| China is a vast country which has a wealth of wind, solar and other renewable energy resources. With the development of distributed generation and microgrid technology, the standalone microgrid system with kinds of distributed generations is one of the most effective ways to solve the problem of remote areas power supply. Because of the random and uncertain power output for the renewable energy, so deploying some energy storage capacity into the microgrid system, at the same time considering the controllable load can ensure its safety and stability, improve its reliability and flexibility distinctly. Based on the above background, this paper carry out the following research work:Firstly, this paper introduced the overall structure of the standalone microgrid system with controllable load and the power model and operational characteristics of its subsystem. It Described the life prediction model for energy storage equipment and the controllable model of groundwater exploitation load emphatically.Then, a power energy allocation strategy coordinating the renewable energy generation, battery energy storage and controllable load is presented with consideration of the controllable load’s auxiliary power regulation characteristic. A model of sizing the energy storage in standalone microgrid is developed considering the unfixed cycle life of battery storage, which using the minimum annual cost as the objective function, charging/discharging power, the state of charge and so on as constraints. The proposed model is carried on a typical wind/photovoltaic hybrid system in Northwest China with load of mining underwater. The results demonstrate that the proposed model is effective and the controllable load is beneficial to accommodating the variability of renewable energy generation.Finally, This paper investigates the sizing of the hybrid energy storage in the combined wind-solar standalone microgrid system with controllable load, considering the complementary characteristics of the battery energy storage and the supercapacitor energy storage. Based on the spectrum analysis of the net load power, the power allocation strategy coordinating the renewable energy generation, battery energy storage, supercapacitor energy storage and controllable load was proposed with consideration of the controllability of load. By analyzing the cost structure of the hybrid energy storage system, a model of sizing the hybrid energy storage in standalone microgrid is developed. Genetic algorithm is used to achieve the minimum annual comprehensive cost of standalone microgrid system. The results demonstrated that the proposed model was technological rationality and economical efficiency, and the significance of considering the controllability of load to the power balance of microgrid system is analyzed deeply. It provides the theoretical and technical basis for the hybrid energy storage planning in the standalone microgrid system. |
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