High-voltage System Research Articles

Solvay introduces new polymer for high-heat EV battery module insulation

On March 23, 2023, Solvay announced the introduction of a new high-heat and flame-retardant grade in the company's Xydar® liquid crystal polymers (LCP) portfolio, which is designed to meet critical safety demands in EV battery components. The new Xydar® LCP G-330 HH material addresses challenging thermal and insulation requirements and is targeted particularly at battery module plates of EV models operating with higher voltage systems.

Si3 N4 Passivation and Side Illumination of High-Power Photoconductive Semiconductor Switch Based on Free-Standing SI-GaN

To meet the needs of wide band gap (WBG) gallium nitride (GaN)-based photoconductive semiconductor switch (PCSS) in high-voltage and high-power microwave systems. Herein, silicon nitride (Si3N4) dielectric films were deposited on GaN PCSS using plasma-enhanced chemical vapor deposition (PECVD) and illuminated from the side of the device. A high refractive index of 2.03 and a high permittivity of 7.97 were obtained from Si3N4 films, which are characterized by high optical and dielectric properties. According to the electrostatic field simulation, Si3N4’s high permittivity minimizes the peak electric field at the electrode boundary of GaN PCSSs. When the 532-nm incident light is side illuminated for the device, the output peak power and rise time are 59.8 kW and 0.52 ns, respectively. At a future date, the proposed GaN-based PCSS will have a practical application for radio frequency microwave systems.

The DC Transformer Power Electronic Building Block: Powering Next-Generation Converter Design

Power electronics has evolved from being only present in a few applications such as variable speed drives in the 1970s to becoming ubiquitous, present in almost every industrial application, and powering our daily life. In this ever-expanding market, power converters have become a mature technology covering a wide range of applications, providing solutions from a few watts (e.g., LED drivers) to gigawatts (e.g., high-voltage direct current systems). Competition has driven technology development in pursuit of cost reduction, increased efficiency, performance improvements, high power quality, higher power density, reliability, and an accelerated time to market. To meet these requirements, power converter design has been driven toward a more modular approach based on embedded systems, intelligent power modules, and power electronics building blocks (PEBBs) <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> .

Adaptive Balancing Strategy for Cell Capacitor Voltage in a Modular Multilevel Converter

Due to the modular structure and voltage scalable features, the Modular Multilevel Converter (MMC) has become an alternative converter for high and medium voltage-based transmission systems. Apart from this, MMC has edible features in controlling the real and reactive power for a high-voltage transmission system compared to the conventional converter. However, some of the technical challenges such as control complexity when subjected to more voltage levels, capacitor voltage balancing issues, increase in capacitor voltage ripples, DC fault handling, and circulating current affect the performance of MMC in various applications. In this paper, an adaptive balancing strategy is proposed for capacitor voltage balancing of each cell connected in the MMC. This approach balances the floating capacitor in a simplified manner and henceforth reduces the capacitor voltage ripples to the permissible limit. In addition, the circulating current present in the MMC circuit will be suppressed in comparison to the conventional method. The proposed strategy is investigated under various operating conditions to analyze the effective performance compared to the traditional technique. A comparative study of the proposed approach is presented with various parameters of MMC performed using MATLAB Simulink software.

Formulas calculating the reactance of tubular busbars and their derivation in primary electrical connection schemes

Electrical switching operation in a substation which locates in a high-voltage transmission system alters operating modes of main wiring in either the substation or the system. Major alterations may have negative influences on the switchgear of main wiring in a short time. The quantitative study of this problem has to be based on establishing equivalent circuits of main wiring, when there rarely are formulas to calculate the reactance of tubular busbars. In this paper on the basis of the electromagnetic field theory, the magnetic induction and flux linkages outside and inside tubular conductors are obtained from the Ampere Loop Theorem, and then the formulas to calculate approximately the reactance of tubular busbars with a three-phase parallel arrangement are derived. From the process and results of the calculation in an example it may be seen that the formulas are applied simply, conveniently and rapidly, and may be valuably spread in practical electrical engineering.

Phosphate-Rich Interface for a Highly Stable and Safe 4.6V LiCoO2 Cathode.

Increasing the upper cut-off voltage of LiCoO2 (LCO) is one of the most efficient strategies to gain high-energy density for current lithium-ion batteries. However, surface instability is expected to be exaggerated with increasing voltage arising from the high reactivity between the delithiated LCO and electrolytes, leading to serious safety concerns. This work is aimed to construct a physically and chemically stable phosphate-rich cathode-electrolyte interface (CEI) on the LCO particles to mitigate this issue. This phosphate-rich CEI is generated during the electrochemical activation by using fluoroethylene carbonate and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyletherare as the solvents. Both solvents also demonstrate high thermal stability, reducing the intrinsic flammability of the commercial organic electrolyte, thereby eliminating the safety concern in the LCO-based systems upon high-voltage operation. This stable CEI layer on the particle surface can also enhance the surface structure by blocking direct contact between LCO and electrolyte, improving the cycling stability. Therefore, by using the proposed electrolyte, the LCO cathode exhibits a high-capacity retention of 76.1% after 200 cycles at a high cut-off voltage of 4.6V. This work provides a novel insight into the rational design of high-voltage and safe battery systems by adopting the flame-retardant electrolyte.

One-Body Capillary Plasma Source for Plasma Accelerator Research at e-LABs

We report on the development of a compact, gas-filled capillary plasma source for plasma accelerator applications. The one-body sapphire capillary was created through a diamond machining technique, which enabled a straightforward and efficient manufacturing process. The effectiveness of the capillary as a plasma acceleration source was investigated through laser wakefield acceleration experiments with a helium-filled gas cell, resulting in the production of stable electron beams of 200 MeV. Discharge capillary plasma was generated using a pulsed, high-voltage system for potential use as an active plasma lens. A peak current of 140 A, corresponding to a focusing gradient of 97 T/m, was observed at a voltage of 10 kV. These results demonstrate the potential utility of the developed capillary plasma source in plasma accelerator research using electron beams from a photocathode gun.

Wind energy-harvesting technologies and recent research progresses in wind farm control models

In order to sustain the overall competitiveness of the wind power industry, unrelenting focus is required on working toward the advancement of enabling technologies and research studies that are associated with wind farm systems. First, wind farm technologies that include various turbine generator systems coupled with different power transmission configurations have enormous impact in determining the quality of wind power production. In addition, modern wind farms are expected to implement robust power control algorithms to meet more advanced requirements of electricity generation. Accordingly, this study explores the statuses of wind energy harvesting technologies and wind farm control strategies by discussing their recent and future impact on transforming the wind power industry. Doubly fed induction generator (DFIG)-based wind energy harvesting technology is well-matured and has exhibited an excellent track-record in past and recent experiences, but its capability of being further scalable for large-scale power production is limited as it is largely incompatible with high-voltage power transmission networks. On the other hand, permanent magnet synchronous generator (PMSG)-based technology is making significant advancements to attain the maximum possible efficiency level in greatly facilitating larger scale power generation, although the construction of bulky and costly power transmission systems is required. In this regard, future technological advances in the wind farm industry are expected to reasonably optimize the design and cost of high-voltage power transmission systems. Similarly, an increasing number of research studies are introducing a number of power optimization-based control models to create an ideal integration of the aforementioned wind farm technologies so as to ultimately enhance the reliability of electricity production by maintaining the systems’ safety. Yet, additional work is still expected to be undertaken in the future for a more extended evaluation of the performances of many different control models under a similar environment.

Special issue on all‐electric and hybrid‐electric flight

Special issue on all‐electric and hybrid‐electric flight

Modelling activity in support of MITICA high voltage system protections

MITICA, the full-scale prototype of ITER Heating Neutral Beam (HNBs), has challenging requirements on its power supplies. In particular its unconventional high voltage system is designed to operate at high power and voltage (up to -1 MV dc and about 54 MW), with many interfaces and high voltage insulation technologies co-existing in a single plant. Moreover, the electrical system must manage frequent breakdowns between the accelerator grids during the operation, creating electrical fast transients characterized by extremely high voltage and current peaks. In the conceptual design phase suitable design provisions were conceived to limit the energy in the grids and to limit the overvoltage on specific components in the case of grids-breakdown. The integration tests of the power supplies showed the capability of the system to generate and sustain voltage as high as 700 kV; at higher voltage the voltage withstanding capability was not confirmed as some breakdowns occurred in the plant. Although the location of the breakdowns has not been identified yet, an impact of such breakdowns was highlighted as a couple of the components of the plant suffered a damage. This paper is focused on the analyses performed for the understanding of the fault occurred on the secondary bushing of the 1 MV insulating transformer dedicated to the supply of the Ion Source and Extraction Power Supply system (ISEPS). An extensive activity of modelling and simulation has been developed for explaining the dynamic occurred. The model is based on the stray parameters of the components, which were not easy to be estimated in the design phase, but which turn out to have relevant effects in local fast transient phenomena. After reaching a full understanding of the phenomena, the models have been used to support the conceptual design of an additional protection system for the transformer, for MITICA but also in view of the ITER installation.

A New Modulation for Leakage Current Reduction of Modular Multilevel Converter

Leakage current is an important problem in non-isolated inverters, especially implemented in a medium- and high-voltage system. First, several analyses had carried out to reduce the high-frequency component of common-mode voltage (CMV) and the leakage current of a three-phase modular multilevel converter (MMC). Then, a new modulation method is proposed to keep CMV as the half of dc voltage and suppress the leakage current effectively. The peak value of leakage current can be suppressed under 5 mA, which complies with the VDE-0126-1-1 standard. Meanwhile, the parasitic capacitor voltage can be balanced automatically without the additional capacitor voltage control. Finally, the proposed scheme is verified in MATLAB/Simulink and tested on the hardware-in-loop platform. The effectiveness of the proposed scheme is verified by the experiment results.

Study on mechanical properties of the cross arm-insulator system under strong wind load

High-voltage transmission tower-line systems in coastal areas are often affected by strong winds, which leads to structural damage to the towers. Detailed analysis of the damage mechanism of towers is very useful to ensure the safety and stability of the power system. This paper examines the mechanical properties of the cross-insulator structure under horizontal wind load, and then the load-carrying capacity and deformation performance were analyzed based on ABAQUS. The results show that the structure is stable under the load, and the main structure is basically in the elastic working stage with insignificant flexural and torsional effects. On the contrary, the local stress of the combined link rod connected with the insulator is large; the bending deformation characteristics of the combined link rod are obvious under the maximum horizontal load the insulator can withstand. This result can provide a reference for cross-arms structural safety design.

Modeling of the Transient Electric Field in Multilayer Dielectric Composites Under Impulsive HV Energization

This article presents the theoretical analysis of composite electrical insulation, formed from layered dielectric materials and subjected to impulsive energization. The 1-D planar and cylindrical geometries were considered, consisting of an arbitrary number of layers with arbitrary relative permittivity and electrical conductivity. Analytical solutions have been successfully derived for the time-dependent electric field inside the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${i}$ </tex-math></inline-formula> th layer. To demonstrate the usage of the model under complex multilayer topologies where analytical solutions are nontrivial, the characteristics of a 20-layer-graded composite under microsecond and sub-microsecond impulses were analyzed and validated against a finite-element (FE) solver. Results indicate that the transient electric field response under impulsive energization is strongly dependent on the interplay between the composite relaxation time constants and the characteristic timescales associated with the applied impulse. The model is a further development for the design and coordination of functionally graded materials (FGMs) and composite insulation for high-voltage (HV) system design. This is particularly relevant under fast-rising impulsive conditions as often encountered in many pulsed power applications.

Replacement of LVDS to HVDS for Reduction in Distribution Losses, Improvement in Voltage Profiles and Economic Analysis for National Saving

Introduction: Rural electrification in India is planned with high-capacity distribution transformers which supply the isolated location loads of various categories like agricultural, household, small business, etc. This distribution system planning with non-optimal distribution transformers leads to poor voltage profiles and high power losses in the distribution network. This paper presents that a High-Voltage Distribution System (HVDS) is more suitable than a Low- Voltage Distribution System (LVDS). Methods: A model is developed to evaluate the technical losses, voltage profiles, and optimal payback period of the investments for the planned HVDS network. The replacement of LVDS with HVDS is achieved by replacing high-capacity distribution transformers with small-capacity at optimal locations. Results: The results of this study are validated on the real 11kV agricultural feeder of the Narshinghpur District of Madhya Pradesh, India. Conclusion: The results demonstrate improvement in voltage profiles, low power losses, and optimal payback period for the proposed problem. The obtained results proved that the replacement of LVDS with HVDS would be more beneficial for rural electric power distribution system planning.

An Improved Phase-Disposition Pulse Width Modulation Method for Hybrid Modular Multilevel Converter

The hybrid modular multilevel converter (MMC) consisting of half-bridge submodules (HBSMs) and full-bridge submodules (FBSMs) is a promising solution for overhead lines high-voltage direct current systems (HVDC) due to the advantages of direct current short circuit fault ride-through (DC-FRT) capability. This paper proposes an improved phase-disposition pulse width modulation (PDPWM) method for the hybrid modular multilevel converter. The number of carriers can be reduced from 3N (N is the number of submodules in each arm) to 6. The theoretical harmonic analysis of the improved PDPWM method for hybrid MMC is performed by using double Fourier integral analysis. The influence of three carrier displacement angles between HBSMs and FBSMs in the upper and lower arms on harmonic characteristics is investigated. The output voltage harmonics minimization PDPWM scheme and circulating current harmonics cancellation PDPWM scheme can be achieved by selecting the optimum carrier displacement angles, respectively. The proposed method for hybrid MMC is verified by the simulation and experimental results.

Battery sizing of 48 V plug-in hybrids considering calendar and cycle degradation

Plug-in hybrid electric vehicles (PHEVs) with battery packs tailored to the driving use case can help to reduce the environmental footprint of the transportation sector. Compared to common high-voltage systems, PHEVs based on a low-voltage level show a higher fuel consumption, but in return benefit from lower component costs and allow the utilization of cheaper high-energy cells. In this paper, the battery size of a 48 V PHEV concept is optimized to minimize the operational costs while taking battery degradation into account and ensure a lifetime-robust system layout. To investigate the applicability of high-energy batteries, 31 automotive-grade cells were investigated experimentally in a calendar and cycle aging study. The results show that calendar aging has a significant contribution of 17.5 % to the overall capacity loss and should be considered during the battery design process. The cycle degradation model is integrated in a Dynamic Programming simulation environment with various real-driving speed and slope profiles, which are extracted from a measured year-round driving profile. The simulation results show, that considering the degradation in the energy management strategy reduces the capacity loss but results in higher operational costs throughout the vehicle lifetime. The extension of a mild hybrid vehicle to a PHEV can reduce the operational costs by 18.5 %. If the vehicle is not charged, the costs increase by 6 % highlighting the need for frequent charging of PHEVs.

A Low-Voltage AC, Low-Voltage DC, and High-Voltage DC Power Distribution System with Grid: Design and Analysis

Low-voltage (LV) and high-voltage (HV) DC distribution systems are being investigated as alternatives due to the growth of DC distribution energy resources (DER), DC loads such as solar and wind power systems, and energy storage sources (ESSs). Furthermore, an HV/LV DC distribution system offers various advantages, including lower conversion losses, an easier connecting strategy for DC DERs, and less complex power management techniques. As renewable energy sources are increasingly incorporated into the electrical grid, it is important to create novel, effective approaches for connecting such sources and loads. It would hence be effective to merge DC distribution with AC distribution to fulfill the energy demands of both DC and AC consumers. To this end, this study proposes a multizone design with four buses: low-voltage direct current (LVDC), high-voltage direct current (HVDC), low-voltage alternating current (LVAC), and an electrical grid. A model of this system that covers crucial elements, including power systems, DER systems, and power electronic devices, to serve as a foundation for the analysis and design of this architecture is proposed. MATLAB/Simulink is used to conduct a simulation study to verify the performance of the proposed design. In this study, a hybrid electrical grid with an LVDC, HVDC, and LVAC distribution network test is used and implemented. Additionally, a transient and steady-state characteristic analysis of the test system is performed.

A Fault-Tolerant Strategy for Three-Level Flying-Capacitor DC/DC Converter in Spacecraft Power System

With the development of space exploration, high-power and high-voltage power systems are essential for future spacecraft applications. Because of the effects of space radiation such as single event burnout (SEB), the rated voltage of power devices in converters for a spacecraft power system is limited to a level much lower than that for traditional ground applications. Thus, multi-level DC/DC converters are good choices for high-voltage applications in spacecraft. In this paper, a fault-tolerant strategy is proposed for a three-level flying capacitor DC/DC converter to increase the reliability with minimal cost. There is no extra hardware needed for the proposed strategy; the fault tolerance of the converter is only achieved by changing the software control strategy. A stage analysis of the proposed strategy is provided in detail for different fault locations and ratios between the input and output voltage. Finally, a simulation model and prototype are built to verify the effectiveness of the proposed strategy.

Fault Detection and Classification for Voltage source converter -High Voltage Systems by Using Different Swarm Optimization Algorithms-Based Neural Network

Fault Detection and Classification for Voltage source converter -High Voltage Systems by Using Different Swarm Optimization Algorithms-Based Neural Network

Stability Analysis and Control Design for Multiterminal HVDC Network With Power Flow Controller

The power flow control in high-voltage direct current (HVDC) grids can be improved by employing the interline dc power flow controller (IDCPFC). This article presents an improved control scheme using IDCPFC to balance power flow in the dc networks. In this work, a differential-mode transformer (DMT) is used in combination with a bidirectional buck converter to form a variable DMT. In comparison to the existing methods, the proposed system is scalable to higher voltages and powers, which makes it suitable for high-voltage dc transmission systems. Analysis of a small-signal model of the proposed method and design of compensator for improvement of transient behavior is performed. A simulation is performed with independent feed-forward and feedback control to show the effectiveness of the proposed method. The proposed method is also validated through a 600-W experimental prototype. The experimental results show that the current flow between lines is controlled for unbalance load conditions.