Wireless Power Transfer DC Link Capacitor Reduction
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Solution Overview
Problem
Conventional wireless power transfer systems face issues with DC link voltage ripple, leading to losses and increased system volume, weight, and cost, as well as unreliable feedback due to high-frequency AC voltage, particularly in single-phase systems.
Innovation Solution
A wireless power transfer system utilizing an off-board module with a DC-link capacitor bank and H-bridge configuration, where control circuitry generates driving signals with a nonlinear phase shift based on the DC voltage signal to convert DC voltage to high-frequency AC voltage, reducing the need for large DC link capacitance and enhancing feedback reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If DC link capacitance is increased to limit ripple voltage, then ripple is reduced, but system volume, weight, and cost increase
Solution Approach 1:
The patent changes the operating parameters by introducing variable switching frequency and variable phase-shift control in the dual-phase bridge converter. By dynamically adjusting the switching frequency and phase-shift angle based on the rectified voltage level, the system achieves ripple current cancellation without requiring excessive DC link capacitance. This parameter variation allows the system to maintain low ripple with reduced capacitor size.
Solution Approach 2:
The patent implements a control system that senses the rectified voltage and uses this feedback to adjust the switching frequency and phase-shift angle of the dual-phase bridge converter. This feedback mechanism enables the system to automatically optimize its operation to cancel ripple currents while maintaining efficient power transfer, thereby reducing the required DC link capacitance.
2Object-affected harmful factors
If DC link capacitance is increased to limit ripple voltage, then ripple is reduced, but system volume and cost increase
Solution Approach 1:
The patent changes the operating parameters by introducing variable switching frequency and variable phase-shift control in the dual-phase bridge converter. By dynamically adjusting the switching frequency and phase-shift angle based on the rectified voltage level, the system achieves ripple current cancellation without requiring excessive DC link capacitance. This parameter variation allows the system to maintain low ripple with reduced capacitor size.
Solution Approach 2:
The patent implements a control system that senses the rectified voltage and uses this feedback to adjust the switching frequency and phase-shift angle of the dual-phase bridge converter. This feedback mechanism enables the system to automatically optimize its operation to cancel ripple currents while maintaining efficient power transfer, thereby reducing the required DC link capacitance.
3Object-affected harmful factors
If active rectification with modulation is used to eliminate ripple, then ripple is reduced, but sensor count and gate drive requirements increase
Solution Approach 1:
The patent introduces a dual-phase bridge converter as an intermediary device between the rectifier and the wireless power transfer system. This intermediary actively controls the ripple current by using two phases with adjustable phase-shift, canceling the ripple before it reaches the output. This approach eliminates the need for complex active rectification circuits with multiple sensors and complex gate drive requirements.
4Device complexity
If conventional single-phase system is used, then system simplicity is maintained, but DC link voltage ripple causes losses and propagates to output
Solution Approach 1:
The patent segments the single-phase system into a dual-phase bridge converter configuration. By dividing the power conversion into two phases with controllable phase-shift, the system can cancel ripple currents through destructive interference of the ripple components from each phase. This segmentation maintains relative system simplicity while effectively eliminating ripple-induced losses.
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 minimizes DC link capacitor size, reduces turn-on switching losses, and maintains a steady output voltage, resulting in a more compact and efficient wireless power transfer system with reduced ripple and increased reliability.
Implementation Method 1
an H-bridge having a first phase leg and a second phase leg, where the H-bridge is coupled with the DC-link capacitor bank and configured to convert the DC voltage to a high-frequency AC voltage
Implementation Method 2
transmitter circuitry with a primary coil configured to wirelessly transmit the high-frequency AC voltage, and the WPT system includes an on-board module comprising a pick-up coil configured to receive the high-frequency AC voltage when the primary coil and the pick-up coil are disposed proximal to each other
Data Source
AI summary
A system and method are provided for a feed-forward control of an inverter to reduce, and potentially minimize, a DC link capacitor of a wireless power transfer system. The feed-forward control may be utilized to reduce the capacitance of the DC link capacitor in a single-phase series-series compensated WPT system.