On-Board Charger Phase Detection for Relay Status Diagnosis
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Solution Overview
Problem
Existing on-board battery chargers (OBCs) for electric vehicles struggle to accurately detect phase-shift between input voltages from a mains supply, which is crucial for determining whether the mains supply is multi-phase or single-phase and for ensuring proper positioning of phase configuration relays.
Innovation Solution
The proposed solution involves a method and system for controlling an OBC that includes multiple rail circuits and relays. Each rail circuit has a controller that generates detection signals based on voltage events, and a main controller compares these signals to determine the phase relationship between input voltages. This allows the OBC to identify whether the mains supply is multi-phase or single-phase and to diagnose the operational status of the relays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the OBC uses a multi-phase configuration with relays to detect phase-shift and determine mains supply type, then the ability to accurately detect phase configuration and diagnose relay status is improved, but the device complexity increases due to multiple rail circuits and relay components
Solution Approach 1:
The OBC is divided into multiple independent rail circuits (first rail circuit, second rail circuit, third rail circuit), each with its own controller that independently detects voltage events. This segmentation allows parallel detection of phase relationships without requiring a single complex detection system, improving measurement precision while distributing system complexity across modular units.
Solution Approach 2:
Each rail controller is designed to perform multiple functions: detecting voltage events, generating detection signals, and participating in phase-shift determination. The relays serve dual purposes by both connecting/disconnecting rail circuits and providing diagnostic information about system status. This multi-functionality reduces the need for separate dedicated components.
2Adaptability or versatility
If the relay is positioned in the closed state to connect rail circuits for single-phase operation, then the OBC can operate with single-phase mains supply, but the risk of improper positioning and operational failures increases
Solution Approach 1:
The system implements feedback by having each rail controller generate detection signals based on voltage events, and the main controller compares these signals to determine phase relationships. This feedback mechanism allows the system to verify relay positioning status and detect improper configuration, enabling corrective actions to ensure reliable operation.
Solution Approach 2:
The system performs preliminary detection of phase configuration and relay status before initiating charging operations. The main controller compares detection signals from multiple rail controllers to determine whether the mains supply is single-phase or multi-phase and whether relays are properly positioned, preventing operational failures before they occur.
3Reliability
If the OBC implements comprehensive phase detection and relay diagnosis functionality, then the operational reliability with both single-phase and multi-phase supplies is improved, but the control system complexity increases
Solution Approach 1:
The control system is segmented into distributed rail controllers and a central main controller. Each rail controller independently monitors its respective rail, generating detection signals based on local voltage events. This segmentation simplifies the control architecture by distributing detection functions rather than requiring a single complex control unit to handle all detection and diagnosis tasks.
Solution Approach 2:
Detection signals serve as intermediaries between the rail circuits and the main controller. Instead of the main controller directly analyzing complex voltage waveforms from multiple rails, it receives simplified detection signals that encode phase relationship information, reducing the computational complexity of the control system while maintaining comprehensive monitoring capabilities.
Data Source
AI summary
An on-board battery charger (OBC) includes first and second rails which generate first and second detection signals based on voltage events, such as zero-crossing or peak voltage events, of input voltages supplied to the rail circuits. The OBC includes a relay switchable between (i) an opened state in which the relay disconnects the rails whereby the rails can respectively receive first and second phase input voltages from a multi-phase mains supply and (ii) a closed state in which the relay connects the rails whereby the rails can both receive a same input voltage from a single-phase mains supply. A controller determines from a comparison of the detection signals at the same time whether input voltages received by the rails from a mains supply are out-of-phase or in-phase to determine therefrom whether the mains supply is multi-phase or single-phase and/or whether the relay is properly or improperly opened or closed.