What are the functions of high-voltage switchgear in energy storage systems?

1. Application in generation-side energy storage systems

In generation-side energy storage power stations, the energy storage system converts the DC power stored in the batteries into AC power via PCS, which is then connected to the power station's main bus or directly to the grid via the high-voltage switchgear.

The core functions of high-voltage switchgear include:

(1) Grid connection control: Ensuring safe connection and disconnection between the energy storage system and the power grid, and cooperating with the PCS to achieve smooth grid connection and disconnection.

(2) Fault protection: Quickly disconnecting the circuit when the energy storage system or the power grid experiences faults such as short circuits, overloads, or overvoltages.

(3) Power distribution: Distributing the power output from the energy storage system to the power grid or the internal load of the power station; monitoring and metering; collecting parameters such as grid connection current, voltage, and power of the energy storage system.

The generation-side energy storage system has a large capacity, typically in the hundreds of megawatts range, and a high grid connection voltage level, mostly 10kV~35kV. Therefore, the high-voltage switchgear needs to possess the following characteristics:High breaking capacity: Sufficient short-circuit breaking current (typically 25kA~40kA) to cope with the large current impact during short circuits in large-scale energy storage systems; High reliability: Adaptable to the outdoor, long-cycle operation environment of new energy power stations, possessing resistance to high and low temperatures, wind and sand, and humidity; Intelligent: Supporting linkage with the power station monitoring system and the energy storage control system (EMS) to achieve remote control, automatic adjustment, and fault early warning.

2. Applications of Grid-Side Energy Storage Systems

Grid-side energy storage is mainly used for peak shaving and valley filling, frequency regulation, voltage support, and emergency backup in power grids. It is a key facility for improving the flexibility and stability of the power grid and is commonly found in substation-supported energy storage and independent energy storage power stations.

Grid-side energy storage power stations are typically directly connected to the power transmission and distribution network. The high-voltage switchgear, acting as the interface between the energy storage system and the grid, undertakes more complex control and protection tasks:

(1) Peak shaving and valley filling control: In coordination with grid dispatch instructions, the energy storage system charges during off-peak hours and discharges during peak hours, rapidly switching between charging and discharging states via the high-voltage switchgear;

(2) Frequency and voltage regulation: When grid frequency or voltage fluctuates, the output power of the energy storage system is adjusted in coordination with the PCS, maintaining grid parameter stability through the rapid response capability of the high-voltage switchgear;

(3) Fault isolation: When a fault occurs within the energy storage system or on the grid side, the high-voltage switchgear quickly disconnects the fault circuit to prevent the fault from spreading to the main grid line, ensuring overall grid safety;

(4) Multi-power source coordination: In power stations with multiple energy storage units operating in parallel, the high-voltage switchgear enables independent control and coordinated operation of each energy storage unit, optimizing power distribution.

3. Applications of User-Side Energy Storage Systems

User-side energy storage is mainly used for peak-valley electricity price arbitrage, emergency power supply, and power quality management. It is suitable for users such as industrial enterprises, commercial buildings, data centers, and hospitals. Its grid connection voltage level is mostly 10kV or 0.4kV (high-voltage switchgear is mainly used at the 10kV level).

User-side energy storage systems connect to the user's internal power distribution network through high-voltage switchgear, achieving bidirectional interaction with the power grid.

(1) Peak-valley arbitrage: During periods of low electricity prices, the system draws power from the grid through the high-voltage switchgear to charge the system, and discharges it during peak hours for the user's own use, reducing electricity costs;

(2) Emergency power supply: When the grid experiences a power outage, the system quickly switches to energy storage power supply mode through the high-voltage switchgear to ensure uninterrupted operation of critical loads (such as data center servers and hospital medical equipment);

(3) Power quality management: Addressing issues such as voltage fluctuations and harmonic pollution within the user's premises, the system works in conjunction with the PCS and high-voltage switchgear to improve power quality.