Protection Scheme And Key Technology’s Research For Large Scale Battery Energy Storage Station

With the development of society, the demand for electricity isincreasing. New energy such as wind, solar has been developedincreasingly. However, due to the instability of new energy, such as windelectricity, the large scale new energy is difficult to access to the powersystem. The battery energy storage station can store electrical energy andsmooth wind power output to some extent. The large capacity new energycan be connected to the network through energy storage system. Thismethod is not only environmental friendly, but also can improve theeconomics of the power system. The rapid economic development hasresulted in the rapid growth of electricity consumption, and also makes thedaily load peak and valley difference gradually widening. If there are noeffective regulating methods, the power system must increase its sparecapacity to meet the peak load demand, which is not economical. Thebattery energy storage station can store the excess power in the trough ofpower system, and release energy to power system to meet the electricity demand during peak periods, which makes the energy storage stationbecome an important way to achieve load shifting. Now more and morebattery energy storage stations are applied to power system, it is necessaryto study the station’s structure, internal grounding way and protectionconfiguration, and optimization algorithms for load shifting. The aboveproblems are studied in theory in this paper, the key findings are as thefollowing:1. The basic structure of battery energy storage station is studied andgeneralized, and the simulation model on the PSCAD/EMTDCsoftware platform is built to analyze the operating characteristics andfailure characteristics of the battery energy storage station.2. Three grounding modes of DC system are firstly put forward in thispaper. The characteristics of electrical quantities of various groundingmodes based on pole-to-pole fault analysis and pole-to-earth faultanalysis are compared. Meanwhile, the fault feature with the influenceof transition resistance is taken into consideration. Then, the groundcoordination between the AC and DC side from the perspective ofstable operation of the entire system is studied and the steadyoperation characteristics of different kinds of grounding modes areanalyzed. Finally, the general principles on how to choose the grounding mode for DC system of large scale battery energy storagestation are proposed.3. Protection strategies are put forward based on the fault analysis. At last,the characteristics of the faults and protection strategies are verified bythe simulation of PSCAD/EMTDC.4. The load shifting algorithms based on power difference is proposed,and load shifting is achieved by using such conditions as the capacityof the battery pack, charge and discharge power and daily load curve.The advantage of power difference algorithm is embodied bycomparing with constant power algorithm. Finally the optimizationresults are verified through simulation calculation.The result in this paper provides valuable theoretical basis andpractical guiding significance for the application of large scale batteryenergy storage station.