Strategy “Energy Arbitrage” sounds economically attractive, but to make it work, the BESS system must be able to intelligently and securely interact with the national grid. This ability is defined by a technical term: Grid-Tied.
A grid-tied BESS is more than just a plug-in system. It is a complex system that can act as both a load (when charging) and a generator (when discharging).
See more: DEFINITION OF ENERGY ARBITRAGE: CORE PRINCIPLE OF GRID-TIE BESS
1. Definition of grid-tied BESS
Grid-Tied BESS, also known as Grid-Interactive BESS, is an energy storage system designed to operate in parallel with the utility grid. The core component that enables this is Power Conversion System (PCS), also known as bidirectional grid-tie inverter.
Unlike Off-Grid systems that only supply power to individual loads, Grid-Tied systems must comply with strict grid rules regarding voltage, frequency and safety.
2. Role of PCS: Synchronization Gate
The PCS is the technical heart of a grid-connected BESS system, and must perform an extremely complex task: synchronization.
The alternating current (AC) grid has its own “beat”, which is a sine wave with a constant frequency (e.g. 50Hz in Vietnam) and voltage (e.g. 380V). In order for the BESS to be able to smoothly pump energy (discharge) into the grid or absorb energy (charge) from the grid, its current must:
- Frequency Match: Must oscillate exactly 50 times per second, exactly like the grid.
- Phase Matching: The peaks and troughs of the sine waveform from the BESS must coincide perfectly with the peaks and troughs of the grid.
- Voltage Control: The voltage of the BESS must be slightly higher than the grid to “push” electricity in (when discharging) and slightly lower to “suck” electricity out (when charging).
PCS performs all these tasks automatically in milliseconds.
3. Technical functions of charging and discharging in the network
a. Charging function
When EMS orders charging during off-peak hours, PCS acts as a Rectifier clever
- “Absorb” AC energy from the grid.
- Convert this AC energy into DC current with the exact voltage and current required by the battery system (BMS).
- From the grid perspective, the BESS system now acts as a controllable load.
b. Discharge function
When EMS orders a discharge during peak hours, PCS acts as a inverter
- “Suck” DC energy from the battery.
- This DC energy is “inverted” into AC current, perfectly synchronized with the grid (as described above).
- This AC current is “injected” into the Plant’s internal electrical system, reducing the amount of electricity the Plant needs to “suck” from the grid.
From the grid perspective, the BESS now acts as a parallel power source.
4. Mandatory safety functions
A critical technical requirement of any grid-connected system is Anti-Islanding capability.
- Define: This is a mandatory safety function that requires the PCS to immediately stop generating power and disconnect from the grid if it detects a national grid failure (blackout).
- Why? To protect utility workers, they must ensure the line is completely dead before working. If a BESS continues to “push” electricity into a downed grid, it will create a dangerous energy situation that could result in fatal electrocution.
Grid-connected BESS is a technical term that refers to a system that is capable of bidirectional interaction and synchronization with the grid. This platform, implemented by an intelligent PCS, is the technical prerequisite to enable economic strategies such as Energy Arbitrage to take place safely and efficiently.
The in-depth technical analysis in this article is the foundation for a safe and high-performance BESS system. At Taiyo Energy, we translate the most stringent international standards (CSC, Bureau Veritas) into comprehensive energy storage container solutions (BESS & ESS), manufactured right here in Vietnam.
With a strategic factory in Hai Phong, advanced technology transfer and a team of international standard welding engineers, we do more than just metal fabrication – we provide complete energy infrastructure solutions, consulting on custom design of suitable BESS container shells, integrating the most complex auxiliary systems (HVAC, Fire Protection, EMS).
Are you looking for a capable partner to execute your BESS Container project? Contact Taiyo Energy today for detailed technical advice and solutions!
