Variable Compensation Inverter for Fixed-Frequency WPT Coupling Shifts
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Solution Overview
Problem
Existing wireless power transfer (WPT) systems face challenges in maintaining effective power transfer when coupling reactance varies due to misalignments or air-gap changes, particularly in high-frequency systems, which requires complex and inefficient design adjustments.
Innovation Solution
The implementation of a variable compensation inverter (VCI) architecture that uses a plurality of high-frequency inverters feeding a lossless resonant network, with controllable input voltages and phase-shifts, to maintain near-resistive loading and compensate for coupling variations at a fixed frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If variable-frequency approach is used to track resonance frequency changes, then effective power transfer is maintained, but design of magnetics and gate driver circuitry becomes challenging
Solution Approach 1:
The patent changes the compensation approach from variable frequency to variable reactance. By using an active variable reactance (AVR) rectifier that can dynamically adjust its reactance parameter, the system maintains resonance at a fixed frequency while compensating for coupling variations, thereby avoiding the complexity of wide-band magnetics and gate drivers
Solution Approach 2:
The AVR rectifier performs multiple functions: it rectifies the AC voltage and simultaneously provides variable reactance compensation. This multi-functionality eliminates the need for separate compensation components on the receiving side, reducing overall system complexity while maintaining effective power transfer
2Reliability
If banks of switchable capacitors or variable inductors are used in compensating network, then resonance frequency remains unchanged, but additional size, weight and losses are introduced
Solution Approach 1:
The patent replaces passive mechanical/physical compensation components (switchable capacitors and variable inductors) with an active electronic system (AVR rectifier). This substitution eliminates the need for large physical components, reducing size and weight, and minimizes energy losses associated with passive components
Solution Approach 2:
The AVR rectifier uses the existing rectifier circuitry to provide compensation functionality. By utilizing the diodes and capacitors already present in the rectifier, the system achieves variable compensation without adding separate compensation components, thereby avoiding additional size, weight, and losses
3Loss of energy
If AVR rectifier is used for variable compensation at fixed frequency, then high efficiency is maintained, but several circuit components must be incorporated on the receiving side where space and weight are at premium
Solution Approach 1:
The AVR rectifier combines rectification and variable compensation functions in a single circuit stage. The same diodes and capacitors used for rectification also provide the necessary reactance compensation, eliminating the need for additional compensation components on the space-constrained receiving side
Solution Approach 2:
The patent merges the rectifier and compensation functions into a single integrated circuit. By combining these functions, the system achieves high efficiency variable compensation without adding extra components to the receiving side, thereby conserving valuable space and weight
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 VCI effectively compensates for coupling variations, maintaining a fixed output power level and high efficiency, even under significant misalignment conditions, by ensuring zero-voltage and near-zero-current switching.
Implementation Method 1
Both inductive and capacitive WPT systems require circuit components that can compensate for the reactance of their coupler. To achieve effective power transfer, WPT systems are typically designed to operate at frequencies close to the resonance frequency of a resonant tank formed by the coupler and the compensation components.
Implementation Method 2
inductive WPT systems, which utilize a pair of magnetically coupled coils
Data Source
AI summary
A high-frequency inverter architecture is provided that compensates for coupling variations in wireless power transfer (WPT) systems, while adapted to operate at a fixed frequency and maintaining high efficiency. This implementation, termed a variable compensation inverter (VCI), includes a plurality of high-frequency inverters feeding a lossless resonant network, with the inputs of the inverters fed by controllable voltages. By appropriately controlling the input voltages of the individual inverters and their relative phase-shift, the VCI can maintain near-resistive, and slightly but sufficiently inductive, loading of the inverters even as the reactance of the WPT coupler changes; hence, providing compensation while maintaining zero-voltage and near-zero-current switching. The VCI also ensures that the output power of the WPT system is maintained at a fixed level even during coupling variations.