Polyphase Wireless Power Transfer Duty Cycle Control for Lower Switching Loss
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing polyphase wireless power transfer systems face challenges in controlling power transfer efficiently due to high switching losses, complexity, and misalignment issues, particularly in high-power applications like electric vehicle charging, where conventional modulation schemes require additional circuitry or higher switching frequencies.
Innovation Solution
The proposed method employs duty cycle modulation in polyphase converters to generate a controllable asymmetric voltage waveform, allowing for independent control of phase windings and reducing switching frequency to the resonant frequency, thereby minimizing switching losses and component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If standard six-step modulation is used with fixed 50% duty cycles, then full control over currents is achieved, but additional circuitry is required to regulate DC voltage
Solution Approach 1:
The patent extracts the DC voltage regulation function from a separate DC-DC converter and integrates it into the PWM control mechanism itself. By manipulating the duty cycles of the six switches, the controller simultaneously achieves both current control and DC voltage regulation, eliminating the need for additional regulation circuitry.
Solution Approach 2:
The PWM control mechanism is designed to perform multiple functions: it controls the AC output currents to the motor and simultaneously regulates the DC link voltage. This multi-functionality is achieved by coordinating the duty cycles of the six switches to satisfy both control objectives without requiring separate dedicated circuits.
2Ease of operation
If variable output voltage modulation with notches and pulses is used, then bridge current is fully controlled, but switching frequency increases to three times the tuned frequency causing high switching losses
Solution Approach 1:
The patent changes the control parameter from complex notch/pulse width modulation at high frequency to simpler duty cycle modulation at the fundamental tuned frequency. By adjusting the duty cycles of the six switches while maintaining operation at the resonant frequency, the system achieves full bridge current control without the excessive switching losses associated with triple-frequency operation.
3Power
If multi-phase converters are used to increase power transfer capability, then smaller current stresses are achieved, but system size and complexity increase
Solution Approach 1:
The patent segments the power conversion function into six independent switch legs, each controlled by its own duty cycle. This segmentation allows the multi-phase system to handle high power with reduced current stress per device while maintaining manageable complexity through modular control of individual legs rather than requiring complex inter-leg coordination.
4Power
If three separate full bridges are used in three-phase IPT systems, then high power capability is achieved, but device count and system complexity increase significantly
Solution Approach 1:
The patent merges three separate full-bridge converters into a single integrated three-phase converter with six switches. This consolidation achieves the same high power capability as three separate bridges but reduces the device count and control complexity by sharing common components and using unified PWM control with six duty cycles instead of three independent bridge controls.
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 efficient power control without additional DC-DC converters, reduces switching losses, and allows for flexible operation under misalignment conditions by utilizing asymmetrical duty cycles, which are filtered by resonant networks, enhancing the overall efficiency and reliability of polyphase wireless power transfer systems.
Implementation Method 1
switching a polyphase converter to produce a periodic asymmetric voltage waveform across at least one of the phase windings of a polyphase wireless power transfer coupler by controlling the switching duty cycle
Implementation Method 2
switching each of the phase windings at a frequency that corresponds to a resonant frequency of the polyphase wireless power transfer primary or secondary and regulating the voltage applied to the resonant circuit of each of the phase windings
Data Source
AI summary
A method of controlling a polyphase wireless power transfer coupler includes using duty cycle control to switch a polyphase converter to produce a periodic asymmetric voltage waveform across the phase windings.