Fuel Cell Voltage Control for Surplus Power Management
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Solution Overview
Problem
During low-efficiency fuel cell operation for warm-up, sudden reductions in electric power generation command values lead to surplus electric power being supplied to external loads, which can cause overcharging of batteries in low-temperature environments and inefficient power management.
Innovation Solution
A fuel cell system that includes a controller to increase the output voltage of the fuel cell when the electric power generation command value reduces, storing surplus electric power in a capacitive component within the fuel cell, and uses map data to correct capacitance values based on actual measurements to accurately store power and switch between low-efficiency and normal operation modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the output voltage of the fuel cell is fixed to a given voltage value lower than the I-V characteristic voltage during low-efficiency operation, then the warm-up operation can be implemented promptly and minimum motor output can be obtained, but surplus electric power is generated when the power generation command value is reduced, causing overcharging of batteries and inefficient power management
Solution Approach 1:
The patent applies dynamics by making the output voltage controllable and adjustable based on operational conditions. Instead of fixing the voltage to a single value, the system dynamically adjusts the voltage between a first value (during warm-up) and a second value (during normal operation), allowing the fuel cell to adapt its electrical characteristics to match varying power demands and avoid surplus power generation.
Solution Approach 2:
The patent changes the electrical operating parameters of the fuel cell by adjusting the output voltage between different values. During warm-up operation, the voltage is set to a first given value to maximize heating efficiency, while during normal operation, it transitions to a second given value to optimize power generation efficiency and prevent surplus power, thereby changing parameters to resolve the contradiction between warm-up effectiveness and power efficiency.
2Productivity
If the flow rate of oxidizing gas is variably controlled according to required electric power during low-efficiency operation, then output control based on required electric power can be achieved, but the air compressor exhibits poor responsiveness to abrupt decreases in accelerator pedal opening due to inertia
Solution Approach 1:
The patent introduces an intermediary control mechanism by adjusting the fuel cell's output voltage as a mediating variable between the power generation command and the actual power output. This allows the system to quickly respond to changes in power demand by changing the voltage setting, thereby compensating for the slow mechanical response of the air compressor and achieving responsive power control without directly manipulating the gas flow rate.
Solution Approach 2:
The system performs preliminary action by pre-setting the output voltage to appropriate values based on the current operational state and predicted power needs. When a sudden change in power demand occurs, the voltage can be immediately adjusted to the pre-determined appropriate level, anticipating or quickly responding to the need before the air compressor's mechanical inertia prevents adequate flow rate adjustment.
3Loss of energy
If the output voltage of the fuel cell is changed during low-efficiency operation, then surplus electric power can be stored in the capacitive component, but electric power may be stored or released in the capacitive component inconveniently causing excess or deficiency of electric power supplied to external loads
Solution Approach 1:
The patent implements feedback control by continuously monitoring the power generation command value and the actual operating state of the fuel cell, and adjusting the output voltage accordingly. The controller uses feedback information to determine when to change the voltage between the first and second given values, ensuring that surplus power is stored in the capacitive component only when appropriate, thereby maintaining stable and controlled power supply to external loads while preventing both excess and deficiency conditions.
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 solution prevents surplus electric power from being supplied to external loads, ensuring efficient power management by storing excess power in the fuel cell's capacitive component and allowing seamless transitions between operation modes without affecting the power supplied to external loads.
Implementation Method 1
A fuel cell is an electric power generating system which oxidizes a fuel by an electrochemical process to directly convert the energy emitted due to an oxidation reaction into electrical energy
Implementation Method 2
an electrolyte membrane for selectively transporting hydrogen ions
Implementation Method 3
controlling the amount of self-heating of the fuel cell by carrying out a low-efficiency operation in which electric power generation efficiency is lower than that of a normal operation
Data Source
AI summary
A fuel cell system increases an output voltage of a fuel cell if an electric power generation command value Pref for the fuel cell abruptly reduces while the fuel cell is being warmed up at a low-efficiency operation, which has lower electric power generation efficiency than that of a normal operation. Thus, the surplus electric power Ws corresponding to the difference between an electric power generation amount Pmes of the fuel cell and the electric power generation command value Pref is stored into a capacitive component of the fuel cell, thereby matching the electric power supplied to an external load of the fuel cell (Pmes-Ws) with the electric power generation command value Pref. This makes it possible to conduct control not to supply the surplus electric power to the external load when the electric power required from the fuel cell suddenly reduces during the low-efficiency operation.