Research On Distribution Network Risk Assessment For High Penetration Distributed Generation

With the continuous development and utilization of clean energy,a large number of clean energy based distributed power sources are incorporated into the distribution system.Due to the increasing scale of distributed generation,the operation and planning of distribution network are greatly affected.Therefore,it is necessary to determine the carrying capacity of distribution network to receive distributed generation.In addition,the output of distributed generation has strong randomness and volatility,which also has a huge impact on the operation safety of power network.It is urgent to evaluate the influence of distributed generation with different permeability on distribution network.Therefore,this paper aims to build the early-warning model of distribution network with different permeability of distributed generation,analyzes the basic risk elements,establishes the early-warning index system of distribution network,and introduces extension theory to build the hierarchical early-warning model of distribution network.This paper discusses the operation status of distribution network under different permeability,and gives an early warning to the operation status based on the distribution network structure and the scale of distributed power supply.At the same time,the corresponding control strategy is proposed based on the early warning level.The main work of this paper is as follows:The first part is to clarify the significance of the research.The current situation of distribution network risk assessment,the application of hierarchical early warning model in distribution network and the influence of various early warning indicators on distribution network are investigated.This paper summarizes the current research status at home and abroad,summarizes the security factors of the distribution network access to the distributed power supply,analyzes the necessity of the risk assessment of the distribution network,puts forward the construction ideas and methods of this paper,and summarizes the context of the paper.The second part analyzes the influence of distributed generation on distribution network.Firstly,it analyzes the characteristics of distributed power,establishes the operation model of distributed photovoltaic and distributed wind power,analyzes the influencing factors of the output of two kinds of power,and summarizes the output model of distributed power.Secondly,according to the different access location and capacity of distributed power,the paper analyzes the impact of distribution network from the perspective of physical model,including static voltage stability index,system loss change rate index,harmonic occupancy rate index,short-circuit rheological rate index.Finally,according to the physical model,we do the example analysis of each index and calculate the fluctuation range of each index.In the third part,the hierarchical early warning model of distribution network is established.Based on the actual needs,the establishment criteria of early warning model and classification criteria of early warning indicators are proposed.Select the risk indicators that affect the normal operation of the distribution network to establish the early warning indicator system,including distributed power,distribution network structure and the degree of impact on the distribution network.According to the selected early warning indicators,the early warning classification principle of each indicator is proposed,and the extension theory is introduced to build the correlation function between the specific value of each indicator and the early warning level.The operation rules of hierarchical early warning model of distribution network with distributed generation are proposed.In the fourth part,the comprehensive weighting method and early warning control strategy are proposed.Firstly,the paper introduces the kinds of weighting of subjective and objective methods.Based on the analytic hierarchy process and entropy method,the weight relationship and preference coefficient of the comprehensive weighting method are proposed through model derivation,so as to weighting each index in the early warning system.Secondly,the ieee33 node model is introduced to build the distribution network model with distributed power supply,and the simulation model is analyzed.In the given model,the distributed power supply is connected in proportion,and the comprehensive warning level of distribution network is calculated.An example of ieee33 node model verifies the correctness and feasibility of the hierarchical early warning model.Finally,on the basis of the comprehensive early warning level of the system,the risk control strategies proposed under different early warning levels are put forward,which can provide intuitive,fast and effective decision-making basis for the emergency risk control of the system scheduling under the emergency risk situation.The last part summarizes the main conclusions of this paper,and puts forward the next research direction.