Research On New Topology Of Inductively Coupled Hybrid HVDC Circuit Breaker

The HVDC circuit breaker is one of the key devices for the DC transmission system to isolate faults and maintain stable operation.Domestic research in this field is more advanced than the international level.However,considering factors such as reliability,quick action and economy,domestic investment most of the key control and protection technologies used in high-voltage and UHVDC transmission projects in China do not include HVDC circuit breaker.The DC line protection used in actual projects generally relies on AC circuit breaker to clear and isolate faults.At present,DC transmission is developing towards the direction of multi-terminal DC networks,so it is of great theoretical significance and engineering application value to carry out in-depth research on high-voltage DC transmission lines.This paper analyzes the classification and structure of existing DC circuit breakers and reviews their historical development.The basic structure and working principle of mechanical DC circuit breakers,solid-state DC circuit breakers and hybrid DC circuit breakers are analyzed in detail,and their respective advantages and disadvantages are elaborated by comparing different types of DC circuit breakers.The configuration and topology of circuit breakers in Nan’ao ±160 k V multi-terminal flexible DC transmission project,Zhoushan ±200 k V five-terminal flexible DC transmission project and Zhangbei±500 k V flexible DC transmission project are analyzed in detail,and the development trend and shortcomings of current DC circuit breakers are studied in conjunction with actual project circuit breakers.Firstly,a topology of coupled hybrid high-voltage DC circuit breaker with currentlimiting function is proposed,which consists of through-current branch,transfer branch,buffer energy-absorbing branch,arrester branch and coupling inductor coil.The throughcurrent branch consists of a fast mechanical switch and transfer switch,the transfer switch is a small number of power electronic devices in series,the mechanical switch bears the main overvoltage and has low through-state losses;the transfer branch consists of a large number of power electronic switches;the buffer and absorber branch consists of resistors,capacitors and diodes;the coupling inductor coil is the main current limiting element,which can be quickly put in after detecting a fault.The structure and working principle of this topology such as closing process,breaking process and reclosing process are analyzed in detail,and the parameters of coupling inductor coil,arrester and capacitor of buffer branch in the structure of coupled hybrid high-voltage DC circuit breaker are selected by combining the opening capacity,voltage withstanding capacity,current withstanding capacity,economic characteristics and energy transfer and release process of DC circuit breaker.Finally,the proposed coupled hybrid high-voltage DC circuit breaker topology with current-limiting function is simulated and analyzed by electromagnetic transient simulation software PSCAD/EMTDC.The simulation results show that the proposed structure can not only quickly clear short-circuit faults,but also reduce the number of IGBT devices,lower the cost of the circuit breaker,and increase its economy.