Power Conversion Device Bus Current Detection Timing
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Solution Overview
Problem
Existing motor control devices face challenges in accurately correcting motor currents due to fluctuations in motor constants caused by temperature and magnetic saturation, making it difficult to mount these devices in low-priced microcomputers and maintain accurate current detection.
Innovation Solution
A power conversion device that detects the bus current at a timing when voltage vectors coincide, reducing current fluctuations and allowing for accurate detection of motor currents without the need for complex calculations, thereby facilitating implementation in low-priced microcomputers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a detected current correction unit calculates correction values using complex formulas including inverter power supply voltage, duty command values, motor counter electromotive voltage information, and motor electrical characteristics, then motor current detection accuracy is improved, but device complexity increases making it difficult to mount in low-priced microcomputers
Solution Approach 1:
The patent extracts only the essential elements needed for current detection (bus current and voltage vector coincidence timing) from the complex correction formula approach, eliminating unnecessary calculation components while retaining detection accuracy
Solution Approach 2:
Instead of calculating correction values to adjust detected currents, the patent inverts the approach by detecting bus current at specifically timed moments when voltage vectors coincide, naturally capturing accurate phase currents without requiring complex correction mathematics
2Measurement precision
If correction calculations account for motor constant fluctuations due to temperature and magnetic saturation, then current detection accuracy is maintained, but further operations are necessary increasing device complexity
Solution Approach 1:
The patent performs preliminary action by detecting bus current at pre-determined timing when voltage vectors coincide, which inherently captures accurate current values even under varying motor conditions, eliminating the need for subsequent correction operations
Solution Approach 2:
The detection method serves itself by using the natural coincidence of voltage vectors to provide accurate current detection without requiring external correction mechanisms or additional calculations for temperature and saturation compensation
3Ease of operation
If bus current is detected at arbitrary timing, then detection flexibility is improved, but current fluctuations increase reducing detection accuracy
Solution Approach 1:
The patent changes the critical parameter of detection timing to specifically coincide with voltage vector coincidence moments, transforming the detection process from a flexible but inaccurate approach to a precise method that naturally minimizes current fluctuations
Data Source
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AI summary
A power conversion device includes an alternating current rotating machine having a multiple of multi-phase windings, a multiple of power conversion means that convert direct current voltage of a direct current power supply based on a multiple of switching signals and apply voltage to the multiple of multi-phase windings, first current detection means that detects a first bus current, which is current flowing between the power conversion means that applies voltage to one multi-phase windings of the multiple of multi-phase windings and the direct current power supply, and first phase current calculation means that calculates the current flowing through the one multi-phase windings based on the first bus current, wherein the first current detection means detects the first bus current at a timing at which a multiple of voltage vectors based on the multiple of switching signals neighbor or coincide.