Design Of Inverter System With Degradation Parameters On-line Measurement Based On SiC MOSFET

Under the background of the rapid development of modern power electronic technology,power electronic converter,as an important intermediate link of power conversion,has been playing the role of undertaking a lot of power conversion tasks.At the same time,as the core of the converter power switching device,its reliability has become an important index and key factor of the overall reliability of power conversion equipment.Compared with silicon(Si)devices,MOSFET made of silicon carbide(Si C)has stronger voltage resistance and higher switching frequency.As the related technology continues to mature,the price of Si C MOSFET has decreased,and it is put into practical industrial applications by more and more equipment manufacturers.These factors make Si C MOSFET which has become a kind of power device with great potential and application market in the future.For the converter,the output quality of the inverter would have been affected by the aging condition of Si C MOSFETs.In view of the aging of Si C MOSFET,it is necessary to measure some thermal and electrical parameters which can reflect the aging state online,and then import them into the health management system for evaluation.However,in the existing applications and studies,most of the devices are used for on-line measurement under DC working condition for a long time opening or shutting down,while in AC working condition,the opening state of MOSFET device is more complex,and its online measurement is difficult to be compatible with the actual working condition,which would have brought some obstacles to the health status evaluation of devices under AC working condition.In this paper,Si C MOSFET under the condition of single-phase full-bridge inverter is taken as the research object,and it is studied in the aspects of measurement principle basis,online measurement method and compatibility scheme of online measurement under the condition of single-phase full-bridge inverter.The following three parts have been included in the main contents :The first part,the basic structure and principle of Si C MOSFET has been studied to determine its in inverter working conditions,according to the principle and research to the existing research results.There are two kinds of parameters that are threshold voltage and the turn-on state drain-source voltage,which are more obvious in the process of Si C MOSFET degradation.At the same time,the health status of Si C MOSFET can be comprehensively reflected both.The on-line measurement scheme based on single-phase inverter Si C MOSFET has been designed respectively,and the measurement system has been built.The second part,the paper has proposed a control model based on the current fundamental wave direction,under the special control mode,the inverter has been transformed into an equivalent of the DC chopper circuit,in order to solve the problem that it is incompatible for the inverter on-line measurement parameters and the working condition.And the simulation of this kind of control mode has been analyzed.The simulation results has shown that the output amplitude has drifted upward slightly in the measurement mode,and there has been a small jump near the zero crossing of the amplitude in the process of sinusoidal fundamental wave change.For solving the problems in the measurement mode,the three methods which has included the P parameter of PI controller adjusted,the measurement threshold changed and appropriately the reference value decreased in the measurement mode have been adopted to improve the quality of waveform and the current distortion rate reduced as much as possible,and certain effects have been achieved.In the third part,on the basis of the simulation model,the hardware modular circuit and software control link have been designed,and the online measurement experiment platform of Si C MOSFET inverter degradation parameters has been set up to verify the influence degree of the measurement state on normal work,the feasibility of the corresponding parameter measurement and the compatible scheme of online measurement.The experimental results show that the two important degradation parameters of Si C MOSFET can be measured with keeping the normal working conditions affected little.