Research On High Reliability DC-DC Converter For Maglev System

Maglev chopper is an important part of the magnetically levitated train,its essence is the DC-DC converter,which is progressing with the development of power electronic technology.As a critical electrical equipment in vehicle,it can supply powers to the magnetic levitation electric system by DC-DC transformation.In order to deal with the complicated and changeable working conditions,whether it can work safely and reliably is related to whether the maglev train can run normally and steadily.Therefore,developing a high reliability maglev DC-DC converter is very significant for more efficient and stable operation of the magnetically levitated train.In this paper,we use the IGBT modules which are mature in technique as the power module for the maglev chopper,and design a magnetic levitation DC-DC converter whose voltage and current level are 330V and 30A.In order to improve the reliability of the maglev chopper,the scheme of double machine hot backup is adopted in maglev chopper which is combined with two H-bridge chopper.And the load characteristics of the chopper in fault is analyzed in detail,so as to improve the stability of the suspension system,the degradation of IGBT can be predicted by monitoring the tube pressure drop V_ce on line.This paper introduces the design of H bridge suspension chopper in detail,including the design of main circuit,control circuit,radiator,protection device,chopper box and so on.The basic principle and control modes of the H bridge maglev chopper are analyzed,and the electrical characteristics of chopper under operation and the load current characteristics under different control modes are also analyzed.The load current characteristics and ripple characteristics of parallel operation under different control modes are studied,and the load characteristics of a chopper fault under parallel operation are researched.At the same time,so as to improve the reliability of power modules of single chopper operation,The shell temperature balance of power module in a single chopper is discussed,and the shell temperature condition in parallel operation of two choppers is also studied.The IGBT module,which consists of a suspended chopper,runs in a better temperature state.The reliability of the chopper during operation is enhanced.For the sake of detecting the wear condition of the power module in the steady state for a long period of operation,the V_ce detection circuit for the tube pressure drop of IGBT is designed.The results show that the operation of chopper in parallel operation is better than the operation of a single chopper.Not only because the ripple of the load current is lower than that,but also because the stability of load current is much higher than that of single chopper.The shell temperature of the power module,by adjusting the mode of freewheeling,also has a greater improvement in the condition of single chopper operation.The reliability of single chopper operation is improved.With the same regulation method,the shell temperature condition of the power modules is also adjusted in parallel operation.