Variable Reactance Control for Inductive Power Transfer Detuning
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Solution Overview
Problem
Inductive power transfer systems for electric vehicles face challenges in maintaining optimal performance due to changes in electrical properties and positional misalignment, leading to detuning and increased energy losses.
Innovation Solution
A method and control system that actively vary the reactance of the vehicle-sided circuit arrangement using an optimization approach, employing a compensating arrangement with adjustable reactance to maintain resonance frequency alignment and minimize energy losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed compensating capacitance is used in the resonant circuit, then the circuit can be tuned at a specific operating frequency, but the resonant frequency drifts due to temperature changes and aging, resulting in detuning and increased energy losses
Solution Approach 1:
The patent applies the dynamics principle by replacing the fixed compensating capacitance with a variable compensating capacitance that can be dynamically adjusted. The control system continuously monitors the resonant frequency and modifies the capacitance value in real-time to maintain resonance at the operating frequency, thereby preventing detuning caused by temperature changes and aging.
Solution Approach 2:
The patent implements feedback by using a control system that measures the actual resonant frequency of the circuit and compares it with the desired operating frequency. Based on this comparison, the control system automatically adjusts the variable compensating capacitance to eliminate frequency deviations, ensuring continuous optimal performance and minimizing energy losses.
2Productivity
If the resonant circuit becomes detuned, then the power transfer capability decreases and semiconductor switches experience increased power losses, but adding complex control mechanisms increases device complexity
Solution Approach 1:
The patent applies self-service by designing a control system that autonomously monitors the resonant frequency and adjusts the compensating capacitance without requiring external intervention. The system automatically detects detuning conditions and corrects them by modifying the capacitance value, thereby maintaining optimal power transfer capability while avoiding the need for complex manual control mechanisms.
3Loss of energy
If a leading current occurs in the WPC, then soft switching conditions of semiconductor switches are eliminated and power losses increase, but preventing this requires additional control measures that increase device complexity
Solution Approach 1:
The patent implements continuity of useful action by maintaining continuous resonance between the inductive power transfer system and the vehicle-sided circuit arrangement. By ensuring the resonant frequency continuously matches the operating frequency through dynamic capacitance adjustment, the system sustains lagging current conditions that enable soft switching, thereby continuously preventing power losses in semiconductor switches without requiring discontinuous or complex control interventions.
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 solution optimizes inductive power transfer by compensating for changing electrical properties and positional misalignment, ensuring consistent system performance with reduced energy losses and complexity in controlling the circuit arrangement.
Implementation Method 1
a receiving device adapted to receive an alternating electromagnetic field and to produce an alternating electric current by electromagnetic induction
Implementation Method 2
a rectifier adapted to convert an alternating current to a direct current
Implementation Method 3
The direct current can be converted into an alternating current by means of an inverter
Implementation Method 4
The first set of windings and the second set of windings form a high frequency transformer to transfer electric energy to the vehicle
Implementation Method 5
the combination of the inductance(s) and the capacitance(s) forms a resonant circuit. A perfect impedance cancellation happens if impedance values of the inductance(s) and the capacitance(s) are chosen such that the natural resonance frequency of the resonant circuit is equal to the operating frequency
Data Source
AI summary
Disclosed is a method of and control system for operating a circuit arrangement, in particular a circuit arrangement of an electric vehicle for inductive power transfer to the vehicle. The circuit arrangement includes at least one phase line with at least one field receiving arrangement and at least one compensating arrangement with a variable reactance, wherein at least one current-dependent cost function is evaluated, wherein the reactance is varied such that the cost function is optimized.