Study Of Microgrid Control And Protection Strategy

Microgrid integrates a variety of distributed generation, storage devieces unit and controllable loads together to form a small power system. Microgrid usually contains multiple distributed generation, so when microgrid is connected to power system, the result may be change power flow distribution in the distribution network, which makes the traditional power distribution protection no longer apply to two-way power flow. At the same time because the interface of microgrid is generally connected to the distribution network through the power electronic inverter device, but the magnitude of the short circuit current will be limited by current limiting device in the inverter, when failure occurs within the network, which makes distribution network protection failure for the protection of microgrid within short circuit current amplitude criterion. Therefore, for further study applicable to microgrid protection has great practical significance and practical value.This thesis firstly introduces the background, development situation of microgrid and protection status. The typical control method of distributed generation is researched, then the control strategy of microgrid is proposed and the strategy is verified by MATLAB. This thesis analyzes the impact of the distributed generation accession on the power flow distribution and relay protection of distribution network. Based on the conclusion, the new method of protection is found to meet the protection requirements and features of microgrid.For the microgrid internal protection, this thesis presents microgrid line protection module and distributed generation voltage offset protection module. Microgrid line protection module based on current traveling wave is built. The module is to determine fault types by disturbance voltages and by using wavelet transform in analyzing current traveling waves to identify faulted location. Distributed generation voltage offset protection module is used to protect distributed generation by distributed generation voltage sage. These two protection modules work together for overall protection. The module combines with distributed generation voltage offset protection module for overall protection. The microgrid module is established in MATLAB and set the typical point of failure and fault type, the result verifies the validity of the microgrid protection module.