Energy storage is a crucial component of the power system’s “generation-transmission-distribution-consumption-storage” process and is fundamental to constructing a new energy microgrid. Renewable energy sources like wind and solar power are intermittent and unstable, often plagued by issues like “wind curtailment” and “generation curtailment.” By buffering electrical energy through storage systems, power quality can be optimized, and the stability of new energy microgrids can be enhanced. So, what role does an energy storage system play in a microgrid? Let’s explore this with insights from Polar Star Smart Grid Online.
Definition of a Microgrid:
A microgrid is a vital part of a smart grid, integrating internal power sources and loads for coordinated operation. It can function in coordination with the main grid or operate independently, meeting and even exceeding user requirements for power quality, reliability, and safety.
There are two typical operational modes for microgrids:
Grid-Connected Mode: When both the main grid and the microgrid are functioning normally, the microgrid operates in parallel with the main grid. The microgrid’s generated power primarily meets local load demands, with any excess or shortfall managed by the main grid.
Island Mode: When a fault or severe power quality issue is detected in the main grid, the microgrid disconnects from the main grid and operates independently to ensure the continuous operation of critical loads.
Key Roles of Energy Storage in Microgrids:
1. Enhancing the Stability of Distributed Energy:
Distributed energy sources like solar, wind, and biomass are significantly influenced by environmental factors such as sunlight, temperature, wind speed, and climate, resulting in random and unstable power generation. In the event of a disconnection from the main grid, the output power of distributed energy in a microgrid fluctuates with environmental changes, making it challenging to provide stable power to the load. By integrating an energy storage system, managed by an Energy Management System (EMS), distributed energy sources, storage systems, and the main grid can be collaboratively controlled. This stabilizes the fluctuations in distributed energy output, ensures stable power delivery, and increases the local utilization rate of distributed energy, avoiding the transmission pressure and power losses associated with long-distance transmission to the main grid.
Additionally, the energy storage system can continue to supply power to critical loads during nighttime or maintenance periods of distributed energy, reducing power outages.
2. Improving Power Quality for Users:
When a microgrid is connected to the main grid, the power quality must meet national standards, including parameters like power factor, voltage asymmetry, current harmonic distortion rate, and voltage sags. Without an energy storage system, the inherent characteristics of distributed energy sources can compromise power quality, particularly voltage stability. The deployment of an energy storage system significantly enhances microgrid power quality. Through the control of the Power Conversion System (PCS) within the storage system, it stabilizes power output while adjusting the active and reactive power output to the microgrid, addressing voltage sags and drops.
When the main grid experiences rapid voltage fluctuations, the energy storage system provides quick power buffering, rapidly absorbing or supplementing power to support active and reactive power, thereby stabilizing voltage variations. The energy storage system also offers harmonic suppression functionality for the microgrid.
3. Peak Shaving:
In a microgrid, the energy storage system can store excess energy generated by distributed sources during off-peak periods and release it during peak demand, balancing load requirements. Serving as an energy buffer, the energy storage system is indispensable in a microgrid. By meeting peak load demands, it reduces the required capacity of generators or transformers.
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