Research Of High Voltage DC Circuit Breaker's Optimization Control Strategy

With the reduction of traditional fossil energy reserves,renewable energy is becoming increasingly important strategically.Mass access of renewable energy presents great challenges to the consumptive ability of power grid,one effective solution is DC grid technology based on conventional and flexible DC technology.However,the protection technology of DC grid is one of the major challenges,because,compared to the AC system,DC power system has higher requirements for the fault response time,and then the traditional protection of AC system is not suitable for DC system.High voltage DC circuit breaker could isolate healthy sections in DC grid from sections with faults,which avoids the blocking of all converters and has the healthy sections unaffected during the fault,and therefore is the key equipment of the DC power grid.There are three different DC circuit breaker technologies: Mechanical DC circuit breakers,semiconductor-based DC circuit breakers,and hybrid DC circuit breakers.Among which hybrid DC circuit breakers could break current fast and controllable with no special cooling equipment and small-state losses.So it's the main direction of high-voltage DC circuit breaker research.A new hybrid DC circuit breakers with simple structure could break current without arc,which accelerates the breaking process and meet the requirement of fast respond.Meantime,its current limiting function could keep the fault current fluctuating around a reference value,and then an additional time is provided for the grid-wide protections to select the appropriate protection actions,which has important engineering application value.In the paper,current research status of high-voltage DC circuit breakers is analyzed first which shows that the hybrid DC circuit breakers with the arcless breaking function are of practical importance.Then the arcless breaking and current limiting control is mostly analyzed,and new breaking and current limiting control method are proposed,which could lower the fault current spike and energy absorbed by arrestors,and therefore prolongs its service life and improves system reliability.