Converter Control Device Phase Correction for Harmonics
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Solution Overview
Problem
The existing converter devices face challenges in maintaining harmonics suppression and power factor enhancement across varying phases, particularly due to increased distortion at zero-cross points, making it difficult to satisfy harmonics specifications without using expensive high-accuracy phase detection circuits.
Innovation Solution
A control device with multiple power factor enhancement circuits, including inductors, switching elements, and diodes, that calculates phase based on zero-cross points and uses form factor correction to generate drive signals, allowing for phase correction without a high-accuracy phase detection circuit, thereby reducing harmonics and enhancing power factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a zero-cross point detection circuit or phase detection circuit with high accuracy is used, then harmonics can be reduced and power factor can be enhanced, but the cost increases significantly
Solution Approach 1:
The patent replaces expensive high-accuracy phase detection circuits with a simple zero-cross point detection circuit that uses inexpensive components. The control device calculates phase based on zero-cross points of input voltage and applies phase correction values derived from form factor calculations, achieving harmonics suppression without requiring costly specialized detection hardware.
Solution Approach 2:
The patent substitutes complex electrical phase detection circuits with a computational approach using a microprocessor. The microprocessor calculates phase from zero-cross points and determines phase correction values through form factor calculations, replacing hardware-based phase detection with software-based computational methods that are more cost-effective.
2Power
If phase is shifted beyond +0.5, then power factor enhancement is achieved, but harmonics specification cannot be satisfied due to increased distortion at zero-cross point
Solution Approach 1:
The patent implements a feedback mechanism where the form factor calculation unit continuously monitors the input current waveform and calculates the form factor. Based on this feedback, the phase correction value setting unit adjusts the phase correction value to maintain the form factor within a predetermined range, thereby simultaneously achieving power factor enhancement and harmonics suppression through closed-loop control.
Solution Approach 2:
The patent dynamically changes the phase correction parameter based on the calculated form factor. The phase correction value is adjusted according to the relationship between form factor and phase, allowing the system to optimize both power factor and harmonics performance by modifying the phase parameter in response to actual waveform conditions.
Data Source
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AI summary
The purpose of the present invention is to satisfy harmonics specifications and enhance a power factor without using an expensive phase detection circuit, or the like. A converter control unit (15) is provided with a phase correction unit (40) for calculating a phase correction value for correcting a phase calculated based on a zero-cross signal. The phase correction unit 40 sets a form factor leading to a power factor of a prescribed value or greater as a target form factor, retains information associating target form factors and input currents beforehand, acquires a target form factor corresponding to an input current value from the information, and sets a phase correction value for causing a form factor to approach the target form factor.