Research On Fault Location For AC/DC Hybrid Distribution Network Based On Impedance Model

The traditional AC power distribution network has been unable to meet the users' demand such as computers,communication equipment and other digital electrical equipment due to its inevitable unbalance,voltage fluctuation,voltage flicker,frequency fluctuation and harmonic pollution,and the electric capacity is limited because of the existence of reactive power.If the traditional AC power distribution network is reformed into DC distribution network,it will not only save a lot of rectifiers and inverters,but also can give full play to the DC power distribution to save resources,reduce the transmission loss,has no synchronization stability problem,limit the short circuit current easily,be more convenient for distribution network expansion and other advantages.The fault location method of AC distribution network has been relatively perfect,but the research on fault location method of DC distribution network is much less.In order to solve this problem,this paper studies the fault location method of AC/DC hybrid distribution network based on the AC distribution network fault location algorithm.First,the failure mechanism is analyzed of AC/DC hybrid distribution network in this paper.Through the switch function model of converter,the influence of AC distribution network fault on DC distribution network is analyzed,and through the analysis of the fault equivalent model of DC distribution network,the influence of DC distribution network fault on AC distribution network is studied.Then the fault criterion is extracted to determine the fault area preliminarily to identify fault occurs in DC distribution network or AC distribution network.Then,the fault location method based on impedance model is extended to the DC distribution network which is adopted in AC distribution network.The mathematical model of electrical components in AC and DC hybrid distribution network is studied and established,meanwhile,a new method of fault eigenvalue is defined based on the node voltage equation and the electric network theory which realized the fault node location by dealing with the voltage current sampling data before and after the fault.Finally,this paper puts forward a fault location method based on improved genetic particle swarm algorithm according to the fault node location results by changing the fault location question into a problem to seek the optimum solution of a fitness function.A hybrid distribution network model is established,and the fault eigenvalue of a certain location is selected as the fitness function,to obtain the accurate fault distance,the improved genetic particle swarm optimization algorithm is applied to search the optimum solution of fault eigenvalues of the fitness function automatically.The simulation results show that the proposed method can be applied to the fault location of the AC/DC hybrid distribution network.