Search Results (4,471)

Autonomous navigation in complex environments requires efficient and reliable road-network representations for fast path planning. However, traditional grid and skeleton-based approaches often suffer from high computational cost and limited path quality. This paper proposes a Hierarchical Topology-Metric Road Graph (HTMRG) framework for autonomous navigation of unmanned ground vehicles (UGVs). The method automatically constructs a hierarchical road graph from grid maps by identifying key intersection structures and generating smooth corridor and intersection connections. In addition, a dedicated start–goal insertion strategy is developed to enable efficient graph-based path planning in previously unexplored scenarios. Extensive simulations and real-world experiments demonstrate that the proposed method can automatically construct hierarchical road graphs and generate smooth, high-quality paths with improved planning efficiency and robustness. The HTMRG framework has also been successfully integrated into a UGV system, validating its effectiveness and practicality in real-world navigation scenarios. Full article

Intelligent energy management systems are increasingly necessary for integrating renewable energy sources within microgrids. This paper investigates the application of a reinforcement learning (RL) neural network to optimize the operation of an electrochemical storage system in an environment composed of residential loads, commercial loads, and a photovoltaic plant, all connected to the grid. A dataset combining market purchase prices, photovoltaic generation, and residential and commercial load profiles was generated and used to train a Twin Delayed Deep Deterministic Policy Gradient (TD3) agent with the primary goal of deriving a reliable and adaptive post-training policy capable of maximizing photovoltaic self-consumption, minimizing operational costs through intelligent price arbitrage, and ensuring strict compliance with battery physical constraints. The system state includes battery state of charge, load demand, PV generation, and normalized market purchase prices, whereas the action represents the battery’s charge/discharge power, which is restricted from exporting energy to the grid. Results show that the agent learns to effectively store surplus PV energy and minimize grid dependency through dynamic charge management. The proposed approach outperforms strategies based solely on storing surplus self-generated energy and maintains the battery within safe operational limits. Tests with previously unseen data demonstrate robust, adaptive, and economically efficient energy management, highlighting the potential of reinforcement learning in intelligent energy systems. Full article

Wind power generation exhibits pronounced volatility and intermittency, and direct grid connection may cause instability in grid frequency. To address this issue, this paper proposes an optimisation strategy for hybrid energy storage systems to mitigate wind power fluctuations, integrating lithium-ion batteries with supercapacitors within wind power systems. Firstly, the grid-connected power of wind turbines and the reference power of the energy storage system are determined through dynamic weight adjustment using a weighted filtering algorithm combining adaptive exponential smoothing and recursive averaging algorithms. Secondly, the fish-eagle optimisation algorithm is employed to refine variational modal decomposition parameters. The modal components derived from decomposing the energy storage system’s reference power are converted into Hilbert marginal spectra. Following determination of the cut-off frequency, high-frequency signal components are managed by supercapacitors, while low-frequency components are handled by lithium-ion batteries. Finally, an optimised configuration model for the hybrid energy storage system is constructed to minimise the annual lifecycle target cost. Case study analysis demonstrates that this approach effectively smooths fluctuations in wind power output while fully leveraging the complementary characteristics of both energy storage types, achieving a balance between system economics and overall performance. Full article

The increasing variability of residential demand, combined with the expansion of distributed generation and electric vehicles, has introduced new challenges to the stability of Smart Grids (SGs). Centralized management models lack the flexibility required to operate under these conditions, reinforcing the need for scalable and data-driven architectures. This study proposes an energy management solution based on microservices, supported by hybrid communication in Low Power Wide Area Networks (LPWAN), integrating Long Range Wide Area Network (LoRaWAN) and LoRaMESH to enhance connectivity, local resilience, and reliability in data acquisition for Internet of Things (IoT) and Demand Response (DR) applications. A prototype composed of a Smart Meter (SM), a Data Aggregation Point (DAP), and a Concentrator (CON) was evaluated in a controlled environment, achieving Packet Delivery Rates above 97%, an average RSSI of −92 dBm, and a Signal-to-Noise Ratio close to 9 dB, validating the robustness of the hybrid communication. At a larger scale, data from 5567 households in the Low Carbon London (LCL) project were used to generate representative Load Profiles (LPs) through seven aggregation and clustering techniques, consistently identifying the 18:00–21:00 interval as the critical peak, with demand reaching up to 42% above the daily average. Fourteen load shifting algorithms were evaluated, and the Hybrid Adaptive Algorithm based on Intention and Resilience (HAAIR), proposed in this work, achieved the best overall performance with a 1.83% peak reduction, US$65.40 in cost savings, a reduction of 60 kg of CO₂, a Comfort Loss Index of 0.04, resilience of 9.5, and reliability of 0.98. The results demonstrate that the integration of hybrid LPWAN communication, modular microservice-based architecture, and adaptive DR strategies driven by Artificial Intelligence (AI) represents a promising pathway toward scalable, resilient, and energy-efficient SGs. Full article

Driven by the large-scale application of distributed power sources, power systems are facing escalating frequency stability challenges in terms of inertia reduction. In this weak grid scenario, grid-connected converters are increasingly required to operate as high-inertia grid-forming (GFM) units to participate in the regulation of grid frequency. However, this high inertia will seriously impair the transient stability of GFM converters. To resolve the conflict, an adaptive hybrid synchronization-based transient enhancement strategy is proposed. Through integrating the traditional droop phase angle with the phase-locked loop-locked grid phase angle, the proposed control can effectively enhance transient stability under the full fault range from mild to severe voltage sags (with a voltage sag depth of up to 90%) without sacrificing system inertia. Moreover, benefiting from this, the proposed hybrid synchronization scheme also avoids the secondary overcurrent issue that occurs after fault clearance in traditional GFM control. Finally, the simulation and experimental results under various voltage sags verify the effectiveness of the proposed control strategy. Full article

The fast growth of electric vehicles (EVs) and renewable energy motivates reliable charging infrastructure with balanced energy management and good power quality. However, conventional converter controllers like proportional and integral (PI) and fuzzy logic controllers (FLCs) exhibit slow dynamic response, poor adaptability to varying solar conditions, unbalanced energy management, low power quality, and higher total harmonic distortion (THD).To overcome these limitations, this work proposes an adaptive neuro-fuzzy inference system (ANFIS) controller for balanced energy management and improved power quality in EV charging stations. The ANFIS controller is a combination of a fuzzy inference system (FIS) and a neural network (NN). The FIS provides the best maximum power point tracking and robust control during changing solar PV conditions. The NN optimally controls the flow of power between the solar PV system, energy storage battery (ESB), EV, and utility grid. The entire system is simulated in MATLAB/Simulink. It consists of a PV system with a capacity of 2kW, an ESB with a capacity of 10kWh and an EV battery with a capacity of 4kWh, which are linked by bidirectional DC/DC converters. A 30kVA bidirectional inverter, along with an LCL filter, is connected between the 500V DC bus and 440V utility grid, allowing for both directions. The results validate the effectiveness of the proposed ANFIS controller in terms of DC bus voltage stability, faster dynamic response, enhanced renewable energy utilization, improved efficiency to 98.86%, reduced voltage and current THD to 4.65% and 2.15% respectively, reduced utility grid stress, and enhanced energy management compared to conventional PI and FLCs. Full article

The integration of electric vehicles into microgrids demands advanced energy management to coordinate charging with renewable generation and storage resources. This study presents a cohesive and comprehensive evaluation of four distinct optimization strategies—genetic algorithm (GA), particle swarm optimization (PSO), ant colony optimization (ACO), and mixed-integer linear programming (MILP)—in coordinating EV charging and energy dispatch within a 55 MW grid-connected microgrid that includes photovoltaic, wind, battery energy storage (BESS), and bidirectional EV systems. Beyond numerical outcomes, this work emphasizes the behavioral and methodological characteristics of each optimization approach, assessing their structural advantages and resource utilization dynamics. A novel MILP solution algorithm is introduced, based on a hybrid branch-and-cut technique integrated with time decomposition, enabling the solver to capture long-horizon optimization dynamics with high precision. All four methods are applied over a year-long simulation with hourly resolution. While each strategy maintains operational feasibility and power balance, the MILP approach consistently achieves the highest economic benefit, delivering approximately $2.43 million in annual cost savings, representing roughly a 72.3% improvement over the best-performing heuristic strategy under the same deterministic operating conditions. GA, PSO, and ACO each capture moderate benefits but show limitations in foresight and storage cycling. The findings not only benchmark algorithmic performance but also provide insight into the internal logic and structural behavior of optimization techniques applied to dynamic energy systems, offering guidance for algorithm selection and design in microgrid EMS. Full article

In grid-connected inverter systems, the Phase-Locked Loop (PLL) is fundamental for achieving and maintaining precise synchronization between the inverter and the electrical grid. Developing an efficient and robust PLL is essential to ensure reliable operation, particularly in the presence of abnormal grid conditions. Among the existing synchronization methods, the Synchronous Reference Frame-based PLL (SRF-PLL) is widely adopted due to its robust performance; however, it suffers from degraded accuracy under unbalanced voltage conditions. To address this limitation, the Second-Order Generalized Integrator-Quadrature Signal Generator (SOGI-QSG) was proposed in previous studies as an alternative approach. Despite its advantages, the SOGI-PLL exhibits weak filtering capability for lower-order harmonics and remains sensitive to DC offset, both of which can affect synchronization quality. As a result, numerous advanced PLLs based on SOGI-QSG have been proposed in the literature to address SOGI-QSG limitations by enhancing DC offset rejection, filtering capability, and dynamic response. This article provides a comprehensive assessment of various three-phase PLLs based on SOGI-QSG under unbalanced grid conditions, focusing on peak-to-peak frequency error, filtering performance, and DC offset rejection. The operational principles and mathematical models of each technique are discussed, and their performances are validated using MATLAB/Simulink (R2025b). The results show that the SRF-PLL exhibits oscillatory behavior under unbalanced conditions, whereas the PLLs based on SOGI-QSG demonstrate stable synchronization with different trade-offs between filtering strength and dynamic response. Therefore, the selection of the appropriate PLLs based on SOGI-QSG depends on the priorities of the specific application. Full article

The rapid growth of renewable electricity generation introduces technical challenges that were previously uncommon. These include, for example, problems with exceeding the permissible voltage values in network nodes, overloading of transformers and line sections located behind the transformer, as well as balance problems. This article proposes an original methodology for eliminating these problems. Four objective functions reflecting different operator priorities were used. Attention is drawn to the increasing importance of the development of electricity storage. The results confirm that coordinated optimisation of voltage regulation, energy storage, and flexible load management enables increased renewable energy connection capacity while reducing power losses and improving the grid voltage profile. The case study results demonstrate the effectiveness of the proposed approach under the considered operating scenarios. The proposed tool can support network operators in managing MV grid operation under the considered scenarios. The ongoing energy transition requires network operators to react quickly to emerging problems. Therefore, advanced computational methods are needed to mitigate operational risks and respond to emerging constraints. Full article

To address the challenges of insufficient frequency regulation capability of individual stations, poor collaborative economic performance, and unfair benefit allocation caused by fluctuations in photovoltaic (PV) output and variations in electric vehicle (EV) connectivity during vehicle-to-grid (V2G) interactions under high-penetration PV integration, this paper proposes a coordinated optimal operation strategy for peer-to-peer (P2P) energy sharing and joint frequency regulation among multiple electric vehicle charging stations (EVCSs). First, a collaborative framework for P2P energy sharing and joint frequency regulation among EVCSs is constructed to describe the operational mechanism of inter-station energy mutual support and coordinated response to frequency regulation signals. Subsequently, an aggregate model of the dispatchable potential for EV clusters within each station is established based on Minkowski Summation (M-sum), characterizing the charging and discharging power boundaries and frequency regulation potential of the EV clusters. Meanwhile, distributionally robust chance constraints (DRCC) based on the Kullback–Leibler (KL) divergence are introduced to handle the uncertainty of PV power generation within the EVCS. On this basis, a dynamic frequency regulation output model for EV clusters and a multi-station P2P energy sharing model are designed, with the optimization objective of minimizing the total operating cost. Finally, to quantify the differential contributions of each EVCS in the collaborative operation, an asymmetric Nash bargaining benefit allocation mechanism is proposed, which incorporates a comprehensive contribution index considering both energy sharing and joint frequency regulation, The model is solved in a distributed manner using the alternating direction method of multipliers (ADMM). Simulation results demonstrate that, compared to non-cooperative operation, the frequency regulation completeness rates of the EVCSs after cooperation increase by 5.7%, 5.2%, and 4.4%, respectively; meanwhile, the total operating cost drops from CNY 16,187.61 under non-cooperative operation to CNY 15,997.47, achieving a reduction of 1.18%. The proposed strategy not only meets grid frequency regulation demands but also enhances the economic efficiency of multi-station collaborative operation and the fairness of benefit distribution. Full article

Low-voltage ride-through (LVRT) capability is essential for grid-connected photovoltaic (PV) systems, especially as rising renewable integration challenges grid stability during voltage disturbances. Existing LVRT methods often target isolated control functions, leading to limited system resilience. This paper presents a unified control strategy integrating DC-link voltage regulation, reactive power injection, and overvoltage mitigation using a coordinated fuzzy logic framework. The proposed architecture employs a cascaded control structure comprising an outer voltage loop and an inner current loop with feed-forward decoupling, synchronized via a Synchronous Reference Frame Phase-Locked Loop (SRF-PLL). At its core is a dual-input, single-output Fuzzy Logic Controller (FLC), featuring optimized membership functions and dynamic rule-based logic to manage multiple control objectives during grid faults. The proposed FLC-based unified LVRT controller for grid-tied PV system was implemented and validated for both symmetrical and asymmetrical fault conditions in MATLAB/Simulink 2023b platform. The proposed FLC-based LVRT controller achieves voltage sag compensation of 97.02% and 98.4% for symmetrical and asymmetrical faults, respectively, outperforming conventional PI control, which achieves 94.02% and 96.5%. The system maintains a stable DC-link voltage of 800 V and delivers up to 78% reactive power support during faults. Fault detection and recovery are completed within 200 ms, complying with Bangladesh grid code requirements. This integrated fuzzy logic approach offers a significant advancement for enhancing grid stability in high-renewable environments and supports reliable renewable utilization, and more sustainable grid operation in developing regions. Full article

Extreme hydro-meteorological events are intensifying under climate change, disproportionately disrupting last-mile healthcare in flood-prone geographies. In this study, flood-adaptive primary care clinics (FAPCCs) integrated with islandable smart microgrids and a rapid-deploy medical technology stack (MedTech) are developed and evaluated to ensure continuity of essential services (triage, maternal and child health, vaccination cold-chain, minor procedures, diagnostics, and telemedicine) during fluvial, pluvial, and coastal flooding. Evidence on resilient health facilities, microgrid architectures, distributed energy resources, and modular clinical systems is presented in a multi-layer systems design: (1) a modular, amphibious, and elevatable clinic chassis; (2) a photovoltaic–battery–diesel hybrid system with demand-aware energy management; (3) redundant connectivity long-term evolution/fifth-generation, satellite, and very high frequency; (4) a rapid-deploy MedTech kit including point-of-care diagnostics, low-temperature cold-chain, negative-pressure isolation, and sterilization modules; and (5) flood-aware logistics using unmanned aerial vehicle/unmanned surface vehicle. A mixed-integer linear programming sizing is formulated and dispatched with a continuity-of-care reliability metric that couples energy availability to clinical throughput. Simulation across three archetypal sites (peri-urban delta, inland riverine, coastal estuary) shows that FAPCCs achieve the service availability of higher than 99.5% across 7-day grid outage scenarios while reducing fuel use by 62–81% relative to diesel-only baselines, maintaining vaccine temperatures within 2–8 °C with <0.1% thermal excursion time, and sustaining telemedicine quality of service with <150 ms median uplink latency in hybrid networks. A life-cycle cost analysis indicates a 7.1–9.8 year discounted payback from fuel displacement and avoided service loss. Deployment playbooks and policy guidance are also proposed for Ministries of Health and Disaster Agencies in monsoon-impacted regions. Full article

Submarine cable systems are essential for intercontinental connectivity and the integration of offshore renewable energy into onshore grids. The reliability of these systems depends on a well-coordinated life cycle process that integrates installation, monitoring, and maintenance technologies. This review synthesizes the key components of submarine communication and power cables, highlighting the processes involved in route survey, cable laying, and burial under complex seabed conditions. The major factors contributing to damage are typically classified into natural hazards and human activities. Particular attention is given to fault diagnosis techniques, including optical time domain reflectometry (OTDR) and time domain reflectometry (TDR). Additionally, practical workflows and processes for fault location and cable repair are outlined. By structuring advancements across installation, monitoring, and maintenance processes, this review offers a comprehensive technical reference for researchers and practitioners, while emphasizing emerging trends aimed at enhancing system resilience, real-time situational awareness, and rapid response, thus supporting global digitalization and the transition to clean energy. Full article

Sub-synchronous oscillations (SSOs) induced by the interaction between doubly fed induction generators (DFIGs) and weak grids pose a critical threat to the grid-connected stability of DFIG-based wind power systems. In this paper, a dual-damping-term compensation filter based on the concept of motion-induced amplification (MIA), together with an optimized design method using a linear quadratic regulator (LQR), is applied to the DFIG system. The effectiveness of the proposed approach in suppressing DFIG shafting oscillations and mitigating grid-connected frequency coupling is verified, and the underlying mechanisms are thoroughly investigated. By establishing a shafting dynamics model for the DFIG and a frequency-coupled oscillation impedance model, this study focuses on revealing the differentiated impacts of the dual damping parameters (${\mathrm{Z}}_{\mathrm{p}}$ and ${\mathrm{Z}}_{\mathrm{q}}$) on system stability under two operating modes: maximum power point tracking (MPPT) and constant power operation. Stability analysis based on the generalized Nyquist criterion (GNC), together with time-domain simulations, demonstrates that coordinated optimization of the dual damping terms can effectively suppress shafting oscillations and frequency coupling, thereby significantly enhancing the grid-connected stability of DFIG systems. Full article

With the increasing penetration of renewable energy, grid-forming inverters that provide voltage and frequency support are receiving significant attention. However, due to the voltage source characteristics of grid-forming Virtual Synchronous Generators (VSGs), they are prone to excessive short-circuit currents during three-phase grid faults. Moreover, conventional short-circuit current analysis methods developed for grid-following inverters cannot be directly applied to VSG-based systems. Consequently, research on fault current calculation for grid-forming VSGs has become critically important. To address this issue, this paper employs mathematical analysis to derive a short-circuit current calculation method for VSG grid-connected systems under three-phase fault conditions. Based on the derived analytical expressions, the short-circuit current characteristics of the VSG system are systematically analyzed. The correctness of the proposed analytical expressions is validated through simulations conducted on the MATLAB/Simulink(R2024b) platform. Simulation results show that the error between the analytical and simulated values remains within 8%, and decreases to below 3% after 2–3 cycles, indicating that the proposed analytical model can effectively capture the dynamic behavior of the fault current. Full article