BESS Grid Integration Studies
Using PSS®E

The CEA advisory dated 20 November 2025 provides key clarifications for studying standalone BESS and hybrid renewable projects connected to the grid. Before preparing the PSS®E model, the installed capacity must be checked against the final connectivity grant.

The following details must match:

• Solar capacity
• Wind capacity
• BESS capacity
• PCS quantity and rating
• Approved connectivity quantum

The installed capacity and technology breakup used in the simulation model must match the connectivity grant. When the number of PCS units in the model exceeds the minimum quantity required to meet the granted capacity, the applicant may need to apply for installed-capacity enhancement.

For example, consider a 100 MW BESS project using 5 MW PCS units.

The minimum required quantity is:

If 21 PCS units are modelled, the installed capacity becomes 105 MW. This difference must be justified or corrected before submission. A capacity summary should be prepared before starting the study. It should include the connectivity quantum, PCS rating, PCS quantity, maximum charging power and maximum discharging power.

Steady-State Study Scenarios

The steady-state analysis is used to check voltage performance, equipment loading and reactive power compensation requirements.

For standalone BESS, two cases are required:

• Charging mode
• Discharging mode

The active power at the POI must remain within the approved connectivity quantum.

The dispatch of solar, wind and BESS must follow the proposed operating method.

Dynamic Study Scenarios

Dynamic studies are required to check the plant response during faults, voltage changes and frequency disturbances. For solar with BESS, the main dynamic case should consider solar operation with BESS charging. The BESS discharging mode must also be studied for frequency-response tests. The same approach applies to wind with BESS.

For solar, wind and BESS projects, the main dynamic case should consider solar and wind operating while the BESS is charging. For standalone BESS, the main dynamic case should consider discharging mode. Charging mode must also be checked for frequency-response studies. Before applying any disturbance, a no-disturbance simulation should be completed.

Immediate Frequency Response

BESS can provide fast active power support during a frequency disturbance. The advisory requires an immediate real power primary frequency response within one second. The minimum response must be 10% of the maximum AC active power capacity when the frequency deviation exceeds 0.3 Hz.

For a 200 MW BESS:

The PSS®E simulation should clearly show whether the BESS changes its active power by at least 20 MW within one second. For hybrid projects, the combined plant response alone is not enough. The individual responses of solar, wind and BESS must also be checked. This helps confirm which source is providing frequency support.

Power Quality Study Conditions

For solar, wind and storage hybrid projects, power quality studies must cover different active power levels from 10% to 100%. The harmonic current contribution of each source must match its dispatch in the selected operating condition.

Two BESS cases are required:

• BESS charging
• BESS discharging

Other operating conditions may also be studied when they are more critical for harmonic filter design. The grid impedance used for power quality studies must be based on the actual grid fault MVA and actual X/R ratio.

Projects Connected at a Common POI

When several plants share a common transmission system and connect at one POI, the later project must consider the earlier approved plant models. The steady-state, dynamic and power quality studies must be performed using a consolidated model.

For example:

• Plant B connects first and studies Plant B.
• Plant A connects later and studies Plant A plus Plant B.
• Plant C connects last and studies Plant A, Plant B and Plant C.

This helps identify interaction between multiple converters, plant controllers and shared transmission equipment.

Final Submission Check

Before submitting the BESS PSS®E study package, confirm that:

• ✓Installed capacity matches the connectivity grant
• ✓Charging and discharging cases are included
• ✓POI power remains within the approved quantum
• ✓Dynamic initialization is stable
• ✓Frequency response is tested in both directions
• ✓Individual source responses are plotted
• ✓Reactive power capability is checked
• ✓Transformer loading is within limits
• ✓Common POI projects use consolidated models
• ✓Study cases, dynamic data and user manuals are included