Fuel Cell Power Leakage Area Identification via Relay Segmentation
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Solution Overview
Problem
In fuel cell vehicles, existing methods cannot accurately distinguish between power leakage areas between the positive side relay and the backflow preventing diode and other areas, leading to incorrect identification of power leakage locations.
Innovation Solution
A fuel cell system with a controller that performs isolation processing by opening the positive side relay and identifies power leakage areas by determining insulation resistance changes, allowing differentiation between the area between the positive side relay and the diode and other areas, using a power leakage detector and relays to input detection signals via the negative side relay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If both side relays are opened to inspect power leakage, then the fuel cell stack is isolated from the load, but the area between the positive side relay and the backflow preventing diode cannot be detected
Solution Approach 1:
The power leakage detection process is segmented into multiple stages: first detecting with both relays closed, then isolating the positive side relay, and finally isolating the negative side relay. This segmentation allows the detection signal to reach different circuit areas in sequence, enabling identification of power leakage locations that would otherwise be inaccessible when both relays are open simultaneously.
Solution Approach 2:
The capacitor is pre-charged during normal operation before power leakage detection begins. When detection is initiated, the capacitor provides the necessary voltage to enable the detection signal to reach the area between the positive side relay and backflow preventing diode, even when relays are opened for isolation.
2Measurement precision
If the area between positive side relay and diode is isolated for detection, then power leakage in that area can be identified, but power supply interruption occurs
Solution Approach 1:
The relay states are dynamically changed during the detection process. The controller sequentially opens the positive side relay and negative side relay based on detection results, allowing the system to transition between different isolation states without permanent power supply interruption. This dynamic control enables precise location identification while minimizing disruption to power supply.
Solution Approach 2:
The detection system provides feedback to the controller about insulation resistance values in different circuit areas. Based on this feedback, the controller determines which area has power leakage and controls the relay states accordingly, enabling precise identification without unnecessary power supply interruption.
3Loss of information
If insulation resistance measurement is performed with both relays closed, then detection signal reaches all areas, but power leakage area cannot be distinguished
Solution Approach 1:
The detection process segments the circuit into different detectable areas by controlling relay states. First, both relays are closed to detect overall insulation resistance. Then, the positive side relay is opened to detect the area between the relay and diode. Finally, the negative side relay is opened to detect the fuel cell stack area. This segmentation enables both comprehensive coverage and precise location identification.
Solution Approach 2:
The system performs multiple detection actions with different relay states rather than a single measurement. By conducting partial detections with specific relay configurations, the system gathers sufficient information to precisely identify power leakage locations while maintaining overall detection coverage.
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
Enables accurate identification of power leakage areas, ensuring correct determination of leakage locations without interrupting the power supply and allowing for isolation of high voltage auxiliary machines.
Implementation Method 1
a power leakage detector configured to output a power leakage detection signal to be input to the fuel cell stack via the negative side relay, and detects reduction of insulation resistance
Implementation Method 2
a diode that prevents backflow of current to a positive electrode of the fuel cell stack
Data Source
AI summary
When reduction of insulation resistance is detected, an FC positive side relay is opened, and a switching element is turned OFF. When the insulation resistance has returned to a normal value as a result of the relay opening and the switching element turning OFF, it is identified that the power leakage is occurring in the area between the positive side relay and the diode.