Current Limiting And Protection Of Low-voltage DC System

Depending on higher efficiency for distributed generations,larger power transportation capacity,convenience to network,being more economical,lower dissipation and higher power quality,the low voltage DC power system becomes the hot topic of construction and development in future distributed network.However,the engineering practice,especially in protection field,is immature.Many key problems in fault current limiting,location and isolation arise in practice.Moreover,still plenty of work and research should be accomplished to propose a fast protection scheme considering economy and reliability.To solve above problems,this paper sums up and concludes plenty of domestic and foreign research achievements to find the innovation and deficiency of previous work.Thus,some key problems in current low voltage power system has been abstracted as following research points.Some research work base on these points is accomplished as follow:Firstly,at the basis of similated model of low voltage power system,the selfblocking and fault ride-through capacities of converters are proposed and its significance for low voltage DC power system protection is illuminated.The topology structure and self-blocking and fault ride-through capacities of different converters are analyzed in low voltage DC power systemSecondary,as the main converter in system does not possess the self-blocking capacity,fault analysis is conducted about that.The difference between high and low valtage system is found and a new fault analysis theory applying to low valtage system is presented.The applicable fault current limiting measures and revelent design method for current limiter are proposed at the basis of fault analysis.Thirdly,according to the difficulties of fault location in low voltage DC power system,a new-type fault location unit and relevant location algorithm are targetedly proposed.Finally,aiming at the problem of DC circuit breaker development,a isolation method bases on semiconductor device and AC circuit breaker are proposed to complete the whole protection scheme.The protection scheme is economic,practicable and reliable.All the theories are vertified by similated experiments in PSCAD/EMTDC simulation environment.The results indicate the rationality and effectiveness of proposed theories.The protection scheme solves some key problems in low voltage DC power system protection and promote the generalization and economical efficiency of distributed level DC power system project.