Power Transfer Capacity Optimization of a Radial Network using Battery Energy Storage Systems

System (BESS) to augment the power transfer capacity of a 220 kV double-circuit radial transmission corridor. The southern zone of the Chilean National Electrical System is employed as a representative case study.

The proposed solution leverages a Grid-booster architecture used as a Remedial Action Scheme

(RAS) that maximizes power transmission normal operating conditions by providing autonomous post-contingency relief. Upon the detection of a contingency on one of the parallel circuits, the BESS initiates high-speed active power injection to mitigate the thermal overload of series equipment on the remaining circuit. This approach effectively increases the operational security limits without the need for immediate phase conductor uprating.

The second phase of this study is dedicated to frequency stability during unintended islanding, which is a critical risk in radial configurations during single-circuit operation due to scheduled outages. The integration of different frequency control strategies is assessed. By combining

Primary Frequency Control (PFC) with event-triggered actuation, the BESS is capable of counteract the rapid frequency decay following a grid separation. These supplementary control logics allow a significant reduction in transmission restrictions during scheduled maintenance or forced outages of parallel circuits. In addition, a conceptual design of the control system architecture is established. Specifically, the monitoring infrastructure requires low-latency communication and localized measurements for the successful coordination of the BESS actuation.

The study also addresses grid strength requirements, utilizing the Effective Short Circuit Ratio

(ESCR) to evaluate potential control interactions in weak-grid scenarios, and suggests the benefits of Grid-Forming (GFM) technology for enhancing the resilience of the isolated subsystem.

To complement the technical study, a systemic cost-benefit analysis is conducted over a 20year lifecycle to validate the economic viability of the proposal. The results show that the project generates highly positive net benefits. The cash flow analysis confirms that the savings in system operational costs outweigh the total capital expenditure and annual operational expenses. Ultimately, the proposed solution not only reduces systemic costs but also guarantees adequate dynamic performance during islanding events, ensuring an uninterrupted power supply for the isolated grid.

Lastly, the strategies and results presented herein provide a versatile framework for any radial interconnection facing operational or islanding-related constraints. The methodology is not restricted by any site-specific features of the Chilean grid and is extensible to any radial system constrained by power transfer limits or islanding stability issues. Nevertheless, a thorough assessment of the underlying transmission constraints is mandatory to verify applicability, alongside a rigorous verification of compliance with grid code standards.