High Voltage Direct Current Power Research Articles

Parameter Estimation Method for Virtual Power Plant Frequency Response Model Based on SLP

In adapting to the double-high development trend of high-voltage direct current (HVDC) receiving-end power systems and solving optimization problems in emergency frequency control (EFC) supporting virtual power plants (VPPs) in large-scale power systems, a parameter estimation method for a VPP frequency response model based on a successive linear programming (SLP) method is proposed. First, a “centralized/decentralized” hierarchical control architecture for VPP participation in EFC is designed. Second, the frequency response characteristics of multiple flexible resources are scientifically analyzed, and the system frequency response (SFR) model and equivalent model of VPP are constructed. Subsequently, parameter estimation of the VPP frequency response model is carried out based on the SLP method, aiming to balance the accuracy and computational efficiency of the model. Finally, the effectiveness of the proposed methodology is verified by using PSD-BPA to simulate and test the three-zone HVDC recipient area grid.

Design, Construction and Programming of a Low-Cost Pulsed High-Voltage Direct Current Power Supply for the Electrophoretic Deposition of Silicon Carbide Mixed with Graphite and/or Alumina for Thermoelectric Applications

This document describes a proprietary design, construction, programming and testing of a low-cost pulsed high-voltage direct current (HVDC) power supply with an output of 430 V and power of 25 W. The design obtained allows costs to be reduced compared to commercial ones, highlighting that the manufacturing of this HVDC is easy to replicate. To demonstrate the operation of the pulsed power supply prototype, coatings of silicon carbide (SiC) and SiC mixed with graphite (C) and/or alumina (Al2O3) were made using the electrophoretic deposition (EPD) method. After processing, samples underwent a heat treatment at 500 °C to evaluate their thermoelectric (TE) efficiency. The samples were analysed via X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, Seebeck coefficient, electrical conductivity and thermal conductivity. The Seebeck coefficient, electrical conductivity and thermal conductivity were measured in a temperature range of 100–500 °C in a nitrogen (N2) atmosphere. The electrical conductivity of the SiC 6C-4Al sample was 0.65 S/cm at 500 °C, while the maximum Seebeck coefficient was 2500 μV/K of the SiC 6C-4Al sample at 200 °C. The thermal conductivity of SiC 6C-4Al was in the range of 0.35–0.37 W/m·K, which was much lower than the SiC sample free of alumina and graphite in the same measured temperature range. In conclusion, the SiC 6C-4Al sample presented the highest figure of merit with a ZT ≈ 0.01.

AI & Physics-Based Bad Command/Data Detection in Large Power Electronics Systems: Multi-Port Autonomous Reconfigurable Solar Power Plant (MARS)

Detection of bad data from measurement sensors and bad commands from control centers need to be carried out to avoid instabilities within large power electronics systems. Towards the same, in this paper, model and data driven methods are proposed to identify anomalies in measured data and commands received by large power electronics systems. The large power electronics system considered in this paper is a multi-port autonomous reconfigurable solar power plant (MARS), which consists of photovoltaic (PV) and energy storage systems (ESSs) that connect to high-voltage direct current (HVdc) system and transmission ac power grid. The proposed algorithms in the MARS power plant to detect bad data from measurements and bad commands from control centers are evaluated in simulations and hardware-in-the-loop (HIL) tests. It has been observed that the proposed algorithms are able to detect bad measurements and commands in all the use cases evaluated.

Transfer operation ride though control strategy of the aircraft power supply system with lithium battery energy storage

The aircraft power supply system turns towards multi-source, and transfer operation will likely happen during flight missions and fault conditions. The transfer may lead to voltage interruptions and current surges, adversely affecting power quality. This paper proposes incorporating a lithium battery energy storage system (ESS) into the aircraft high-voltage direct current (HVDC) power system. The ESS employs a voltage control model with a lower voltage reference base, facilitating a smooth transfer operation during power interruptions. This approach reduces voltage fluctuations in the power supply system, enhances power quality, and enables seamless power transfer during the transfer operation.

AC/DC Hybrid Power System Damping Control Based on Estimated Model Predictive Control Considering the Real-Time LCC-HVDC Stability

High Voltage Direct Current (HVDC) can quickly vary its power to stabilize an AC power system when the latter is subject to a disturbance. Typically, linear control is used to design that control strategy. However, due to the uncertainties of the faults and the system model, it is necessary to estimate the linear model of the post-fault power system using real-time measurements. This leads to two main problems: Firstly, after the fault, the HVDC will quickly evolve to steady-state operating conditions and, therefore, result in an unobservable control matrix. Secondly, the HVDC power should not exceed its stable range, which is limited by the post-fault system. To address the above issues, the main novelties are as follows: First, this paper proposes a novel system identification method to handle that case when there is no control input excitation. Second, this paper presents an AC/DC hybrid power system control strategy that fully considers the real-time stability constraints of the HVDC. More specifically, this paper proposes to estimate the system matrix and the control matrix separately. Based on the linearized model of the AC/DC hybrid system, the control matrix is calculated using the sensitivities of the active powers of the generators with respect to those of the HVDC. Then, the system matrix is estimated in real-time using measures of the power angle and frequency. Finally, by processing the local voltage and current measurements, the associated Thevenin equivalent parameters on the system side of the HVDC connecting point are estimated in real-time and the upper bound of the DC power is determined. According to the linearized model and the HVDC power constraints, a control strategy is proposed using the model predictive control method. Simulation results reveal the effectiveness of the proposed strategy.

The Mitigation of Interference on Underground Power Lines Caused by the HVDC Electrode

High Voltage Direct Current power links are usually designed to adopt, on a continuous basis or during emergency operations, two grounding plants using the soil or seawater as a link–current return path. Such DCs flowing into the ground can cause problems, of which one of the most important is the increased risk of the corrosion of metallic structures in the area. Normally, the simplest mitigation technique is to keep an adequate distance between the main grounding plants and any metallic structure that can be corroded. Normally, such distances are not less than 5 km. However, there are situations where this approach cannot be applied, for example due to geographical constraints. In this paper, we describe and analyze the behavior of a mitigation technique that can be adopted when the HV pole cable is laid closer than the recommended distance to the main ground electrode. This paper is focused on the minimization of deleterious effects on the cable’s metallic sheath and its earthing points, distributed along it by means of sheath segmentation. The suggested approach appears well-suited to substantially diminishing the current flowing through the sheath of an HVDC power cable. In the segmented scenario, the sheath’s power dissipation is less than one-hundredth of that in the typical continuous configuration.

Dynamic Performance Improvement of Wound Rotor Synchronous Starter/Generator System Based on PWM Rectifier

This paper proposes an active field current tracking (AFCT) control strategy for pulse width modulation (PWM) rectifier, which can remarkably enhance the system’s dynamic performance of wound rotor synchronous starter/generator (WRSSG) system when the load changes. WRSSG system uses a PWM converter in the aero-engine starting process and can reuse the power circuit as a PWM rectifier for high-voltage direct current (HVDC) power generation, thus simplifying the system structure, volume, and weight. The mathematic model of WRSSG system with PWM rectifier is introduced. Based on the system model, the PI controller of armature current loop is designed. The nonlinear PI controller of excitation voltage loop is also illustrated. A 15kW WRSSG system based on PWM rectifier is implemented. The AFCT control strategy and its high dynamic performance are verified by experiments. The simple system structure and distinguished dynamic performance of PWM rectifier with AFCT control can make the WRSSG system more competitive in aircraft applications.

Economic environmental operation in bulk AC/DC hybrid interconnected systems via enhanced artificial hummingbird optimizer

Innovative technologies of multi-terminal high voltage direct current (HVDC), often known as “MTDC,” represent additional features for better active and reactive power control when hybridized with traditional AC power systems. In this sequence, optimal operation in hybrid AC and MTDC power systems becomes highly economically and environmentally necessary. This paper presents an Improved Artificial Hummingbird Optimizer (IAHO) technique for reducing total generation fuel costs, environmental pollution, and whole power losses in AC-MTDC power systems. The proposed IAHO includes a variety of territorial foraging tactics (TFTs) and a Linear Control Process (LCP) which improve both local and universal searching capabilities. The proposed IAHO and AHO are performed on modified IEEE 57-bus and 30-bus hybrid AC and multi-terminal HVDC power systems. The simulation findings declare high economic, environmental, and technical benefits based on the proposed IAHO. A significant reduction in fuel costs, emissions, and losses with 22%, 59.51%, and 71.83% compared to the initial case for the IEEE 57-bus hybrid AC-MTDC power system. Also, the IEEE 30-bus hybrid AC-MTDC power system significantly reduced fuel costs, emissions, and losses by 17.01%, 16.04%, and 28.49% compared to the initial case. Moreover, the significant outperformance of the proposed IAHO is demonstrated over several reported algorithms.

A Region-Folding Electromagnetic Transient Simulation Approach for Large-Scale Power Electronics System

This paper proposes a region-folding electromagnetic transient simulation approach for large-scale power electronics systems to boost simulation speed. In the region-folding approach, the loop tear method is proposed to decouple the connections among power electronics blocks, the grouping and pre-calculating method of identical structural blocks is proposed to avoid computing the inverse of matrices repeatedly, and the global simultaneous response procedure is proposed to handle the simultaneous and multiple switching events. The implementation of the proposed approach is combined with high-performance parallelization technology to shorten the simulation time. The Modular Multilevel Converter (MMC)-based High Voltage Direct Current (HVDC) model and DC photovoltaic power station model are simulated respectively to validate the accuracy and efficiency. Simulation results indicate that the proposed approach has the same accuracy as other Electromagnetic Transients (EMT) commercial software with better efficiency.

Polyethylene Based Ionomers as High Voltage Insulation Materials

AbstractPolyethylene based ionomers are demonstrated to feature a thermo‐mechanical and dielectric property portfolio that is comparable to cross‐linked polyethylene (XLPE), which may enable the design of more sustainable high voltage direct‐current (HVDC) power cables, a crucial component of future electricity grids that seamlessly integrate renewable sources of energy. A new type of ionomer is obtained via high‐pressure/high‐temperature free radical copolymerization of ethylene in the presence of small amounts of ion‐pair comonomers comprising amine terminated methacrylates and methacrylic acid. The synthesized ionomers feature a crystallinity, melting temperature, rubber plateau modulus and thermal conductivity like XLPE but remain melt‐processable. Moreover, the preparation of the ionomers is free of byproducts, which readily yields a highly insulating material with a low dielectric loss tangent and a low direct‐current (DC) electrical conductivity of 1 to 6·10−14 S m−1 at 70 °C and an electric field of 30 kV mm−1. Evidently, the investigated ionomers represent a promising alternative to XLPE‐based high voltage insulation, which may permit to ease the production as well as end‐of‐use recycling of HVDC power cables by combining the advantages of thermoset and thermoplastic materials while avoiding the formation of byproducts.

Research on the energy consumption mechanism and characteristics of the gallium indium tin liquid metal arcing process

For high-voltage direct current (HVDC) power grid transmission with higher voltages, the energy-consuming branch of the DC circuit breaker is required to dissipate huge energies of more than megajoules in a short time in the case of a fault and short circuit. The requirements for huge volume and weight are difficult to meet with energy-consuming equipment based on ZnO. In this paper, a new energy consumption method is proposed based on gallium indium tin (GaInSn) liquid metal in the arcing process, and a test platform with adjustable short-circuit current is built. The mechanism triggering GaInSn liquid metal arcing energy consumption is studied. It is found that short-circuit current and channel aperture are the key parameters affecting the energy consumption of liquid metal arcing. The characteristics of GaInSn liquid metal energy consumption are investigated, and four stages of liquid metal energy consumption are found: oscillatory shrinkage, arc breakdown, arc burning phase change and arc extinction. The influence of short-circuit current and channel aperture on the energy consumption characteristics of GaInSn liquid metal is investigated. To further explore the physical mechanism of the above phenomena, a magneto-hydrodynamic model of energy consumption in the GaInSn liquid metal arcing process is established. The influence of short-circuit current and channel aperture on the temperature distribution of the liquid metal arc is analyzed. The mechanism of the effect of short-circuit current and channel aperture on peak arc temperature and the temperature diffusion rate is clarified. The research results provide theoretical support for this new liquid metal energy consumption mode DC circuit breaker.

A Low-cost Optocoupler-Based Isolator System for IoT-Based Voltage Measurement in Low and High voltage DC Applications

Internet of things (IoT) connected devices operate at extremely low voltages that are susceptible to common-mode noise and electromagnetic interference. As a result of this, integrating IoT devices with low or high-voltage direct current power sources requires galvanic isolation which is often expensive to attain. In this work, the use of a low-cost conventional optocoupler (4N35) in the galvanic isolation of an IoT voltmeter required to measure the potential difference of a low voltage direct current source with a maximum relative error of 1% was investigated and experimentally verified. The proposed isolator circuit was first simulated using NI Multism and then fabricated on a printed circuit board for experimental verification after satisfactory simulation results. Measurement results from the experimental verification process were used to fit quadratic and cubic regression equations that approximate the input signal voltage from the isolator’s output voltage measured by the IoT voltmeter. Lastly, the isolator and IoT voltmeter were connected to a variable 100-1000 VDC source via a potential divider network for performance verification at a voltage step of 100 VDC. Here, the isolator successfully achieved its primary goal of providing galvanic isolation between the voltage source and the IoT voltmeter while maintaining a maximum relative error of 1%.

Aggregated SFR model for VSC HVDC interconnected power systems with high penetration of wind power

This letter proposes a novel aggregated system frequency response (ASFR) model, which can fully capture the frequency characteristics of the voltage source converter-based high voltage direct current (VSCHVDC) interconnected power system with high penetration of wind power. First, a multi-machine SFR model is presented, considering the inertia and frequency control processes of VSCHVDC and wind turbines (WTs). Then, a novel aggregation approach is proposed to transform the multi-machine SFR model into a single-machine SFR model on the basis of different control modes of the VSCHVDCs and WTs. Finally, simulation studies are conducted to validate the performance of the proposed ASFR model and its application in frequency response analysis.

IoT Supervised PV-HVDC Combined Wide Area Power Network Security Scheme Using Wavelet-Neuro Analysis

Power system networks are one of the most widely used methods in the real world for transferring large amounts of electrical energy from one location to another. At present, High Voltage Direct Current Transmission is preferred for long distances over hundreds of miles due to minimal power loss and transmission cost of transmission.Due to an increase in power demand, integration of renewable sources to minimise the voltage fluctuations and compensate for power loss is necessary. This is a mandatory requirement to produce sophisticated protection methods for mainly smart systems under various balanced and unbalanced fault conditions. The system protection scheme must respond as quickly as possible to protect the connected devices in a smart environment. The network must be monitored and protected under various weather conditions as well as electrical parametric problems. The proposed research work is carried on the basis of physical monitoring with the aid of the Internet-of-Things and electrical parameters calibrated with the help of wavelet analysis. A wavelet is a mathematical tool to investigate the behaviour of transient signals at different frequencies, which provides important information related to the detailed analysis of faults in power networks. The major goals of this research are to analyse faults using detailed coefficients of current signals through the bior-1.5 mother wavelet for fault identification and artificial neural network analysis for fault localization. This proposed approach furnishes an IoT supervised Photovoltaic - High Voltage Direct Current (HVDC) combined wide area power network security scheme using wavelet detailed coefficients under various types of faults with Fault-Inception-Angles.

Enabling High-Performance Polypropylene Nanocomposites With Interfacial Deep Traps

Polymer nanocomposites are the material of choice for dc insulation. The emerging demand for high-capacity high voltage direct current (HVdc) power transmission requires polymer nanocomposites capable of safe and stable operation at high temperatures. However, the high-temperature electrical properties of current polymer nanocomposites are still unsatisfactory. Here, we report that the modulation of polymer/nanoparticle interfaces can greatly improve the high-temperature insulation properties of polypropylene (PP)-based nanocomposite for recyclable HVdc cable insulation application. The nanoparticles are surface-modified with PP-graft-maleic anhydride (PP- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${g}$ </tex-math></inline-formula> -mah), which is not only well miscible with PP but also contains polar groups to act as interfacial deep traps. We demonstrate that the interfacial deep traps can improve the dc breakdown strength and the electrical resistivity of polymer nanocomposite by inhibiting the charge injection. This work deepens the understanding of interfacial effects in polymer nanocomposites and provides new opportunities for designing high-performance recyclable insulation materials for HVdc cables.

Magnetic fields generated by submarine power cables have a negligible effect on the swimming behavior of Atlantic lumpfish (Cyclopterus lumpus) juveniles.

Submarine power cables carry electricity over long distances. Their geographic distribution, number, and areal coverage are increasing rapidly with the development of, for example, offshore wind facilities. The flow of current passing through these cables creates a magnetic field (MF) that can potentially affect marine organisms, particularly those that are magnetosensitive. The lumpfish (Cyclopterus lumpus) is a migratory species that is widely distributed in the North Atlantic Ocean and Barents Sea. It migrates between coastal spawning grounds and pelagic offshore feeding areas. We tested whether lumpfish respond to MFs of the same intensity as those emitted by high voltage direct current (HVDC) submarine power cables. Laboratory experiments were conducted by placing juvenile lumpfish in an artificial MF gradient generated by a Helmholtz coil system. The intensity of the artificial MF used (230 µT) corresponded to the field at 1 m from a high-power submarine cable. The fish were filmed for 30 min with the coil either on or off. Swimming speeds, and presence in the different parts of a raceway, were extracted from the videos and analyzed. Juvenile lumpfish activity, defined as the time that the fish spent swimming relative to stationary pauses (attached to the substrate), and the distance travelled, were unaffected by exposure to the artificial MF. The swimming speed of juvenile lumpfish was reduced (by 16%) when the coil was on indicating that the fish could either sense the MF or the induced electric field created by the movement of the fish through the magnetic field. However, it seems unlikely that a 16% decrease in swimming speed occurring within 1 m of HVDC cables would significantly affect Atlantic lumpfish migration or homing.

HVDC Fault Detection and Classification with Artificial Neural Network Based on ACO-DWT Method

Unlike the more prevalent alternating current transmission systems, the high voltage direct current (HVDC) electric power transmission system transmits electric power using direct current. In order to investigate the precise remedy for fault detection of HVDC, this research proposes a method for the HVDC fault diagnostic methodologies with their limits and feature selection-based probabilistic generative model. The main contribution of this study is using the wavelet transform based on ant colony optimization and ANN to detect the different types of faults in HVDC transmission lines. In the proposed method, ANN uses optimum features obtained from the voltage, current, and their derivative signals. These features cannot be accurate to use in ANN because they cannot give reliable accuracy results. For this reason, first, the wavelet transform applies to the fault and non-fault signals to remove the noise. Then the ACO reduces unimportant features from the feature vector. Finally, the optimum features are used in the training of ANN as faulty and non-faulty signals. The multi-layer perceptron used in the suggested method consists of many layers, enabling the creation of a probability reconstruction over the inputs by the model. A supervised learning method is used to train each layer based on the selected features obtained from the ant colony optimization-discrete wavelet transform metaheuristic method. The artificial neural network technique is used to fine-tune the model to reduce the difference between true and anticipated classes’ error. The input signal and sampling frequencies are changed to examine the suggested strategy’s effectiveness. The obtained results demonstrate that the suggested fault detection and classification model can accurately diagnose HVDC faults. A comparison of the Support vector machine, Decision Tree, K-nearest neighbor algorithm (K-NN), and Ensemble classifier Machine techniques is made to verify the suggested method’s unquestionably higher performance.

Secondary Frequency Control Considering Optimized Power Support From Virtual Power Plant Containing Aluminum Smelter Loads Through VSC-HVDC Link

The growing number of renewable energy replacing conventional generators results in a loss of the reserve for frequency control in power systems, while many industrial power grids often have excess energy supply due to abundant wind and solar energy resources. This paper proposes a secondary frequency control (SFC) strategy that allows industrial power grids to provide emergency high-voltage direct current (HVDC) power support (EDCPS) for emergency to a system requiring power support through a voltage source converter (VSC) HVDC link. An architecture including multiple model predictive control (MPC) controllers with periodic communication is designed to simultaneously obtain optimized EDCPS capacity and minimize adverse effects on the providing power support (PPS) system. Moreover, a model of a virtual power plant (VPP) containing aluminum smelter loads (ASLs) and a high penetration of wind power is established for the PPS system. The flexibility and controllability of the VPP are improved by the demand response of the ASLs. The uncertainty associated with wind power is considered by chance constraints. The effectiveness of the proposed strategy is verified by simulation results using the data of an actual industrial power grid in Inner Mongolia, China. The DC voltage of the VSCs and the DC in the potlines of the ASLs are also investigated in the simulation.

Centralized Reactive Power Controller for Grid Stability and Voltage Control

The integration of renewable energy sources like solar and wind energy into the transmission and distribution grid has increased gradually for quenching the increasing demand for alternative sources to fossil fuels. However, due to the intermittent nature of the renewable sources primarily solar and wind, the injection of the renewable power generation into the grid shall also be fluctuating which in turn will impact the voltage profile of the transmission and distribution grid. Also, in case of any major load disconnection or generator tripping in a weak grid, the voltage profile will be severely impacted in a weak grid. The aim is to control the sudden major voltage profile disturbance of a weak grid in case of variation of power injected into the weak grid from solar and wind energy and also due to sudden load tripping or generator tripping in the weak grid by controlling the reactive power in the weak grid. In this paper, a centralized reactive power controller has been proposed to control reactive power injection or absorption in the grid. By controlling the reactive power sources and sinks centrally via the centralized controller, any contingency can be met to prevent major disturbance of the voltage profile in the weak grid. This controller shall aim to control the connected reactive power sources &amp; sinks based on the voltage profile of the transmission grid and it shall also engage the Line Commutated Converter (LCC) High Voltage Direct Current (HVDC) Reactive Power Controller. Various cases have been analyzed in this paper for implementation of the centralized reactive power controller for voltage control in the transmission grid.

Comparative Analysis of XLPE and Thermoplastic Insulation-Based HVDC Power Cables

The application of cross-linked polyethylene (XLPE) cables to voltage sourced converter (VSC)-based high voltage direct current (HVDC) systems has already been technically verified and has become common, and thermoplastic (TP) is attracting attention as an insulation material for next-generation cables due to the recent development of material-related technologies. However, studies related to TP cables are mainly focused on improving material properties, and studies related to cable systems are insufficient. In this paper, XLPE and TP cables were designed for application to VSC-based HVDC systems, and major characteristics such as electric field distribution and thermal stability were compared and analyzed through overvoltage simulation. The insulation design method of HVDC cable was presented, and the design was performed using XLPE and TP insulation materials. The temperature and electric field profiles of the cables were also analyzed through a finite element method simulation. To analyze the performance of the designed cable, it was simulated with the PSCAD/EMTDC program. Based on the simulation results, the major characteristics of XLPE and TP cables were compared and analyzed. Results showed that in the case of TP cables, insulation properties were excellent, but thermal conductivity was relatively low; therefore, countermeasures are needed.