Wireless Power Transfer Foreign Object Detection via Phase Difference
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Solution Overview
Problem
Foreign objects, such as metal or magnetic materials, between the transmission and reception coils in a wireless power transfer (WPT) system can disrupt the magnetic field, leading to abnormal system operation and reduced power transfer efficiency, and potentially cause temperature increases, affecting system stability.
Innovation Solution
A method using zero phase angle (ZPA) control to detect foreign objects by comparing the phase difference between input current and voltage, determining their presence based on reference values, and controlling the power transfer converter to stop the WPT process if a foreign object is detected, without requiring additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a WPT system operates with transmission and reception coils, then wireless power transfer is enabled, but foreign objects between the coils can disrupt the magnetic field causing abnormal operation and reduced efficiency
Solution Approach 1:
The system performs preliminary detection of foreign objects by monitoring the phase difference between input current and voltage before power transfer operations can cause harmful effects. The FOD detector continuously monitors the resonant network during operation and detects foreign objects early, allowing the system to take preventive action before abnormal operation or temperature increases occur.
Solution Approach 2:
The system implements feedback control by continuously monitoring the phase difference between input current and voltage through the FOD detector. When a foreign object is detected, the controller receives feedback and automatically adjusts the operation by stopping or preventing power transfer, thereby maintaining system reliability while preserving wireless power transfer capability.
2Measurement precision
If foreign object detection is implemented using phase difference monitoring, then detection accuracy is improved, but system complexity increases due to additional control requirements
Solution Approach 1:
The FOD detector is integrated into the existing resonant network of the WPT system, allowing it to perform multiple functions: normal power transfer operation and foreign object detection. The controller that manages power transfer also handles FOD detection and response, eliminating the need for separate dedicated detection hardware and reducing overall system complexity.
Solution Approach 2:
The system uses its own operational parameters (input current and voltage phase difference) for foreign object detection rather than requiring external detection equipment. The resonant network's inherent characteristics provide the detection mechanism, and the system self-regulates by stopping power transfer when foreign objects are detected, without needing additional complex control systems.
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 effective detection and prevention of foreign object interference during WPT operations, maintaining system stability and efficiency by identifying and responding to phase differences between input current and voltage.
Implementation Method 1
a magnetic induction type WPT system uses an electromagnetic induction phenomenon between a transmission coil in the GA and a reception coil in a vehicle assembly to transfer electric power
Implementation Method 2
the reception coil in the VA mounted on the EV makes an inductive resonance coupling with the transmission coil in the GA located in the charging station or the charging spot, and charges the battery in the EV using power transferred from the GA through the inductive resonance coupling
Implementation Method 3
when a foreign object, which may affect a magnetic field, exists between the transmission coil and the reception coil, such as metal or magnetic material, there is a direct influence on the resonant network of the WPT system
Data Source
AI summary
A method for detecting a foreign object between a transmission pad and a reception pad for wireless power transfer (WPT) may comprise: performing, by a processor, a zero phase angle (ZPA) control for a power transfer converter included in or connected to the transmission pad; detecting, by the processor, a phase difference between an input current and an input voltage of the power transfer converter; and determining, by the processor, whether or not the foreign object exists between the transmission pad and the reception pad by comparing the phase difference with a reference value.