Development And Application Of Laminated Busbar Technology in Power Systems For Solar-plus-Storage And New Energy Vehicles

With the rapid development of photovoltaic power generation, energy storage systems, new energy vehicles, and high-power power electronics, power converters are evolving toward higher power density, higher switching frequencies, and greater reliability. While the performance of power semiconductor devices continues to improve, parasitic parameters arising from conductor layout, interconnection structures, and device packaging have increasingly become critical factors affecting overall system performance.

 

As a key interconnection structure within the power circuit, the role of laminated busbars has expanded beyond simple power transmission to encompass parasitic parameter control, thermal management, and electromagnetic compatibility (EMC) design. Particularly under high-frequency switching conditions, the busbar structure directly influences the stray inductance of the commutation loop and voltage overshoot during the switching of power devices; consequently, it has become a vital component in the structural design of PV-plus-storage systems and electric drive systems for new energy vehicles.

 

 

 

In traditional low-frequency power systems, busbars primarily handle high-current transmission, with engineering designs focusing on rated current, temperature rise, insulation clearance, and mechanical strength. However, the adoption of power semiconductor devices-such as IGBTs and SiC MOSFETs-capable of high-speed switching has led to significantly higher rates of change for current and voltage. As a result, the parasitic inductance inherent in the conductors themselves exerts a more pronounced influence on the switching process.

 

When significant stray inductance exists in the power circuit, rapidly changing currents generate transient voltages across the inductance. Voltage overshoot can increase voltage stress on power devices and trigger high-frequency oscillations and electromagnetic interference. Therefore, reducing the stray inductance of the commutation loop is a crucial design objective for enhancing the stability of high-power converters.

 

Structurally, traditional single-layer copper bars or cable connections often require long current paths and maintain substantial spacing between positive and negative terminals, creating large loop areas. In contrast, laminated structures minimize the distance between positive and negative conductors, bringing current paths flowing in opposite directions closer together. This enhances the magnetic field cancellation effect, thereby reducing the equivalent stray inductance of the entire power circuit.

 

Currently, laminated busbars are widely utilized in high-power converters, inverters, energy storage power conversion systems (PCS), motor controllers, and electric drive systems for new energy vehicles. In high-power converters, laminated busbars utilize a compact, layered structure to shorten power loops, thereby providing a more controllable electrical connection environment for high-speed switching devices.

 

 

Laminated busbars typically consist of multiple conductive metal layers and insulating dielectric layers. Conductive layers may be made of materials such as copper or aluminum, depending on system requirements for current, voltage, and mechanical structure; insulating layers provide electrical isolation between layers while ensuring thermal resistance, voltage withstand capability, and mechanical reliability.

 

Their low-inductance characteristic stems primarily from the tight coupling between positive and negative conductors. When currents flowing in opposite directions pass through two conductor layers, the resulting magnetic fields are also oppositely directed. Because the distance between the two current paths is minimal, a significant portion of the magnetic flux cancels out in the surrounding space, thereby reducing the magnetic field energy stored within the commutation loop.

 

Consequently, parameters such as conductor spacing, effective loop length, conductor width, and current path layout are critical factors in laminated busbar design. Generally, reducing loop length, minimizing the effective spacing between positive and negative conductors, and optimizing conductor width help to lower parasitic inductance.

 

This structural advantage makes laminated busbars suitable not only for standard power transmission but also for power electronics systems requiring high dynamic response. For instance, low-inductance laminated busbars are often structurally optimized for high-speed switching circuits, using low-inductance designs to mitigate voltage overshoot during device switching.

 

 

 

Photovoltaic (PV) inverters and energy storage converters typically comprise multiple power circuits, including the DC side, power switching modules, filtering units, and the AC output side. As system power ratings increase, traditional wiring and discrete copper busbar connections face challenges such as excessive space requirements, long circuit paths, and complex electromagnetic coupling.

 

In energy storage systems, DC power output from battery clusters requires power conversion for grid integration, load supply, or recharging. Rapid, high-current fluctuations within the DC link place stringent demands on busbar structure. Excessive distance between power modules and DC link capacitors can increase the commutation loop area, thereby raising stray inductance.

 

Consequently, modern energy storage power converters often employ a coordinated layout for DC capacitors, power modules, and busbars to minimize high-frequency current paths and achieve tight coupling between positive and negative terminals through laminated conductors. For equipment requiring a balance between high current-carrying capacity and efficient space utilization, laminated busbars offer a compact, multi-layer interconnection solution.

 

In high-voltage energy storage and specialized industrial power systems, busbar design must also account for insulation clearance, electric field distribution, mechanical mounting, and safety under abnormal operating conditions. Therefore, design cannot focus solely on "low inductance"; instead, a rational balance must be struck among electrical, insulation, thermal, and mechanical performance characteristics.
 

 

 

Electric drive systems in new energy vehicles typically require high-power interconnections between batteries, capacitors, inverters, and motor controllers within a confined space. As vehicle platform voltages shift toward higher levels, power circuits increasingly demand low inductance, low losses, and high integration.

 

Within electric drive inverters, busbars must handle significant transient currents while maintaining appropriate spatial relationships with power modules, DC link capacitors, and control systems. Laminated busbars for electric vehicles utilize multi-layer structures to shorten current paths and employ compact layouts to maximize space efficiency in power interconnection systems.

 

Furthermore, busbars in new energy vehicles must withstand demanding environmental conditions, including vibration, thermal cycling, mechanical shock, and sustained current loads. Compared to simple wiring methods, structured busbars facilitate standardized designs for mounting positions, insulation clearances, and connection interfaces.

 

For varying voltage levels and functional circuits, layered designs-categorized by positive/negative terminals, DC links, AC outputs, and control interfaces-can be implemented to enhance the modularity of the electrical interconnection system. A well-designed busbar structure reduces unnecessary connection points and minimizes the assembly space consumed by complex wiring harnesses.

 

 

With the advancement of high-voltage power electronics, multi-level inverters are increasingly utilized in energy storage, motor drives, and industrial power systems. Compared to traditional two-level topologies, three-level systems feature more complex power circuits and multiple potential levels; consequently, busbars must manage both the interconnection and insulation requirements across multiple electrical nodes.

 

In the case of laminated busbars for three-level inverters, multiple conductive layers must typically be configured according to the specific topology to maintain appropriate spatial relationships between power paths at different potentials. The design process requires considering not only the current-carrying capacity of each conductor layer but also the parasitic inductance and mutual inductance relationships between the layers.

 

Structural symmetry is also crucial for multilayer busbars. Significant discrepancies in path lengths, conductor cross-sectional areas, or connection points among parallel branches can lead to uneven dynamic current distribution across power modules. Over long-term operation, this imbalance can manifest as localized temperature rises and variations in component stress.

 

Consequently, the design of multilayer busbars requires a comprehensive analysis integrating circuit topology, 3D spatial layout, and electromagnetic simulation, rather than relying solely on 2D mechanical dimensions.

 

 

The insulation material within a laminated busbar serves not only to isolate layers but also influences the overall structural dimensions, voltage withstand capability, thermal performance, and long-term reliability. In high-voltage systems, insulation design must account for operating voltage, transient overvoltage, creepage distance, clearance, temperature, and environmental conditions.

 

While reducing the distance between conductor layers helps lower stray inductance, it simultaneously places greater demands on the insulation design. Therefore, the spacing between layers must be optimized based on operating voltage and material properties, rather than simply minimizing insulation thickness.

 

For applications involving high voltages or harsh environments, high-voltage explosion-proof inverter busbars must also address potential risks such as abnormal short circuits, partial discharge, thermal expansion, and mechanical shock. Key insulation properties-including dielectric strength, temperature rating, and long-term stability-must be verified through appropriate testing.

 

Furthermore, areas such as conductor edges, bolt holes, connection terminals, and interlayer transitions are prone to electric field concentration; measures such as rounding, chamfering, insulation wrapping, and structural optimization are required to mitigate local electric field intensity.

 

 

Although laminated busbars offer excellent spatial integration, their multilayer structure alters heat transfer paths. During long-term operation with high currents, copper busbars generate Joule heat, while the insulation layer influences heat conduction between the various conductor layers.

 

Consequently, busbar design requires a comprehensive assessment of factors such as conductor thickness, current density, ambient temperature, heat dissipation methods, and the thermal distribution of adjacent power components. For high-power equipment, thermal simulations or actual temperature-rise tests are essential to verify temperature distribution across different zones.

 

Excessive local current density can lead to significant hotspots. Therefore, conductor width and connection points should be optimized to ensure uniform current distribution, preventing significant current crowding at bolted connections, terminal bends, and areas with cutouts.

 

 

As the integration level of power electronic equipment increases, relying on fully standardized busbar dimensions has become increasingly difficult. Significant variations exist across equipment regarding power modules, DC capacitors, installation space, and interface locations; thus, busbars are typically designed to suit specific circuit topologies and mechanical constraints.

 

Customized design goes beyond merely adjusting length or width; it encompasses multiple aspects, including the number of conductor layers, copper thickness, insulation materials, terminal types, mounting hole locations, and bending configurations. The "Customized Laminated Busbar for IGBT" represents a typical design approach where the structure is tailored to match specific power module interfaces and system layouts.

 

In practical engineering, the development of customized busbars typically involves several stages: electrical schematic verification, 3D structural design, electromagnetic simulation, thermal analysis, prototype fabrication, and testing/validation. This process allows for the early detection of potential issues-such as physical interference, excessive temperature rise, inductance concerns, or insulation failures-before mass production.

 

 

Beyond the sectors of new energy and industrial converters, laminated busbars are increasingly being adopted in telecommunications power supplies, servers, data centers, and high-density power systems. As the power density of computing equipment rises, traditional cabling and distributed connection methods face growing challenges regarding space utilization and current distribution efficiency.

 

In high-density power architectures, multi-layer composite connection bars enable the integration of multiple potential layers into a compact structure, facilitating centralized power distribution across various nodes in accordance with the system topology. Data centers and telecommunications equipment typically demand high reliability for continuous operation; consequently, busbar design must address not only current-carrying capacity but also temperature rise, insulation, maintenance clearance, and mechanical reliability. Compact laminated connection configurations help minimize complex cabling and improve the organization of power connections within equipment cabinets.

 

 

Rail transit systems are characterized by high power requirements, the need for high reliability, and complex operating environments. Power components within traction converters must operate under conditions involving frequent start-stop cycles and fluctuating loads; therefore, power connection structures must simultaneously meet requirements for low inductance, high current capacity, and mechanical reliability.

 

Laminated busbars are suitable for compact power connections in rail transit power conversion equipment; optimized layouts shorten power loops and reduce the space footprint associated with traditional cable connections.

 

In equipment such as industrial variable frequency drives (VFDs), motor controllers, and uninterruptible power supplies (UPS), busbars facilitate DC-side power transmission and the interconnection of switching components. As equipment power density increases, busbars are evolving from simple conductive components into functional structural elements that are integral to the system's overall electrical, thermal, and mechanical design.

 

 

 

As wide-bandgap semiconductors-such as SiC and GaN-see wider adoption, the switching speeds and operating frequencies of power devices will continue to rise. Consequently, power connection structures will need to exhibit lower parasitic parameters and superior high-frequency performance.

 

A key future direction for laminated busbar technology is the further shortening of power loops and the deeper integration of capacitors, sensors, and other functional elements directly into the busbar assembly. Co-designing structural, electrical, and thermal management aspects enables further increases in the power density of the entire power conversion system.

 

Simultaneously, busbar manufacturing will increasingly rely on digital design and simulation-based validation. Techniques such as 3D electromagnetic simulation, thermal simulation, and mechanical finite element analysis (FEA) allow for the prediction of key performance metrics before prototyping, thereby reducing costs associated with iterative design modifications.

 

In terms of application scope, laminated busbars will continue to expand into sectors such as new energy vehicles, energy storage, industrial variable frequency drives, rail transit, data centers, and high-power power supplies. Their core value proposition will shift from simple high-current connectivity toward low parasitic parameters, high integration, high reliability, and system-level power interconnection solutions. Overall, although laminated busbars are fundamental interconnect components in power electronic systems, their structural design directly impacts the switching performance of power devices, system EMI, thermal management, and long-term operational reliability.

 

For high-power, high-frequency, and high-voltage equipment, busbar design has become a critical intersection between electrical and structural engineering. As new energy and high-end power electronic equipment continue to evolve toward higher power densities, busbar technologies focused on low inductance, highly reliable insulation, uniform current distribution, and modular integration will become key areas for the optimization of power interconnection systems in the next stage of development.