Research On The Fault Location And Fault Restoration Strategy For Microgrid

In twenty-first Century, there is large dependence on electric power industry whether the progress and development of economic society nor about human basic necessities. But the sharp drop in traditional energy and the pollution have caused people to start looking for new alternative energy sources. So the new energy, such as wind energy, solar energy and other new, renewable, less polluting energy are considered to be used by humans. So a new generation technology——Distributed generation technology had been proposed. These distributed generations are connected to the distribution network in the form of microgrid. Therefore, the development of microgrid technology is a hot research topic at home and abroad at present. Microgrid is usually composed of a variety types of distributed generations, protection devices, load and energy conversion devices to be an independent operation or grid operation system. As an independent small power system, microgrid can control the output power of large power grid and microgrid. Due to the access of the distributed generation, the stable operation of the system is affected. The premise of stable operation of microgrid is to control the occurrence of faults. But the traditional method of fault location and fault restoration in distribution network is no longer suitable for microgrid. So it is very necessary to study the fault location and fault recovery strategy of microgrid.On the basis of analyzing the characteristics of microgrid and traditional large power grid, fault location and fault recovery strategy are proposed in this paper. The recovery of the power supply is divided into two parts after the fault of the microgrid.The first part is the fault location after the fault of microgrid. Based on the characteristics of bidirectional power flow structure and small fault current of microgrid, method of combination of Hilbert-Huang Transformation and Three terminal traveling wave fault location without the influence of wave velocity and line sag is used. Firstly, Intrinsic Mode Function of the fault current traveling wave signal is extracted by the method of Empirical Mode Decomposition. Then IMF1 is analyzed by Hilbert Spectrum Analysis, and the corresponding instantaneous frequency spectrum is obtained. According to the abrupt change point of the instantaneous frequency spectrum, it is accurate to detect the time of the first arrival of the traveling wave. Use MATLAB to build simulation model and carry out the simulation experiment by changing the fault type of the module. According to analysis of simulation results of microgrid under different fault types, it is concluded that the method proposed in this paper is effective and feasible, and it can meet the requirements of positioning accuracy.The second part is the power recovery after the fault of the microgrid. Fault recovery of microgrid is essentially a network reconfiguration after fault, that is to adjust the contact switch and the section switch of the line. The fault recovery of microgrid is a nonlinear combination problem with multiple constraints. It needs a long time and more iterations to use a single algorithm. In this paper, a hybrid algorithm based on adjacency matrix and binary differential evolution is proposed. The fault recovery of microgrid is a optimization problem in discrete space and needs binary encoding for traditional evolution algorithm to form binary differential evolution algorithm. Firstly, the adjacency matrix algorithm is used to screen the topology of the network. Then, the improved differential evolution algorithm is used to find the optimal algorithm and recover the power supply fast for non-fault loss area. The 33 node system uder the microgrid prototype and microgrid standard given by the United States electrical reliability technology solutions is regarded as the research object and do simulation analysis to micro system. The result shows that the algorithm can solve the fault recovery problem of microgrid, the actual effect is good and it can be applied to the actual microgrid operation.