Research On Module Level Fault Simulation And Redundancy Analysis Of Power Electronic Transformer

With the construction and development of the energy internet,power electronic transformer(PET),as the core equipment of the "energy router",has become a hot spot in academic and engineering research in recent years.With the increasing switching frequency of power electronic devices,the dead-time effect of MAB-type PET topology can not be ignored.At the same time,due to the complexity and diversity of the internal fault types of the module,the actual engineering needs to integrate and optimize the more detailed device-level model to establish a module-level high-precision model that can reflect the fault characteristics.In order to ensure the reliability of the system,the corresponding redundancy protection must be designed so that the converter can cope with the failure of a small number of sub-modules.Therefore,it is of great theoretical and engineering significance to build PET module level fault simulation and redundancy analysis research.In view of the above problems,the main research work of this paper is as follows:First of all,aiming at the periodic blocking of sub-modules,an equivalent modeling method of dead-time effect electromagnetic transient acceleration for multi-active bridge PET topology is proposed.Combined with MAB topology,the switching dead zone of the model is divided into unilateral dead zone and bilateral dead zone.For the one-side dead zone,corresponding mapping functions are established for the rectifier side and the inverter side respectively;For the two-side dead zone,the state types are divided,and the current zero-crossing point is pre-calculated to realize the switching prediction of the diode turn-on signal.Considering the relationship between different dead-time settings and control parameters,the electromagnetic transient equivalent model of MAB PET switch dead-time under different voltage regulation ratios is established.The simulation accuracy and acceleration ratio of the model are verified by PSCAD/EMTDC simulation.Secondly,based on the analysis of preset fault types,a high-precision fault simulation equivalent modeling method for multi-active bridge PET topology is proposed.According to the characteristics of each device,the IGBT devices,diodes and transformers inside the MAB module are equivalent with high accuracy.After classifying the internal fault types of MAB module,the fault characteristics are analyzed respectively.Combining the fault characteristics with the high-precision equivalent model,the highprecision fault simulation equivalent model of MAB PET topology is established.The simulation characteristics of different fault types are verified through PSCAD/EMTDC simulation.Finally,aiming at system reliability,a fault redundancy equivalent modeling method for multi-active bridge PET topology is proposed.Combined with the topology of multiactive bridge PET,the advantages and disadvantages of two commonly used redundancy schemes are analyzed,and a combined standby redundancy protection scheme that can combine their respective advantages is proposed.After introducing the topology and implementation process of the combined redundancy protection scheme,the PSCAD/EMTDC simulation is compared with the two commonly used redundancy schemes,and the reliability of the combined standby redundancy protection scheme is verified.