Fault Identification And Fault-tolerant Operation For Swicth On Vienna Rectifier

VIENNA rectifier is a three-level power converter with low input current harmonics,no dead zone,and simple structure,which has been used in medium or high power applications such as communications,aviation and new energy fields.Especially with the depletion of fossil energy and the popularization of electric vehicles,VIENNA rectifier,as an important part of DC charging piles,has received more and more attention.However,the power switchs are in the state of high frequency and high load for a long time,so they are prone to failure,which seriously affect the reliability of the system.Therefore,it is of great significance to study fault identification and fault-tolerant operation of VIENNA rectifier.In this thesis,the VIENNA rectifier based on one-cycle-control is taken as the research object,the mathematical model of the VIENNA rectifier in the three-phase static coordinate system is derived,the core equation of VIENNA rectifier based on one-cycle-control is calculated,and the mid-point voltage balance characteristics is analyzed.The inductance parameter,capacitance parameter,sampling conditioning circuit and driving circuit are designed.The simulation model and experimental prototype of VIENNA rectifier are built,and the functional test is conducted on it.The test results achieve the desired effect,which provides experimental conditions for further research.The influence of open-circuit faults on the operating characteristics of the rectifier is investigated,and it is found that whether the zero-value platform has a spike or not is determined by the boost ratio.The characteristics of the input current under different switchs open-fault are summarized.Open-fault is found to increase the output voltage ripple coefficient,single switch open-fault and double switchs open-fault of different phase will destroy the rectifier’s midpoint voltage automatic balance ability.It is found that the open circuit fault may lead to the increase of the minimum junction temperature and junction temperature fluctuation of the healthy switchs,which reduces the reliability of the rectifier.The rotating frequency of the current vector of VIENNA rectifier are used to quickly determine the time of failure.By analyzing the input current data,it is found that the fault characteristic vector constructed by kurtosis and mean value can effectively represent different open fault modes.From the point of data-driven,a fault identification method for VIENNA rectifier based on BA-BP neural network is proposed,and the effectiveness of the method is verified by simulation.By analyzing the current angle characteristics under different open-circuit fault modes,a fast and on-line fault identification method for single switch open-fault is presented.The effectiveness and rapid-ness of the method are verified by simulation and experiment.The experiment shows that the identification program is compatible with the control program and can be implanted into the control chip of rectifier for online identification.The traditional VIENNA rectifier topology is improved.Combined with the above identification method,the fault-tolerant operation scheme is given.The simulation shows that the topology can realize fault-tolerant operation,which is helpful to improve the reliability of rectifier.