Contactless Power Transmission Inverter Control
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Solution Overview
Problem
Existing contactless power transmission systems face issues where transmission power exceeds a limit value unexpectedly when the drive frequency of the inverter is adjusted, particularly when the coupling coefficient between the power transmission and reception coils is small, leading to unstable power control.
Innovation Solution
A contactless power transmission device with a voltage-source inverter and a control unit that executes both transmission power control by adjusting the duty of the output voltage and turn-on current control by adjusting the drive frequency, where the control unit decreases the target power when transmission power exceeds the limit value, using a correction amount proportional to the excess amount to prevent overshoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the drive frequency of the inverter is adjusted to control turn-on current, then the turn-on current is controlled, but the transmission power may exceed the limit value unexpectedly
Solution Approach 1:
The control unit continuously monitors transmission power and uses feedback to adjust the duty ratio when transmission power approaches or exceeds the limit value. This closed-loop feedback mechanism prevents transmission power from exceeding the limit while maintaining turn-on current control through drive frequency adjustment.
Solution Approach 2:
The system dynamically adjusts two parameters (drive frequency and duty ratio) based on real-time operating conditions. The drive frequency is adjusted for turn-on current control, while the duty ratio is dynamically modified in response to transmission power levels, creating a adaptive control system that handles varying coupling coefficients and power demands.
2Productivity
If the transmission power is controlled by adjusting the duty of inverter output voltage, then the transmission power follows the charging power command, but the transmission power may still exceed the limit value when drive frequency is adjusted
Solution Approach 1:
The control unit predicts potential transmission power overshoot by monitoring the relationship between drive frequency adjustments and transmission power changes. When transmission power approaches the limit value, the control unit preemptively adjusts the duty ratio to prevent exceeding the limit, rather than reacting after overshoot occurs.
Solution Approach 2:
The system changes two key parameters (drive frequency and duty ratio) to achieve dual control objectives. Drive frequency is changed for turn-on current control, while duty ratio is changed to maintain transmission power within limits. This multi-parameter adjustment strategy resolves the contradiction between power transmission efficiency and limit compliance.
3Reliability
If a limit value is placed on transmission power, then the transmission power is constrained, but the transmission power needs to be maintained at a value less than or equal to the limit value which reduces control flexibility
Solution Approach 1:
The control system dynamically adjusts the duty ratio based on real-time transmission power levels and coupling conditions. This dynamic adjustment maintains transmission power within limits while adapting to varying operating conditions, preserving control flexibility rather than using a fixed constraint.
Solution Approach 2:
The system uses parameter changes in the duty ratio to maintain both limit compliance and control flexibility. By adjusting the duty ratio in response to transmission power levels and coupling coefficient variations, the system achieves reliable limit compliance while maintaining adaptability to different operating conditions and power demands.
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 configuration effectively prevents transmission power from exceeding the limit value, ensuring reliable power control and minimizing the reduction in target power, thereby stabilizing the power transfer process.
Implementation Method 1
a power transmission unit configured to transmit electric power to a power reception device in a contactless manner
Data Source
AI summary
A control unit executes a first control and a second control. The first control is to control transmission power to target power by adjusting a duty of an output voltage of an inverter. The second control is to control a turn-on current by adjusting the drive frequency, the turn-on current indicating an output current of the inverter at a rising of the output voltage. When the transmission power exceeds a limit value larger than the target power during adjustment of the drive frequency by the second control, the control unit decreases the target power in the first control.