Fuel Cell Battery SOC Control During Regenerative Braking
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Solution Overview
Problem
Fuel cell electric vehicles (FCEVs) face challenges in modulating fuel cell power to simultaneously maintain battery state-of-charge (SOC) and meet vehicle power demands, especially during regenerative braking, as existing strategies either ignore SOC variations or conflict with battery charging limits.
Innovation Solution
A dual-loop control system is implemented, where an inner loop controller uses an integral controller to manage battery current based on fuel cell current, and an outer loop controller uses a proportional controller to modulate target battery SOC, allowing for continuous feedback and modulation to balance SOC and power demand in both tractive and regenerative directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If fuel cell power is modulated to match vehicle power demand, then power demand is met, but battery state-of-charge varies and may go out of acceptable range
Solution Approach 1:
The patent implements a feedback control system where the fuel cell power modulation is continuously adjusted based on the battery state-of-charge measurement. The controller receives SOC feedback and modulates the fuel cell power accordingly to maintain SOC within the acceptable range, resolving the contradiction between meeting power demand and maintaining reliable battery charge levels.
Solution Approach 2:
The battery serves as an intermediary energy storage device between the fuel cell and the motor. It absorbs excess energy when fuel cell power exceeds immediate demand and supplies energy when demand exceeds fuel cell output, thereby mediating the contradiction between fuel cell power modulation and battery SOC maintenance.
2Loss of energy
If fuel cell power is reduced during regenerative braking, then regenerated charge is maximized, but vehicle power demand may not be met
Solution Approach 1:
The system dynamically adjusts fuel cell power modulation strategy based on operating conditions. During regenerative braking, the controller determines the optimal level of fuel cell power reduction that maximizes energy recovery while ensuring sufficient total power (fuel cell + motor) is available to meet vehicle demand, resolving the contradiction between energy recovery and power supply.
Solution Approach 2:
The controller changes the fuel cell power output parameter dynamically based on the braking state and power demand conditions. By adjusting this parameter in real-time, the system optimizes the balance between maximizing regenerative charging and maintaining adequate vehicle power, resolving the contradiction between these two opposing requirements.
3Reliability
If battery state-of-charge is maintained at a specific target, then battery health is preserved, but transient power demands cannot be met
Solution Approach 1:
The system allows temporary deviations from the target SOC (partial action) to meet transient power demands. The fuel cell power is modulated to provide additional power during high-demand transient events, accepting temporary SOC variations while maintaining long-term battery health, thus resolving the contradiction between strict SOC maintenance and transient power capability.
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 effectively maintains SOC within an appropriate range, supports transient demands, and optimizes fuel cell power usage, reducing the risk of overcharge/overdischarge while accommodating regenerative braking requirements, with tunable system responses for improved performance.
Implementation Method 1
Fuel cells in vehicles may generate electricity using oxygen sourced from ambient air and hydrogen stored onboard the vehicle
Implementation Method 2
the battery may respond instantly to changes in power demand, and may also absorb excess power produced by operation of the FCEV; e.g., power generated via regenerative braking
Data Source
AI summary
Ways of controlling a fuel cell and a battery are provided that include controlling a current of the battery using a current of the fuel cell and where a target battery state of charge is controlled using an actual state of charge of the battery. Systems and methods may employ an inner loop controller and an outer loop controller. The inner loop controller may be configured to control current of the battery using current of the fuel cell, where the inner loop controller includes an integrating controller operating on a time-averaged basis. The outer loop controller may be configured to control a target battery state of charge using an actual state of charge of the battery, where the outer loop controller includes a proportional controller operating using continuous modulation.