Traction Network Inverter Layout for Integrated AC Charging
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Solution Overview
Problem
Existing traction networks for motor vehicles are not compact enough and have a high component count, which leads to issues with voltage resistance in semiconductor switches and inconsistent charging infrastructure, limiting maximum charging capacity and increasing circuit complexity.
Innovation Solution
A compact traction network design that includes a high-voltage battery, a DC/DC converter, an intermediate circuit capacitor with a neutral point, an inverter with monolithic bidfets, and a three-phase AC charging connection, which integrates a PFC rectifier into the inverter to eliminate a separate rectifier and enable vehicle-to-grid, vehicle-to-home, and vehicle-to-utility operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a separate rectifier is used for AC charging, then the charging function is reliable, but the device complexity and volume increase
Solution Approach 1:
The patent combines the rectifier function with the inverter by integrating bidirectional FETs into the inverter module housing. The inverter now performs both inverting functions (during driving) and rectifying functions (during AC charging), eliminating the need for a separate rectifier component while maintaining reliable charging operation through the bidirectional capabilities of the integrated FETs.
Solution Approach 2:
The inverter is designed with universal functionality to perform both inverting and rectifying operations. The bidirectional FETs enable the same hardware to operate in different modes: converting DC to AC during driving and converting AC to DC during charging, thus making the inverter a multi-functional component that replaces what would traditionally require separate dedicated devices.
2Strength
If traditional semiconductor switches are used, then the design is simple, but the voltage resistance is insufficient for high-voltage operation
Solution Approach 1:
The patent employs bidirectional FETs that integrate both N-channel and P-channel transistor structures within a single monolithic device. This composite semiconductor structure provides enhanced voltage resistance capabilities for high-voltage operation (800V nominal) while the integration into a single module housing reduces the overall circuitry complexity compared to using separate switches with additional protection circuits.
3Adaptability or versatility
If the inverter is designed for driving only, then the design is straightforward, but it cannot support AC charging or vehicle-to-grid functions
Solution Approach 1:
The inverter is designed as a universal power conversion device that can operate in multiple modes: inverting mode during electric driving, rectifying mode during AC charging, and bidirectional power flow mode for vehicle-to-grid and vehicle-to-home functions. The DC/DC converter with bidirectional capability further enhances this versatility, allowing the system to adapt to different charging infrastructures (400V or 800V DC) and enable the vehicle to function as a mobile charging station.
Solution Approach 2:
The system employs dynamic switching control where the bidirectional FETs and DC/DC converter can switch between different operational states and power flow directions based on the required function. This dynamic adaptability allows the same hardware configuration to serve multiple purposes without requiring separate dedicated circuits for each function, managing design complexity through intelligent control rather than hardware multiplication.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves a more compact and efficient traction network with reduced component count, improved voltage handling, and flexibility in charging infrastructure compatibility, allowing for optimal performance and reduced energy losses.
Implementation Method 1
an intermediate circuit capacitor formed from at least two capacitors connected in series and having a neutral point
Implementation Method 2
The inverter has three half-bridges, each half-bridge being assigned a monolithic BIDFET
Implementation Method 3
The three AC charging lines are connected to an AC voltage filter
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to a traction network (1) for a motor vehicle, comprising at least one high-voltage battery (2), a DC/DC converter (11), an intermediate circuit capacitor (C) formed from at least two capacitors (C1, C2) connected in series and having a neutral point (N), an inverter (3), and a three-phase AC charging connection (6), wherein the three AC charging lines (L1-L3) are connected to an AC voltage filter (7), wherein the inverter (3) has three half-bridges (H1-H3), each half-bridge (H1-H3) being assigned a monolithic BIDFET (10), wherein the high-side transistors of the BIDFETs (10) are each connected to a center tap (M) of their assigned half-bridges (H1-H3), and the low-side transistors of the BIDFETs (10) are each connected to the neutral point (N) of the intermediate circuit capacitor (C), wherein the three AC charging lines (L1-L3) are connected to the center taps (M) of the half bridges (H1-H3).