Fault Diagnosis Of Power Converter In Switched Reluctance Drive System

Switched reluctance motor(SRM)has the characteristics of high reliability and strong fault tolerance.It is commonly used in the occasions requiring high reliability.In the high reliability requirements of the occasion,once the failure,the loss will be huge.This paper focuses on the main switch of the power converter,which is the most prone to failure.Combined with theoretical analysis,the fault diagnosis methods under different chopper modes are studied to further improve the reliability of the switched reluctance drive(SRD)system.Firstly,the SRD system is introduced.The basic control strategy and chopper mode are proposed.Meanwhile,the applicable occasions of the SRD system under different control strategy and chopper mode are analyzed.The types of electrical faults in the drive system of SRM are summarized and classified.This paper takes the three-phase asymmetric half-bridge converter as the research object.The changes of current path under different working modes are studied.It provides ideas for the proposal of fault diagnosis methods below.Then,for the hard chopper mode,the fault diagnosis method of power converter based on combined branch current analysis is presented.Under the hard chopper mode,the upper and lower main switches have the same function,so the fault location cannot be directly located from the phase current.The principle of the diagnosis method is that by changing the winding,more current information can be obtained from the combined current.Different switching modes also correspond to different theoretical current paths.According to the difference between theoretical current paths and actual current paths,the corresponding fault types and fault locations can be obtained.Simulation and experimental results demonstrate the effectiveness of the proposed diagnostic method under different control strategiesFinally,for soft chopper mode,the fault diagnosis scheme of power converter based on current variation is presented.In soft chopper mode,the main switch can be divided into chopper switch and position switch.The current always passes through the position switch in the opening interval.Therefore,the control of the motor can be realized only by observing the change of the current of the position switch.There are three operating states in soft chopper mode,and the current change can also be divided into three states: up,down and zero.Therefore,the working state can be corresponding to the current change to a certain extent.On this basis,once fault occurs,there will be a new state.So the fault can be found through this new state.In addition,according to the calculation method of current change,it is divided into fixed frequency and random frequency.The advantages and disadvantages of the two methods in fault diagnosis are analyzed.Simulation and experimental results demonstrate the feasibility of the two methods under different control modes.There are 95 figures,8 tables and 92 references in the thesis.