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High-voltage direct-current transmission : converters, systems and DC grids
This comprehensive reference guides the reader through all HVDC technologies, including LCC (Line Commutated Converter), 2-level VSC and VSC HVDC based on modular multilevel converters (MMC) for an in-depth understanding of converters, system level design, operating principles and modeling. Written in a tutorial style, the book also describes the key principles of design, control, protection and operation of DC transmission grids, which will be substantially different from the practice with AC transmission grids. The first dedicated reference to the latest HVDC technologies and DC grid developments; this is an essential resource for graduate students and researchers as well as engineers and professionals working on the design, modeling and operation of DC grids and HVDC. Key features: Provides comprehensive coverage of LCC, VSC and (half and full bridge) MMC-based VSC technologies and DC transmission grids. Presents phasor and dynamic analytical models for each HVDC technology and DC grids. Includes HVDC protection, studies of DC and AC faults, as well as system-level studies of AC-DC interactions and impact on AC grids for each HVDC technology. Companion website hosts SIMULINK SimPowerSystems models with examples for all HVDC topologies.
eBook
Simulation of Linear Anode-Pipe Cathodic Protection System: Primary and Secondary Current and Potential Distribution Analysis
Nowadays, the use of a linear anode in an impressed current cathodic protection system is one of the most interesting technical solutions to guarantee the corrosion protection of short pipe in common and even in congested area. The determination of the minimum distance between linear anode and pipe, and the effective parameters to reach the protection potential, can be studied at two different levels. First, the use of a primary current distribution analysis allows finding the proper distance based on the geometry, physical environmental parameters, and maximum allowable potential difference of two sides of the pipe. The second level is to consider the polarizability of the cathode, then to apply the so-called secondary current distribution analysis. The primary current distribution shows that the linear anode-to-pipe distance is mainly affected by soil resistivity and pipe diameter. Secondary current distribution analysis emphasizes that the proper minimum distance is influenced by the polarization of the cathode, i.e., the overvoltages of the two cathodic reactions of oxygen reduction and hydrogen evolution. In both approaches, soil resistivity has a predominant effect on potential distribution on the pipe surface.
Journal Article
Inversion Method of Lightning Current Distribution on a Surface Conductor Represented by Thin Lines
Electromagnetic simulation and pre-analysis of electromagnetic compatibility for lightning effects are important. It is difficult to estimate the surface current of surface structures represented by thin lines. In this study, we simplified the partial element equivalent circuit (PEEC) equation and deduced an equation for the magnetic field based on the thin-line representation method. An inversion method was used to determine the surface current in a frequency-domain PEEC. Parallel computing technology was used to improve the inversion efficiency. Additionally, the capacitive and inductive characteristics of the elements of Darney’s circuit method were developed for PEEC. The results were compared with calculations using the finite integration technique. The application of the thin-line representation method was broadened, and its efficiency has been improved.
Journal Article
Numerical simulation of the impact of casing on the buried metal pipeline cathodic protection potential
Metal casings shield the cathodic protection current and detection signals of buried metal pipelines, making the corrosion protection and detection technology of pipelines at the casing one of the challenges for safe operation and integrity evaluation of pipelines. This paper uses the primary current distribution physics interface in the COMSOL Multiphysic simulation software to study the effects of the coating quality of the casing and pipeline, the installation of sacrificial anodes in the casing, the conductivity of the electrolyte, and defects in the pipeline coating in the casing on the pipeline potential. The influence of distribution. The results show that: The coating quality of the outer surface of the casing and the pipe inside the casing has a great influence on the cathodic protection potential of the pipeline. The better the coating quality, the more negative the cathodic protection potential is, and the less cathodic protection current required by the pipeline, so the power consumption of the forced current law is reduced, and the service life of the sacrificial anode is longer. Installing sacrificial anodes in the casing has a positive effect on the cathodic protection of this special pipe section. The conductivity of the electrolyte in the casing has a certain impact on the cathodic protection potential of the pipeline. When the conductivity of the internal electrolyte is greater, the protective potential of the pipeline becomes more negative. However, impurities such as soil, groundwater, and silt make the pipeline more susceptible to corrosion, so keeping the annular space relatively dry is an important prerequisite for anti-corrosion. When there is a coating defect on the inner and outer pipes of the casing, the potential at the damaged point will have a potential peak. The larger the potential peak difference, the more serious the coating defect is.
Journal Article
Power flow analysis of DC distribution system in a ship with non-electric propulsion
Direct current (DC) shipboard power distribution system offers higher power efficiency and voltage stability compared to the alternating current (AC) systems due to lower impedance. The implementation of DC distribution system in all-electric ship seems to be worthy since the reduction of power loss and voltage drop could overcome the drawback of DC system. However, the effectiveness of DC distribution system in ship with non-electric propulsion has not been investigated yet. Unlike in an all-electric ship, electric power flow in the distribution system of a ship with mechanic propulsion is considerably lower. The study aims to provide numerical analysis of power loss and voltage drop reduction on DC distribution system that applied to a ship with mechanic propulsion. The power flow analysis is performed on a tanker ship. Contrary to the hypothesis, the results show that the DC power distribution increase the power losses about 15% compared to AC system due to the addition of rectifier and inverter. However, the voltage drops are decreased in DC distribution system. Further investigation in the other aspects should be performed before concludes whether DC distribution system is worthy to be used in the aforementioned ship.
Journal Article
Multi-Resolution Resistor Network-Driven 3D Forward Modeling of HVDC Monopolar Geoelectric Current
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.
Journal Article
A current-informed statistical characterization of regional seawater reflectance based on hyperion observations
Sea surface reflectance is a key underlying-surface parameter for remote sensing retrievals of sea fog, sea wind, and marine aerosols, and it exhibits significant variability across different times and ocean-current-controlled regions, with maximum variations of up to approximately 15%. Long-term use of a fixed seawater reflectance as an a priori input may introduce systematic biases in radiative transfer simulations and atmospheric correction. Based on hyperspectral observations acquired by the EO-1/Hyperion satellite from 2003 to 2017 over major global ocean-current regions, this study statistically retrieved multi-regional and multi-seasonal sea surface reflectance characteristics and constructed a lookup table constrained by ocean current distribution and seasonal variation. Radiative transfer forward simulations were conducted in representative regions influenced by the Canary Current, California Current, and East Australian Current using both Landsat-8 OLI and Sentinel-2 MSI sensors. The results show that when the lookup-table-based reflectance is used as the ocean surface input, the mean relative error between simulated and observed at-sensor radiance in the visible to near-infrared bands is stably controlled within approximately 6%–9%, and consistent error convergence behavior is observed across different sensors, which is consistently lower than that of the constant-reflectance scheme. These results indicate that incorporating ocean-current and seasonal information into reflectance characterization can effectively improve the consistency and engineering feasibility of marine background radiative modeling, thereby providing a practical improvement for underlying-surface parameter specification in multi-source ocean remote sensing applications. However, the proposed dataset should be interpreted as a statistically stratified regional parameterization rather than a globally complete operational product.
Journal Article
Analysis and Design of Compact Single-Band Slots on Patch Antenna for Wireless Communication
This paper presents, a monopole rectangular patch antenna (0.57 × 0.52 × 0.035 λ
3
) featuring two horizontal slots and vertical rectangular slits, designed for single-band application. The analysis focuses on its suitability for single-band wireless communication applications. The proposed antenna resonates at frequency of 6.6 GHz and has a bandwidth of 500 MHz (from 6.38 to 6.88 GHz). The simulated results, including reflection coefficient, radiation pattern, gain, and surface current distribution, are presented in this paper. At the operating frequency of 6.6 GHz, the antenna achieves a gain of 3.24 dBi and a reflection coefficient of − 32.2 dB. The simulated and measured results of the proposed antenna are in good agreement, demonstrating its suitability for wireless communication applications.
Journal Article
Plug-in gate-loop compensators for series-connected IGBT drivers in solid-state fault current limiter
A solid-state fault current limiter (SSFCL) is the key protective equipment in a direct current distribution network. In order to meet the high voltage requirements and reduce costs, implementing a SSFCL based on series-connected insulated gate bipolar transistors (IGBTs) is a promising approach. However, voltage unbalancing of IGBTs would be introduced if the gateloops of the IGBTs are non-identical. In this paper, a plug-in gate-loop compensator with discrete gate voltage feedback and pulsewidth current compensation is proposed. The main merits are: 1) with the plug-in structure, the extra current sources only provide small power to fine-tune the gate-loop without affecting the functions provided by the commercial IGBT gate driver; 2) the gate-emitter voltages of IGBTs are compared with the preset thresholds to obtain control criterion, and the pulsewidths of the current sources are controlled for gate-loop compensation, thus both analog-digital and digital-analog converters are avoided; 3) the control law is easy to implement in FPGA, and is robust to voltage variation of power-loops. With the proposed compensator, the voltage unbalancing is alleviated immediately at the present switching cycle, and further eliminated cycle-by-cycle during the current limitation process. Experimental results verify the feasibility of the proposed compensator.
Journal Article