Power conversion apparatus, motor drive apparatus, blower, compressor, and air conditioner
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Solution Overview
Problem
Existing power conversion technologies that equalize reactor currents require individual current detection for each phase, leading to increased manufacturing costs.
Innovation Solution
A power conversion apparatus with a converter circuit comprising unit converters and a current detector that sums currents through reactors, along with a control device generating pulse width modulation signals based on detected values to equalize reactor currents without individual phase current detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If individual current detection is performed for each phase to equalize reactor currents, then current equalization precision is improved, but manufacturing cost increases due to requiring multiple current detectors
Solution Approach 1:
The patent combines multiple current detection functions into a single current detector by measuring the neutral point current, which represents the sum of phase currents. This allows derivation of individual phase currents through calculation rather than direct measurement, reducing the number of detectors needed while maintaining current equalization capability
Solution Approach 2:
The patent introduces the neutral point current as an intermediary measurement. By measuring this intermediate quantity (sum of currents) and using it to calculate individual phase currents, the system achieves accurate current detection without requiring separate detectors for each phase
2Measurement precision
If multiple current detectors are installed for individual phase detection, then current detection precision is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple current detection functions into a single detection system by utilizing the neutral point current measurement. This consolidation reduces the number of detection devices and simplifies the overall detection system architecture while preserving the ability to monitor and equalize individual phase currents
Solution Approach 2:
The single current detector at the neutral point serves multiple functions: it detects the sum of all phase currents, enables calculation of individual phase currents, and provides data for current equalization control. This multi-functional approach reduces system complexity compared to having separate detectors for each phase
Data Source
AI summary
A power conversion apparatus includes a converter circuit converting alternating current voltage output from an AC power supply into direct current voltage. The converter circuit includes unit converters. The power conversion apparatus generates a reference duty based on detection values of a current detector and a voltage detector, and generates a pulse width modulation signal based on a result of comparison between a carrier signal and a corrected duty obtained by correcting the reference duty. When a first reference duty in a first carrier period differs from a second reference duty in a second carrier period subsequent to the first carrier period, a first corrected duty of a first phase in a first carrier period in one power supply period after and a second corrected duty of a second phase in the first carrier period in one power supply period after are controlled to have different values.