| Distributed generation(DG)has the advantages of low cost,easy installation,efficient power generation,flexible control,environmental protection,etc.It provides an effective way to solve the problems of global energy depletion and environmental pollution.So it has developed rapidly in recent years,especially distributed photovoltaic(DPV).However,the integration of large-scale DPV has changed the characteristics of traditional distribution network,posing a great challenge to the safe and stable operation of distribution network.At the same time,due to the influence of solar irradiance,temperature,wind speed and other factors,the DPV output has significant intermittent and random nature,which causes the uncertainty in operation of distribution network.In addition,the distance of each node in the distribution network is relatively close,which makes the meteorological conditions are similar.Therefore,the correlation of DPVs output is remarkable,which aggravates the safety risk of distribution network operation.Based on this,this paper has carried out a research on distribution network characteristics evaluation,distribution line-type selection and energy storage allocation considering the random nature and correlation of PV output.The specific contents are as follows:1.In order to accurately assess the impact on the operation of distribution network caused by the randomness and correlation of PV output,this paper establishes a probabilistic evaluation index system from three aspects of voltage,current carrying capacity and line loss.And based on the modified Nataf transformation,this paper proposed a probabilistic load flow using the three-point estimation method with correlation input variables to calculate each evaluation index.The impact of PV access on the operation characteristics of distribution network under different load types,access capacity,power generation correlation and distribution line configuration is analyzed by an example..2.For the traditional 10 kV distribution line selection planning guidelines,it is difficult to adapt to the problem of large-scale distributed PV access.And aimed at it,this paper established a 10 kV distribution line selection planning model considering the random nature,correlation and load growth of PV output.In the model,the objective function is to minimize the annual sum of initial investment,operation and maintenance,operation loss,power failure loss,decommissioning and recovery costs in the whole life cycle of the distribution line.By analyzing the simulation results of the generalized model of 10 kV radial distribution network under different power supply zones,load types,PV access capacity and other boundary conditions,the Suggestions for optimal distribution line selection and configuration of PV distribution network are summarized.3.In view of the continuous increase load and the voltage peak regulation caused by largescale PV access,this paper proposed an energy storage optimization configuration method based on the newly increased load benefit considering voltage peak regulation.And established a stochastic double-layer optimal configuration of energy storage with the objective to maximize the annual net income of distribution network company due to voltage peak regulation in the whole life cycle after energy storage access,given the random nature and correlation of PV output as well as the decrease of energy storage life.The proposed model is jointly solved by the catastrophic genetic algorithm,the three-point estimation of the probabilistic load flow based on the modified Nataf transformation and the stochastic optimal power flow decoupling method based on the branch and bound optimization.The simulation of the example shows that by rationally configuring the energy storage,it can improve the load balance on the distribution line,accept the newly increased load,and create profitable possibilities for distribution network companies. |
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