Research On Protection Strategy Of Hybrid AC/DC Microgrid

With the development of micro grid,the research on topology,operation control,protection strategy and other aspects of micro grid will certainly enter a period of rapid development.However,as far as the current situation is concerned,there are still many deficiencies and unsolved problems.At present,there is little research on the protection strategy of hybrid ac-dc micro grid,and due to the particularity of the fault characteristics of micro grid and the uncertainty of distributed power supply,the protection principle is faced with great difficulties.In order to solve these problems,this paper conducts the following research contents:1)Through the detailed analysis of the control strategy of the distributed power supply integrated into the ac micro grid and the dc micro grid,and the further study of the micro grid control mode,the simulation model of the ac/dc hybrid micro grid was built in PSCAD,and the simulation verified the operational reliability of the model.2)Various fault types are set up in ac microgrid,fault characteristics of distributed power supply with different control strategies are analyzed,the equivalent model of distributed power supply in fault additional circuit is given,and then the fault additional circuit of ac microgrid is obtained,and the correctness of fault direction determination by using mutation direction is verified by simulation.3)The influence of the control strategy of the bi-directional converter on the principle of the direction difference of the sudden change is analyzed,and the setting fault on the ac side of the tie line of the ac and dc bus is simulated and verified;The fault characteristics of dc side are analyzed,the applicable protection principle is given,and the protection scheme of bi-directional converter is proposed.4)The basic function of the microcomputer relay protection experimental device zpt-100 relay protection experimental device was designed.The hardware circuit design part is described in detail,and the design scheme of voltage forming circuit,mode conversion circuit,switching input circuit,switching output circuit and Ethernet interface circuit is given.The dual-core system consisting of ARM+DSP is described and their characteristics are analyzed.The block diagram of DSP based on Fourier algorithm is given,and how to exchange data between DSP and ARM is illustrated.Finally,the protection scheme based on the principle of difference direction of mutation is taken as an example to give a detailed protection development process.To sum up,on the basis of summarizing previous achievements,this paper builds a PSCAD simulation model,conducts fault analysis on the hybrid ac-dc micro grid,and proposes a suitable protection scheme,which provides a guarantee for the reliable operation of the hybrid ac-dc micro grid.