Digital Phase Shift Control for EV Wireless Charging Resonance
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Solution Overview
Problem
Existing contactless charging systems for electric vehicles by magnetic induction are complex and expensive, particularly in adapting the frequency of the current flowing in the circuit to achieve resonance between the transmitter and receiver coils, which can lead to excessive power refusal by the vehicle battery.
Innovation Solution
A method that converts the phase shift between voltage and current into a digital value, digitally controlling the frequency of the switching instructions sent to the inverter, minimizing hardware components and using a software loop for flexible frequency adjustment, thereby simplifying the system and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If analog circuits and modules are used to measure and control phase shift between voltage and current, then resonance can be achieved, but the system becomes complex and expensive
Solution Approach 1:
The patent replaces complex analog electronic circuits with digital processing. Specifically, it uses a microcontroller to digitally measure voltage and current signals, calculate phase shift through digital signal processing, and control the inverter frequency. This substitution of digital for analog systems reduces hardware complexity while maintaining the ability to achieve and maintain resonance.
Solution Approach 2:
The patent uses digital sampling to create discrete representations of continuous voltage and current waveforms. By capturing multiple samples of each waveform and processing these digital copies through algorithms (such as cross-correlation or Fourier analysis), the system can accurately determine phase shift without requiring complex analog phase detection circuitry.
2Productivity
If frequency is varied to achieve resonance, then power transfer efficiency improves, but the vehicle battery may refuse excessive power transfer
Solution Approach 1:
The patent implements a closed-loop control system where the microcontroller continuously monitors the phase shift between voltage and current, and adjusts the inverter frequency accordingly. By maintaining phase shift close to zero (indicating resonance), the system optimizes power transfer efficiency while the gradual frequency adjustment prevents sudden power surges that could cause battery refusal.
Solution Approach 2:
The system dynamically adjusts the operating frequency based on real-time conditions. The microcontroller varies the frequency in small increments, monitoring the phase shift response, and adapts the frequency to match the resonant frequency of the coupled coils. This dynamic adaptation ensures efficient power transfer while responding to changing load conditions and battery acceptance levels.
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 allows for easy performance tuning and resonance detection at low power levels, making the system more robust and cost-effective while maintaining flexibility in frequency control, thus ensuring efficient power transfer between the primary and secondary coils.
Implementation Method 1
Charging is carried out by magnetic induction: in a location called the 'charging zone', a current is made to flow in a ground circuit having a transmitter coil - or primary
Implementation Method 2
The phenomenon of magnetic induction takes place only if the primary and secondary coils are sufficiently close to each other, and the transmitted power depends partly on the resonance of the ground circuit
Data Source
Figure 1~8
Figure 2~3
Figure 4~5
AI summary
The invention relates to a method for the contactless charging of the battery (Batt) of an electric automobile (30) by magnetic induction using a transmitter coil (11) of a charging device and a receiver coil (21) of the vehicle, wherein the method includes the steps of: controlling (140) the power supply of a converter (3), at the terminals of which the transmitter coil (11) is connected, according to a variable frequency (N_PWM); measuring (100), in an analog circuit, the value of the current (U) and of the voltage (I) at the terminals of the transmission coil (11); and calculating (110) the phase shift between the current (U) and the voltage (I). The method is essentially characterized in that it further includes the steps of: converting (120) the phase shift into a digital value; and locking (130) the variable frequency of the converter to the phase-shift value by digital processing.