Studies necessary to connect a BESS to the network

Why studies are required

A BESS can behave as a load when charging and as a source when discharging. Furthermore, since it is connected by inverters, its response to faults and disturbances depends on electronic controls and requirements of the network operator.

Therefore, its connection must be analyzed with electrical studies that allow for anticipating impacts.

Load flow

Load flow analyzes voltages, currents, active and reactive power flows, losses and equipment loadability.

In a BESS project it allows you to answer questions such as:

• Does the transformer support the new power?
• Are the bars, cables or lines overloaded?
• Is the tension kept within acceptable ranges?
• What happens when the BESS charges at maximum power?
• What happens when you discharge at maximum power?

short circuit

The short circuit study calculates available fault currents at different points in the system. This allows you to verify whether switches, panels, cells and transformers have sufficient capacity to withstand or interrupt faults.

In BESS it must be considered that inverters do not behave the same as synchronous generators. Its contribution to failure may be limited by electronic controls and manufacturer features.

Protection coordination

The coordination of protections seeks to ensure that, in the event of a failure, the correct device operates and only the affected part is disconnected. In a BESS this includes protections on the AC side, DC side, transformer, connection point, inverter and battery system.

Poor coordination can lead to unnecessary trips, complete disconnections or loss of availability.

Harmonics

BESSs use power electronics. Although modern inverters include advanced filters and controls, possible harmonic distortion must be evaluated, especially in weak networks, installations with drives, solar plants or capacitor banks.

Power quality

In addition to harmonics, phenomena such as voltage variations, flicker, transients, unbalance and interruptions can be evaluated. This allows us to review whether the BESS may affect the operation of sensitive equipment or compliance with applicable limits.

Stability and dynamic response

In larger scale projects, the network operator may request dynamic studies. These evaluate the response of the BESS to faults, frequency variations, voltage changes, current limits, charge and discharge ramps, and active or reactive power control.

Network code

Each country, operator, transmitter or distributor may require specific criteria. Therefore, in addition to technical studies, compliance with the applicable network code or technical standard must be reviewed.

common mistake

A common mistake is to study the BESS as if it were just a load or just a source. Both modes must be analyzed: loading and unloading, in addition to normal scenarios, contingencies and critical conditions.

Conclusion

Connection studies allow problems to be anticipated before they appear on the ground. A well-studied BESS project reduces technical risks, network operator observations, delays and redesign costs.