Hybrid Vehicle Emergency Operation via DC-Link Voltage Control
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Solution Overview
Problem
Hybrid vehicles face operational challenges when the high voltage main relay is abnormally off, leading to disconnection of power supply to high voltage components, resulting in vehicle immobilization and battery discharge, especially during EV and HEV modes.
Innovation Solution
An emergency operation method that charges the DC-link terminal using counter electromotive forces from the first and second motors, allowing controlled voltage supply to high voltage components like LDC and electronic oil pumps, enabling the vehicle to operate in a limp-home mode even when the main relay is off, by using the second inverter to manage the DC-link terminal voltage and controlling the torque of the first motor to zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the main relay is used to supply high voltage power to components, then the components can operate normally, but the vehicle becomes immobilized when the main relay fails
Solution Approach 1:
The patent introduces a DC-link terminal as an intermediary power supply node that can receive power from either the main relay or the first motor generator. This intermediary structure allows the system to bypass the failed main relay and maintain power supply to critical components, resolving the contradiction between reliability and adaptability.
Solution Approach 2:
The patent changes the power supply parameter by switching from main relay-based power supply to first motor generator-based power supply. By controlling the first motor generator to operate in generator mode and supply power to the DC-link terminal, the system adapts to the main relay failure condition while maintaining vehicle operability.
2Reliability
If the first motor generates power to charge the DC-link terminal, then the vehicle can operate in emergency mode, but the voltage control performance deteriorates in high speed regions
Solution Approach 1:
The patent dynamically adjusts the torque of the first motor generator based on vehicle speed conditions. In high speed regions, the controller reduces or sets the torque to zero to prevent excessive voltage generation that would compromise voltage control performance, while still maintaining emergency operation capability at lower speeds.
Solution Approach 2:
The patent implements feedback control by monitoring the torque command of the first motor generator and adjusting it based on vehicle speed. The controller uses speed feedback to determine when to reduce torque in high speed regions, thereby maintaining optimal voltage control performance while preserving emergency operation capability.
3Reliability
If the vehicle operates in EV mode with the main relay off, then the low voltage battery discharges continuously, but operating in HEV mode with engine clutch connected allows power generation
Solution Approach 1:
The patent enables the first motor generator to serve dual purposes: as a motor during vehicle propulsion and as a generator for self-charging the DC-link terminal and low voltage battery. This self-service capability allows the system to generate its own power when operating in HEV mode with the engine clutch connected, eliminating continuous battery discharge.
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 the hybrid vehicle to perform emergency operations and maintain voltage control performance in high speed regions, preventing battery discharge and ensuring the vehicle can travel in both EV and HEV modes by using the DC-link terminal as a power supply, even when the main relay is malfunctioning.
Implementation Method 1
charging a DC-link terminal with a first counter electromotive force of the first motor generated by driving energy of the vehicle transmitted from the vehicle wheel
Implementation Method 2
a second counter electromotive force of the second motor generated by power of the engine
Data Source
AI summary
An emergency operation method of a hybrid vehicle, which includes an engine, a first motor connected to the engine through an engine clutch and transmitting power to a vehicle wheel, and a second motor connected with the engine to directly transmit power, includes charging a DC-link terminal with a first counter electromotive force of the first motor and the second motor generated by driving energy of the vehicle or power from the engine when a main relay is off while the vehicle travels. A voltage of the DC-link terminal is controlled by using a second inverter which is connected between the DC-link terminal and the second motor in a driving state of the engine. Power is supplied by using the DC-link terminal, of which the voltage is controlled, for an emergency operation of the vehicle.