含DAB型直流变换器的中低压直流配电系统极间短路故障穿越方法

Inter-pole short circuit fault ride through method for medium-and low-voltage DC distribution system with DAB-type DC converter

极间短路故障是直流配电系统中最为严重的故障类型,当含双有源桥(DAB)型直流变换器的直流配电系统中压侧发生极间短路故障时,DAB闭锁,低压侧电压大幅下跌,故障清除后恢复速度较慢。为解决上述问题,提出了一种新型故障穿越方法。通过对传统DAB结构进行改进,增设故障电流阻断模块和补偿电容支路,能在故障发生后迅速识别、切断故障并投入补偿电容。故障持续期间,DAB无需闭锁,依靠模块电容以及补偿电容向低压侧负荷进行供电,有效改善了低压侧电压跌落。故障清除后电容能够快速充电至正常运行状态。PSCAD/EMTDC平台中的仿真结果验证了所提方法能够有效减小中压侧极间短路故障对于负荷的影响,并且具有良好的故障恢复特性。

Inter-pole short circuit fault is the most serious fault type in DC distribution system.In the DC distribution system with DAB(Dual Active Bridge)-type DC converter,when inter-pole short circuit fault occurs at medium-voltage side,DAB blocks,the voltage at low-voltage side drops sharply,and the recovery speed is slow after the fault is cleared.To solve the above problems,a new fault ride through method is proposed.By improving the traditional DAB structure and adding fault current blocking module and compensation capacitor branch,the fault can be quickly identified and cut off right after the fault,and the compensation capacitor is also put into operation.During the fault duration,the DAB does not need to block,and relies on the module capacitor and the compensation capacitor to supply power to the low-voltage side load.It can effectively reduce the voltage drop at low-voltage side,and the capacitor can be quickly charged to the normal operation state after the fault is cleared.The simulative results on PSCAD/EMTDC platform show that the proposed method can effectively reduce the impact of inter-pole short circuit fault on load at medium-voltage side,and has good fault recovery characteristics.