Fuel Cell Ripple Cancellation via Modular DC/DC Converter Segmentation

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Solution Overview

Problem

Fuel cell power systems face inefficiencies and potential damage due to ripple currents, which are AC components that can decrease fuel cell performance and require reduction to ensure reliable operation.

Innovation Solution

A power conversion system with a two-bus approach and center-tapped neutral line is employed, utilizing modular architecture with DC/DC converters and DC/AC converters to manage fuel cell segments, ensuring that the number of individually wired stack columns is evenly divisible by 6, and using DC/DC converters in specific configurations to minimize ripple currents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If fuel cells are combined into stacks with series connections to meet voltage requirements, then the voltage output is improved, but ripple currents are generated that can damage the fuel cells

Engineering Contradiction:

Improvevoltage outputVSAvoidripple currents

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The fuel cell system is divided into multiple segments (first fuel cell segment and second fuel cell segment) that can be independently controlled. Each segment is connected to separate DC/DC converter branches, allowing independent current management to reduce ripple effects while maintaining required voltage output through series connections.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system changes the electrical parameters by using multiple DC/DC converter branches with different connection configurations (series and parallel combinations). This allows transformation of the current waveform characteristics to minimize ripple content while maintaining the required voltage level, directly addressing the harmful ripple currents generated by series connections.

Inventive Principle:

Principle #35Parameter changes

2Power

If many fuel cell segments are required for higher power applications, then the power output is improved, but the system complexity and wiring requirements increase

Engineering Contradiction:

Improvepower outputVSAvoidwiring requirements

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The DC/DC converter branches are designed with universal functionality to handle multiple fuel cell segments. The same converter architecture can accommodate different numbers of segments (evenly divisible by 6) through modular expansion, reducing overall system complexity despite increased power requirements. The neutral line serves multiple functions including reference potential and ripple cancellation.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system employs a nested modular architecture where fuel cell segments are grouped in series connections that are further organized into parallel branches. Each branch contains nested series connections of two segments, creating a hierarchical structure that scales efficiently for higher power applications while maintaining manageable wiring complexity through the established divisibility rule.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Use of energy by moving object

If individual stack current is controlled to improve fuel utilization, then fuel efficiency is improved, but ripple currents are generated that can damage the fuel cells

Engineering Contradiction:

Improvefuel utilizationVSAvoidripple currents

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

DC/DC converter branches are introduced as intermediary devices between the fuel cell segments and the load. These converters act as mediators that can independently control the current drawn from each segment to optimize fuel utilization, while simultaneously filtering and canceling ripple currents before they reach the fuel cells, thus resolving the contradiction between individual current control and ripple reduction.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The harmful ripple current component is extracted and separated from the useful DC current through the DC/DC converter branches. The converters isolate the ripple generation mechanism from the fuel cells while maintaining the beneficial individual current control capability, allowing fuel utilization optimization without exposing the fuel cells to damaging ripple currents.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS8289730B2Ripple cancellation

Publication Date: 2012.10.16 BLOOM ENERGY CORP

AI summary

Systems, methods and devices for power generation systems are described. In particular, embodiments of the invention relate to the architecture of power conditioning systems for use with fuel cells and methods used therein. More particularly, embodiments of the present invention relate to methods and systems usable to reduce ripple currents in fuel cells.