Research Of Battery Energy Storage System Control Strategy And Capacity Allocation

With the increasing of wind power capacity and penetration, the adverse impacts to the grid have become more and more prominent. The contradiction between the demand of wind farm connected into the grid and the receptivity of the grid is getting expanded. Energy storage systems have been widely used to reduce the wind power fluctuations and improve receptivity of the grid. In response to this situation, this paper analyzes the characteristics of wind power and proposes the control strategy of single type and multi-type energy storage system, and analyses the capacity configuration method. Main contents are as follows.Firstly, this paper propose two methods for stabilizing wind power fluctuation. Wind power is decomposed by EMD into two parts, the low-frequency parts are used as wind power grid-connected value and the high-frequency parts are stored by battery energy storage system (BESS); Based on fuzzy control method, the orders of EMD filter can be adaptively adjusted according to the state of charge (SOC) and fluctuation rate of wind power-output. Simultaneously, according to the state of charge, adjust power outputs of the energy storage to avoid over-charge or over storage discharge. Simulation result shows that the stabilizing effect is remarkable, and gives full play to the characteristics of the energy storage devices, maintaining the stability of state of charge. Another method is to make coordinated control of energy storage battery and power storage battery to smooth the fluctuations of wind power-output. According to the EMD method, IMFs are obtained by decomposing the wind power signal. The low frequency parts are used as grid-connected power and the high frequency parts are the total power of the energy storage system. The total power can adaptively allocate into two parts. We consider SOCs of two different types of battery to correct the power. Simulation results show that the method proposed in this paper can effectively smooth the fluctuations of wind power-output and avoid the over-charging and over-discharging of energy storage system so as to keep the SOCs stable.Secondly, we use EMD method to divide the energy storage power from the frequency domain and assign it to the energy storage battery and the super capacitor. The paper establishes capacity allocation model using the minimum annual cost as objective and SOC, confidence level as constraints based on a fuzzy corrected-chance programming theory. The fuzzy simulation genetic algorithm is used to solve the fuzzy model. The capacity and power of the storage battery and the super capacitor are obtained by simulation calculation. The hybrid energy storage system can meet the requirements of the fluctuations of wind power-output and the characteristics of the storage battery and the super capacitor.Finally, owing to Matlab GUI is very interactive and flexible,.the paper develops an energy storage application platform using Matlab GUI graphical interface, and compiles it as an independent executable file. The software can be used for various wind farm power stabilizing and capacity configuration analysis.