An energy storage coordinated control strategy based on model predictive control for smoothing wind power fluctuations

Abstract

Based on the nature of wind, wind power fluctuations can cause significant problems in the distribution network. One of the solutions is to integrate an energy storage system with wind farm to mitigate the output power fluctuations. Therefore, an energy storage coordinated control strategy based on model predictive control is proposed to smooth minute-scale fluctuations of wind power. By analysing the limitations of traditional control strategy, four operating modes of battery energy storage system which are determined by the predicted state of charge obtained by model predictive control, are designed to avoid violating the state of charge limitation, and an energy state feedback control is designed to adjust the initial power allocation orders of batteries. Finally, the effectiveness of the proposed control strategy can be verified by the real-time digital simulator. The results indicate that the developed approach reduces the switching times of batteries and improves the ability of the battery energy storage system to smooth wind power fluctuations significantly.

Torque Limit-based Inertial Control Method Based on Delayed Support for Primary Frequency Control of Wind Turbines

“…The sudden power drop easily causes the SFD, which can even be worse than the condition without the power support provided by the WT. To address this problem, the TLIC method was proposed in [12], [14]. The linear relationship is established between the TLIC power and the rotor speed, so the power decreases gently with the decrease of rotor speed, thus avoiding the large and sudden power drop.…”

“…Different from virtual inertial control and droop control responding to the frequency variation, the PFCs proposed in [8]- [14] preset the power curves. When the frequency event (e.g., the load increase) occurs in the grid, the electrical power of WTs is set according to the curve which is irrelevant to the frequency variation, such as the curve obtained by SIC [8]- [11] and TLIC [12]- [14].…”

“…Wind turbines (WTs) are urgently required to participate in the primary frequency control (PFC) [1]- [5]. According to whether the electrical power of WTs is related to the frequency, the existing PFCs can be divided into two types: PFC strategies responding to the frequency variation such as virtual inertial control [6], [7] and droop control [7], and PFC strategies presetting the power curves such as stepwise inertial control (SIC) [8]- [11] and torque limit-based inertial control (TLIC) [12] - [14]. This paper mainly focuses on the second type.…”

“…2) Improved methods with the characteristic of gradual power drop [12] - [14], [16] - [18]. Considering that the steep power drop is the root cause of SFD, the improved methods were proposed so that the electrical power of WTs varies along with the rotor speed, e. g., TLIC [12], [14].…”

“…2) Improved methods with the characteristic of gradual power drop [12] - [14], [16] - [18]. Considering that the steep power drop is the root cause of SFD, the improved methods were proposed so that the electrical power of WTs varies along with the rotor speed, e. g., TLIC [12], [14]. Since the rotor speed decreases gradually with the release of kinetic energy, the electrical power of WTs in the frequency support stage decreases slowly, thus avoiding the impact of the exit of WTs on the active power balance.…”