Research On IGBT Open Circuit Fault Diagnosis And Efficiency Loss Evaluation Model Of Photovoltaic Grid-connected Inverter

Photovoltaic inverters are the pivotal equipment of photovoltaic power generation systems,and their operating conditions have an important impact on the reliable operation of the entire photovoltaic power generation system.However,the actual natural environment of a photovoltaic power station is generally harsh,and the internal equipment will endure high electrical stress and high thermal stress for a long time.At the same time,the impact of disturbances in the power grid and the DC side will also increase the failure rate of photovoltaic inverters.The failure of the photovoltaic inverter will cause serious losses to the overall efficiency of the photovoltaic power station.In order to improve the fault diagnosis ability of the photovoltaic inverter and quantify the degree of efficiency loss caused by the fault,this paper proposes a fault diagnosis model based on extremum ratio method and support vector machine.An inverter failure efficiency loss evaluation model based on the combination of the bestworst method and the entropy-weight method is also proposed.First,based on the photovoltaic grid-connected inverter with LCL filter and its current double closed-loop control strategy,the inverter faults are classified from multiple angles,and the common fault types and externalities in photovoltaic inverters are summarized.In the performance,the reasons for the failure of the photovoltaic inverter IGBT open circuit and short circuit are emphatically explained.Secondly,the Matlab/Simulink simulation platform is used to realize the establishment of the photovoltaic grid-connected inverter model,which effectively simulates various opencircuit faults of IGBT,and performs fault analysis on the three-phase current waveform output from the AC side.On this basis,a method for extracting extremum ratio fault feature quantities is proposed,which effectively reduces the dimensionality of feature quantities and provides good conditions for fault diagnosis and recognition.Then,the support vector machine(SVM)is applied to the fault diagnosis of photovoltaic inverter,and the fault diagnosis method based on the extremum ratio method and the support vector machine is proposed.Using the superior search and classification characteristics of SVM,the feature quantities extracted from 22 types of IGBT open faults are diagnosed and classified.The diagnosis result is compared with the traditional neural network fault diagnosis method.The result shows that the SVM classification method has the characteristics of strong anti-interference ability and high fault diagnosis accuracy.Finally,an efficiency loss evaluation model of photovoltaic inverter IGBT open-circuit failure based on the combined weighting method is established.In view of the characteristics of the subjective and objective weighting method,a combination of the best-worst method(BWM)subjective weighting and the entropy-weight method(EWM)objective weighting is used to determine the evaluation index weights.It is demonstrated through simulation experiments that the evaluation method can effectively quantify the severity and efficiency loss of various IGBT open-circuit faults in the inverter.