Research On Model Parameter Identification Method Of Miniature Circuit Breaker Electrothermal Current Measurement System

With the continuous breakthroughs in technology such as computer miniaturization and communication,intelligence has become the mainstream development trend of today's power grid.Among the power grid equipment,power distribution equipment led by low-voltage electrical appliances has been widely used in many fields such as life and production.Today,in people's actual life,the low-voltage electrical appliances that can be accessed and used in the widest range are circuit breakers.Therefore,it has become one of the popular research projects to make low-voltage circuit breakers have intelligent control effects.Current detection and overload protection are important components of low voltage electrical intelligence technology,and are also the key research part of low voltage circuit breakers.In recent years,there have been many research results in detecting current in circuit breakers,including electronic circuit breakers as the first,the use of current transformers for accurate measurement of current,but because of its large size,can not be installed in the use of the largest base of micro-circuit breakers,and small circuit breakers are limited by volume,so that its intelligent research results are relatively small.Therefore,how to realize the purpose of current detection in the limited space is of great significance to realize the intelligence of micro-circuit breaker.In this thesis,an electric current detection method based on the electrothermal coupling effect is proposed,which has the advantages of small space,electrical isolation and accurate prediction of current size.This topic comes from the National Natural Science Foundation of China: new thermal electromagnetic hybrid intelligent small circuit breaker and intelligent low voltage distribution microsystem research(project number: 51777129).Firstly,this thesis uses Solidworks software to establish a spherical closed current measurement cavity model,which is used to replace the bimetallic sheet in bimetallic circuit breakers for current detection,and the model as a system,under the law of thermal conservation,to solve the transfer function of the system.According to the transfer function,the differential equation between current and temperature rise is sorted out.Then,using the appropriate mathematical modeling method,two different mathematical models are obtained for system identification,one model input is the heating power generated by the current,the output is corresponding to the temperature rise,and the other model input and output is interchangeable.Using the push-by-tin to identify the unknown parameters in the mathematical model,the simulation model is constructed by the Simulink module in Matlab,the algorithm is programmed,the resulting result of the identification parameters is analyzed,the mathematical model with large errors is eliminated,and after carefulanalysis of the actual situation is carefully analyzed.The model and algorithm are improved,the simulation verification is re-simulated by the least square method of oblivion factor push.Finally the temperature-up measurement experiment is carried out,the equipment used in the experiment,the process of making the current measurement cavity and the labVIEW software system used are briefly introduced,and the temperature-up graph chart under different currents is observed.By validating the experimental data into the improved algorithm and model,it can be found that the electrothermal current detection method used in this thesis can meet the design requirements of intelligent current measurement of small circuit breakers.