Fuel Cell System Series Stack Current Equalization
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Solution Overview
Problem
In fuel cell systems, connecting multiple stacks in series to increase voltage is challenging due to variations in voltage-current characteristics, leading to uneven gas consumption and potential reduction in service life, especially when trying to adjust coolant and gas distribution to match current deviations across stacks.
Innovation Solution
A fuel cell system with two or more fuel cell groups connected in series, each with its own power converter, where oxygen-containing and hydrogen-containing gases are supplied through pipes of equivalent diameter to maintain balanced current flow across the stacks, allowing for precise control of output currents and gas distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple fuel cell stacks are connected in series to increase voltage, then the voltage level and inverter efficiency are improved, but the voltage exceeds high voltage thresholds and strict compliance rules are required
Solution Approach 1:
The system divides the fuel cell stacks into multiple groups (first fuel cell group and second fuel cell group), each connected in series to form separate voltage sources. This segmentation allows the total voltage to be distributed across multiple manageable units, reducing the complexity of high-voltage compliance while maintaining the benefits of series connection for improved inverter efficiency.
2Power
If multiple fuel cell stacks are connected in parallel to avoid high voltage, then the voltage level is reduced, but the string current varies due to characteristic variations and reduces gas utilization efficiency
Solution Approach 1:
The system employs a control device that measures the current flowing through each fuel cell stack and adjusts the amount of hydrogen-containing gas and oxygen-containing gas supplied to each stack based on the measured current values. This feedback mechanism ensures that stacks with higher current receive more gas, maintaining optimal gas utilization efficiency and preventing waste, while allowing parallel connection to avoid high-voltage compliance issues.
3Device complexity
If equal amounts of gas and coolant are distributed to each fuel cell stack, then the system configuration is simplified, but variations in current deviation affect gas utilization rate and service life
Solution Approach 1:
The system applies different gas supply amounts to different fuel cell stacks based on their individual current characteristics. Instead of uniform distribution, each stack receives a customized gas supply proportional to its current output, optimizing local performance and extending service life. The control device calculates and adjusts gas supply amounts for each stack individually, ensuring that stacks operating at higher currents receive more hydrogen and oxygen, thereby maintaining efficient gas utilization across the entire system.
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 allows for equalization of output currents across fuel cell groups, optimizing gas utilization and reducing power consumption, thereby extending the service life and efficiency of the fuel cell system.
Implementation Method 1
A fuel cell system has been conventionally known as directly converting chemical energy contained in fuel into electricity. This fuel cell system causes an electrochemical reaction between hydrogen-containing gas and oxygen-containing gas to occur to thereby directly extract electricity.
Implementation Method 2
a first power converter and a second power converter, the first power converter controlling a first power to be generated by the first fuel cell group according to a first output current, the second power converter controlling a second power to be generated by the second fuel cell group according to a second output current
Data Source
Figure 1
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AI summary
According to the present embodiment, a fuel cell system (1) includes a first fuel cell group(10a), a first power converter(12a), a second fuel cell group(10b), a second power converter(12b), and a first pipe(L14). The first fuel cell group(10a) is formed of a plurality of fuel cell stacks connected in series. The first power converter(12a) is capable of controlling a first power to be generated by the first fuel cell group(10a) according to a first output current. The second fuel cell group(10b) is formed of a plurality of fuel cell stacks(100b) connected in series, the fuel cell stacks(100b) corresponding respectively to the fuel cell stacks(100a) in the first fuel cell group(10a). The second power converte(12b)r is capable of controlling a second power to be generated by the second fuel cell group(10b) according to a second output current. Oxygen-containing gas is supplied through the first pipe(L14) to each of the fuel cell stacks(100a) in the first fuel cell group(10a) and each of the fuel cell stacks(100b) in the second fuel cell group(10b).