HV AC System Leakage and Ground Fault Detection
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Solution Overview
Problem
Existing fault detection methods for electric and hybrid electric vehicles do not effectively address AC leakage, which can cause extreme voltage and current swings, potentially damaging vehicle equipment, and are not specifically designed for high voltage alternating current systems.
Innovation Solution
A method and circuit for detecting ground faults in electric drive systems using alternating current leakage, involving a detection means such as an electromagnetic device to receive first and opposing direction currents, and a fault determination module to compare induced currents or voltages to predetermined thresholds to determine the presence of a ground fault.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing fault detection methods are used, then leakage between traction battery and auxiliary battery can be detected, but AC system leakage and ground faults cannot be effectively detected
Solution Approach 1:
The patent changes the detection parameter from DC voltage/current (used in existing methods) to AC current leakage detection. The system specifically monitors AC current imbalance between phases and detects ground faults by measuring current leakage to chassis ground, adapting the detection approach to AC system characteristics rather than applying DC-based methods to AC systems.
Solution Approach 2:
The patent introduces an intermediary detection circuit that measures AC current leakage through a current sensor or differential transformer. This intermediary device detects the imbalance between outgoing and returning AC currents, providing an indirect but effective means to detect ground faults without directly exposing the high voltage AC system to the detection electronics.
2Productivity
If ground faults are not detected, then system operation continues, but extreme voltage and current swings can damage vehicle equipment
Solution Approach 1:
The patent implements a feedback mechanism where the detected AC current leakage signal is fed back to a control system that monitors the magnitude of leakage. When the leakage exceeds a predetermined threshold, the system provides feedback to shut down the inverter or trigger protective devices, creating a closed-loop protection system that continuously monitors and responds to ground fault conditions.
Solution Approach 2:
The patent applies preliminary anti-action by detecting ground faults before they cause extreme voltage and current swings. The system proactively monitors AC current leakage and takes preventive action by shutting down the inverter or activating protective devices before the fault can propagate and damage vehicle equipment, thereby preventing the harmful effects rather than responding to them after occurrence.
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 provides a reliable and economical means to detect AC current leakage, preventing damage by identifying ground faults and allowing for timely shutdown of the inverter operation, thus protecting vehicle components.
Implementation Method 1
an electromagnetic detection means to provide an induced current
Data Source
AI summary
Apparatus and methods for detection of a ground fault on a DC side as well as on an AC side of an inverter are presented. A detection means can receive forward and reverse current and provide an induced current based on the difference between them. A parameter associated with the induced current, or a parameter associated with a voltage generated by conduction of the induced current through a device, can be used to detect a ground fault. In addition, a detection means can be configured to receive transient current, and a resulting voltage at the detection means can be used for fault detection. A detection means can be disposed at the DC side of an inverter or at the AC side of the inverter. Apparatus and methods can be configured to detect AC leakage current caused by a ground fault.