Distributed energy storage systems regulate load, absorb peak power, and inject power when power supply suddenly decreases. On-site energy storage can mitigate power fluctuations caused by renewable energy production and output. Distributed energy storage systems offer flexible access locations and are currently widely used in medium- and low-voltage distribution networks, distributed generation and microgrids, and on the user side.
1. Peak shaving and valley filling
In recent years, the peak-to-valley load difference in the power grid has been widening, and the increasing penetration rate of renewable energy generation in the grid has further increased the pressure on grid peak shaving. Utilizing energy storage devices to discharge during peak load periods and recharge from the grid during off-peak periods reduces peak load demand, saves electricity costs, and thus improves load characteristics and participates in system peak shaving. By implementing peak shaving and valley filling, the utilization rate of power system equipment can be improved, and the expansion and upgrading of equipment in the generation, transmission, and distribution links can be delayed or reduced.
2. Improve power supply reliability and power quality
To prevent economic losses for critical users of the power system during grid failures or power outages, configuring energy storage systems of a certain capacity as emergency or uninterruptible power supplies can effectively improve power supply reliability. Furthermore, energy storage systems can achieve efficient and rapid active and reactive power control, quickly respond to system disturbances, adjust frequency and voltage, compensate for load fluctuations, improve system operational stability, and enhance power quality.
3. Frequency Modulation
Energy storage systems, especially battery energy storage technology, offer advantages such as fast response and bidirectional regulation capabilities, making them more efficient than traditional frequency regulation methods. However, due to economic constraints, the capacity of battery energy storage systems is smaller than that of traditional frequency regulation power sources. Therefore, energy storage systems participating in system frequency regulation are generally used in combination with traditional frequency regulation power sources. Regarding energy storage's participation in primary frequency regulation, some literature has studied control strategies for energy storage systems assisting conventional generating units in primary frequency regulation, primarily using improved droop control methods. Energy storage systems can also be combined with wind power to improve the primary frequency regulation capability of wind turbines; in this mode, the amount of wind curtailment from wind farms will also be reduced accordingly. Regarding energy storage's participation in secondary frequency regulation, addressing the problems of slow response speed and low ramp-up rate of thermal power units in traditional frequency regulation, this paper mainly proposes a control method for energy storage systems participating in frequency regulation based on fuzzy control, genetic algorithms, and sensitivity analysis, thereby improving grid frequency regulation performance.
4. Distributed renewable energy consumption
The randomness and volatility of distributed renewable energy generation, such as wind and solar power, can impact the operation and control of the distribution networks they are connected to. Energy storage systems can smooth out active power fluctuations in distributed wind and solar power, improve power quality, and enhance the ability to track planned output, thereby reducing the impact of distributed wind and solar power on the grid and promoting the grid's ability to accommodate high-penetration distributed renewable energy generation. Currently, research on control technologies for improving centralized large-scale renewable energy generation using energy storage systems mainly focuses on smoothing wind and solar power output fluctuations and tracking planned output, with significant achievements to date.
