Hybrid Vehicle DC Link Voltage Control via Motor Generator Back-EMF
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Solution Overview
Problem
In hybrid electric vehicles, the failure of high voltage parts leads to the inoperability of critical components, causing safety risks and reduced drivability due to the inability to maintain normal battery charging and power supply when the high voltage main relay is turned off, as existing fail-safe methods like transmission map dualization result in unstable voltage supply and low output voltage, making it difficult to stably drive high voltage parts.
Innovation Solution
A fail-safe method and apparatus that determines the status of the high voltage main relay and uses counter electromotive force generated by a motor generator to charge a DC link, with voltage control by an inverter to maintain uniform voltage, enabling the operation of high voltage parts like electric oil pumps and air conditioners even when the relay is off, by generating regenerative or driving torque commands based on voltage discrepancies and using diode regeneration when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transmission map dualization is used to charge the 12V battery when the main relay is turned off, then the 12V battery can be charged, but the voltage supply is unstable and output voltage is low, making it difficult to stably drive high voltage parts
Solution Approach 1:
The patent introduces a DC-DC converter as an intermediary device between the high voltage battery and the 12V battery. This converter mediates the power transfer, enabling stable voltage conversion and supply even when the main relay is turned off. The DC-DC converter acts as a buffer that isolates the instability from the 12V battery charging system while maintaining reliable charging capability.
Solution Approach 2:
The patent changes the voltage parameter by introducing a DC-DC converter that performs voltage conversion. This allows the system to operate with stable voltage levels for high voltage parts while simultaneously charging the 12V battery, resolving the contradiction between charging capability and voltage stability.
2Reliability
If the high voltage main relay is turned off due to abnormality, then safety is improved by isolating the fault, but high voltage parts become inoperative and vehicle driving is disabled
Solution Approach 1:
The patent segments the high voltage system into two independent pathways: one through the main relay for normal operation and fault isolation, and another through the DC-DC converter for fail-safe operation. This segmentation allows the system to maintain critical functions even when the main relay is turned off due to abnormalities.
Solution Approach 2:
The patent prepares a fail-safe pathway using the DC-DC converter before the main relay fails. This beforehand cushioning ensures that when the main relay is turned off due to abnormality, the system can immediately switch to the alternative power supply path, maintaining vehicle drivability while still isolating the fault.
3Loss of energy
If the 12V battery discharges below certain voltage during vehicle driving, then power consumption is reduced, but control power of MDPS is turned off and steering wheel is locked, threatening driver safety
Solution Approach 1:
The DC-DC converter acts as an intermediary power supply that supplements the 12V battery during vehicle operation. This ensures that the 12V battery voltage is maintained above critical thresholds, preventing MDPS control power loss and steering wheel locking, while still allowing controlled power consumption.
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
This solution ensures the stable operation of high voltage parts and prevents 12V battery discharge, enabling continued vehicle operation and extended drivable distance by maintaining a controlled voltage range of 200V to 300V, thus enhancing safety and convenience during emergency driving scenarios.
Implementation Method 1
charging a voltage into a direct current (DC) link using a counter electromotive force generated in a motor generator linked with a revolution of an engine
Implementation Method 2
generating regenerative or driving torque commands based on voltage discrepancies
Implementation Method 3
using diode regeneration when necessary
Data Source
AI summary
A fail-safe method and apparatus for high voltage parts in a hybrid vehicle is provided. In the fail-safe method, it is determined whether or not a high voltage main relay is turned off. Here, when the high voltage main relay is turned off, a voltage is charged into a direct current (DC) link using a counter electromotive force generated in a motor generator linked with a revolution of an engine. Voltage control is performed such that the voltage of the DC link is uniformly maintained using an inverter for the motor generator.