Fuel Cell Air Compressor Control During Regenerative Braking
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Solution Overview
Problem
Existing methods for determining the speed of the air compressor in fuel cell vehicles during regenerative braking fail to consider the amount of energy available for recovery, leading to potential overvoltage at the main bus terminal and reduced efficiency in energy recovery.
Innovation Solution
A controller calculates the target speed of the air compressor to match the sum of power generation from the fuel cell stack, air compressor, and drive motor with the battery's chargeable amount, using multiple index values to ensure the sum is close to or less than the battery's capacity, thereby preventing overvoltage and optimizing energy recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the air compressor speed is determined based on target current and air flow rate without considering regenerative braking energy, then the fuel cell stack can generate sufficient power, but overvoltage occurs at the main bus terminal and energy recovery efficiency deteriorates
Solution Approach 1:
The patent changes the control parameter from fixed target speed calculation to dynamically adjusted speed that considers regenerative braking energy. The air compressor speed is adjusted based on the chargeable amount of the battery, transforming the control strategy from static to adaptive parameter adjustment, thereby preventing overvoltage while maximizing energy recovery.
Solution Approach 2:
The patent implements a feedback mechanism where the controller continuously monitors the chargeable amount of the battery and adjusts the air compressor speed accordingly. This closed-loop control uses the battery's energy state as feedback to optimize the air compressor operation, ensuring that power generation matches the battery's chargeable capacity and preventing overvoltage conditions.
2Reliability
If the air compressor speed is reduced to match battery chargeable amount, then overvoltage is prevented, but the amount of energy recovered during regenerative braking decreases
Solution Approach 1:
The patent optimizes the air compressor speed parameter by considering multiple factors including regenerative braking energy, battery chargeable amount, and vehicle operating conditions. Rather than simply reducing speed, the system dynamically adjusts the parameter to find the optimal balance between preventing overvoltage and maximizing energy recovery, thereby resolving the contradiction between reliability and energy loss.
3Quantity of substance
If the air compressor operates at target speed calculated from target current, then sufficient air supply is provided to the cathode, but the actual speed differs from target speed causing error in energy generation calculation
Solution Approach 1:
The patent implements feedback control where the actual air compressor speed and regenerative braking energy are continuously monitored. This feedback mechanism allows the system to detect deviations between target and actual performance, enabling real-time corrections that improve the precision of energy generation calculations while maintaining sufficient air supply to the cathode.
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 approach prevents overvoltage at the main bus terminal, enhances the durability of the fuel cell vehicle, and ensures efficient recovery of regenerative braking energy.
Implementation Method 1
A fuel cell is a device that generates electrical energy through an electrochemical reaction inside a fuel cell stack by receiving hydrogen and air supplied from the outside
Implementation Method 2
the air supply system operates an air compressor to supply the inhaled external air to a cathode (an air electrode) of the fuel cell stack
Implementation Method 3
a battery; an air compressor that supplies air to the fuel cell stack and generates power during regenerative braking
Data Source
AI summary
A fuel cell vehicle includes a fuel cell stack and a battery; an air compressor that supplies air to the fuel cell stack and is able to generate power during regenerative braking; a drive motor that provides driving force to a vehicle and is able to generate power during the regenerative braking; and a controller that controls operation of the air compressor so that a sum of power generation of the fuel cell stack and power generation of the regenerative braking of the air compressor and drive motor is close to a chargeable amount of the battery.