Understanding energy storage systems for commercial and industrial (C&I) applications | Part 2

Commercial and Industrial Applications use 3-phase AC power ranging popularly between 380V to 415V. It uses 3 phases of power with each phase ranging between 220V to 240V. A single AC phase when multiplied by √3 becomes its respective 3 phase voltage. For example, 220V single phase AC power is equivalent to 380V during when it is 3 phase AC power.

Popular commercial and industrial battery systems use 280Ah and 314Ah LFP prismatic cells with high cycle life. Air-cooling and Liquid-cooling systems are commonly used, and both have advantages. The air-cooling system has smaller modules, but the number of modules is higher – the system is easier to assemble. In contrast, the liquid-cooling system has larger modules, which are fewer in number – a compact overall system.

16S1P module is popular for air-cooling battery systems. 15 modules are connected in series to make the system 240S1P (768V). 280Ah cell-based battery system would have a 215kWh rating, and 314Ah cell-based battery system would have a 241kWh rating. This system is operated above 850V DC, so it needs a PCS capable of handling 900V DC.

52S1P module is popular for liquid-cooling battery systems. 5 modules are connected in series to make the system 260S1P (832V). 280Ah cell-based battery system would have a 233kWh rating, and a 314Ah cell-based battery system would have a 261kWh rating. This system is operated above 900V DC, so it needs a PCS capable of handling 950V DC.

The above high-voltage battery system is one cluster, and multiple clusters can be combined in parallel (keeping the voltage the same) to make larger-capacity battery systems.

Power Conversion System (PCS)

PCS is a bi-directional inverter that allows the power to flow in both directions, unlike a solar inverter, which is unidirectional and allows only one direction of power flow. PCS can convert AC power from the grid to DC power to store in a battery system and convert DC power from the battery system to AC power to supply to the grid. PCS used for commercial and industrial applications takes in 3-phase AC power and works with under 1000V DC battery system. 100kW and above capacity rated PCS are generally not Hybrid, meaning they do not support DC solar power input.

Upto 100kW (sometimes higher) rated PCS support 3-phase AC output with neutral and PE (protective earth/ground). Neutral helps to connect with single-phase loads as well as 3-phase loads. Higher-rated PCS generally doesn’t have neutral AC output in 3-phase and only supports 3-phase loads.

Popular PCS sizing for C&I applications are 100kW, 250kW and 500kW.

For a single container system requiring a PCS rating of more than 500kW, multiple PCS are paralleled, but it needs to be ensured that the same number of clusters are connected to each PCS.

Four Modes of Battery System Operation

• Charging Mode: This mode has constant current and voltage charging modes.

• Discharging Mode: The discharging mode is constant AC power discharge mode.

• Standby Mode: The PCS does not work and accept the start-up instructions. The PCS and the BMS will also be set to standby mode when the whole system is in standby mode to keep the power consumption lowest. The protection and remote dispatching of EMS will stay activated.

• Shutdown Mode: Includes fault shutdown and no-fault shutdown. When a fault occurs in the power conversion system (PCS), the inverter power supply immediately disconnects the AC and DC side contactors and shuts down the system to ensure system safety. If the fault is not eliminated, the fault state is maintained; when the fault is eliminated, the start-up command is manually reset.

About the author

Rahul Bollini is an R&D expert in Lithium-ion cells with 9 years of experience. He founded Bollini Energy to assist in deep understanding of the characteristics of Lithium-ion cells to EV, BESS, BMS and battery data analytics companies across the globe. Rahul can be reached at +91-7204957389 and bollinienergy@gmail.com.

This article was first published in EVreporter Dec 2024 magazine.

Also read: Understanding energy storage systems for commercial and industrial (C&I) applications | Part 1