Busbar Design Research Articles

Optimizing the design of parallel busbars to suppress the Taylor Instability in large-scale liquid metal batteries

Abstract In this study, we utilize the open-source software OpenFOAM to numerically simulate the Tayler instability in liquid metal batteries. The simulation depicts the dynamic evolution of the electrolyte layer, fluid flow, and magnetic field distribution in the battery at different operating times. Special attention is paid to the influence of optimizing the parallel busbar configuration on Tayler instability and battery capacity. It is found that the additional magnetic field generated by the busbars can effectively alter the magnetic field distribution inside the battery, thereby significantly reducing the Lorentz force and suppressing the Tayler instability within the battery. Therefore, by optimizing the parallel busbar configuration, the stable operating time of the battery is prolonged, and the battery capacity is enhanced. This study provides theoretical support and practical guidance for the application of liquid metal batteries in large-scale grid-level energy storage systems and offers new insights into the development of energy storage technology.

Design and Characterization of Bus Bars for 1MVA Three-level ANPC Inverters in Aerospace Applications

Design and Characterization of Bus Bars for 1MVA Three-level ANPC Inverters in Aerospace Applications

Optimal Busbar Design for the Press-Packed IGBT-Based Modular Multilevel Converter Submodule Considering Both Normal and Fault Ride-Through Conditions

Optimal Busbar Design for the Press-Packed IGBT-Based Modular Multilevel Converter Submodule Considering Both Normal and Fault Ride-Through Conditions

Novel busbar design for screen-printed front side Al metallization of high-efficiency solar cell

The need to reduce the silver consumption for future global PV production requires novel approaches for cell metallization and module integration. A screen-printed aluminum cell metallization on the front side could contribute here, but requires a redesign of the solder pads and busbars. A compromise between shading and resistive losses is needed. We investigate the inclusion of Ag solder pads in high-aspect-ratio Al finger grids on the front side of p-type back junction solar cells featuring passivating polysilicon on oxide (POLO) contacts on the rear side. In order to determine the optimal geometric dimensions of the solder pads, we characterize the resistance at the interface between the Ag solder pads and the Al finger grid in dependence on the size of the overlap between the two paste. A contact resistance of 285 mΩ is determined for 200 μm-narrow Al busbars and small solder pads of 750 μm in length. This would require tens of solder pads per busbar for acceptable power losses below 0.5 % coming along with significant shading. Therefore, a new metallization design is developed. We use narrow Ag busbars with a widened intersection to the Al fingers in order to reduce the contact resistance caused by the Ag–Al alloy. Thereby, the shading losses of the solderable busbars and pads are less than 1.5 %.

Economic Implementation of 99.98% Efficiency in Natural-Cooling Modular MVDC SSCBs

This paper presents a modular medium voltage direct-current (MVDC) solid-state circuit breaker (SSCB) with high efficiency. The presented design method is modularity oriented, which includes thermal analysis of conduction cell, busbar design of conduction disk, and structure design of conduction tower. The implementation includes both continuous current conduction and fault current interruption. This paper includes three major contributions. First, it presents an economic analysis in terms of efficiency and cost as the design guideline for the main conduction configuration of SSCBs. Second, it provides a complete modular SSCB design procedure, showing both parallel and cascade scalability. Third, this paper investigates the effect of main conduction path stray resistances on SSCB efficiency and power loss. A medium-voltage SSCB prototype rated at 4kV/100A are experimentally implemented. The power density achieves 26.2 kW/L. The continuous conduction tests are conducted at 100A for 1hour, the steady-state efficiency achieves 99.98% with maximum temperature of 37°C. The fault interruption tests are successfully conducted at 4 kV/ 137A and 4 kV/ 1 kA with different system inertia.

A Megawatt-Scale Si/SiC Hybrid Multilevel Inverter for Electric Aircraft Propulsion Applications

This paper presents the design and development of a megawatt-scale medium-voltage (MV) hybrid inverter prototype to validate its feasibility and potentials for the electric propulsion on the next-generation electric aircraft system with an onboard MV dc distribution, e.g., 3 kV dc bus in this work. The proposed hybrid converter consists of a three-level active-neutral-point-clamped (ANPC) stage using 3.3 kV silicon IGBTs cascaded with an H-bridge stage using cost-effective 1.2 kV SiC MOSFETs in each phase. Comprehensive design and evaluation of the full-scale prototype are elaborated, including the low-inductance busbar design, converter architecture optimization and system integration. In addition, a low computational cost space vector modulation with common-mode voltage (CMV) reduction feature is proposed to fully exploit the benefits of SiC MOSFET in this hybrid topology. Extensive simulation and experimental results are provided to demonstrate the performance of each power stage and the full converter assembly in both the steady-state operation and variable frequency operations. Compared with the widely adopted IGBT based ANPC converter in MV applications, the proposed 7-L hybrid inverter system features higher power efficiency, reduced harmonics, higher dc voltage utilization, reduced CMV and lower dv/dt, while remains cost effective compared to the solution using MV SiC MOSFETs.

Bus Design for the Poloidal Field Coils of the NSTX-Upgrade Fusion Device

The National Spherical Torus eXperiment (NSTX) has undergone a major upgrade to NSTX-U at Princeton Plasma Physics Laboratory (PPPL). NSTX upgrade (NSTX-U) will double the toroidal field, plasma current, and neutral beam injection heating power, as well as significantly increase the pulse duration. NSTX-U uses three poloidal field (PF) coils at the vessel top and three at the bottom near the divertor areas to control the local plasma shape there. These shaping coils operate at a maximum terminal voltage of 2 kV, corresponding to a maximum current about 20 kA. To supply the power to the PF coils, hard copper bus bars are typically used near the vacuum vessel, while water cooled flexible cables are used away from the vessel. The detailed design of the hard copper bus bars will be covered in this article. During operation, these hard bus bars are subject to high electromagnetic (EM) forces, thermal displacement loads, as well as plasma halo loads due to disruption. The EM, thermal, and structural analysis were performed, and the results revealed that, with the worst loads combined, the new design meets the NSTX-U thermal, structural, and fatigue cycle requirements. The manufacturing and installation process of the bus work will be discussed at the end of this article.

XNOR-Nets with SETs: Proposal for a binarised convolution processing elements with Single-Electron Transistors

Deep neural network (DNN) and Convolution neural network (CNN) algorithms have significantly increased the accuracies in cutting-edge large-scale image recognition and natural-language processing tasks. Generally, such neural nets are implemented on power-hungry GPUs, beyond the reach of low-power edge-devices. The binary neural nets have been proposed recently, where both the input activations and weights are constrained to + 1 and − 1 to address this challenge. Here in the present proof-of-concept study, we propose a simple class of mixed-signal circuits composed of single-electron devices and exploit the nonlinear Coulomb staircase phenomena to alleviate the challenges of binarised deep learning hardware accelerators. In particular, through SPICE modeling, we demonstrate the realisation of space-time-energy efficient XNOR-Accumulation (XAC) operation, reconfigurabilty of XAC circuit to perform 1D convolution and a busbar design to augment a contemporary accelerator. These nanoscale circuits could be readily fabricated and may potentially be deployed in low-power deep-learning systems.

Transverse energy confinement and resonance suppression in SAW resonators using low-cut lithium tantalate

This paper discusses the applicability of double busbar design to surface acoustic wave (SAW) devices employing low-cut lithium tantalate (LT) with a multi-layered structure. This design offers good energy confinement, scattering loss suppression and transverse mode suppression for a wide frequency range. In addition, the effectiveness of manipulating the slowness curve shape for transverse mode suppression is demonstrated. First, three different lateral edge designs are applied to the layered SAW configuration on low-cut LT, and their performances are compared using the periodic three-dimensional finite-element method powered by the hierarchical cascading technique. Then, the discussion is extended to the influence of the SAW slowness shape to the transverse mode suppression.

Unit Partition Resonance Analysis Strategy for Impedance Network in Modular Power Converters

In modular power converters, the dc-link capacitor has the highest failure rate due to thermal stress, reducing system performance and reliability. Current harmonics are one of the prominent causes of thermal stress on the dc-link capacitor that may get instigated by the resonance between the dc-link capacitor and stray inductance of the busbar. The dc-link capacitor current harmonics mitigation through busbar design optimization has not been reported. The challenge lies in analyzing the profound resonance characteristics of high order dc-link busbar impedance network as no insightful information can be obtained from impedance analyzers. This paper features a new strategy for high power modular converters that splits the high order dc-link busbar impedance network into corresponding lower-order sub-units. Then, the required relationship between resonating components and corresponding resonance frequencies is attained by exploiting the structural symmetry of the standard modular power unit as well as the inheritance relationship between sub-circuit units and the combined network. Finally, leveraging the derived resonant frequencies expressions, busbar structure is optimized, and up to 23% reduction in capacitor RMS current is achieved. Simulation and experimental results are provided to validate the efficacy of the proposed analysis method. The in-depth theoretical study featured in this paper can dictate not only the busbar design optimization but also a key to improve capacitor lifetime and reliability of the system.

Optimized Design of Laminated Busbar for Large-Capacity Back-to-Back Converters

As a key component of a large-capacity converter, the laminated busbar can improve the reliability, integration and power density of the converter and has great advantages in reducing the parasitic inductance of the switching loop. The laminated busbar suitable for a high-capacity back-to-back converter has a complex structure, and couple with each side converter. It has been challenging to optimize the equivalent inductance by using the traditional single-converter busbar design method. In this paper, the coupling inductance model of the back-to-back converter is established, and the relationship between the voltage stress of the switch tube and the stray inductance is analyzed in detail. Based on this, the design principle of the laminated busbar is proposed, and an optimized design structure of the laminated busbar suitable for the large-capacity back-to-back converter is given. Finally, the results were effectively verified by simulation analysis and a 180 kW integrated intermediate frequency auxiliary power converter.

EMI Performance of Active Neutral Point Clamped Phase Leg for Dual Active Bridge DC–DC Converter

This article evaluates the electromagnetic interference (EMI) caused by active neutral point clamped (ANPC) phase leg undergoing zero voltage switching (ZVS). ZVS, together with a high fundamental frequency operation is encountered in dual active bridge (DAB) converters. This allows ANPC phase leg to be operated in a different manner than its inverter counterpart. A comprehensive evaluation of four switching schemes for NPC/ANPC-DAB with regard to their EMI performance, voltage overshoot, and losses have been done. Switching state redundancies have been used to reduce the EMI of the ANPC phase leg. To further help in reduction of high frequency EMI and voltage overshoot, a low inductance busbar design has been presented for through-hole discrete devices. Finite element simulation and measurement results show a busbar inductance of 7.7 nH for long commutation loops. Finally, EMI performance (conducted and radiated) together with the busbar design has been experimentally validated for two of the most useful switching schemes. The switching schemes and the busbar design can boost adoption of NPC/ANPC-DAB by ensuring EMI compliance and improved efficiency without affecting the normal DAB operation or using additional hardware.

A Novel Method for Busbar Design of Electric Vehicle Motor Drive

At present, the DC busbar design is one of the bottlenecks restricting the improvement of the power density of motor drives. Therefore, this paper proposes a three-dimensional line probe algorithm, which can realize the automatic routing of laminated busbar in motor drives. The specific rules and implementation of this method are introduced in detail in this paper. Finally, an example of busbar design of a vehicle motor drive is given to verify the routing rate and execution speed of the algorithm.

DC-Link Busbar Network Design and Evaluation Method for the Large-Capacity Power Electronic Converter

For the dc-link busbar in a high-capacity converter, the large-size laminated busbar is not adoptable due to the machining difficulty and limitation in current capability. In contrast, the regular nonlaminated busbar solution guarantees the required power capacity with a lower cost and easier installation. The main challenges exist in the large stray inductance and corresponding resonance phenomenon. Related analysis and accurate synthesis theory have not been reported. In this article, a matrix analysis method is proposed for the formed multiport and high-order network in a dc-link busbar. First, the multiport interaction and coupling are mathematically derived based on the subnetwork admittance matrix combination. The multipeak resonance phenomena are explained in detail. Meanwhile, it is manifested that proposed matrix method can be applied with the positive and negative sequence current analysis. Then accurate resonate currents can be obtained under the nonsinusoidal busbar current consideration. Finally, a resonance current gain (RCG) value is formed for the quantitative capacitor current evaluation and busbar design guidance. Proposed design and evaluation method is verified in a 315-kW converter system. More than 49% resonant current in the capacitor gets depressed by the enhancement. Its effect is close to the laminated busbar solution.

Electrothermal design of DC busbars for fusion facilities

The power supplies of nuclear fusion facilities are normally placed far (hundreds of meters) from the load coils and are connected to them through proper DC busbars. The design of such busbars is not trivial, as it must identify a tradeoff among different specifications. In this paper, the busbar electrothermal design is approached by specific tools and optimization criteria, taking into account the expected operating scenarios. The developed practical formulae, after being validated and extended by a finite-element method (FEM), were used to size the busbars according to the adopted criteria. It interesting that different criteria are predominant in case of steady-state or pulsed busbars, leading to selection of different materials and configurations. The described algorithms were applied for the design of the busbar system of the DTT facility, but they can also be exploited in many applications and fields.

Integrated Busbar Design for Stray Inductance and Volume Reduction in a High-Power SiC Traction Inverter

<div class="section abstract"><div class="htmlview paragraph">This paper presents a compact, partially laminated busbar design to connect the DC-link capacitor, high-voltage DC (HVDC) connector, and power module using a single integrated busbar. The proposed busbar design is designed for a high-power and high-voltage Silicon Carbide (SiC) traction inverter. The proposed solution eliminates the need for using separate busbars: one for the connection between the HVDC connector and the DC-link capacitor, and the other one between the connection of the DC-link capacitor and the power module. Incorporating two busbars in a single traction inverter increases the total volume of the inverter and the parasitic components. Thus, the main design goals in this paper are minimizing the parasitic inductances, increasing the power density, and achieving a uniform current distribution across the capacitor cores. Additionally, the compact busbar design allows a reduction in the parasitic resistance compared to two separate busbars and, hence, it reduces the power loss. The voltage overshoot and maximum allowable stray inductance of the busbar are investigated in detail. Current density and its effect on the busbar temperature rise are analyzed using 3D finite element analysis.</div></div>

A design proposal for the European DEMO superconducting bus bars and current leads

The integration of the feeder system in a tokamak involves complex engineering, manufacturing and logistics issues. Therefore, within the pre-conceptual design activities of the European DEMO fusion reactor, it is important to provide a preliminary sizing of the feeders at an early stage. Here we present the conceptual design of superconducting bus bars and current leads for the DEMO feeder system. The proposal is based on three main components: Nb3Sn lead extensions, NbTi bus bars and HTS current leads. We propose three different bus bar designs – for the TF, CS and PF coil feeders, respectively. Two additional values of the TF operating current are considered. The structural verification of the bus bars, including an S-bend geometry for reducing the mechanical loads due to cool down, is performed both analytically and by means of 3D finite-element simulations. In addition, we present an outline design of the HTS current leads, based on the minimisation of the cryogenic heat load and the simulation of a loss-of-flow accident. Finally, we briefly discuss the main characteristics of the joints, as well as some integration and assembly challenges.

A Review of Architectural Design and System Compatibility of Power Modules and Their Impacts on Power Electronics Systems

The architectural design of a power module determines its application. And the efficacy of a power module layout appears in the system performance by assisting low-inductive busbar design. In this article, some of the previously proposed power modules are reviewed and analyzed considering their system-level applications and their impacts on the architectural design approach. A codesign methodology is then described that accounts for power module system compatibility. The resultant module designs improve the performance of widebandgap (WBG) power semiconductor devices with respect to their interaction with the rest of the power electronics system, such as gate drivers and dc-link capacitor bank. A few common power modules are categorized by architecture and layout; the interdependency of the power modules to each other in a multiphase system and the impact of the power module layout on the busbar and system design are investigated using ANSYS Q3D to elaborate the effectiveness of the proposed power module design methodology.

Power Loop Busbars Design and Experimental Validation of 1 kV, 5 kA Solid-State Circuit Breaker Using Parallel Connected RB-IGCTs

This article investigates the design of a 1 kV, 5 kA solid-state circuit breaker by using parallel connection of reverse blocking IGCTs (RB-IGCT). The presented breaker topology is based on the parallel connection of low conduction loss RB-IGCTs which delivers efficiency as high as 99.9%. The focus of this article is on the power loop design and experimental validation of parallel connection of two and three RB-IGCTs with emphasis on current sharing during dynamic events such as short-circuits. A 3-D CAD-based design of power loop busbars was verified by several simulation test cases to represent dynamic current sharing under variations in RB-IGCT package impedances. An optimized busbar design approach and its tradeoffs are also discussed with simulation verification. The experimental results confirm that the parallel topology is able to perform current interruption during overload and short-circuit situations up to 10 kA for two devices in parallel and up to 14 kA for three devices in parallel - with current deviation from the mean as little as 6%.

CFD Investigation of Bath Flow and Its Related Alumina Transmission in Aluminum Reduction Cells: Slotted Anodes and Busbar Designs

Alumina is an indispensable raw material for the modern aluminum electrolysis industry. The distribution and transmission of alumina within the bath is of great significance to maintain stable operation and reduce energy consumption. In this study, a computational fluid dynamics (CFD) model was developed to investigate the bath flow and its related alumina transmission in aluminum reduction cells. The bath flow driven by bubbles, electromagnetic force, and aluminum flow presented two different sized vortices in the horizontal plane of the anode–cathode distance (ACD). Both numerical results and industrial data show that the average alumina concentration in the half-cell at the duct end is slightly larger than that of the tap end. With the application of slotted anodes, the maximum velocity of the bath flow increased and the average velocity decreased slightly in the horizontal plane, resulting in a more uniform distribution of alumina than that in the use of unslotted anodes. The symmetrical nature of the bath flow vortices became more obvious with the upgrade of the busbar design and the alumina concentration gradient became smaller within the bath.