Research On Topology Reconstruction Technology Of Marine Medium Voltage DC Distribution System

In recent years,with the development of semiconductor technology,the application of new semiconductor materials,and the advancement of electrical equipment on ships,these factors have put forward higher requirements for future ships and also brought huge development space.These factors make the medium voltage DC integrated power propulsion system widely concerned.In this paper,the ship medium voltage DC propulsion system is studied from the aspects of power flow calculation and fault reconstruction.First of all,the power flow calculation model and algorithm of distribution network are studied.The steady-state mathematical model of DC-DC voltage converter and DC-AC/ ACDC converter under non-ideal conditions are established.Through the established mathematical model,the equivalent resistance of the voltage converter and the equivalent node current of the converter are calculated through the established mathematical models,and then the node admittance matrix of the entire DC distribution network is obtained.According to the characteristics of DC distribution,the classification method of node definition is redefined,and the AC newton-raphson algorithm is improved to complete the power flow calculation.Secondly,the topology expression of medium voltage DC integrated power system is studied.The structure of marine medium voltage integrated electric propulsion system is equivalent to the vertex and edge of data structure diagram,which is convenient for system information expression and computer program implementation.The information in different matrix representations is defined and the structure and operation state transformation of ship MVDC integrated electric propulsion system is described completely by matrix element changes.Finally,the reconfiguration technology of distribution network is studied.According to the characteristics of DC area distribution,this paper proposes two-stage reconstruction of power loss area after system fault: In the first stage,breadth-first search algorithm and depthfirst search algorithm are adopted to search for a path that can provide sufficient power supply to the underpowered area of the system,and the active power flow distribution of the line is given in the process.The second stage of reconstruction is based on the reconstruction results of the first stage to solve the problem of insufficient generation capacity in the system after the failure.In other words,according to the importance of the load and the capacity of ship power generation,the genetic simulated annealing algorithm is used to select power supply for the load in the distribution network,so as to supply power for the critical load of the system operation and unload the non-critical load.Using the two-stage reconstruction strategy proposed above,fault recovery is carried out for 3-area system structure and 5-area system structure respectively,and the effectiveness of the reconstruction strategy is verified.