Inductive Power Transfer Control for ZVS Under Coil Misalignment
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Solution Overview
Problem
Existing inductive power transfer (IPT) systems face challenges in regulating power with optimal efficiency and providing zero voltage switching (ZVS) for electronic switches due to coil misalignment and load variations, particularly in wireless electric vehicle charging.
Innovation Solution
A comprehensive control strategy that optimizes load impedance by controlling the operating frequency, duty cycle, and relative phase angle to minimize converter losses and achieve ZVS, using a series-series resonant network and a two-step approach to determine optimal operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional control strategies are used in IPT systems, then power transfer can be maintained, but optimal efficiency cannot be achieved and ZVS cannot be provided for electronic switches under coil misalignment and load variations
Solution Approach 1:
The patent implements dynamic control of the operating frequency and duty cycle that continuously adapts to changing load conditions and coil misalignment. The controller adjusts these parameters in real-time to maintain optimal efficiency and ZVS, transforming the static control approach into a dynamic one that responds to system variations.
Solution Approach 2:
The patent changes key operating parameters (frequency and duty cycle) to optimize system performance. By varying these parameters based on detected system conditions, the controller achieves both minimal converter losses and maintained ZVS across different operating scenarios, directly addressing the contradiction between efficiency and adaptability.
2Loss of energy
If the operating frequency is controlled to optimise load impedance, then converter losses are minimized, but additional control complexity is introduced
Solution Approach 1:
The patent employs feedback control where the controller monitors system performance and adjusts the operating frequency accordingly. This closed-loop approach automatically optimizes load impedance and minimizes converter losses without requiring complex manual intervention, resolving the contradiction by using intelligent feedback rather than sheer complexity.
3Loss of energy
If the duty cycle or relative phase angle is controlled to minimize converter losses, then efficiency is improved, but the system becomes more complex to implement
Solution Approach 1:
The patent implements self-service control where the system automatically adjusts its own operating parameters (duty cycle and phase angle) based on internal feedback. The controller monitors converter losses and autonomously optimizes these parameters, eliminating the need for external complex control mechanisms and reducing overall system complexity while maintaining high efficiency.
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
The control strategy effectively regulates power at optimal efficiency while maintaining ZVS for converters, even with significant coil misalignments and wide load variations, achieving efficiencies up to 96.5% in experimental prototypes.
Implementation Method 1
wireless power transfer (WPT) technology. Wired charging is the most common way of charging EVs but long charging cables pose trip hazards, and it is not ideal for in harsh and hostile conditions where there are snow, ice and chemicals. In contrast, wireless EV charging, based on inductive power transfer (IPT) technology, is gaining recognition as a convenient way to charge EVs through weak magnetic coupling between a coil on each of the primary and secondary sides of the system with no physical connections.
Implementation Method 2
A comprehensive control strategy that optimizes load impedance by controlling the operating frequency, duty cycle, and relative phase angle to minimize converter losses and achieve ZVS, using a series-series resonant network and a two-step approach to determine optimal operating conditions.
Data Source
AI summary
A method of controlling the primary or secondary side converter of a wireless power transfer (WPT) or an inductive power transfer (IPT) system includes optimising a load impedance, and controlling one or more of a duty cycle or relative phase angle to reduce or minimize the converter losses at the optimal load impedance