Modular Cascaded H-Bridge Inverter for Charge Balancing and Lower Loss
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Solution Overview
Problem
Existing inverter topologies for electric vehicles face issues with energy loss, heat dissipation, high voltage risks, complexity, and safety concerns due to rapid switching and high DC bus voltages, requiring costly and complex cooling systems and additional equipment for battery balancing and AC charging, which increase weight and reduce allocatable volume for batteries.
Innovation Solution
A multi-level inverter using cascaded H-bridges with modules containing H-bridge power stages, balancing circuits, and a control unit for efficient voltage balancing and communication, allowing for modular design, reduced complexity, and simplified cooling, while supporting various power sources and loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If PWM switching is used to control output voltages, then motor speed control is achieved, but energy loss and heat dissipation increase
Solution Approach 1:
The inverter is divided into multiple independent H-bridge modules, each operating at lower switching frequencies. This segmentation allows distributed PWM control across motor phases while reducing individual module energy loss compared to a single high-voltage PWM inverter operating at high frequency.
Solution Approach 2:
The patent employs periodic switching patterns in the H-bridge modules to achieve motor control. By using coordinated periodic switching across multiple modules rather than continuous high-frequency PWM, the system reduces switching losses while maintaining effective motor speed control.
2Power
If high DC bus voltages are used to reduce current, then power density improves, but safety risks and heat dissipation requirements increase
Solution Approach 1:
The high voltage system is segmented into multiple H-bridge modules operating at lower individual voltages. Each module handles a portion of the total power, reducing the voltage stress on individual components and lowering safety risks while maintaining high overall power density through modular configuration.
Solution Approach 2:
The patent changes the voltage parameter distribution from a single high-voltage bus to multiple lower-voltage modules. This parameter transformation allows the system to achieve high power density through increased current capacity in parallel modules while reducing the harmful effects associated with high voltage such as arcing and insulation breakdown.
3Temperature
If liquid cooling systems are added to dissipate heat, then thermal management is improved, but system weight and complexity increase
Solution Approach 1:
The cooling system is segmented and integrated at the module level rather than requiring a centralized complex cooling system. Each H-bridge module has its own cooling path, allowing simpler thermal management for each unit and reducing overall system complexity through modular heat dissipation.
Solution Approach 2:
Each H-bridge module is designed to manage its own heat dissipation independently. The modular structure allows each unit to serve its own thermal management needs without requiring complex inter-module cooling coordination, reducing overall system complexity.
4Adaptability or versatility
If additional equipment is added for battery balancing and AC charging, then functional versatility improves, but allocatable volume for batteries decreases
Solution Approach 1:
The H-bridge modules serve multiple functions: they enable battery balancing through controlled charge redistribution, support AC charging operations, and provide motor drive functionality. This multi-functionality eliminates the need for separate dedicated equipment for each function, preserving battery pack volume while achieving full functional versatility.
Solution Approach 2:
The patent merges battery balancing and AC charging functions into the same H-bridge power conversion modules that drive the motor. By combining these functions in shared hardware rather than using separate equipment, the system achieves versatile functionality without the volume penalty of additional dedicated components.
5Reliability
If galvanic isolation is implemented to reduce leakage currents, then safety improves, but system complexity and cost increase
Solution Approach 1:
The system uses galvanic isolation at the module level within the H-bridge structures. Each isolated module handles specific voltage levels and functions, providing safety through distributed isolation rather than requiring a single complex isolation system for the entire high-voltage architecture.
Data Source
AI summary
A multi-level inverter using cascaded H-bridge modules, where each module can balance its at least two charge storage elements by means of voltage equalization. Modules are arranged in series into at least one cascade inverter phase with optional center taps, and modules communicate with a control unit by being addressed over at least one serial communication bus. Additional features that can be included in embodiments are the configuration of modules to react to multiple specific addresses in order to increase the maximum output voltage slew rate, metal circuit breaking springs to provide fusing within modules, and the ability to interconnect multiple physically distinct inverters into a single unit. This inverter is predominantly intended for electric vehicle applications, and the optional incorporation of a switching array allows the possibility for power transfer to or from a wide range of voltage sources including other inverters.