Polyphase Coil Assembly Resonance for Balanced Wireless EV Charging
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Solution Overview
Problem
Polyphase wireless power transfer systems face limitations in power transfer capability due to non-zero interphase mutual-inductance and unbalanced phases, which compromise efficiency and speed.
Innovation Solution
The implementation of a polyphase inductive power transfer system with compensating capacitance networks that account for balanced and unbalanced inter-phase mutual inductances, featuring orthogonal resonant modes and specific coil configurations, including bipolar and unipolar phases with compensating capacitance connected in series with each coil, and a controller to adjust switching pairs based on receiver type and alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single phase coil system is used, then the system design is simpler, but power transfer capability is limited by electromagnetic field emissions requirements and foreign object heating limits
Solution Approach 1:
The patent divides the single-phase system into multiple phases (polyphase system with at least two phases). Each phase has its own coil assembly, allowing the system to achieve higher power transfer capability while distributing electromagnetic field emissions across multiple phases, thereby reducing peak emissions and improving safety margins.
2Power
If polyphase wireless transfer systems are designed to increase power transfer, then power transfer capability increases, but non-zero interphase mutual-inductance causes unbalance between phases which compromises power transfer capability
Solution Approach 1:
The patent implements a controller that monitors the actual power transfer and phase balance conditions, then adjusts the switching pairs and resonant frequency accordingly. This feedback mechanism compensates for unbalanced interphase mutual inductance by dynamically optimizing the operation of each phase to maintain balanced power transfer.
Solution Approach 2:
The patent adjusts operational parameters including resonant frequency, switching timing, and coil excitation levels to compensate for unbalanced interphase mutual inductance. By changing these parameters dynamically, the system maintains optimal phase balance and power transfer capability despite inherent unbalances in the polyphase configuration.
3Productivity
If higher power charging is implemented, then charging rate increases, but system size and mass of transmitting and receiving coil assemblies increase
Solution Approach 1:
The patent employs dynamic resonance tuning where the system automatically adjusts the resonant frequency and switching parameters based on load conditions and coupling strength. This allows the coil assemblies to operate at optimal efficiency across a range of power levels, achieving high power transfer without requiring proportionally larger coil masses.
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 enhances power transfer efficiency and speed by enabling independent excitation of resonant modes, improving power density and specific power, while maintaining safety and emissions compliance.
Implementation Method 1
The value of the compensating capacitance, for each phase, is determined such that the transmitter has at least two independently excitable resonant modes at a resonant frequency
Implementation Method 2
Single phase designs work by pulsing the flux produced by the primary coil with time. Part of this time-varying flux couples with the secondary coil and induces a voltage. The induced voltage causes a current to flow, transferring power to the load.
Implementation Method 3
Certain polyphase wireless transfer systems have been designed to increase power transfer for electric vehicles, however, since there is a non-zero interphase mutual-inductance, which may be unbalance between phases, power transfer capability may be compromised and reduced for these systems.
Data Source
AI summary
Polyphase wireless power transfer systems are provided. The transfer system may be used for charging hybrid and electric vehicles. The systems are capable of transferring over 50 KW over an air gap of 15 cm. The systems use a rotating magnetic field to transfer power. The system may comprise transmitter coil assembly. The coil assembly may be one or more layers. The system may employ either unipolar or bipolar coils. The transmitter also comprises compensating capacitance connected in series with at least one coil for each phase. A value of the compensating capacitance for each phase is determined such that the transmitter has at least two independently excitable resonant modes at a resonant frequency. The transmitter is compatible with a plurality of different receivers including three-phase, single phase with a circular coil and single phase with DD coils.