Dual-Bank EV Propulsion Fault Handling at High Back-EMF Speeds
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing propulsion systems for electric vehicles face challenges in handling faults such as sensor failures in electric machines or inverters, particularly when operating at different charging voltages like 400V and 800V, which can reduce vehicle functionality and safety during high-speed operations.
Innovation Solution
A dual battery bank propulsion system with dual and/or multiphase inverters and electric machines that can operate in safe-state modes like safe pulse-off and active short-circuit modes, allowing for enhanced redundancy and limp home functionality by managing back-EMF and brake torque levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a propulsion system uses a single battery bank and single three-phase system, then the device complexity is low, but the reliability and redundancy are insufficient when faults occur at high speeds
Solution Approach 1:
The propulsion system is divided into two independent three-phase systems (first and second), each with its own inverter and battery bank connection capability. This segmentation allows one system to fail while the other continues to operate, providing redundancy and improved fault handling capability without requiring a completely complex re-architecting of the entire propulsion system.
Solution Approach 2:
The propulsion system is designed with universal components that can function in multiple modes: the dual battery banks can operate independently or in parallel, the inverters can handle both 400V and 800V charging voltages, and the control system can switch between normal operation, safe-state mode, and limp home mode. This multi-functionality improves reliability across different operating conditions without proportionally increasing complexity.
2Reliability
If the vehicle operates at high speed when a fault occurs, then the productivity is maintained, but the safety risk increases due to insufficient time to reduce speed to safe levels
Solution Approach 1:
The system implements beforehand cushioning by pre-configuring safe-state modes that can be immediately activated when faults are detected. The dual battery bank architecture and redundant three-phase systems are prepared in advance, allowing the system to transition to safe-state mode without requiring speed reduction, thus maintaining productivity while ensuring safety through pre-established protective mechanisms.
Solution Approach 2:
The propulsion system performs self-service by automatically detecting faults and transitioning to appropriate safe-state modes without external intervention. The control system monitors system health continuously and can independently switch between operational modes, maintain safe-state conditions, or activate limp home functionality, eliminating the need for manual speed reduction or external control during fault conditions.
3Reliability
If the inverter transistors are kept in open state during safe pulse-off mode, then the component damage risk is reduced, but the back-EMF voltage must remain below the battery voltage limiting the speed range
Solution Approach 1:
The system applies parameter changes by switching between different safe-state modes based on operating conditions. When back-EMF is below battery voltage, safe pulse-off mode is used with transistors in open state for component protection. When back-EMF exceeds battery voltage at higher speeds, the system transitions to active short-circuit mode, changing the transistor state from open to closed, thus extending the operational speed range while maintaining component protection through appropriate mode selection.
Solution Approach 2:
The propulsion system implements dynamics by making the inverter transistor states adjustable and switchable rather than fixed. The system can dynamically transition between safe pulse-off mode (transistors open) and active short-circuit mode (transistors closed) based on real-time back-EMF measurements and operating conditions, allowing the system to adapt to varying speeds while maintaining component protection and expanding the safe operational range.
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
Enables safe operation and extended functionality during faults, allowing vehicles to maintain safe-state modes at higher speeds and reduce the risk of overcharging or component damage, thereby improving redundancy and limp home capabilities.
Implementation Method 1
The safe pulse-off mode can be used as long as the back-EMF (back electromotive force) in the electric machine is lower than the corresponding DC-voltage of the battery
Data Source
AI summary
A propulsion system for an electric vehicle comprising a high voltage battery unit having a first high voltage battery connected in series with a second high voltage battery, which may also be referred to as a first and second battery bank, and one or more power inverters arranged to connect the battery banks to one or more electric machines. The one or more power inverters and the one or more electric machines are configured to form a first and a second three-phase system. The described architecture incorporating dual battery banks, and dual and/or multiphase inverters and electric machines can provide enhanced redundancy and limp home functionality in cases where a fault or error occurs in the inverter and/or in the electric machine so that a faulty three-phase system can be operated in a safe-state mode.