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Energy Storage PCS Busbar Design Discussion

11/14

2025

 

1. Discussion Topic

Design discussion and optimization of laminated busbar solutions for Energy Storage PCS
(Power Conversion System).
 

2. Scope of Discussion

This document aims to discuss:

         2.1. Energy storage cabinet power: MW-level, rated voltage 1000~1800V, rated current 1000~2000A.

         2.2. Partial discharge is not within the scope of this discussion.

 

3. Content

As shown in the figure, a typical current market structure is the 3-level configuration,
composed of one capacitor busbar and three IGBT busbars.
This layout has three core drawbacks:

       3.1. High Current-Carrying Cost:

The IGBTs are arranged vertically (bottom to top), resulting in relatively narrow IGBT busbars. Under high-current conditions, the copper thickness must be significantly increased (often to 4mm or even 5mm) to meet current-carrying requirements, substantially increasing material costs.

       3.2. Poor Thermal Performance:

The design consists of six copper layers. The stacking of multiple thick copper plates severely impedes heat conduction, preventing the efficient dissipation of heat generated by IGBT operation, which affects the long-term stability of the module.

       3.3. Unbalanced Current Paths:

The layout causes inconsistent length and cross-sectional area for the current paths to the IGBT positive and negative terminals. This easily leads to differences in parasitic inductance, causing uneven current distribution, which may increase localized device losses and even affect switching characteristics.

 

4. Recommended Layout Optimization

         4.1. Adjust IGBT Arrangement Direction:

Change the IGBT layout to a horizontal, parallel arrangement. This significantly increases thebusbar width without increasing the overall module volume, allowing copper thickness to be reduced from 4-5mm to 2-3mm, while also reducing current density and heat generation.

         4.2. Optimize Number of Busbar Layers and Structure:

Reduce the number of copper layers.

         4.3. Symmetrical Current Path Design:

Plan the busbar routing symmetrically according to the positions of the IGBT positive andnegative terminals. Ensure the current path length and cross-sectional area are consistent forpositive and negative paths, reducing parasitic inductance, achieving uniform current distribution, and minimizing device losses.


5. Optimization Results

         5.1. Significant Improvement in Electrical Characteristics:

Current paths are symmetrical, shorter, and busbars are wider, leading to more balanced current distribution (uniformity ≥ 95%). Total parasitic inductance decreased from 32nH in the original design to 25nH. The inductance difference between positive and negative paths was reduced from 20%-30% to less than 5%.
This greatly optimizes module switching characteristics and noise immunity, reducing switching losses.

       5.2. Dual Optimization of Cost and Volume:

Copper thickness halved (4-5mm → 2-3mm), number of layers reduced (6 layers → 4 layers). Material cost reduced by approximately 35%-40%. Overall module thickness reduced by 60%, making it more suitable for compact installation spaces.Under an ambient temperature of 65°C, the module's maximum temperature is only 80°C, and the busbar temperature rise is controlled within 15°C. This effectively extends IGBT lifespan (estimated 20%-25% increase) and ensures long-term stable operation under high-current conditions.

It is worth mentioning that this design adopts a laminated busbar for the AC output connection, fully utilizing the space on the IGBT module's AC output terminals and allowing that section of the busbar to be widened appropriately. In contrast, typical domestic designs use a single-piece copper busbar for the AC output, requiring the laminated busbar to avoid this area. This prevents efficient use of the space, increases the required copper thickness, and reduces overall space utilization.

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