Fuel Cell Stack Current Limiting via Feed Forward Control

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Solution Overview

Problem

Existing current limiting logic in fuel cell stacks fails to predict performance deterioration, leading to rapid current drops, causing jerking or shock during vehicle travel and continuous durability deterioration due to unanticipated cell damage.

Innovation Solution

Implementing a feed forward control type current limiting logic that determines performance deterioration in advance, gradually reducing and restoring the current of the fuel cell stack to prevent sudden output drops, using a controller to check accelerator pedal opening degrees and adjust current limiting values through primary, secondary, and n-th steps with a predetermined release slope.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If existing current limiting logic is applied when cell performance deteriorates, then the current of the fuel cell stack is limited to protect durability, but the current drops rapidly causing jerking or shock during vehicle travel

Engineering Contradiction:

Improvedurability of fuel cell stackVSAvoiddriving feeling

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The controller performs preliminary determination of cell performance deterioration using voltage ratio comparison before implementing current limiting. This advance detection allows the system to prepare for current reduction and implement it more gradually, preventing sudden current drops that cause jerking while still protecting the deteriorated cells from further damage.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If current limiting is implemented after performance deterioration occurs, then cell damage is prevented, but the output of the fuel cell vehicle is rapidly lowered

Engineering Contradiction:

Improveprevention of cell damageVSAvoidoutput of fuel cell vehicle

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The controller continuously monitors the voltage ratio between the minimum voltage cell and average voltage cells to detect performance deterioration. This feedback mechanism allows the system to identify deteriorated cells and adjust current limiting strategies in real-time, balancing cell protection with maintaining acceptable vehicle output power.

Inventive Principle:

Principle #23Feedback

3Reliability

If feedback control method is used for current limiting, then cell damage is prevented, but the control response is delayed as deterioration has already occurred

Engineering Contradiction:

Improveprotection from cell damageVSAvoidcontrol response time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The voltage ratio comparison method provides preliminary detection of cell performance deterioration before significant damage occurs. This early warning system enables the controller to implement preventive current limiting measures in advance, rather than reacting after deterioration has already progressed, thus reducing the effective response time and preventing further cell damage.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11557779B2Method of limiting current of fuel cell stack

Publication Date: 2023.01.17 HYUNDAI MOTOR CO LTD

AI summary

A current limiting method of a fuel cell stack is capable of preventing current of the fuel cell stack from rapidly dropping to prevent jerking or shock from occurring while a vehicle travels. The method includes: determining whether performance deterioration of a unit cell of the fuel cell stack has occurred, employing a feed forward control type current limiting logic of the fuel cell stack before an output of the fuel cell vehicle is lowered, decreasing the current of the fuel cell stack to a predetermined level by the feed forward control type current limiting logic, and gradually restoring the current of the fuel cell stack to a maximum current usage value from a point in time when the current of a load is used.