Fuel Cell Voltage Control for Dry Membrane Acceleration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Fuel cell systems face inadequate power generation performance when electrolyte membranes are dry, leading to insufficient power supply to motors during acceleration due to poor I-V characteristics, resulting in reduced drivability.
Innovation Solution
A fuel cell system with a controller that reduces the voltage between the fuel cell stack and inverter below the normal lower limit voltage to increase current and water generation, using a relaxation voltage to rapidly improve power generation performance during increased power demands, assisted by a battery to ensure motor power requirements are met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the voltage of fuel cells is reduced to increase power output during acceleration, then power supplied to motor increases, but current output is restricted when electrolyte membranes are dry, preventing power generation performance recovery
Solution Approach 1:
The patent changes the voltage parameter dynamically based on the wet/dry state of electrolyte membranes. When membranes are wet, voltage is reduced to increase current and power output. When membranes are dry, voltage is maintained at normal levels to prevent performance degradation. This parameter change resolves the contradiction by adapting power output capabilities to the actual membrane state.
Solution Approach 2:
The patent implements feedback control by detecting the wet/dry state of electrolyte membranes and adjusting the voltage command accordingly. The controller monitors membrane state and provides feedback to modify voltage reduction strategy, ensuring power output is optimized only when membrane conditions permit, thus maintaining reliability while maximizing power when possible.
2Ease of operation
If voltage reduction is applied to meet motor power demand during acceleration, then drivability improves, but water vapor generation is restricted, delaying electrolyte membrane wetting
Solution Approach 1:
The patent applies preliminary action by pre-wetting electrolyte membranes before acceleration demands occur. The system monitors membrane state and ensures adequate wetting is achieved before high power demand situations arise, preventing the time loss associated with membrane drying during acceleration events.
Solution Approach 2:
The patent implements periodic voltage reduction strategies rather than continuous reduction. Voltage is reduced in periodic cycles that allow membrane wetting to occur during non-acceleration periods, then power output is increased during acceleration periods when membranes are adequately wetted. This periodic action balances drivability improvement with membrane maintenance.
3Reliability
If normal voltage lower limit is maintained to protect inverter, then inverter reliability is ensured, but power output is insufficient when fuel cells are dry
Solution Approach 1:
The patent makes the voltage lower limit dynamic rather than fixed. The voltage command to fuel cells is adjusted dynamically based on membrane wet/dry state detection. When membranes are wet, the voltage lower limit is reduced to allow higher current and power output. When membranes are dry, the normal lower limit is maintained to protect the inverter. This dynamic adjustment resolves the contradiction between inverter protection and power output capability.
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 promptly enhances fuel cell power generation performance during acceleration, improving drivability by increasing stack current and water generation, while preventing excessive battery discharge and maintaining motor output.
Implementation Method 1
a fuel cell stack 1 that generates power
Implementation Method 2
an inverter 4 that converts power output from the fuel cell stack 1 into alternating-current power and supplies the alternating-current power to the driving motor 5
Implementation Method 3
a battery 2 that assists power generation of the fuel cell stack 1
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A fuel cell system includes a battery, a fuel cell configured to generate power in accordance with a load, an inverter configured to convert power output from the fuel cell into alternating-current power and supply the alternating-current power to a motor, and a converter configured to control voltage between the inverter and the fuel cell using power output from the battery. The fuel cell system includes a voltage control unit configured to control the converter such that the voltage between the inverter and the fuel cell does not fall below a voltage lower limit of the inverter, and a lower limit voltage control unit configured to, when power required by the motor increases, cause the voltage between the inverter and the fuel cell to fall below the voltage lower limit of the inverter.