Inverter Harmonic Filter Zero-Cross Control
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Solution Overview
Problem
In contactless power supply systems, it is challenging to control the driving frequency of the inverter to maximize harmonic attenuation due to difficulties in directly measuring harmonic components of the current flowing through the power transmission coil, leading to incomplete harmonic reduction.
Innovation Solution
A power conversion device with an inverter, a harmonic filter comprising a first and second filter reactor, a filter capacitor, and a filter current detector, along with a controller that synchronizes the zero-cross points of the inverter output current and filter current to optimize the inverter driving frequency for maximum harmonic reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a harmonic filter is used to reduce harmonic current, then harmonic attenuation is improved, but the driving frequency cannot be optimized to maximize harmonic reduction due to measurement difficulties
Solution Approach 1:
The patent introduces an intermediary measurement approach by detecting the zero-cross point of the filter current through the second filter reactor, rather than directly measuring the harmonic components of the power transmission coil current. This intermediary measurement enables frequency optimization without requiring direct harmonic measurement capabilities
Solution Approach 2:
The patent replaces the need for complex harmonic measurement systems with a simpler zero-cross point detection mechanism. By using the zero-cross point coincidence method, the system substitutes sophisticated measurement equipment with a more feasible detection approach that can be implemented in practical contactless power supply systems
2Object-affected harmful factors
If the inverter driving frequency is controlled to maximize harmonic attenuation, then harmonic reduction effect is improved, but this requires direct measurement of harmonic components which is difficult to implement
Solution Approach 1:
The patent uses the zero-cross point of the filter current as an intermediary indicator to infer the optimal driving frequency. Instead of directly measuring and analyzing harmonic components, the system uses this intermediary signal to achieve frequency optimization, thereby reducing device complexity while maintaining effectiveness
Solution Approach 2:
The system achieves self-optimization by using the filter current's zero-cross point information to automatically adjust the inverter driving frequency. The measurement system serves itself by utilizing the existing filter current signal rather than requiring separate, complex harmonic measurement equipment
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 enhances the degree of harmonic reduction in the harmonic filter, enabling efficient harmonic-reduced power supply to the load.
Implementation Method 1
a filter interposed between an inverter and a power transmission coil for the purpose of reducing a harmonic current flowing through the power transmission coil
Implementation Method 2
a power-receiving coil being magnetically coupled with the coil supplied with the high-frequency power
Implementation Method 3
a rectifier for rectifying an output from the power-receiving coil
Data Source
AI summary
A power conversion device includes: an inverter for supplying high-frequency power to a coil; a harmonic filter connected to an output side of the inverter; and a controller for performing control to make a zero-cross point of an output current from the inverter coincide with a zero-cross point of a filter current of the harmonic filter. Through this, harmonic reduction effect can be fully exerted. Further, a contactless power supply system using the power conversion device can supply, to a load, power in which harmonics are significantly reduced, addressing a problem that inverter driving frequency cannot be controlled to a frequency at which harmonic reduction effect is maximized, and harmonic reduction effect cannot be fully exerted.