Busbar Design Research Articles

Methodology of Low Inductance Busbar Design for Three-Level Converters

Three-level (3L) converters are more susceptible to parasitics compared with two-level converters because of their complicated structure with multiple switching loops. In this article, the methodology of busbar layout design for 3L converters based on the magnetic cancellation effect is presented. The methodology can fit for 3L converters with symmetric and asymmetric configurations. A detailed design example is provided for a high-power 3L-active neutral point clamped (ANPC) converter, which includes the module selection, busbar layout, and dc-link capacitor placement. The loop inductance of the busbar is verified with simulation, impedance measurements, and converter experiments. The results match with each other, and the inductances of short and long loops are 6.5 and 17.5 nH, respectively, which are significantly lower than the busbars of NPC-type converters in other references.

Busbar Design and Optimization for Voltage Overshoot Mitigation of a Silicon Carbide High-Power Three-Phase T-Type Inverter

The silicon carbide (SiC) devices have faster switching speed than that of the conventional silicon (Si) devices, which however may cause excessive device voltage overshoot. Larger gate resistance can help to restrain the overshoot, it however slows down the switching speed and increases switching losses. There are other methods that can mitigate the voltage overshoot, e.g., using low-inductance busbars, adding snubber circuits, etc. In this article, the busbar design for a 250-kW SiC three-level T-type inverter is investigated. The current commutation loops (CCLs) are first analyzed using a single-phase equivalent circuit. Then the detailed busbar design methods, especially a 3-D busbar design concept, are proposed to select the optimal stacking order for the multilayer laminated busbar and to address constraints posed by the physical terminal arrangements of SiC modules and dc-link capacitors. The stray inductance in each CCL is extracted via a finite element analysis and validated on the actual inverter busbar prototypes using an impedance analyzer. To further minimize the busbar stray inductance, a hybrid busbar structure with printed circuit board based buffer circuit using high-frequency decoupling capacitors is designed and evaluated in this article. Finally, the effectiveness of the designed busbars as well as the buffer circuit are validated using experimental studies.

Fractal solar panels: Optimizing aesthetic and electrical performances.

Solar energy technologies have been plagued by their limited visual appeal. Because the electrical power generated by solar panels increases with their surface area and therefore their occupancy of the observer’s visual field, aesthetics will play an increasingly critical role in their future success in urban environments. Inspired by previous psychology research highlighting the aesthetic qualities of fractal patterns, we investigated panel designs featuring fractal electrodes. We conducted behavioral studies which compared observers’ preferences for fractal and conventional bus-bar electrode patterns, along with computer simulations which compared their electrical performances. This led us to develop a hybrid electrode pattern which best combines the fractal and bus-bar designs. Here we show that the new hybrid electrode matches the electrical performance of bus-bars in terms of light transmission and minimizing electrical power losses, while benefiting from the superior aesthetics of fractal patterns. This innovative integration of psychology and engineering studies provides a framework for developing novel electrode patterns with increased implementation and acceptance.

A mathematical investigation of the impact of gridline and busbar patterns on commercial silicon solar cell performance

The cost and efficiency of solar generation are two parameters that must be optimized if it is to replace fossil-fuel sources in the electricity production market. Since the single-junction cell structure still holds the promise of cost-effectiveness and simple production, it is imperative to find ways to increase the efficiency above 20% in production. A comprehensive empirical grid model is first established herein to investigate front grid designs with three, four, and five busbars, the results of which are compared with numerical analysis using Griddler 2-D modeling software. It is found that a combination of segmented tapered metal grids (SG) and uneven busbars (UEB) leads to an increased short-circuit current density (JSC) and open-circuit voltage (VOC) without sacrificing the fill factor. The five-busbar SG–UEB combination results in efficiency above 20% for industrial-sized solar cell without an additional step or layer. The improvement in the cell efficiency obtained using the uneven busbar design is attributed not only to the decreased shading but also to reduced contact recombination underneath the busbars. In addition to increasing the efficiency, the results show that the cost of the front Ag metallization for each cell can be reduced by 1.4¢ per cell by using the presented segmentation method.

Modeling and Mitigation of Multiloops Related Device Overvoltage in Three-Level Active Neutral Point Clamped Converter

This article establishes an analytical model for the device drain–source overvoltage related to the two loops in three-level active neutral point clamped (3L-ANPC) converters. Taking into account the nonlinear device output capacitance, two common modulation methods are investigated in detail. The results show that the line switching frequency device usually has higher overvoltage, and the switching speed of the high switching frequency device is not strongly influenced by the multiple loops. By keeping the nonactive clamping switch off , the effect of the nonlinear device output capacitance can be significantly mitigated, which helps reduce the overvoltage. Moreover, the loop inductance can be reduced with vertical loop layout and magnetic cancellation in the printed circuit board and busbar design. A 500-kVA 3L-ANPC converter using silicon carbide mosfet s was built and tested. The experimental results validate the overvoltage model of the two modulation methods as well as the busbar design. With the nonactive clamping switch off , the overvoltage of both the high and line switching frequency devices is significantly reduced, which helps achieve higher switching speed.

Estimation, Minimization, and Validation of Commutation Loop Inductance for a 135-kW SiC EV Traction Inverter

With growing interests in low-inductance silicon carbide (SiC)-based power module packaging, it is vital to focus on system-level design aspects to facilitate easy integration of the modules and reap system-level benefits. To effectively utilize the low-inductance modules, busbar and interconnects should also be designed with low stray inductances. A holistic investigation of the flux path and flux cancellations in the module-busbar assembly, which can be treated as differentially coupled series inductors, is thus mandatory for a system-level design. This article presents a busbar design, which can be adopted to effectively integrate the CREE’s low-inductance 1.2-/1.7-kV SiC power modules. This article also proposes a novel measurement technique to measure the inductance of the module-busbar assembly as a whole rather than deducing it from individual components. The inductance of the overall commutation loop of the inverter that encompasses the SiC power module, interconnects, and printed circuit board (PCB) busbar has been estimated using finite-element analysis (FEA). Insights gained from FEA provided the guidelines to decide the placement of the decoupling capacitors in the busbar to minimize the overall commutation loop inductance from 12.8 to 7.4 nH, which resulted in a significant reduction in the device voltage overshoot. The simulation results have been validated through measurements using an impedance analyzer (ZA) with less than 5% difference between the extracted loop inductance from FEA and measurements. The busbar design study and the measurement technique discussed in this article can be easily extended to other power module packages. Finally, the 135-kW inverter has been compared to a similar high-power inverter utilizing a laminated busbar to highlight the performance of the former.

Low Stray Inductance Busbar Design and Optimization for SiC-Based Three-Level Device

In this paper, the sensitivity of switching-off voltage spikes of SiC MOSFET and Si IGBT to stray inductance at the same voltage and current levels is compared and analyzed. The influence of the geometric structure of simple stacked busbar on its stray inductance is analyzed and the general guiding principle of busbar design is given. Aimed at the three-level circuit topology involved in this project, based on the analysis of its working principle and commutation circuit, the stray inductance network of stacked busbar is successfully extracted with the help of finite element simulation software ANSYS Q3D, and the idea of optimizing stray inductance of maximum commutation circuit is putted forward. A set of three-level AC-DC-AC power electronic device is designed, and a series of iterative optimization design and optimization results analysis of the busbar of the device are made.

Design and Evaluation of Laminated Busbar for Three-Level T-Type NPC Power Electronics Building Block With Enhanced Dynamic Current Sharing

This article focuses on providing the laminated busbar design guidance for a three-level T-type neutral-point-clamped (3L-TNPC) inverter to achieve low stray inductance and balanced inductance distribution between paralleled power switches. As a result, equalized dynamic current sharing can be accomplished. To discover the design strategy, this article first derives the mutual-inductance-decoupled equivalent circuit for 3L-TNPC. Then, the effects of each inductance item on switching performance can be unveiled, and the parametric targets are then summarized. Accordingly, the busbar design considerations are discussed. A step-by-step busbar design procedure to achieve the aforementioned design targets is provided in the next. The design procedure starts from 2-D optimization to achieve the optimal component and terminal allocation, and then, it increases the optimization degree to 3-D. Using this design procedure, we proposed a novel double-side-end busbar structure to achieve the busbar stray inductance of 12.7 nH and the inductance differences between the paralleled switches to be less than 2 nH. Extensive experiments are carried out in the end to evaluate the design procedure and demonstrate the performance of the busbar.

BUS BAR DAMPING IS A WAY OF INCREASING THE VIBRATION RELIABILITY OF TURBOGENERATOR STATORS

Abstract: The work is devoted to the consideration of the bus bar ring damping of turbogenerator stators. The urgency of the problem of ensuring the vibrational reliability of high-power turbogenerator stators is shown. On the model problem, a series of computational studies on the effect of damping properties of materials on the amplitude-frequency characteristics of the stator buses of turbogenerators was carried out. Based on the results of the computational studies, a bus bar design is proposed, comprising a layer of a vibration-absorbing material. The use of a vibration-absorbing polymeric material in bus bar ring can reduce the amplitude of oscillations up to two times and, accordingly, significantly improve the vibration reliability of the stator elements of the turbogenerator. The results of the research are protected by a patent.

Optimum Wire Busbar Design by Genetic Algorithm

Optimum Wire Busbar Design by Genetic Algorithm

Current sensing by magnetic shielding of high birefringent fibre

Power coupling due to Faraday rotation effect in high birefringent optical fibre is a function of periodicity of field spacing. This idea has been explored to design a new current sensor which is geometrically highly versatile and does not require special design of busbars. The approach used is one of periodic magnetic shielding. This paper provides a description about such a sensor. Formation of such a sensor in practical environment is also stated. For comparison of efficacy of shielding, the same sensor is tried over a simple prototype busbar. In addition, a detailed theoretical analysis for temperature dependence of such a sensor is also given.

Bus Bar Design for High-Power Inverters

This paper presents a comprehensive analysis about bus bar design procedure. Some applications in terms of rated power and shape are investigated regarding their particular requirements and challenges. The dc-link capacitor selection is one of the first and most important steps. It not only dictates the bus bar complexity but also is the key to accomplish a high-power density prototype. Current density and distribution is discussed in this paper based on simulation results. Moreover, the effects of stray inductance and capacitance are explained along with the dc-link capacitors and power semiconductor devices. Simulated results are compared with measurements by a high precision impedance analyzer, which shows the reliability of 3-D modeling-based designs.

Research of mechanical and void properties of composite insulation for superconducting busbar

Pre-preg material has been widely-used in the industry of the aerospace, the wind power, which has many advantages on manufacture process, and can be chosen as an effective complementary insulation method for the Wet-winding and Vacuum Pressure Impregnation technology in the field of superconducting fusion magnets. ASIPP undertaken many engineering tasks on the superconducting coil and busbar design and manufacture for the large fusion device, the pre-preg material and the relevant curing technology were researched as a new method for the high voltage potential components in ITER Feeders, such as the busbars and current leads. Two types of Chinese industrial glass fiber pre-preg insulation composite material were studied and pre-qualified using vacuum bag and silicone rubber assistance technique in ASIPP. The mechanical properties including the ILSS and UTS at 77K, and void content of this composites were measured and discussed in this paper in detail.

3D thermal model and experimental validation of a low voltage three-phase busduct

The thermal behavior of an industrial low voltage non-segregated three-phase busduct was analyzed by means of the comparison of a 3D numerical model with experimental results. This model has been carried out using COMSOL Multiphysics, software based on finite element method. The numerical model replicates the short-circuit test, using the same geometry configuration and the boundary conditions of the laboratory in which this assay was carried out. The standard IEC 61439 was applied, both in test and model, in order to obtain the steady state temperatures in several parts of the busbar system. As a result of the data comparison can be concluded that the experimental test was replicated by the numerical model with sufficient accuracy. The temperature differences between simulation results and those of the heating tests were in a narrow range. On the other hand, a sensitivity analysis was carried out with the intention to study the influence of sensors positioning on the temperature measurement in the laboratory test, thus concluding no high precision was needed in the location of the temperature meters. As a final conclusion of this study, it is needed to point out that the numerical model has the enough exactness to be used in the first steps of the busbar design.

Intercell Busbar Design for Copper Electrowinning

The design of intercell bars is of primary relevance to control electrowinning costs. Two intercell technologies for designing these busbars are presently available: current source (CS) or voltage source. For this research project, we selected CS based on tankhouse operational data that consistently show better performance than its counterpart. Both technologies can be implemented in dogbone or central busbar configurations. Dogbone was chosen because of the better contact distance and larger heatsink area. The proposed design ensures hot swapability. Conventional busbars suffer premature aging, corrosion, and contact deterioration. Industrial samples show these phenomena. Multiphysics finite-element method modeling highlights the origin of this accelerated aging. This work provides design guidelines for S-shaped connectors to overcome previous design flaws. For completeness, the paper includes a design example for an industrial site. The resulting design surpasses standard design practices and secures hot-spot free operation.

Switching Transient Analysis and Design of a Low Inductive Laminated Bus Bar for a T-type Converter

Distributed stray inductance exerts a significant influence on the turn-off voltages of power switching devices. Therefore, the design of low stray inductance bus bars has become an important part of the design of high-power converters. In this study, we first analyze the operational principle and switching transient of a T-type converter. Then, we obtain the commutation circuit, categorize the stray inductance of the circuit, and study the influence of the different types of stray inductance on the turn-off voltages of switching devices. According to the current distribution of the commutation circuit, as well as the conditions for realizing laminated bus bars, we laminate the bus bar of the converter by integrating the practical structure of a capacitor bank and a power module. As a result, the stray inductance of the bus bar is reduced, and the stray inductance in the commutation circuit of the converter is reduced to more than half. Finally, a 10 kVA experimental prototype of a T-type converter is built to verify the effectiveness of the designed laminated bus bar in restraining the turn-off voltage spike of the switching devices in the converter.

Determination of the parameters of a shielded busbar with a rectangular monolithic bus under steady-state conditions with sinusoidal current

A technique to determine the parameters of a shielded busbar with a rectangular monolithic bus at steady-state conditions under sinusoidal current is suggested. The resistances, inductances, magnetic inductions, induced screen current, and bus voltage are calculated taking into account the sinusoidal current frequency and bus and screen materials. The developed technique is based on electromagnetic field equations, which can be programmed using the Mathcard software for engineering calculations of the busbar parameters during computer-aided design of busbars. The validity of the technique is corroborated by the satisfactory agreement between the results of resistance and inductance calculations and the results obtained using the Elcut computer simulation program.

Characterization and Implementation of Dual-SiC MOSFET Modules for Future Use in Traction Converters

Silicon (Si) insulated-gate bipolar transistors are widely used in railway traction converters. In the near future, silicon carbide (SiC) technology will push the limits of switching devices in three directions: higher blocking voltage, higher operating temperature, and higher switching speeds. The first silicon carbide (SiC) MOSFET modules are available on the market and look promising. Although they are still limited in breakdown voltage, these wide-bandgap components should improve traction-chain efficiency. Particularly, a significant reduction in the switching losses is expected which should lead to improvements in power–weight ratios. Nevertheless, because of the high switching speed and the high current levels required by traction applications, the implementation of these new modules is critical. An original method is proposed to compare, in terms of stray inductance, several dc bus-bar designs. To evaluate the potential of these new devices, a first set of measurements, based on a single-pulse test-bench, was obtained. The switching behavior of SiC devices was well understood at turn-off and turn-on. To complete this work, the authors use an opposition method to compare Si-IGBT and SiC-MOSFET modules in voltage source inverter operation. For this purpose, a second test-bench, allowing electrical and thermal measurements, was developed. Experimental results confirm the theoretical loss-calculation of the single-pulse tests and the correct operation of up to three modules directly connected in parallel. This analysis provides guidelines for a full SiC inverter design, and prospects for developments in traction applications are presented.

Simulation Study of Multi-wire front Contact Grids for Silicon Solar Cells

Multi-wire (MW) front-contact schemes represent a promising alternative to standard H-pattern structure with ribbon busbar (BB) in silicon solar cells. In the case of MW schemes, busbar are replaced by copper wires. MW have been demonstrated to enhance the photo-generation with respect to a standard H-pattern structure with ribbon busbar when solar cells are encapsulated and assembled in modules. However, the influence of the geometrical and optical properties of the encapsulation layers as well as of wires on the optical effective shading is not exhaustively treated by the literature. In this work, we have performed electro-optical simulations of MW and BB based solar cells in order to calculate the effective optical shading factor, the enhancement of conversion efficiency and the saving of contact-paste, with respect to the BB design. Specifically, we have studied by means of a ray-tracing simulation tool the significant impact of the front contact grid geometry, of the encapsulation layer thickness and of the optical properties of the cell front interface on the effective optical shading. The calculated values of effective optical shading are used to determine the enhancement of the figures of merit and the paste saving with respect to the reference silver BB scheme. On the basis of our calculations the adoption of optimized MW designs may enhance the conversion efficiency up to 0.5%abs, allowing paste saving up to 50mg per cell.

Numerical Validation of a New Approach to Model Single Junction Low Concentration PV Cells under Non-Uniform Illumination

This study presents a numerical validation of a new approach to model single junction PV cell under non-uniform illumination for low-concentration solar collectors such as compound parabolic concentrators (CPC). The simulation is achieved by finite element modelling (FEM). To characterize the results, the model is simulated with five different non-uniform illumination profiles. The results indicate that increasing the non-uniformity of concentrated light will introduce more resistive losses and lead to a significant attenuation in the PV cell short-circuit current. The FEM modelling results are then used to validate the array modelling approach, in which a single junction PV cell is considered equivalent to a parallel-connected array of several cell splits. A comparison between the FEM and array modelling approaches shows good agreement. Therefore, the array modelling approach is a fast way to investigate the PV cell performance under non-uniform illumination, while the FEM approach is useful in optimizing design of fingers and bus-bars on a PV.