Analysis On Power Flow Of DC Power Distribution Network

Compared with AC power distribution network,DC distribution network has many outstanding advantages such as more flexible and convenient access for renewable energy and energy storage devices,larger power supply capacity and higher power quality.The power flow calculation is an important research content of DC distribution network,which can provide theoretical basis for the analysis of DC distribution network.Thus,this paper carries out research on the power flow calculation of DC distribution network.DC distribution network power flow calculation methods based on Newton-Ralph usually get results by listing out power deviation equations.This paper firstly attempts to list out branch resistance deviation equations and presents a DC distribution network power flow calculation method,and combines it with the characteristics of DC distribution network,and simplifies the Jacobian matrix,which makes the formation process of Jacobian matrix of the proposed method extremely convenient.At the meantime,this paper also considers DC distribution network power flow calculation after adding the DC/DC converters.The analysis shows that adding DC/DC converters will not affect the original Jacobian matrix calculation formula.Finally,the correctness and effectiveness of the proposed method are verified by several examples.The results of examples show that the proposed method is suitable for DC distribution network power flow.In order to enhance the efficiency of power flow calculation and avoid the problems of convergence and low calculation efficiency of iterative methods,considering the droop control of DC distribution network and DC/DC converters,the unified power equations are listed out and a linear power flow model of DC distribution network is established.The example results show that,The results show that,when the deviation of node voltage from the balanced node voltage is no more than 5%,the voltage error of linear power flow model is within the level of 10-4,which has relatively high calculation accuracy.For the quantitative analysis of the influences of uncertain factors such as intermittent renewable energy sources and random on the DC distribution network,combined with the linear power flow model and affine arithmetic,an interval linear power flow model of DC distribution network is established.The model needs no iterations and can be directly solved through the affine linear equations.The results show that the interval linear power flow model has the advantages of completeness,low conservativeness and high efficiency,and is suitable for the interval power flow analysis of DC distribution network.In order to avoid the problem of multiple alternating iterations in AC/DC system when using alternating iterative method to perform power flow calculation of hybrid distribution network based on voltage source converter(VS C),a new VSC power flow calculation model is established by reshaping the VSC power flow calculation model.In this model,the active loss of VSC is equivalent to the DC side and the boundary of the AC/DC system is redefined,which avoids the multiple alternating iterations problem of the AC/DC system and reduces the power flow computational burden of the hybrid system.The result shows the effectiveness and high eficiency of the proposed model.