Electricity

Planning battery energy storage systems (BESS) in transmission networks requires accounting for the effects of component failures on supply continuity. This paper proposes a reliability-oriented methodology based on a Mixed Gray Wolf Optimizer (MGWO) to determine BESS locations, rated active power capacities, and technology selection between lithium-ion (Li-ion) and vanadium redox flow (VRF) batteries. The framework incorporates stochastic reliability models for transmission lines, transformers, busbars, and BESS units. The objective is to minimize the equally weighted average of annual energy not supplied (ENS) across single-generator-outage scenarios, subject to technical constraints and an investment budget. BESS sizing refers to rated power in MW; energy capacity and chronological state of charge are not explicitly modeled. The methodology is evaluated using the IEEE 39-bus New England test system with representative hourly demand profiles. Under a maximum investment budget of USD 300 million, the selected solution comprises 338.66 MW of installed BESS capacity, including 280.78 MW of Li-ion storage and 57.88 MW of VRF storage, at a total investment of USD 299.87 million. Relative to the reference case, SAIDI and SAIFI decrease by 13.76% and 13.11%, respectively. During optimization, the fitness value decreases from approximately 0.878 to 0.828 p.u., representing an improvement of about 6.5% relative to the initial solution. Ten independent runs yield final fitness values between 0.8213 and 0.8300 p.u. These results demonstrate the framework’s ability to identify feasible BESS configurations that improve reliability under the adopted modeling assumptions.

This paper proposes an Adaptive Dynamic Binary Whale Optimization Algorithm (AD-BWOA) for solving the Distribution Network Reconfiguration (DNR) problem. The proposed method combines a nonlinear adaptation of the convergence parameter, a hybrid deterministic–stochastic mechanism for position-update selection, a binary transfer strategy, and a stagnation-based stopping criterion to improve the balance between exploration and exploitation and reduce unnecessary search iterations. The algorithm is implemented in Python and integrated with DIgSILENT PowerFactory, which performs the load-flow calculations and verifies the operational constraints of each candidate configuration. The performance of AD-BWOA is evaluated on 69-, 94-, and 135-bus distribution systems through 100 independent runs. The results show that the proposed method consistently reaches the best or reference solutions reported for the evaluated systems, with high repeatability in the 69- and 94-bus cases and competitive performance in the 135-bus system. In addition, the adaptive mechanisms contribute to reducing the number of iterations required for convergence under the adopted stopping criteria. The results indicate that AD-BWOA is a promising and reliable approach for discrete DNR problems, particularly when search-space reduction and adaptive control mechanisms are combined.

Gavdos is assessed as a non-interconnected island without mainland electricity exchange over the adopted planning horizon. A configuration with 340 kWp of photovoltaics, an 800 kW wind turbine, and surplus-fed electrolysis is evaluated for electricity supply and ferry hydrogen. Twelve public HEDNO monthly day-ahead files were concatenated into an 8760 h rolling-year demand series. RETScreen-based F-chart solar calculations and a Weibull wind distribution (k = 2) provided twelve representative monthly 24 h renewable profiles, mapped by month and hour to the dispatch chronology. Renewable generation first serves demand; deficits are assigned to conventional generation and surplus to electrolysis. Annual demand is 662.630 MWh, of which renewables supply 650.633 MWh directly (98.19%); the residual deficit is 11.997 MWh across 419 h. The 302.6 kW baseline electrolyzer produces 34.488 t H₂ year⁻¹ gross versus a ferry demand of 33.890 t H₂ year⁻¹. Although daily production is lower than demand in 130 days, accumulated hydrogen keeps the gross inventory non-negative. The maximum seasonal drawdown is 947.4 kg, giving a usable hydrogen-mass requirement of 1133.1 kg including a two-day reserve. The results demonstrate gross-production compatibility under the adopted assumptions; net ferry-fuel adequacy requires detailed assessment of component operation, auxiliary loads, storage, delivery, and vessel duty.