Multi-Energy Storage Cycle Life Optimization via Buck-Boost Control
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Solution Overview
Problem
In vehicle drive systems, the cycle life of high energy storage devices is often compromised due to their high cost and weight, and the need for increased size or energy rating, which can reduce acceleration rates and increase costs, especially when used in multi-source power systems.
Innovation Solution
A multi-energy storage device system that includes a first energy storage device coupled to a DC link and a bi-directional buck/boost converter assembly, where a second energy storage device with a higher cycle life is used to assist the first device during acceleration events, with a system controller managing energy flow to optimize the cycle life by boosting the voltage of the second device and supplying it to the DC link, ensuring the state of charge is maintained within usable limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the size and energy rating of the high energy source are increased to extend cycle life, then the cycle life is improved, but the cost and weight increase
Solution Approach 1:
The energy storage system is divided into two separate devices: a high energy density battery for sustained power and a high specific-power ultracapacitor for transient power demands. This segmentation allows each device to be optimized for its specific function, enabling the battery to operate at lower power levels that extend its cycle life without requiring increased size.
Solution Approach 2:
The ultracapacitor acts as an intermediary device between the battery and the load. It absorbs transient power demands during acceleration and regenerative braking events, protecting the battery from deep discharge cycles and extending its operational life without requiring the battery to be oversized.
2Reliability
If the size and energy rating of the high energy source are increased to extend cycle life, then the cycle life is improved, but the cost increases
Solution Approach 1:
The system segments the power delivery function between two specialized devices rather than using one oversized battery. This allows the battery to be sized appropriately for its energy storage function, reducing material costs while the smaller, cheaper ultracapacitor handles transient power demands that would otherwise require battery oversizing.
Solution Approach 2:
The ultracapacitor serves as a sacrificial component with a much longer cycle life than the battery, absorbing wear and tear from transient operations. This protects the more expensive battery from degradation, extending its life without requiring costly oversizing or replacement.
3Reliability
If the energy rating of the high energy source is increased to extend cycle life, then the cycle life is improved, but the acceleration rate decreases
Solution Approach 1:
The power delivery system is segmented into two devices with complementary characteristics: the battery provides sustained energy and the ultracapacitor provides high-specific power for acceleration. This segmentation enables the battery to maintain a moderate energy rating suitable for extended cycle life while the ultracapacitor supplies the additional power needed for high acceleration rates.
Solution Approach 2:
The system changes the power delivery parameters by introducing a second energy storage device with different electrical characteristics. The ultracapacitor's ability to rapidly charge and discharge at high currents complements the battery's steady-state performance, enabling both high acceleration rates and extended cycle life without increasing battery energy rating.
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 approach extends the operating life of the first energy storage device, reduces the need for high-rated sources, lowers system costs, and optimizes energy usage by utilizing the entire usable energy range of the second device during acceleration events, thereby reducing deep discharge effects and prolonging the cycle life.
Implementation Method 1
cause the first bi-directional buck/boost converter to boost the voltage of the second energy storage device and to supply the boosted voltage to the DC link
Data Source
AI summary
A multi-energy storage device system is provided that includes a first energy storage device (ESD) coupled to a direct current (DC) link. A bi-directional buck/boost converter includes an output channel coupled to the DC link and an input channel. A second ESD coupled to the input channel has a usable energy storage range defining an entire amount of usable energy storable therein. A database includes stored information related to a known acceleration event. A system controller is configured to acquire the stored information related to the known acceleration event and, during the known acceleration event, cause the buck/boost converter to boost the voltage of the second ESD and to supply the boosted voltage to the DC link such that after the known acceleration event, the state of charge of the second ESD is less than or substantially equal to a minimum usable energy storage state of charge.