Research On Microcomputer Relay Protection Of Control Rod Drive Mechanism Power Supply System Based On DSP

The control rod drive mechanism power supply system is one of the important systems of nuclear power plants,whose task is to ensure stable power supply to the coils of the control rod drive mechanism,and its operation condition will directly affect the safe and economic operation of nuclear power plants.The control rod drive mechanism power supply system of Fuqing nuclear power commercial unit has experienced many drawer tripping events,resulting in the loss of power to the 380 V bus causing transient instability of the unit and endangering the reliable operation of key sensitive equipment.In order to improve the reliability of the control rod drive mechanism power supply system protection device and reduce the economic loss,it is very important to study the protection principle,algorithm and setting value.In this paper,two parts of protection principle,algorithm and protection device are studied.For the protection principle and algorithm.After carefully analyzing the causes of overstep tripping,this paper points out that the original protection configuration is not enough,the protection setting is not reasonable,and the protection algorithm cannot remove the calculation error caused by Decaying Direct Current is the main reason.Firstly,the protection principle and setting value are optimized and adjusted,then the advantages and disadvantages of the traditional protection algorithm are analyzed based on Matlab simulation,and finally the full-wave Fourier algorithm is improved based on half-period delay sampling.The optimized principle and fixed value are more in line with the operation mode of the control rod drive mechanism power supply system;the improved algorithm not only can completely filter out the DDC component and improve the accuracy of the calculation of fundamental wave amplitude and phase,but also avoid the calculation of attenuation parameters in the filtering process,which is easy to implement by microcomputer.For the protection device.This paper uses the fast digital signal processing capability of DSP to design a microcomputer protection device with TMS320F28335 as the core.Firstly,it introduces the selection principle of the core microprocessor and designs the related hardware circuits,including mutual sensor circuit,conditioning circuit,AD conversion circuit,switching input and output circuit,power supply,etc.Then,the software control system based on the model design is built in Matlab/Simulink,and the code can be automatically generated and downloaded,which effectively simplifies the development process of software control system。Finally,in this paper,the fixed value simulation system of the control rod drive mechanism power supply system is built in Matlab/Simulink,and combined with semiphysical test platform,the protection principle,fixed value and full-wave Fourier improvement algorithm of microcomputer protection device are verified by setting faults such as phase short circuit,ground short circuit,excitation failure and power loss,etc.The results show that all the protections can operate correctly and reliably with reasonable coordination,which verifies the reliability of the microcomputer protection device and the feasibility of the improved algorithm.