Research On Evaluation And Improvement Strategy Of Distributed New Energy Carrying Capacity In Distribution Network

The large-scale exploitation and utilization of traditional fossil energy has caused environmental pollution problems on a global scale,which has increasingly significant negative impacts on the sustainable and healthy development of the economy and society.In order to achieve the goal of carbon peak and carbon neutrality,high-quality primary energy sources such as wind and solar energy have been rapidly developed in China.However,with a high proportion of distributed new energy being connected to the distribution network,the grid has encountered a bottleneck in the carrying capacity of distributed new energy,and some areas have even abandoned wind and photovoltaic.On the one hand,considering the lack of a targeted evaluation index system for time-to-time quantitative analysis of the carrying capacity,how to establish observable evaluation indicators to make them comparable become one of the key research contents.On the other hand,due to the inherent randomness and fluctuation of distributed new energy,how to consider the multiple uncertain factors of source and load in the optimization evaluation process is also worth discussing.At the same time,due to the limited use of distributed new energy by electric loads in a single area,how to coordinate and dispatch multi-energy distribution networks under the concept of Energy Internet and reduce the phenomenon of abandoning wind and photovoltaic are also worth thinking about.In this context,this paper mainly focuses on the optimization evaluation and promotion strategy of the distributed new energy carrying capacity in the distribution network.The main research contents of this paper are as follows:1)An observable evaluation index system of the distributed new energy carrying capacity in the distribution network is established.First,an evaluation framework for the carrying capacity of distributed new energy is proposed.Furthermore,based on the analysis of the demand characteristics and construction principles of the carrying capacity evaluation indicators,a comprehensive evaluation index system including the target level,the criterion level and the index level is established,and specific indicators are proposed from the dimensions of quality,technology,economy,and flexibility.In addition,the dynamic weight determination method based on subjective and objective combination weighting and the min-max normalization method transform the evaluation indicators into calculation models that are convenient for comprehensive scoring.2)An optimization evaluation method for the carrying capacity of distributed new energy,which takes into account multiple uncertain factors,is proposed.First,analyze and model the uncertainty of distributed new energy and load,and adjust the degree of source-load fluctuation by changing its robust cost.Furthermore,the flexible resources in active distribution networks(ADN),are accurately modeled to form a deterministic optimal power flow scheduling model oriented to maximize the carrying capacity of distributed new energy.Based on the concept of adjustable robust cost,a carrying capacity robust optimization evaluation model of distributed new energy is established.In addition,with reference to relevant national standards and industry standards,a classification standard of carrying capacity is proposed.Finally,taking the improved IEEE33 node distribution network as an example,the beneficial effects of the flexible resources in the model proposed in this paper are verified and analyzed.The optimal dispatch results and comprehensive evaluation results of indicators under the worst source-load case are analyzed in detail.In this way,the key factors restricting the carrying capacity of distributed new energy in ADN are identified.3)A method to improve the carrying capacity of distributed new energy based on the coordinated operation of multiple energy regions is proposed.For the multi-energy distribution network with electricity,gas,and heat coupling,a mixed time-scale coordinated dispatch strategy that takes into account the integrated demand response is proposed.First,considering user satisfaction and comfort,an integrated demand response model for electricity,gas,and heat loads is constructed.Furthermore,in order to improve the economy of system operation and the carrying capacity of distributed new energy,with the goal of minimizing the operating cost of energy equipment,the penalty cost of abandoning wind and photovoltaic,and the cost of interacting with the superior grid,the optimal energy flow scheduling model in the day-ahead period is formulated.In the intra-day period,the smaller the time granularity,the more accurate the source and load forecasting information.The objective function is constructed to minimize the deviation of the scheduling plan between the intra-day and the day-ahead period.In addition,considering the difference in energy equipment response time and heterogeneous energy flow transmission characteristics,the intra-day optimization phase is decomposed into two time scales.In the longer time scale,the natural gas and thermal subsystems are dispatched and the integrated gas and heat load demand response is activated.While in the shorter time scale,the power subsystem is finely dispatched and the electricity load demand response is activated.In addition,the multi-energy flow constraint is relaxed and transformed to reduce the complexity of model solving.Finally,a multi-energy distribution network composed of improved 33-node distribution network,20-node natural gas system,and 6-node thermal system is taken as an example to verify the effectiveness of the coordinated dispatch strategy.The economic benefits of integrated demand response and the schedulable potential of load-side resources under different distributed new energy penetration rates are analyzed.And the carrying capacity improvement effect of distributed new energy is compared and analyzed.