Contactless Energy Transfer Parameter Determination
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Solution Overview
Problem
Contactless electrical energy transfer systems face inefficiencies in power transfer and alignment verification due to weak coupling between coils in applications like electric vehicle charging, where the coupling factor is low and air gaps are large, leading to challenges in accurately determining system parameters for efficient energy transfer.
Innovation Solution
A method and system that align the first and second coil circuits, short the terminals of the second coil, apply an alternating voltage to the first coil, and measure currents to determine parameters like inductance and coupling factor, allowing for improved power transfer efficiency and alignment verification through processing these currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the air gap between coils is increased for electric vehicle charging applications, then the flexibility and applicability of the system is improved, but the coupling factor decreases leading to reduced power transfer efficiency
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the switching frequency of the resonant circuit to compensate for variations in coupling factor caused by changes in air gap distance. When the air gap increases and coupling factor decreases, the system adjusts the operating frequency to maintain optimal power transfer efficiency, thus resolving the contradiction between flexibility and energy loss.
2Ease of operation
If the air gap and misalignment between coils are increased for vehicle charging, then the ease of operation is improved, but the coupling factor and power transfer efficiency deteriorate
Solution Approach 1:
The patent implements feedback control by continuously monitoring the coupling factor and power transfer efficiency, then adjusting the switching frequency accordingly. This closed-loop feedback mechanism allows the system to maintain high efficiency even when air gap and misalignment vary during operation, thus resolving the contradiction between ease of operation and energy loss.
3Device complexity
If conventional parameter estimation methods are used in weakly coupled systems, then the device complexity is reduced, but the measurement precision and reliability of parameter determination deteriorate
Solution Approach 1:
The patent applies preliminary action by performing parameter estimation during a dedicated test phase before normal power transfer begins. During this preliminary phase, the system measures currents under controlled conditions (with secondary coil shorted) to accurately determine primary coil parameters such as inductance and resistance, ensuring high measurement precision without adding complexity to the main power transfer operation.
4Measurement precision
If iterative parameter estimation methods are employed to achieve reliable parameter determination, then the measurement precision is improved, but the time required for parameter determination increases
Solution Approach 1:
The patent resolves this contradiction by performing parameter estimation as a preliminary action during a dedicated test phase before power transfer begins. This approach allows iterative methods to achieve high precision without delaying the actual power transfer operation, as all necessary measurements are completed in advance during the preliminary characterization phase.
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 enables rapid and reliable determination of system parameters, enhancing power transfer efficiency and control in contactless energy transfer systems, particularly in scenarios with weak coupling, by processing current measurements to accurately assess and adjust for inductance and coupling factor.
Implementation Method 1
The primary coil, which is driven by an alternating current (AC), generates an electromagnetic field which induces an alternating current in the secondary coil
Implementation Method 2
an alternating voltage is applied to terminals of the first coil circuit while the terminals of the second coil circuit are shorted. The alternating voltage induces a first current in the first coil circuit and a second current in the second coil circuit
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Determining parameters of a contactless electrical energy transfer (CEET) system (10) comprise inductively coupling a first coil circuit (12) to a second coil circuit (22), shorting terminals (223) of the second coil circuit, and applying an alternating voltage to terminals (123) of the first coil circuit. The alternating voltage induces a first current in the first coil circuit and a second current in the second coil circuit. Next, the terminals (123) of the first coil circuit are shorted while the second current is flowing, followed by measuring the first current and/or the second current and determining the parameters on the basis of the measured current.