Research On Fault Evolution Mechanism And Forecasting Method Of Ship Power System

Ships in the sea will suffer a variety of harsh environments,in this work under the influence of environmental factors led to the ship's power system failure rate increases,so that the stability of the work will be affected to power system of various electrical equipment.Safety of ships and ship workers will be threatened.It is difficult for the ship to ensure that the power system does not fail,but it can be used to evaluate the health of the electrical equipment according to some information in the operation state of the ship's electric power equipment,to predict the failure of the power equipment,to eliminate the fault in the bud,Thereby improving the safety and stability of the ship's power system.In this paper,the fault evolution mechanism and prediction method of ship power system DC / DC converter and ship cable are deeply researched and analyzed,and the following research work is mainly completed:1)The equivalent circuit model and aging failure mechanism of the filter capacitor,diode,power MOFSET and inductor in the DC / DC converter are analyzed.The aging characteristics and its variation of these devices are determined by analyzing the equivalent circuit model and aging failure mechanism.2)According to the equivalent circuit model and aging failure mechanism of filtering capacitor and a filtering capacitor aging prediction method is proposed.First,according to the equivalent model of the filter capacitor,then derive equivalent series resistance equivalent circuit of DC/DC converter,lastly propose a method to predict the aging of the filter capacitor.Load voltage will pass through the band-pass filter,the RMS module and the low-pass filter,last analysis the situation of capacitor aging according to the response.The simulation results of Buck Converter,Boost Converter and Buck-Boost Converter show that the method can predict the situation of capacitor aging,and estimate the critical state of capacitor aging.The simulation results show the prediction method is feasible.3)This paper analyzes the aging mechanism and the phenomena of the ship's cable in the special working environment of the ship,and analyzes the aging mechanism of the heat aging,the mechanical aging and the electrical aging.At the same time,the process of gradually generating the arc during the aging process of the ship's cable is analyzed.The Cassie arc model is derived from the energy balance theory.4)Based on the Cassie arc model,the ship cable model is established.Based on this,theaging process of the ship cable is analyzed,and the change rule of the impedance and the effective value of the arc current is obtained.Then a ship cable aging prediction method is proposed based on the Kalman filter algorithm.Firstly,it derives the Kalman filter algorithm prediction process for ship cable impedance,and predicts the impedance value in the process of cable aging,and expresses the impedance mutation by using the residual of the impedance value of the next state and the current state.And residual can detect pre-fault critical state.And by detecting the effective value of the arc current changes to determine the critical state of the ship after the safety and stability of the power system.The simulation results show the feasibility of the proposed method.