Search Results (828)

While the generation mechanisms of high-frequency oscillations caused by voltage source converter-based high-voltage direct current (VSC-HVDC) systems have been widely investigated, their propagation paths and spatial influence within the power grid remain largely unexplored. To address this critical gap, this paper proposes a novel oscillation propagation analysis method based on branch high-frequency active power distribution. First, from the perspective of equivalent impedance, the mechanism of high-frequency oscillation caused by the VSC-HVDC system in a single-machine system is elaborated. Then, mathematical modeling and theoretical derivations reveal that synchronous generators primarily act as passive impedances at high frequencies and that transmission lines significantly distort high-frequency voltage and current amplitudes. Crucially, high-frequency active power remains inherently stable and immune to these line distortion effects. Building upon these characteristics, an instantaneous power calculation method using broadband measurement data is derived to trace the propagation path. Comprehensive case studies using a 4-machine 2-area system and the New England 10-machine 39-bus system demonstrate that the proposed method can accurately map actual physical propagation paths, evaluate an oscillation’s influence range, and reliably locate a high-frequency oscillation’s source. Full article

Processes for generating clean hydrogen from waste plastics through thermochemical methods such as pyrolysis and gasification are a promising solution for both waste management and clean energy initiatives. Then, this derived hydrogen powers the fuel cell, which produces electricity that can be directly fed to charge electric vehicles (EVs). Although this complex process has many challenges related to energy efficiency during the conversion processes—starting from the generation of hydrogen from thermochemical processes and hydrogen storage and followed by fueling the fuel cells and charging EV infrastructure—the simplistic conceptual modeling developed for this research demonstrates how an ecosystem of such processes can be made feasible commercially. Clean hydrogen generated using known techniques reported in the literature is promising for commercialization, but harnessing hydrogen from plastics offers additional benefits, such as reducing greenhouse gas (GHG) emissions. Overall, the feasibility of clean hydrogen using this methodology is not limited by potential cost inefficiencies, especially when savings from GHG emissions reduction are taken into account. EVs have become commercially viable thanks to high-energy-density Li-ion batteries. And therefore, research continues to optimize charging performance through the integration of renewable energy and battery storage systems. This study examines another potential of clean hydrogen: its use as a power source in grids, especially V-2-G (vehicle-to-grid) systems. Additionally, direct current (DC) power from a fuel cell powers an EV charger at DC input voltages for e-ambulances. In particular, this designed system operates on DC voltages throughout the power system, combining high-voltage direct current (HVDC) lines, renewable energy sources, DC-DC converters, DC EV chargers, and other supporting components. The literature review identified gaps in plastics production, waste management, and processes for converting them into useful energy. The presented model is a stepping stone towards a novel, innovative process for clean hydrogen production to power electric vehicle charging infrastructure for emergency response systems in healthcare, thereby improving public safety. The limitations of the study would be governed by the effective establishment of locations where waste management services are performed (for example, landfills) and adoption by local government authorities with deregulated power systems. Full article

Tropical estuarine hydrodynamic processes are governed by complex interactions between tides, monsoons, and fluvial runoff. To obtain long-term (≥30 years) hydrodynamic conditions of the Mekong River Estuary, this study established a Finite Volume Coastal Ocean Model (FVCOM) coupled with validated Weather Research and Forecast (WRF) wind forcing for a 32-year (1988–2019) high-resolution simulation. Validation against in situ observations confirms the model’s robustness. Temporal–spatial patterns of water level and current were analyzed, and extreme parameters for 1–100 year return periods were derived via the Pearson-III probability distribution. Results indicate the study area is a mesotidal environment (tidal range = 3.58 m) dominated by SSE-NNW reciprocating tidal currents. Relative to Vietnam’s national elevation datum, 100-year return period extreme high/low water levels are 2.15 m and −2.03 m, with a maximum storm surge setup of 2.09 m. The 100-year return period maximum current velocity reaches 4.58 m/s (A21 station), and Mekong River runoff exerts a negligible influence (<5% velocity change). This study provides high-precision baseline data for offshore wind farm engineering and disaster risk assessment, offering a methodological reference for tropical estuarine hydrodynamic simulations. Full article

To mitigate the inertia deficiency and weak damping in receiving-end grids caused by the large-scale integration of the offshore wind power-integrated MMC-HVDC system, this paper proposes a coordinated inertia support strategy. First, the transient support capability of submodule capacitors within the HVDC system is quantitatively analyzed. Subsequently, a capacitor energy-based grid-forming control is developed. A decoupled control mechanism is implemented to eliminate the coupling between submodule capacitor voltage and DC voltage, enabling maximum utilization of the converter’s internal transient energy while maintaining DC voltage stability. Furthermore, by introducing a frequency deadband mechanism, a coordinated inertia support strategy mediated by DC voltage is established. This facilitates a hierarchical support sequence wherein capacitors prioritize responses to minor disturbances, while the offshore wind farm (OWF) participates cooperatively during severe frequency deviations. PSCAD/EMTDC 4.6.2 simulations demonstrate that the proposed strategy achieves optimal capacitor energy utilization and effective multi-entity coordination. It reduces the maximum deviation in the grid by 33.3%, significantly enhancing system frequency stability. Full article

Accurate electric field measurement in high-voltage direct current (HVDC) environments is essential for power system monitoring. This study systematically investigates the output characteristics of a micro-electro-mechanical system (MEMS) electric field sensor under DC ionized field conditions. Using a controlled experimental platform capable of generating independent nominal electric fields and ion flows, the influence of ion current density on sensor sensitivity and offset was quantitatively analyzed. Experimental results reveal that ion flow leads to a progressive output drift and significant measurement deviations when using conventional electrostatic calibration. To address this issue, a joint calibration method incorporating ion current density is proposed. Validation experiments demonstrate that the proposed method significantly improves measurement accuracy, reducing the maximum relative error from 29.28% to approximately 5.07%. This work provides a reliable experimental basis and calibration methodology for utilizing MEMS electric field sensors in complex ionized DC environments. Full article

Floating offshore wind turbines (FOWTs) are subjected to complex oceanic environmental loads, which can result in non-collinear wind and wave directions that may not align with the rotor axis, potentially leading to complex variations in aerodynamic characteristics. In this study, the aerodynamic performance and wake of the NREL 5 MW wind turbine under different inflow angles and platform surge motions in various directions were investigated using the actuator line model (ALM) implemented in OpenFOAM. The results demonstrate that an increase in surge amplitude primarily amplifies the cyclic fluctuations in rotor thrust and torque, while the direction of surge motion has a negligible influence. In contrast, yawed inflow leads to a substantial reduction in both the mean and peak values of thrust and torque. Wake analysis further reveals that the mean wake recovery is predominantly governed by the yaw angle. Under aligned inflow conditions, the wake remains nearly symmetric and shows limited sensitivity to platform surge motion. Conversely, yawed inflow induces significant wake deflection with an asymmetric distribution of turbulent kinetic energy and enhanced mixing in the downstream region. Full article

In MMC-HVDC-integrated offshore wind farms, the Wind-Farm-side MMC (WFMMC) is increasingly adopting Virtual Synchronous Generator (VSG) control to provide active support. However, this control strategy may introduce high-frequency oscillations that cannot be predicted by conventional stability analysis. Existing suppression strategies, designed for WFMMC under conventional V-f control, fail to account for frequency coupling effects in the high-frequency range, making it difficult to effectively analyze or suppress such oscillations. To address this issue, this article reveals a significant high-frequency-range frequency coupling effect between the wind turbine’s Grid-Side Converter (GSC) and the VSG-controlled MMC, which is distinct from systems with conventional V-f control. It is further identified that the asymmetric control structure introduced by the VSG control and control delay are the key factors driving this coupling. Based on this finding, an oscillation suppression strategy incorporating a band-stop filter in the WFMMC voltage sampling loop is proposed. Time-domain simulations demonstrate the effectiveness of this strategy under various operating conditions. Full article

This study proposes a three-dimensional forward modeling framework for geoelectric current distribution under high-voltage direct current (HVDC) monopolar operation. The proposed approach is based on a multi-resolution resistor network (MR-RN) discretization, in which gradient fusion interpolation is employed to suppress flux discontinuities at coarse–fine interfaces, and exterior equivalent boundary resistors are introduced to approximate open boundaries, enabling efficient and stable large-scale three-dimensional forward modeling. Compared with the traditional structured grid and finite element method (FEM), the proposed MR-RN achieves comparable accuracy while reducing computation time by up to 96% and the number of degrees of freedom by two orders of magnitude. Case studies on layered Earth, boundary extension, and substation–field coupling demonstrate that the MR-RN model maintains errors within 1–3%, confirming its suitability for large-scale HVDC ground return simulations and geoelectric safety assessment. Full article

According to CIGRE, the usual arrangement of electrodes in a shoreline electrode station for HVDC interconnections is straight with the following form: forming straight frames with the electrodes at equal distances and placing the frames parallel to the longitudinal axis of the breakwater, successively at fixed distances between them. In a previous paper by the authors, 10 alternative configurations of placement of such straight frames were examined to determine which placements mainly affect the near-field results. In particular, radial or circumferential arrangements of the straight frames on a central base in the open sea improve the overall field results, such as the absolute potential and electrode station resistance to remote earth, satisfying the requirements of the maximum electric field strength. In this paper, the nonlinear configuration of the frames will be studied from an electric field perspective at the level of a preliminary study forming innovative configurations in order to check their suitability with respect to the relevant requirements of the CIGRE guidelines B4.61/2017. These arrangements, located in electrode stations, are evaluated and compared with the older configurations for two cases, those of Korakia in Crete and Stachtoroi in Aegina, Attica, for the HVDC Crete-mainland Greece interconnection of 1 GW, ±500 kV. Full article

HVDC technologies based on fully controlled devices offer numerous technical advantages, such as flexible active and reactive power control and black-start capability, making them highly promising for large-scale renewable energy integration and long-distance power transmission. However, their widespread adoption is constrained by high costs and significant power losses. Unlike existing hybrid HVDC schemes predominantly based on LCC-MMC structures, this paper proposes a novel hybrid current source converter-based HVDC (HCSC-HVDC) topology composed of IGCTs and thyristors, which enables power decoupling and achieves an approximate 70.5% reduction in high-voltage capacitor requirements, fundamentally improving system economy and structural efficiency. Firstly, the topological structure of the HCSC is introduced and a mathematical model is established. Then, the power operating range of the hybrid converter is quantitatively analyzed, and an optimization method for AC filter parameters is derived, based on which a power decoupling control strategy and a reactive power coordination control (RPCC) strategy are proposed. Finally, PSCAD electromagnetic transient simulations verify the effectiveness and feasibility of the proposed topology and control methods. Full article

The global shift toward decarbonized power systems is driving unprecedented penetration of variable renewable energy sources, especially wind and solar PV. Legacy grid architectures, built around centralized, dispatchable synchronous generation, are ill-suited to manage the bidirectional power flows, reduced inertia, and new stability constraints introduced by inverter-based resources. Existing research offers deep but fragmented insights into individual elements of this transition, such as advanced power electronics, microgrids, or market design, but rarely integrates them into a coherent architectural vision for resilient, high-renewable grids. This review closes that gap by synthesizing technical, architectural, and institutional perspectives into a unified framework for resilient grid design toward 2030 and beyond. First, it traces the evolution from traditional hierarchical grids to smart, prosumer-centric, and modular multi-layer architectures, highlighting the implications for reliability and resilience. Second, it critically examines the core technical challenges of high VRES penetration, including stability, power quality, protection, and operational planning in converter-dominated systems. Third, it reviews the enabling roles of advanced power electronics, hierarchical control and wide-area monitoring, microgrids, and hybrid AC/DC networks. Case studies from Germany, China, and Egypt are used to distil context-dependent pathways and common design principles. Building on these insights, the paper proposes a scalable multi-layer framework spanning physical, data, control, and regulatory/market layers. The framework is intended to guide researchers, planners, and policymakers in designing resilient, converter-dominated grids that are not only technically robust but also economically viable and socially sustainable. Full article

The high-frequency switching noise of insulated-gate bipolar transistors (IGBTs) limits the sensitivity of online partial discharge (PD) monitoring in ultra-high-voltage flexible DC (VSC-HVDC) transmission systems. To address this challenge, this study investigates the underlying mechanisms and evolution of this interference and develops an anti-interference signal separation method. Simulation and experimental results indicate that the energy of IGBT switching noise is concentrated in the 30–180 MHz range, which significantly overlaps with the ultra-high-frequency (UHF) band used for PD detection. This research further reveals the pronounced modulation effect of device aging on the interference spectrum: bond wire aging triggers “spectral reconstruction” via altered parasitic parameters, where severe collector aging leads to an abnormal surge in turn-off interference amplitude. In contrast, gate oxide layer degradation manifests as characteristic “global spectrum attenuation” and a shift in peak frequency toward lower bands. Confronted with the challenges of strong interference and spectrum drift induced by aging, this paper proposes an adaptive signal separation method based on feature optimization of the time–frequency cumulative energy function. This method constructs novel characteristic parameters—namely, oblique intercept width and morphological gradient steepness—to effectively capture the fundamental differences in the energy accumulation process of the signals. Experimental verification demonstrates that even under conditions of varying interference characteristics, the proposed method achieves high-precision separation of PD signals from IGBT noise, outperforming traditional equivalent time–frequency and wavelet principal component analysis methods. This research provides crucial theoretical and technical support for insulation condition monitoring and device aging diagnosis in VSC-HVDC converter valves. Full article

The DC converter constitutes a pivotal component within medium-voltage direct current (MVDC) collection systems, performing functions such as voltage boosting, isolation, and power transmission. To accommodate the demand for high-capacity DC converters in MVDC collection systems for new energy sources, a full-bridge medium-frequency converter featuring low voltage and current stress on auxiliary switching devices is proposed. Based on the principles of dual-transformer configuration and component sharing, this converter employs a half-bridge circuit and a full-bridge circuit sharing two switching devices. Utilizing mixed-frequency modulation, the full-bridge main circuit operates at medium frequency to transmit the majority of power, while the half-bridge auxiliary circuit regulates overall power and voltage through high-frequency chopping control. This achieves zero-current switching for the medium-frequency switching devices across the entire load range, significantly reducing switching losses in the converter. This paper details the converter’s operating principles and analyzes key parameter design methodologies. Finally, a 240–6000 V/7200 W prototype was constructed to validate the proposed converter’s performance. Full article

This paper explores the potential contributions of modern High-Voltage Direct-Current (HVDC) transmission systems to the Italian National Power System, with a focus on adequacy and security, and providing an overview of their role in system stability. An operational methodology is proposed to assess the impact of planned infrastructure developments, within the context of medium- to long-term forecast scenarios. To this end, starting from a model of the current transmission network, a prospective model of the primary transmission grid for the year 2040 was developed, covering voltage levels of 230 kVAC, 400 kVAC, and 525 kVDC. Load-flow analysis under both N and N-1 conditions was performed, with particular emphasis on the Ionian–Tyrrhenian HVDC backbone “Priolo–Rossano–Latina”. Full article