EV On-Board Charger Relay Control for Fast V2G Protection
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Solution Overview
Problem
Existing electric vehicle (EV) on-board chargers (OBCs) and external chargers (EVSEs) face challenges in performing fast fault diagnosis and relay off operations during Vehicle-to-Grid (V2G) mode, particularly due to the difficulty in coordinating the operations of multiple relays and preventing misdiagnosis.
Innovation Solution
An OBC system that includes a controller for quickly determining and controlling the operations of internal and external relays using power-related parameters, employing a control pilot (CP) signal to manage relay operations, ensuring fast and coordinated relay off operations in both the OBC and EVSE.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the EVSE performs fault diagnosis and relay off operations, then the system can achieve V2G protection, but the response time exceeds the required 90ms limit due to the EVSE's simple charger functionality
Solution Approach 1:
The patent introduces the OBC as an intermediary component that bridges the gap between the EVSE and the vehicle battery. The OBC performs fast fault diagnosis and relay control operations, acting as a mediator that enables the EVSE to achieve rapid response without requiring the EVSE itself to have complex diagnostic capabilities. This resolves the contradiction by placing the fast response function in the OBC while maintaining the EVSE's simple charger role.
Solution Approach 2:
The patent segments the fault diagnosis and relay control functions between two independent components: the EVSE and the OBC. The EVSE handles basic charging functions while the OBC handles fast fault diagnosis and relay control. This segmentation allows each component to be optimized for its specific function, with the OBC providing rapid response capability within the 90ms requirement.
2Reliability
If multiple independent relays are used for galvanic cutoff between the vehicle battery and the grid, then safety is improved, but the control complexity increases due to the need to coordinate relay off sequences to prevent misdiagnosis
Solution Approach 1:
The patent merges the control of multiple relays (first relay in EVSE and second relay in OBC) under a single control entity - the OBC controller. Instead of having independent control systems for each relay, the OBC controller coordinates both relay operations, simplifying the control architecture while maintaining the safety benefits of multiple relays. This resolving the contradiction by reducing control complexity while preserving reliability.
Solution Approach 2:
The patent implements a feedback mechanism where the OBC controller monitors the status of both relays and coordinates their off sequences based on fault conditions. The controller receives feedback about relay positions and fault states, then adjusts the relay off timing accordingly to prevent misdiagnosis. This feedback loop enables coordinated control of multiple relays without increasing system complexity.
Data Source
AI summary
An on-board charger for an electric vehicle includes a vehicle port configured to be connected to an external charger comprising a first relay located on an internal first power supply path, a power converter, a second relay located on a second power supply path between the vehicle port and the power converter, and a controller configured to turn off the first relay and the second relay in response to triggering a vehicle-to-grid (V2G) protection operation based on power-related parameters.