Fuel Cell Converter Direct Coupling for Voltage Stability

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Solution Overview

Problem

In power conditioning systems with fuel cells, overshooting and undershooting of DC link voltage during startup can lead to electrical component breakdown and anode electrode deterioration due to excessive output current hunting, exceeding the breakdown voltage and causing fuel gas shortages.

Innovation Solution

A power conditioning system with twin converters, including a fuel cell converter and a battery converter, uses a converter direct coupling unit to directly couple the input and output sides during startup and a fuel cell output voltage increasing unit to set the fuel cell output voltage to a predetermined value by supplying oxidant gas, preventing step-up operations that cause voltage overshooting.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the output voltage of the fuel cell is controlled to a predetermined voltage during startup, then the voltage can be stabilized, but overshooting beyond the DC link voltage may occur causing hunting of output current

Engineering Contradiction:

Improvevoltage stabilityVSAvoidsystem reliability

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The converter direct coupling unit directly couples the input and output sides of the fuel cell converter before the fuel cell is fully started, establishing the DC link voltage through the battery converter first. This preliminary action prevents voltage overshooting when the fuel cell output current increases, as the direct coupling path allows immediate voltage regulation without waiting for the fuel cell to stabilize.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The battery converter acts as an intermediary during startup by controlling the DC link voltage to a predetermined value before the fuel cell is fully coupled. This intermediary control prevents the fuel cell output voltage from exceeding the DC link voltage, thereby avoiding hunting of output current and potential system damage.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stability of the object's composition

If the DC/DC converter operates to reduce input side voltage, then output voltage can be reduced, but hunting of output current occurs and electrical components may break down

Engineering Contradiction:

Improvevoltage controlVSAvoidhunting and component breakdown

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The converter direct coupling unit establishes a direct coupling path between input and output sides before the fuel cell is fully started. This preliminary coupling allows the battery converter to control the DC link voltage first, preventing the need for aggressive voltage reduction operations that cause hunting and component breakdown.

Inventive Principle:

Principle #10Preliminary action

3Power

If excessive output current is produced, then power demand can be met, but anode electrode deteriorates due to fuel gas shortage

Engineering Contradiction:

Improvepower outputVSAvoidelectrode durability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The control unit monitors the output current of the fuel cell and adjusts the oxidant gas supply accordingly. When output current increases after coupling, the control unit increases oxidant gas supply to prevent fuel gas shortage and anode electrode deterioration, while still meeting power demands through coordinated control of both converters.

Inventive Principle:

Principle #23Feedback

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 solution effectively suppresses DC link voltage overshooting and undershooting, preventing electrical component damage and anode electrode deterioration, while ensuring stable fuel gas supply by maintaining the fuel cell output voltage within safe limits during system startup.

Implementation Method 1

a fuel cell to be connected to a load... supplying fuel gas (e.g. hydrogen) and oxidant gas (e.g. air) to the fuel cell

Methodology Applied

Scientific EffectFuel cell electrochemical conversion: Fuel Cell

Implementation Method 2

a DC/DC converter for converting an output voltage at a predetermined required voltage ratio

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentEP3336943B1Power adjustment system and control method therefor

Publication Date: 2019.10.09 NISSAN MOTOR CO LTD

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AI summary

A power conditioning system that includes a fuel cell to be connected to a load, a fuel cell converter connected between the fuel cell and the load, the fuel cell converter converting an output voltage of the fuel cell at a predetermined required voltage ratio, a battery connected in parallel with the fuel cell with respect to the load, the battery serving as a power supply source different from the fuel cell, a battery converter connected between the battery and the load, the battery converter converting an output voltage of the battery at a predetermined required voltage ratio. The power conditioning system includes a converter direct coupling unit configured to directly couple an input side and an output side of the fuel cell converter during startup of the power conditioning system and a fuel cell output voltage increasing unit configured to increase the output voltage of the fuel cell to a predetermined voltage by supplying oxidant gas during startup of the fuel cell.