| In recent years, the rapid development of energy storage technology has attracted wide attention in society. Power supply users located at the end of distribution network such as islands and remote mountain areas widely exist in the whole country. Energy storage system is able to provide both active and reactive power support, stabilize node voltage level of the end of power network, improve the efficiency of distribution transformers, enhance distribution network acceptability for new energy and distributed generation and provide emergency power during power system breaks down or is being overhaul. Therefore energy storage technology is one of the efficient technology means to improve the reliability and power supply capability of the end of typical distribution network.The research material in this paper is from the science and technology project "The Key Technology Research and Application Demonstration of Improving Power Supply Capability Based on Energy Storage Technology in the End of Distribution Network" which is took charge by Electric Power Research Institute of Fujian Electric Power Company Limited. This paper aims to achieve the goal of distribution network optimal control strategy and working mode of energy storage system on the island. The main task is to build optimization model of energy storage system. Then use an appropriate calculation method based on the characteristics of the model to solve problems of power output in energy storage system, and study its working mode.This paper begins with a brief introduction of the main problems caused by power supply in the end of typical distribution network and some correlation study of energy storage system and improving power supply capability of distribution network at home and abroad. Secondly, describe the system solution of large-capacity energy storage station, which is mainly composed by the parts of battery system, energy control system, monitoring and protection system and other components.Then, this article studies a kind of charge-discharge control strategy of large-capacity energy storage system based on short-term power load forecasting. After summarizing the various forecasting methods and analyzing the load characters of the island, we select the load derivation method, time series method and gray forecasting method finally. If the prediction accuracy of each prediction method does not meet the requirement, we combine these three methods by optimal weight method to improve the prediction accuracy. The final result of numerical examples demonstrates the validity of the model.On the basis of short-term power load forecasting data, this paper establishes optimization model of energy storage system. The goal of power network is flatting the load curve as much as possible. If take the original load and output power of energy storage system as a whole, which is considered as a new network load, the goal of the models of energy storage system is to flat the new load curve as much as possible. Therefore use the minimum variance in load curve as the objective function of optimization model of energy storage system. Furthermore, use the active set algorithm and genetic algorithm to solve it. The result shows that the active set algorithm and genetic algorithms both can be used to solve the global optimization problems.Finally, this paper makes a comprehensive discussion about application mode of energy storage systems on the island distribution network. Large-capacity storage system access to lOkV distribution network on the island with four working modes:grid-connected mode, off-grid mode, grid-connected to off-grid mode, off-grid to grid-connected model. There are different control strategies in different working modes. The working mode used by this paper can effectively improve the supply reliability of distribution network on the islands. This paper finally adopts the method of failure mode and effects analysis to verify the correctness of the working mode. |
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