Fuel Cell Vehicle Limp-Home Control via Regenerative Power Management
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Solution Overview
Problem
When the secondary battery converter fails in a fuel cell vehicle system, it is difficult to start the vehicle on a slope using regenerative braking due to the prohibition of regeneration, which can lead to secondary failures such as air compressor damage from reactive current application during limp-home traveling.
Innovation Solution
A fuel cell system with a control unit that detects secondary battery converter failures, prohibits regeneration when not needed, applies a reactive current to the air compressor to consume regenerative power and prevent rearward travel, and stops the reactive current application after reverse rotation detection to prevent air compressor failure, while also managing application and cessation times to prevent overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If regeneration is prohibited when the secondary battery converter fails, then the vehicle can perform limp-home traveling using the output from the secondary battery, but the vehicle cannot start on a slope using regenerative brake
Solution Approach 1:
The control unit dynamically changes the regeneration control parameter based on vehicle operating conditions. When the vehicle is stopped on a slope and the accelerator pedal is depressed, the control unit allows regeneration by adjusting the control parameters, enabling the drive motor to generate regenerative electric power for braking force. This resolves the contradiction by making the regeneration function conditional rather than uniformly prohibited.
2Ease of operation
If regenerative electric power is consumed by applying reactive current to the air compressor, then the vehicle can start on a slope by using regenerative brake, but the air compressor may be damaged by reverse rotation
Solution Approach 1:
The control unit performs preliminary detection of the air compressor's rotation direction before applying reactive current. By detecting the rotation direction in advance and determining whether it is a normal or reverse rotation, the control unit can prevent reverse rotation damage by controlling the timing and conditions of reactive current application, thereby protecting the air compressor while enabling slope starting.
Solution Approach 2:
The control unit continuously monitors the air compressor's rotation direction and provides feedback control. When reverse rotation is detected, the control unit adjusts or prohibits the application of reactive current to prevent damage. This feedback mechanism ensures the air compressor operates safely while still allowing regenerative braking functionality.
3Use of energy by moving object
If the air compressor rotates in reverse direction by supplying reactive current, then regenerative electric power can be consumed, but secondary failure of the air compressor may occur
Solution Approach 1:
The control unit performs preliminary detection of the air compressor's rotation direction before applying reactive current. By detecting the rotation direction in advance and determining whether it is a normal or reverse rotation, the control unit can prevent reverse rotation damage by controlling the timing and conditions of reactive current application, thereby protecting the air compressor while enabling slope starting.
Solution Approach 2:
The control unit continuously monitors the air compressor's rotation direction and provides feedback control. When reverse rotation is detected, the control unit adjusts or prohibits the application of reactive current to prevent damage. This feedback mechanism ensures the air compressor operates safely while still allowing regenerative braking functionality.
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 vehicle to travel in the intended direction by consuming regenerative power and preventing secondary failures of the air compressor, including overheating, when the secondary battery converter fails.
Implementation Method 1
an air compressor configured to supply oxygen to the fuel cell by rotating in one direction
Implementation Method 2
a drive motor having a function of a motor generating a driving force of the vehicle and a function of a generator generating a regenerative electric power
Implementation Method 3
a fuel cell converter configured to boost electric power from the fuel cell and output electric power to the load
Implementation Method 4
a secondary battery converter that is provided between the secondary battery and the load, that is configured to boost electric power from the secondary battery and output electric power to the load, and that is configured to step down electric power for charging the secondary battery
Data Source
AI summary
A fuel cell system installed in a vehicle includes: a fuel cell; a secondary battery; a load including a drive motor and an air compressor; a fuel cell converter; a secondary battery converter; a failure detection unit; a first state determination unit; a reverse rotation detection unit; and a control unit. The control unit performs a limp-home traveling control that supplies electric power from the secondary battery to the drive motor when the secondary battery converter fails. When the vehicle is not in the first state, the control unit prohibits regeneration of the drive motor. When the vehicle is in the first state, the control unit supplies a reaction current to the air compressor. When the reaction current is applied and a reverse rotation of the air compressor is detected, the control unit does not apply the reaction current thereafter.