Fuel Cell Precharge Circuit Limits Inrush Current
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Solution Overview
Problem
Conventional fuel cell power generation systems face issues with rapid voltage reduction during startup, leading to potential performance and durability deterioration, as well as hydrogen and water loss in the solid polymer electrolyte membrane, due to large current flows when connecting a capacitor with a significantly different terminal voltage to the fuel cell.
Innovation Solution
A control device is implemented that includes a current limiting mechanism using a DC-DC chopper and precharge circuits to regulate the output current from the fuel cell, preventing excessive current flow until the terminal voltages of the fuel cell and capacitor reach equilibrium, thereby maintaining stable voltage and preventing hydrogen evaporation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the capacitor is connected to the fuel cell at startup when the terminal voltage of the capacitor greatly differs from the terminal voltage of the fuel cell, then the capacitor can be charged quickly, but a large current flows which causes the terminal voltage of the fuel cell to reduce rapidly, deteriorating performance and durability
Solution Approach 1:
The patent applies preliminary action by precharging the capacitor through a current-limiting circuit before connecting it to the fuel cell. This preliminary charging step raises the capacitor's terminal voltage closer to the fuel cell's terminal voltage, thereby reducing the voltage difference and limiting the inrush current when connection occurs, which protects the fuel cell from voltage collapse and durability deterioration
Solution Approach 2:
The patent introduces a current-limiting circuit as an intermediary component between the capacitor and the fuel cell. This intermediary circuit controls and limits the current flow during the charging process, preventing excessive current from causing rapid voltage reduction in the fuel cell while still enabling effective charging of the capacitor
2Stability of the object's composition
If the terminal voltage of the fuel cell is reduced due to large current flow, then the voltage equilibrium between fuel cell and capacitor is restored, but hydrogen or water content in the solid polymer electrolyte film is lost and durability decreases
Solution Approach 1:
By precharging the capacitor before connection, the voltage difference between fuel cell and capacitor is reduced in advance. This preliminary action prevents the formation of large current flows that would otherwise cause rapid voltage reduction and subsequent loss of hydrogen and water from the solid polymer electrolyte membrane
Solution Approach 2:
The current-limiting circuit acts as an intermediary that controls current flow during voltage equilibrium restoration. By limiting the current, it prevents the voltage collapse that would lead to evaporation of hydrogen and water from the electrolyte membrane, thus preserving the fuel cell's substance composition while still achieving voltage balance
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
The solution effectively limits the output current from the fuel cell during startup, preventing rapid voltage drops and maintaining the long-term stability and performance of the fuel cell by gradually charging the capacitor, thus extending its service life.
Implementation Method 1
a current limiting mechanism using a DC-DC chopper and precharge circuits to regulate the output current from the fuel cell
Implementation Method 2
preventing excessive current flow until the terminal voltages of the fuel cell and capacitor reach equilibrium
Implementation Method 3
a capacitor (for example, power storage unit 12 in the embodiment) for assisting the supply of electric power to the load and for storing generated energy of the fuel cell
Implementation Method 4
a fuel cell (for example, a fuel cell 11 in the embodiment) supplying electric power to a load
Data Source
AI summary
A control device for starting a fuel cell is provided which is capable of preventing an excessive reduction of the terminal voltage of the fuel cell. A primary precharge portion, provided with a high voltage switch and a current limiter, is disposed at the output portion of a power storage unit, and a secondary precharge portion, provided with a DC-DC chopper and a control portion, is disposed at the output side of a fuel cell. The primary precharge portion controls the output current to flow in a path via a resistor having a predetermined resistance. The secondary precharge portion controls an output current of the fuel cell based on a current command value IFCCMD for the fuel cell.