution network fuzzy cone optimization model is established by representing the load and output of distributed generation with trapezoidal fuzzy numbers,representing the power balance constraint with fuzzy chance constraint based on credibility theory and applying second order cone transformation to the model.The model is applied to a extended 50-node AC/DC system,and the effectiveness of the model is verified by comparing with the existing optimization methods.Finally,the ability of the fuzzy optimization model to cope with uncertain forecast data is limited,and it is difficult to fully deal with the shortcomings of real-time data fluctuations when the forecast data has a large error,the double-time scale fuzzy optimization model of AC/DC distribution network is established based on the characteristics that the accuracy of predicted data is improved with the decrease of time scale.In the long time scale,fuzzy day-ahead scheduling cone optimization model which makes the active loss as the objective function is established by representing long time scale predicted data with trapezoidal fuzzy numbers.In the short time scale,fuzzy intraday cone optimization model which makes the active loss and nodal voltage deviation as the objective functions is established by representing short time scale predicted data with triangular fuzzy numbers,so as to realize the safe and economical operation of distribution network.The results of example analysis show that the uncertainty of the prediction data can be incorporated into the optimization model by the fuzzy chance constraint based on the credibility theory,reasonable selection of the confidence level can coordinate the system security level and optimization results well.The influence of the inaccuracy of predicted data on the operation of distribution network can be reduced and the ability of the model to deal with real-time prediction fluctuations can be improved by the double time scale.The application of second-order cone programming to the operation optimization of distribution network can not only ensure the accuracy of solution,but also improve the solving speed of optimization model.