Floating Base Load Strategy for Fuel Cell Durability
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Solution Overview
Problem
Fuel cell systems in hybrid vehicles face reduced durability and lifetime due to frequent and rapid power changes, which stress components and lead to voltage fluctuations, necessitating a strategy to mitigate fast voltage transients.
Innovation Solution
A floating base load strategy is implemented, where the power request from the electric traction system is processed to calculate an average power demand and a weighting function based on the state of charge of the electrical energy storage system, filtering the demand to reduce fast voltage transients by adjusting the output power of the fuel cell stack in conjunction with the energy storage system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fuel cell stack directly meets the power demand of the electric traction system, then the system response is fast and simple, but the fuel cell system experiences frequent voltage transients and reduced durability
Solution Approach 1:
The control strategy calculates the average power demand over a predetermined time period before the current moment, and uses this pre-calculated average value to adjust the fuel cell base load power output. This preliminary action smooths out rapid power fluctuations before they reach the fuel cell stack, reducing voltage transients and improving durability while maintaining system reliability
Solution Approach 2:
The patent introduces an intermediate control mechanism that acts as a mediator between the power demand signal and the fuel cell stack. The control strategy processes the power demand through multiple calculation steps (average power calculation, weighting function application, base load determination) to generate a smoothed power command for the fuel cell, thereby protecting it from direct exposure to rapid demand changes
2Volume of moving object
If the electrical energy storage system provides supplemental power during high demand, then the fuel cell system size can be reduced, but fast power transients still occur when switching between power sources
Solution Approach 1:
The control strategy dynamically adjusts the fuel cell base load power output based on real-time conditions including average power demand, state of charge of the energy storage system, and current power demand. The weighting function processor dynamically modifies the average power signal based on SOC levels, creating a flexible and adaptive control approach that optimizes the split between fuel cell and energy storage system power contribution, reducing stress on the fuel cell while maintaining system compactness
Solution Approach 2:
The patent changes the operational parameters of the fuel cell system by dynamically adjusting the base load power output based on multiple varying parameters including average power demand, state of charge, and current power demand. The weighting function varies the influence of average power based on SOC, transforming the fuel cell operation from fixed to variable parameters, thereby optimizing durability while maintaining reduced system size
3Productivity
If the fuel cell system operates at high power levels to meet peak demand, then vehicle performance is improved, but the fuel cell components experience increased stress and reduced lifetime
Solution Approach 1:
The control strategy applies partial action by determining a base load power output that is only a portion of the total power demand, with the remainder supplied by the electrical energy storage system. The base load power is calculated as a weighted average rather than meeting full demand, thereby reducing the stress and power level exposure on the fuel cell stack while still maintaining the capability to deliver high vehicle power output when needed through coordinated energy storage system contribution
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 effectively reduces fast voltage transients, enhancing the durability and performance of the fuel cell system by smoothing power demand transitions and optimizing the operation between the fuel cell stack and the energy storage system, ensuring efficient power distribution and extended system lifespan.
Implementation Method 1
A fuel cell stack in a hybrid fuel cell vehicle converts a chemical energy to an electrical energy to operate an electric traction system (ETS)
Implementation Method 2
the EESS provides the extra 30 kW of power
Data Source
AI summary
A fuel cell system employing a floating base load hybrid strategy for reducing fast voltage transients of a FCPM. A power request signal is applied to an average power calculation processor that calculates the average power requested over a predetermined previous period of time. A weighting function processor provides a weighting function based on the state of charge of an EESS. The power available from the FCPM and the EESS is applied to a power comparison processor. The available power is compared to the power request to provide a difference value between what is currently being provided and what is desired. The difference value is compared to power limit values of the EESS. The output value of this comparison is added to a filtered value to generate a signal for the change in the output power of the fuel cell stack based on the power request.