Multi-Input DC/DC Converter for Hybrid Vehicle Energy Storage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing energy storage systems for hybrid electric vehicles face inefficiencies due to the limitations of direct parallel connections between batteries and ultracapacitors, leading to oversized battery packs, high internal resistance losses, and the need for complex and costly bi-directional DC/DC converters, as well as inadequate battery conditioning methods that do not efficiently utilize the entire battery pack during vehicle operation.
Innovation Solution
A multi-input, one-output bi-directional DC/DC converter system connects multiple batteries and ultracapacitors, allowing separate control of each power source to optimize performance and reduce system complexity, while a controller manages power distribution between the battery and ultracapacitor subsystems to stabilize output voltage and current, and implements a battery conditioning strategy to prevent sulfation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a direct parallel connection of battery and ultracapacitor is used, then the system structure is simple, but the power delivery capability is limited and battery pack size must be oversized
Solution Approach 1:
A DC/DC converter is introduced as an intermediary device between the battery and ultracapacitor modules. This converter enables independent voltage control of each module, allowing the ultracapacitor to deliver high power pulses while the battery provides steady-state power, thereby overcoming the power delivery limitations of direct parallel connections without requiring oversized battery packs.
2Power
If a bi-directional DC/DC converter system is used, then power distribution is optimized, but the system complexity and cost increase
Solution Approach 1:
The energy storage system is segmented into multiple independent modules (battery modules and ultracapacitor modules), each with its own voltage control capability. The DC/DC converter controls each module independently through separate duty cycle adjustments, enabling optimized power distribution while maintaining manageable system complexity through modular architecture.
Solution Approach 2:
The system employs dynamic voltage control where the DC/DC converter continuously adjusts the voltage of each module based on real-time power demands and state of charge levels. This dynamic adjustment allows the system to optimize power distribution efficiency by directing power flows to where they are most needed while adapting to changing operating conditions.
3Reliability
If battery conditioning is performed by taking single cells offline, then sulfation is prevented, but system weight increases and complexity increases
Solution Approach 1:
The battery conditioning function is integrated into the normal operation of the energy storage system. The DC/DC converter performs conditioning by redistributing charge among battery modules during regular power management operations, eliminating the need for separate conditioning equipment and reducing overall system weight while maintaining battery reliability.
Solution Approach 2:
The DC/DC converter is designed to perform multiple functions: power distribution, voltage regulation, and battery conditioning. By combining these functions into a single device, the system avoids the weight and complexity penalties of adding separate conditioning equipment, while still effectively preventing sulfation through charge redistribution.
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 configuration enhances the efficiency and longevity of the energy storage system by optimizing power distribution, reducing weight and cost, and preventing sulfation in lead-acid batteries, thereby improving overall system performance and extending battery life.
Implementation Method 1
A multi-input, one-output bi-directional DC/DC converter system connects multiple batteries and ultracapacitors
Implementation Method 2
Due to their high specific power and near instantaneous charge and discharge capabilities, ultracapacitors have been considered for transient power supply and recovery in hybrid power trains
Implementation Method 3
The electric motor is powered by an energy source such a battery or an ultracapacitor. The energy source needs to store adequate energy to meet the averaged demand that is required from the electric motor under various driving conditions
Data Source
AI summary
An electric energy storage system (EESS) for providing a power management solution for a multi-subsystem energy storage in electric, hybrid electric, and fuel cell vehicles. The EESS has a controller that determines when to draw power from each subsystem as needed by the vehicle.