Analysis Of Power Quality And Disturbance Detection In DC Distribution Network

With the development and utilization of new energy power generation and the appearance of new types of electricity,more and more DC equipment access to the grid.In order to adapt to this change,the concept of DC distribution network is put forward.Because the DC distribution mode has its own particularity in structure and operation,making the causes and manifestations and influencing characteristics of DC power distribution have new characteristics.Reasonable and systematic analysis of power quality problem in DC power distribution network is one of the important contents of the DC distribution network research and planning stage,which will help to promote the construction and popularization of DC distribution network.Based on this,this paper analyzes the power quality of DC distribution network.First of all,combining with the topology and load type of the DC distribution network,and drawing on the research results of the power quality of the AC system,the possible types and the formation mechanism of disturbances are analyzed from both the steady state and the transient type.Defines the coefficients that measure the severity of the power quality.Among them,the formation mechanism of the ripple problem is complex,mainly due to the converter equipment is essential in the DC distribution network,and the control mode and the non-ideal situation of the AC side will affect the power quality level of the DC side.Secondly,the typical problems caused by ripple are analyzed,and the superposition characteristics of different AC harmonics after the converter are analyzed quantitatively.Relationship between ripple superposition and AC harmonic characteristics is also presented.In addition,the equivalent circuit of DC distribution network with converter equipment is established,and the access number and access to the location of the converters which has an influence on ripple resonance is deduced.Considering the coupling effect between converter equipment,coupling coefficient between each of the converter is calculated,and the influence of the coupling effect on the ripple resonance is studied.Simulation examples of DC distribution network show that the theoretical analysis and the model are reasonable.Finally,on the basis of the above analysis,considering the characteristics of various types of DC power quality problems and their particularity,the coherent atom dictionary of the DC distribution network disturbance signal are constructed.A new algorithm combined PSO with MP for first roughly searching and then carefully searching is proposed.The number of atoms in the atomic library is reduced.The method of disturbance detection based on matching pursuit(MP)algorithm is improved,which ensures the accuracy of the algorithm and improves the speed of the calculation,and complete the DC power quality disturbance detection.Examples are given to demonstrate the feasibility and effectiveness of the proposed algorithm for DC disturbance detection based on the coherent atom dictionary.