Inverter Controller Activation for Key-Off UCG Mode Mitigation
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Solution Overview
Problem
In electrified powertrain systems, the uncontrolled generator (UCG) mode during high-speed, low or no load conditions leads to excess charging current, potentially damaging inverter and high-voltage battery components due to back-emf exceeding the voltage on the high-voltage bus.
Innovation Solution
An electrified powertrain system with an inverter module, low-power DC/DC converter, and auxiliary power module that detects and mitigates key-off UCG mode by activating the inverter controller and supplying power to low-voltage actuators, using a low-power DC/DC converter to manage voltage and prevent overcharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the electric machine operates in uncontrolled generator mode during high-speed conditions, then electrical power can be generated, but motor back-emf increases causing output voltage to exceed high-voltage bus voltage, resulting in excess charging current that damages inverter and battery components
Solution Approach 1:
The inverter controller is activated before the key-off UCG mode occurs through voltage detection by the low-power DC/DC converter. When the controller detects voltage on the high-voltage DC power bus exceeding a threshold (indicating impending UCG mode), it proactively wakes up and prepares mitigation measures, preventing the harmful excess charging current before it damages components.
Solution Approach 2:
The system implements continuous voltage monitoring on the high-voltage DC power bus. The inverter controller receives feedback about voltage levels and automatically adjusts its state (sleep vs. active) based on this feedback. When voltage exceeds the threshold, the controller activates to control the inverter and prevent UCG mode, creating a closed-loop control system that responds to real-time conditions.
2Reliability
If the inverter controller remains activated continuously to detect and mitigate UCG mode, then component protection is improved, but power consumption increases
Solution Approach 1:
The inverter controller transitions between two operational states: a low-power sleep mode and an active control mode. The controller dynamically switches between these states based on real-time voltage conditions on the high-voltage DC power bus. This dynamic state change allows the system to maintain reliability when needed while minimizing power consumption during normal operation.
Solution Approach 2:
The low-power DC/DC converter autonomously monitors the high-voltage DC power bus voltage and automatically activates the inverter controller when voltage exceeds the threshold, without requiring continuous controller operation. This self-service mechanism enables the system to protect components only when necessary, significantly reducing overall power consumption while maintaining reliability.
3Reliability
If a high-power DC/DC converter is used to manage voltage during UCG mode, then voltage control effectiveness is improved, but system cost and complexity increase
Solution Approach 1:
The system replaces an expensive high-power DC/DC converter with a low-power DC/DC converter that only needs to detect voltage thresholds and activate the controller. The actual voltage control and power management functions are handled by the inverter controller and inverter module, which are already present in the system. This substitution dramatically reduces system cost and complexity while maintaining voltage control effectiveness.
Solution Approach 2:
The inverter controller is designed to perform multiple functions: it controls the inverter during normal operation, detects UCG mode conditions, activates in response to voltage thresholds, and manages power flow during mitigation. This multi-functionality eliminates the need for dedicated separate components, reducing overall system complexity while maintaining effective voltage control.
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
Effectively manages voltage during key-off UCG mode, preventing overcharging and reducing wear on components, while maintaining system functionality and reducing power losses by employing low-cost DC/DC converters and standby controllers.
Implementation Method 1
The low-power DC/DC converter electrically connects between the high-voltage DC power bus and the inverter controller
Implementation Method 2
The auxiliary power module electrically connects between the high-voltage DC power bus and a low-voltage DC power bus
Implementation Method 3
an electric machine, e.g., a permanent magnet (PM) motor may operate in an uncontrolled generator (UCG) mode, wherein motor back-emf increases
Implementation Method 4
Back-emf (electromotive force) refers to voltage generated in an electric motor caused by motion of an armature in relation to magnetic fields from field magnets or windings
Data Source
AI summary
An electrified powertrain system for a vehicle includes an electric machine coupled to a driveline. An inverter controller communicates directly with an auxiliary power module. An ignition module indicates either a key-on state or a key-off state. When the ignition module is in a key-off state, a low-power DC/DC converter generates an output voltage originating on the high-voltage DC bus having a magnitude sufficient to activate the inverter controller. The inverter controller detects a key-off uncontrolled generator (UCG) mode. The inverter controller directly communicates detection of the key-off UCG mode to the auxiliary power module. The inverter controller controls the inverter. The auxiliary power module supplies electric power to operate low-voltage electrically-powered powertrain actuators.