Study On Condition Monitoring Method And Measurement Device Of Core Components In Wind Power Converter

During the 13th Five-Year Plan period,China’s new energy power generation technology has been rapidly developed,and the scale of wind power and its related industries is also expanding and maintaining a sustained growth trend.IGBT module and DC bus capacitor are the core components of wind power converter.Once the failure of the two or one of the components,the reliable operation of wind power system will be affected.The development of the state monitoring technology for the core components of wind power converters,mainly IGBT modules and DC bus capacitors,has a very important guiding signif icance for the optimization of converter maintenance plan and the improvement of the reliability of wind power system.In view of the problems and deficiencies in the current state monitoring methods for the core components of wind power converters,this p aper takes the IGBT modules in the wind power converters and the aluminum electrolytic capacitors at the DC bus as the research objects,and develops the IGBT modules and aluminum electrolytic capacitors.The state monitoring technology of the failure mech anism is researched,and the corresponding measurement system is designed for experimental verification.The main research contents are as follows:（1）Through a combination of theoretical analysis and analytical description,the reasons for the aging and failure of IGBT modules and aluminum electrolytic capacitors are discussed in detail.And from the perspective of the failure of the IGBT module bonding wire,the quantitative relationship between the aging of the bonding wire and the saturated conduction voltage drop of the IGBT module is analyzed,which provides theoretical support for the subsequent state monitoring of the IGBT module.The failure of the DC bus aluminum electrolytic capacitor is mainly manifested in the volatilization of the electrolyte and the reduction of the aluminum foil area,which in turn increases the equivalent series resistance R_ESR and the capacitance value C decreases.Finally,the quantitative relationship between the aging of aluminum electrolytic capacitors and the R_ESR and capacitance value C is derived,which provides theoretical support for the subsequent state monitoring of aluminum electrolytic capacitors.（2）A method for monitoring the bond wire status of IGBT module based on saturation conduction voltage drop is propo sed.Firstly,A multi-physical field simulation model of IGBT module based on electro-thermal coupling was built in COMSOL 5.4,and the effects of the number of disconnected bonding lines and the external ambient temperature on the saturation voltage drop and junction temperature of IGBT module were studied.Secondly,a method for monitoring the state of the IGBT module bonding wire based on the saturation conduction voltage drop is proposed.The health evaluation of the IGBT module bonding wire is achieved by measuring the saturation conduction voltage drop under high current.Finally,a high precision measurement system for the saturation voltage drop of IGBT module based on the isolated operational amplifier is designed.The system can not only effectivel y detect the saturation voltage drop of IGBT module,but also have high reliability and accuracy.（3）A state monitoring method for aluminum electrolytic capacitors based on Equivalent Series Resistance（ESR）and capacitance value is proposed.Firstly,A three-dimensional finite element simulation model of electrolytic capacitor based on electro-thermal coupling was built in ANSYS 15.0.The effects of capacitor structure（height to diameter ratio）,external ambient temperature and injection ripple current on the core temperature of electrolytic capacitor were discussed.Secondly,a monitoring method of ESR and capacitance value based on the discharge law of aluminum electrolytic capacitor was proposed.By sampling the voltage curve in the discharge process of aluminum electrolytic capacitor in real time,and combining with the relationship between voltage and current in the discharge process,the calculation model of ESR and capacitance value was established.Finally,a system was designed to monitor ESR and capacitance changes of aluminum electrolytic capacitors,and the health status of aluminum electrolytic capacitors was evaluated by the measured R_ESR and capacitance values C.