Research Of The Relay Protection And The Algorithm Of The Distribution Network With Dg

Since the<renewable energy law> was promulgated in2006, Our DG interconnection capacity and control technology developed rapidly. However, too large DG capacity may make the traditional relay protection scheme unapplicable. Aiming at DG control strategy in two operating modes, New relay protection solutions for the distribution network containing DG, distribution network fault location algorithm Containing multiple DG, this article has conducted a series of research.Firstly, this paper established the mathematical model of DG inverters dividing DG into two categories, namely power and control. And designed the corresponding controllers (PQ controller and V/f controller), The LC filter to eliminate higher harmonics. Tracking grid voltage phase using SPLL technology. This article establish three micro grid models containing DG using MATLAB/Simulink to Made a simulation for power distribution and current voltage waveform and harmonic content of. the DG under different operating mode in island mode and the parallel mode.Secondly, conducted modeling and analysis research in influence of DG’s access to distribution network to relay protection. Several main factors influencing the short-circuit current are analyzed And then studied its impact on distribution network of relay protection. And then established the model of distribution network containing DG in the PSCAD/EMTDC software. Simulated and analysed the influence of distribution network containing DG to relay protection under different fault location and DG capacity. MATLAB software is used to calculate DG injection capacity and short circuit position changes, the value of the short circuit current through protecting device. Finally, carrid a simulation and calculation in the PSCAD/EMTDC software, Verified the correctness of the analysis results Through the comparation of theoretical calculation results of the MATLAB and the simulation results of PSCAD/EMTDC.With three-step current protection principle as constraint conditions, This article Build a model to analyze the DG access capacity and grid location of the different impact on short circuit current, mainly analyzed adaption of relay protection setting conditions. When grid position fixed DG capacity and DG capacity fixed grid location changes. Solve the problem including DG distribution network of relay protection with the combination of Longitudinal direction protection and overcurrent protection. Finally proves the reliability of the protection scheme in the PSCAD/EMTDC software with simulation of a DG interconnection of10kv distribution network system.Finally, aiming at fault location problem of distribution network systems containing several DG, locating the through the method of comparing the amplitude amplitude of the current nodes and Relations of the current phase between the two nodes. And put forward a new fault location algorithm making use of the maximum fault characteristic information criteria, The algorithm has certain fault tolerance and the quickness of search in fault location.