Abstract
In a large-scale wind power generation system, active power fluctuation caused by random wind speed will have a serious impact on the power grid. In order to limit the power fluctuation that wind farm transmits to the power grid and protect the energy storage battery, this paper has proposed a model predictive control method of hybrid energy storage by optimizing the objective function and constraint conditions. Firstly, the mathematical model of predictive control method has been established in a wind power system with hybrid energy storage. Then, with the goal of minimum energy storage output and maximum charging-discharging capacity of the super-capacitor, the predictive control process has been optimized. Meanwhile, the constraint on the output power of the battery has been dynamically changed to reduce its charging-discharging switching frequency, and the model predictive control strategy of the hybrid energy storage has been formed. Finally, compared with the model prediction control method of single energy storage, based on a wind farm data, the simulation results show that the proposed method can smooth wind power fluctuation, reduce the time that the power does not satisfy the fluctuation requirements, ensure the capability of the super-capacitor, and reduce the charging-discharging switching frequency of the energy storage battery.
Highlights
In the process that large-scale integrated wind farm transmits power to power grid, its volatility and randomness have a great impact on the safe operation and reliable control of power systems[1] [2]
2) Under the model predictive control method of a single energy storage battery system with rated power of 9MW and capacity of 1MWh, the maximum fluctuation is 8.88MW, and the time required to meet the grid-connected power fluctuation is shortened to 4 minutes, as shown in area A in Fig 4, the reduction is 97.08%. 3) The proposed method is applied to hybrid energy storage systems with the same power and capacity to limit the grid-connected power fluctuation to 5MW, which fully meets the grid-connected power fluctuation requirements
The number of charge and discharge switching is only 12 times, compared to single energy storage battery the time is reduced by 89.74% The energy storage battery charge and discharge energy is reduced by 73.18%, which means that the hybrid energy storage model predictive control strategy proposed in this paper significantly reduces the charge and discharge switching number and energy of of the energy storage battery, ensuring the energy storage operation life
Summary
In the process that large-scale integrated wind farm transmits power to power grid, its volatility and randomness have a great impact on the safe operation and reliable control of power systems[1] [2]. On the basis of this idea, the literature [18] combined with the model predictive control idea, while smoothing the wind power fluctuation, greatly reducing the charge-discharge switching frequency of the energy storage battery, and verified the superiority of the proposed method from the perspective of economic cost. Literature [23] used the model predictive control theory to obtain the total energy storage load of the energy storage system with smooth wind power, and based on the characteristics of the battery and super-capacitor, the first-order low-pass filter cutoff frequency was designed using the Hilbert-Huang Transform. In the study of smoothing wind power fluctuations, many literatures have proposed a number of energy storage battery and hybrid energy storage coordinated control methods, the discussion about the frequent charge and discharge constraints of energy storage batteries and the optimization of super-capacitor capabilities are less.
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