Design And Characteristic Research Of Micro Circuit Breaker System

With the introduction of the Intelli Grid Architecture,the intelligentization of power grid equipment has become a research hotspot.As the circuit breaker with the largest base in the power grid,the miniature circuit breaker is limited by the size of the current detection equipment,and its intelligent process is very slow.The existing miniature circuit breaker tripping method adopts "thermal magnetic" tripping,and its protection characteristics and functions can no longer meet the requirements of smart grid.The realization of the intelligent miniature circuit breaker will make its action of protection more accurate,its functions more diversified,and its human-computer interaction ability stronger,which will make the operation of the smart grid more reliable,and will also bring huge opportunities of business.Based on this,the current detection method and intelligent controller of miniature circuit breakers are studied,and a miniature intelligent circuit breaker based on thermoelectric current measurement method is designed.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,the thermoelectric current measurement method is studied.In order to detect the current,the mathematical model of thermoelectric current measurement method is established based on the internal parameters of miniature circuit breaker obtained by parameter identification.In order to verify its accuracy,Pt100 temperature sensor is pasted inside the miniature circuit breaker,and the temperature rise measurement experimental platform is built for temperature rise current calculation experiment.In order to solve the problem of long time to achieve stable temperature rise,a fast current calculation algorithm with series advance correction is proposed to provide a stable current detection method for miniature intelligent circuit breaker.Secondly,the controller hardware circuit which can realize the miniature intelligent circuit breaker is designed.In order to realize the protection performance and various functions of the miniature intelligent circuit breaker,a minimum system of single-chip microcomputer with STM32F103C8T6 as the core is built.Through the method of modular design,the circuit design of the signal acquisition and processing module,the human-computer interaction module,the CAN bus communication interface module and the protection action module is carried out respectively.In order to ensure the stability of the controller’s work,two measures of grounding and isolation are adopted to realize the anti-interference performance of the controller hardware.Thirdly,the KEIL MDK platform is used to program the system functions and protection strategies in C language.In order to realize the rapid measurement of the current value,the programming of the thermoelectric current measurement method and the recursive algorithm of the series lead correction is completed.In order to achieve intelligence,an overload protection strategy of cumulative thermal effect is proposed,and a discrete mathematical model is derived.The delay time can be obtained through iterative calculation.In order to realize intelligent control,the programming and debugging of overload protection program and other intelligent protection programs have been completed.Finally,the PCB of the hardware circuit is drawn with Altium designer,and the prototype of the controller is completed through welding and debugging.After building the experimental platform,the feasibility of the design is verified through constant current overload protection experiments and variable current overload protection experiments.