Integrated Diagnosis Method For Inverter Sensor Fault And Transistor Fault

Power electronic converters play a key role in new energy system,electric vehicle,power grid and many other fields,but they are also very vulnerable.Therefore,the researches to improve their reliability and avoid system shutdown are of great significance.Comprehensive and accurate fault diagnosis is the basis for timely fault tolerant control.Integrated diagnosis of different types of faults can reduce false diagnosis and system diagnosis complexity,which has important application value.How to achieve fast and robust diagnostic performance within wide load range without adding hardware circuits and only using existing signals is still worth studying.This paper studies sensor fault and transistor fault of three-phase inverters,and proposes two integrated diagnosis methods.Firstly,a method based on voltage and current double diagnosis variables is proposed for current sensor fault and transistor fault integrated diagnosis in three-phase inverters.The bridge arm line voltages and the sum of the three-phase output currents are taken as the diagnostic variables.The characteristics of the inverter under different faults are deeply analyzed,and the average model of the diagnostic variables are derived in detail.In addition,the influence of wide load range on diagnosis performance is also considered.The dynamic calculation error caused by sampling error,inductance nonlinear deviation,dead zone and delay under different load conditions is analyzed quantitatively and a self-adjusting threshold design scheme is presented to make the diagnosis applicable to wide-load application and ensure robustness.Compared with the existing current sensor and transistor fault integrated diagnosis methods,the proposed method can shorten the diagnosis time and solve the problem that model-based methods are susceptible to the load change,and makes the threshold selection much easier.Secondly,an integrated fault diagnosis method for DC bus voltage sensor,AC output voltage sensor,current sensor and transistor is proposed based on multiple diagnostic variables.Due to the coupling of the characteristics of these faults,it is easy to cause false diagnosis when one of them occurs without overall consideration.This paper uses the deviation characteristics of the bridge arm line voltages,the sum of the three-phase line currents and the sum of the three-phase output voltages,combining with the polarity characteristics of the output currents and the duty cycle of the transistors to detect and locate the multi-type faults.Firstly,the characteristics of these variables under different types of faults are obtained through analysis.Then the calculation of diagnostic variables and thresholds is derived.Finally,the integrated diagnosis algorithm logic and fault location criteria are given.The proposed method can realize the simultaneous diagnosis of these four kinds of faults in the inverter.Each fault can be diagnosed fast.