| Wind, solar and other renewable energy with low-carbon and energy saving advantages,is being attached great importance to all over the world. In recent years, green energy power generation represented by wind power developed rapidly. However, due to the irregular change of wind resources under natural conditions, the output of wind power has the disadvantages of intermittence and randomicity. The large-scale connection of wind farms with power grid has adverse effect on the safety of power system, which will restrict the development of wind power industry. Therefore, the study of how to smooth the fluctuant output of wind power has positive significance for the security and stability of power system and the long-term healthy development of the wind power industry. Energy storage system can effectively stabilize the fluctuations of wind power, improve the capacity of integrated wind power. This paper focuses on using energy storage devices to smooth the fluctuant output of wind power, taking into account the protection of energy storage devices, and the main content is as follows:1. Based on the analysis of fluctuation characteristics of wind power, the configuration of energy storage system in wind farm is presented in this paper, analyzes the principle of smoothing the fluctuant output of wind power by using the low-pass filter, and demonstrates the relation between filter time constant of filter and battery capacity configuration by simulations.2. For the shortage of fixed time constant filter method, the cloud model control algorithm with strong processing ability for uncertainties is introduced in this paper. Based on the theory of cloud model, the one-dimension cloud model controller is constructed to adjust filter time constant timely according to the volatility of wind power. This method reduces wind power volatility rate, but also reduces the configuration capacity of energy storage system effectively.3. Taking into account the wind power smoothing effect and the protection of energy storage devives in wind-storage combined power system, the two-dimension cloud model controller is introduced to the control of the energy storage system. By building a double-layer protection mechanism, battery energy storage system can work in a safe range. The first layer protection mechanism can adjust the filter time constant of low-pass filter timely, and reduce the occurrence of overcharged and excessive discharge to the battery energy storage system while smoothing wind power fluctuations. Considering the delayed effect of filters,the second layer protection mechanism is added to adjust power reference value of energy storage system directly when the state of charge (SOC) of battery close to the security line.This protection mechanism could effectively avoid the out-of-limit phenomenon of battery SOC, and achieve the purpose for prolonging battery life. |
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