| All countries are trying to use wind,solar,tidal energy and other new energy as the main energy.In the process of new energy power generation,the operating conditions of the converter change at any time,which can cause severe fluctuations in the internal junction temperature of IGBT,thereby accelerating its fatigue failure and reducing the overall lifespan of the converter.Therefore,accurate life assessment and effective life optimization of IGBT modules operating in actual working conditions are of great significance for improving the overall reliability of the converter.In response to these issues,this article designs a hardware platform for applying condition replication,and based on this platform,studies the online detection method of IGBT module junction temperature,as well as the life evaluation and optimization method of IGBT module.The main research content is as follows:Firstly,the requirements for the application scenario replication platform were analyzed.And a three-layer system structure with dSPACE as the controller was designed according to the requirements of the working condition reproduction platform.Subsequently,the circuit topology structure based on H-bridge topology was introduced,and the design of various parameters in the circuit was elaborated in detail,including the parameter design of load inductance,bus capacitance,infrared temperature sensor,IGBT module,power supply part,charging part,and discharge part.Finally,the operation steps of conducting inverter experiments on the working condition reproduction platform were introduced,and the functional integrity of the platform was verified through the inverter experimental results.Then,the causes and corresponding calculation methods of various losses during normal operation of IGBT modules were introduced.At the same time,a Foster thermal network model considering thermal coupling effect was designed,and the heat capacity and resistance parameters in the thermal network model were extracted using ANSYS thermal simulation.On this basis,a composite junction temperature observer was designed to address the problems faced by conventional open-loop observers and closed-loop observers in practical applications.Finally,an IGBT module junction temperature online extraction model was designed in Simulink,and experiments were conducted on a working condition replication platform based on this model.The accuracy of the designed junction temperature online extraction method was verified by comparing it with measured junction temperature data.Finally,taking the application scenario of photovoltaic power generation as an example,a study was conducted on the life assessment and optimization of IGBT modules for photovoltaic grid connected converters based on the working condition replication platform.Firstly,two sets of photovoltaic operating conditions were replicated on the experimental platform under different switching frequencies and maximum load current conditions.Subsequently,the life assessment of IGBT modules was completed by combining linear fatigue cumulative damage theory,rain flow counting method,and IGBT life prediction model.The effects of switching frequency and maximum load current on the life of IGBT modules were discussed.Finally,in response to the sudden change in load current,a life optimization method for IGBT modules based on variable switching frequency was designed,and its effectiveness and feasibility were verified on a working condition replication platform. |
