Hybrid Vehicle Overvoltage Protection and Relay Status Detection
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Solution Overview
Problem
In hybrid vehicles, when a voltage on the battery side becomes overvoltage during regenerative control, the booster converter is shut down to prevent further overvoltage, but this makes it impossible to check if the system main relay is turned off, leading to the battery being charged or discharged unexpectedly, which can cause breakdowns and prevent the vehicle from traveling in limp home mode.
Innovation Solution
The hybrid vehicle includes an engine, generator, motor, drive circuit, battery, low-voltage and high-voltage electric power lines, a booster converter, and a system main relay, controlled by an electronic control unit to shut down the booster converter, turn off the system main relay, and start the engine, allowing the vehicle to travel without battery charging or discharging, and to check if the system main relay is stuck on.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the booster converter is shut down to prevent overvoltage, then the overvoltage state is inhibited, but the ability to check system main relay status is lost
Solution Approach 1:
The system performs a preliminary check of the system main relay status by attempting to activate the booster converter immediately after an overvoltage event. This preliminary action determines whether the relay is stuck in the closed position before deciding on the limp home mode, resolving the contradiction by restoring detection capability without causing harmful overvoltage.
2Productivity
If the system main relay is not checked, then the vehicle can travel in limp home mode, but the battery may be charged or discharged unexpectedly causing breakdown
Solution Approach 1:
The system implements a feedback mechanism where the status of the system main relay is actively checked by attempting to operate the booster converter. This feedback ensures that the relay is properly open before allowing limp home mode, preventing unexpected battery charging or discharging while maintaining vehicle mobility.
3Difficulty of detecting and measuring
If the booster converter is activated to check relay status, then relay status can be determined, but overvoltage may occur again
Solution Approach 1:
The system performs a preliminary check of the system main relay status by attempting to activate the booster converter immediately after an overvoltage event. This preliminary action determines whether the relay is stuck in the closed position before deciding on the limp home mode, resolving the contradiction by restoring detection capability without causing harmful overvoltage.
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 enables the hybrid vehicle to travel in limp home mode without battery charging or discharging, preventing potential battery breakdowns and ensuring safe operation by determining if the system main relay is off, and removing overvoltage states early.
Implementation Method 1
The booster converter is connected to the low-voltage electric power line and the high-voltage electric power line and is configured to boost the electric power on the low-voltage electric power line side and supply the boosted electric power to the high-voltage electric power line side
Implementation Method 2
The generator can crank the engine, and the generator is configured to generate electric power by using power from the engine
Implementation Method 3
The motor is configured to input and output the power to a driveshaft that is coupled to an axle
Data Source
AI summary
When such an abnormality that a battery voltage system voltage is brought into an overvoltage state during regenerative control of a motor occurs, a booster converter is shut down, a system main relay is brought into a non-arc state and turned off. Then, an engine is started when an operation of the engine is stopped. The booster converter is used to determine turning-off of the system main relay, and a battery-less travel is started thereafter. In this way, inconvenience that possibly occurs by starting the battery-less travel at a time when abnormality of the system main relay being stuck to be on occurs can be avoided.