Variable Compensating Circuit for Inductive Power Transfer Detuning
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Solution Overview
Problem
Inductive power transfer systems for electric vehicles face performance detuning due to temperature changes and aging, leading to increased energy losses and operational instability, particularly due to changes in compensating capacitance, which results in a mismatch between resonant and operating frequencies.
Innovation Solution
A circuit arrangement with a variable compensating arrangement that adjusts impedance by switching capacitors in and out of the circuit, synchronized with the phase current, to maintain optimal performance and reduce energy losses, using semiconductor switches and diodes for bidirectional behavior and minimal energy loss switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed compensating capacitance is used in the resonant circuit, then the circuit can be简单地 manufactured and operated, 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 making the compensating capacitance variable instead of fixed. The circuit switches between different capacitance values (C1, C2, C3) based on operating conditions, allowing the resonant frequency to be adjusted and maintained despite temperature changes and aging. This dynamic adjustment resolves the contradiction between reliability (frequency stability) and device complexity.
Solution Approach 2:
The patent changes the electrical parameter (capacitance) of the compensating capacitance based on operating conditions. By switching between different capacitance values, the resonant frequency can be adjusted to compensate for drift caused by temperature and aging, thereby maintaining tuning without requiring a completely complex redesign of the circuit.
2Productivity
If the resonant circuit becomes detuned due to capacitance drift, then the system performance degrades and power transfer capability is reduced, but increasing the capacitance tolerance to account for drift increases the energy losses and eliminates soft switching conditions
Solution Approach 1:
The patent implements feedback by monitoring the resonant frequency or tuning status of the circuit and adjusting the compensating capacitance accordingly. The control unit switches between different capacitance values based on detected conditions, ensuring the circuit remains tuned and maintains optimal power transfer capability while minimizing energy losses through soft switching.
Solution Approach 2:
By dynamically adjusting the capacitance value based on operating conditions, the circuit maintains optimal tuning and prevents detuning that would reduce power transfer capability. This dynamic adjustment ensures continuous operation at peak efficiency with minimal energy losses.
3Reliability
If a variable compensating arrangement with multiple switching elements is implemented, then the resonant frequency can be adjusted to compensate for detuning, but the switching operations may cause energy losses if not synchronized properly
Solution Approach 1:
The patent applies periodic action by synchronizing the switching operations with the alternating current cycle. The switching elements are activated at specific points in the AC cycle (e.g., when voltage or current is zero), which minimizes switching losses while maintaining accurate tuning of the resonant circuit.
Solution Approach 2:
The patent replaces mechanical switching with semiconductor switching elements (such as IGBTs or MOSFETs) that can be controlled electronically. This substitution allows for precise timing and synchronization of switching operations, minimizing energy losses while maintaining accurate resonant frequency adjustment.
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 allows for continuous optimization of inductive power transfer efficiency by compensating for changing electrical properties, maintaining system performance akin to a perfectly tuned state while minimizing energy losses and reducing operational complexity.
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), which can comprise the main or mutual inductance and/or the leakage inductance, and the capacitance(s), which can comprise the compensating capacitance, forms a resonant circuit
Data Source
AI summary
A circuit arrangement, in particular a circuit arrangement of an electric vehicle for inductive power transfer to the vehicle includes a pick-up arrangement and at least one variable compensating arrangement. The variable compensating arrangement includes a capacitive element, a first switching element and a second switching element. The first switching element and the second switching element are connected in series, and the series connection of the first and the second switching element is connected in parallel to the capacitive element of the variable compensating arrangement. Also disclosed is a method of operating the circuit arrangement and a method of manufacturing the circuit arrangement of the electric vehicle and the electric vehicle.