Fuel Cell Drive Relay Control for Reverse Current Protection
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Solution Overview
Problem
In drive systems, the disconnection of a relay due to a short-circuit fault in the reverse current protection diode can cause the relay's contact to melt, especially when the relay is small in size, leading to potential reverse current flow to the fuel cell.
Innovation Solution
The drive system incorporates a controller that detects a short-circuit fault in the diode, stops the secondary battery step-up converter, and disconnects the relay when the fuel cell voltage is higher than the secondary battery voltage, or increases the fuel cell voltage relative to the secondary battery voltage by adjusting reactant gas supply, thereby minimizing the risk of reverse current flow and preventing relay contact melting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the relay is disconnected immediately upon detecting a short-circuit fault in the diode, then the reverse current protection function is restored, but the relay contact may melt due to current flow during disconnection
Solution Approach 1:
The controller performs preliminary actions by stopping the secondary battery step-up converter and adjusting fuel cell voltage before disconnecting the relay. This sequence ensures that current flow is minimized or eliminated before the relay contact opens, preventing contact melting while maintaining reverse current protection functionality.
Solution Approach 2:
The controller changes system parameters by adjusting the fuel cell's output voltage to match or exceed the secondary battery voltage before relay disconnection. This parameter adjustment prevents reverse current flow through the relay contact, allowing safe disconnection while maintaining protection against fuel cell reverse current damage.
2Volume of moving object
If the relay is made smaller to reduce system size, then the system becomes more compact, but the relay contact becomes more susceptible to melting during disconnection
Solution Approach 1:
The controller executes preliminary steps (stopping the secondary battery step-up converter and adjusting fuel cell voltage) before relay disconnection. This allows smaller relays to be used safely since the current is controlled or eliminated before the contact opens, preventing the contact melting that would otherwise limit miniaturization.
Solution Approach 2:
By dynamically adjusting the fuel cell voltage parameter to prevent reverse current flow, the system enables the use of smaller relays with less robust contacts. The parameter control compensates for the reduced contact durability inherent in smaller relays.
3Reliability
If the fuel cell voltage is increased relative to the secondary battery voltage to prevent reverse current, then reverse current protection is improved, but additional control complexity is required
Solution Approach 1:
The controller implements a feedback control mechanism that monitors the voltages of both the fuel cell and secondary battery, then adjusts the fuel cell voltage accordingly. This feedback loop automatically maintains the voltage relationship needed to prevent reverse current, managing the control complexity through automated monitoring and adjustment.
Solution Approach 2:
The controller performs voltage adjustment as a preliminary action before relay disconnection. By proactively setting the fuel cell voltage higher than the secondary battery voltage beforehand, the system prevents reverse current without requiring complex real-time control during the critical disconnection moment.
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 the likelihood of relay contact melting during disconnection and ensures non-arc discharge, allowing for the use of smaller relays while preventing reverse current flow to the fuel cell, thus enhancing system reliability.
Implementation Method 1
a fuel cell; a fuel cell step-up converter connected between the fuel cell and the drive device
Implementation Method 2
the fuel cell step-up converter including a diode configured to prevent a flow of a current to the fuel cell
Implementation Method 3
a fuel cell voltage sensor configured to measure a voltage of the fuel cell; a secondary battery voltage sensor configured to measure a voltage of the secondary battery
Data Source
AI summary
A drive system includes a drive device including an electric power generator; a fuel cell; a secondary battery; a fuel cell step-up converter including a diode; a relay connected to wiring between the fuel cell step-up converter and the drive device; a secondary battery step-up converter connected; a fuel cell voltage sensor; a secondary battery voltage sensor; and a controller. The controller stops the secondary battery step-up converter when a short-circuit fault of the diode is detected, disconnects the relay when a voltage of the fuel cell is higher than a voltage of the secondary battery after stopping the secondary battery step-up converter, and when the voltage of the secondary battery is higher than or equal to the voltage of the fuel cell, executes a voltage control process which increases the voltage of the fuel cell relative to the voltage of the secondary battery, and disconnects the relay.