Fuel Cell and Regen Power Limiting for FCEV HV Over-Voltage
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Solution Overview
Problem
Conventional hydrogen fuel cell electric vehicles face issues with over-charging of the battery pack and over-voltage in the high voltage bus, leading to disconnection of contactors, loss of traction power, and degraded driving performance.
Innovation Solution
A powertrain control system with a controller that manages power limits of the fuel cell and regenerative braking to prevent over-voltage by continuously monitoring and arbitrating battery cell and bus voltages, using proportional derivative controllers to adjust power limits when thresholds are exceeded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the battery pack is charged via regenerative braking or fuel cell stack, then the battery pack state of charge is improved, but over-charging occurs causing contactors to open and loss of traction power
Solution Approach 1:
The controller proactively limits fuel cell and regenerative braking power before over-voltage conditions occur. By monitoring voltage levels and preemptively adjusting power input from these sources, the system prevents contactor opening and maintains continuous traction power availability, rather than reacting after over-charging damage occurs.
Solution Approach 2:
The controller continuously monitors battery pack voltage and state of charge, using this feedback to dynamically adjust the power limits of the fuel cell and regenerative braking systems. This closed-loop control ensures the battery is charged efficiently while preventing over-voltage conditions that would cause contactor opening and loss of propulsion.
2Use of energy by moving object
If the fuel cell DC/DC converter operates to recharge the battery, then energy utilization is improved, but over-voltage causes the converter to shut down resulting in loss of traction power
Solution Approach 1:
The controller preemptively limits fuel cell power output before over-voltage conditions develop. By anticipating voltage thresholds and adjusting power limits in advance, the system prevents DC/DC converter shutdown and maintains continuous energy transfer from the fuel cell to the battery, ensuring uninterrupted propulsion capability.
Solution Approach 2:
The controller uses real-time voltage monitoring feedback to dynamically control the fuel cell power limit. This ensures the DC/DC converter operates within safe voltage ranges, maintaining energy utilization while preventing shutdown conditions that would eliminate the fuel cell's ability to support traction power.
3Reliability
If the controller monitors and limits power from multiple sources, then over-voltage protection is improved, but system complexity increases
Solution Approach 1:
The controller consolidates the monitoring and control of both fuel cell power and regenerative braking power into a single control unit. This unified approach integrates multiple protection functions into one system, reducing overall complexity while maintaining comprehensive over-voltage protection across all power sources charging the battery pack.
Solution Approach 2:
The controller performs multiple functions: monitoring battery voltage, calculating state of charge, determining power limits for both fuel cell and regenerative braking, and preventing over-voltage conditions. This multi-functional design eliminates the need for separate control systems for each power source, simplifying the overall architecture while providing comprehensive protection.
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
Prevents over-voltage by proactively reducing power limits, maintaining vehicle propulsion, and ensuring stable operation by prioritizing fuel cell power reduction before regenerative braking, thus avoiding contactor disconnection and power loss.
Implementation Method 1
a fuel cell stack (FCS) configured to generate electricity to recharge the HV battery and/or power the electric traction motor
Implementation Method 2
an electric traction motor configured to drive the FCEV and generate power through regenerative braking
Data Source
AI summary
A fuel cell electric vehicle (FCEV) includes an electric traction motor configured to drive the FCEV and generate power through regenerative braking, a high voltage (HV) battery system including a HV bus and a HV battery configured to power the electric traction motor, and a fuel cell stack (FCS) configured to generate electricity to recharge the HV battery and/or power the electric traction motor. A powertrain control system for preventing over-voltage of the HV bus and HV battery includes a controller having one or more processors configured to control (i) a fuel cell power limit of the FCS, and (ii) a regenerative braking power limit of the electric traction motor. The controller is programmed to measure a voltage of the HV battery system, and selectively limit the fuel cell power limit and/or the regenerative braking power limit when the measure voltage exceeds a predetermined threshold.