Power Conversion Device Modulation Switching for Ripple and Noise Control
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Solution Overview
Problem
Existing power conversion devices face issues with noise and vibration due to noise being mixed into current detection values, particularly when the medium and minimum phase voltage commands are close, affecting the accuracy of current detection and introducing ripple current in capacitors.
Innovation Solution
A power conversion device with a control unit that calculates and adjusts three-phase voltage commands to minimize noise by switching between different calculation processes based on differential values between voltage commands, ensuring that the voltage applied to minimum phase commands meets specific reference thresholds, thereby avoiding switching during current detection periods and reducing ripple current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If first two-phase modulation is carried out to reduce ripple current in capacitor, then ripple current is suppressed, but noise is mixed into current detection values when medium and minimum phase voltage commands are close
Solution Approach 1:
The patent dynamically switches between first two-phase modulation and second two-phase modulation based on the differential value between medium and minimum phase voltage commands. When the differential value exceeds a threshold, first two-phase modulation is used to suppress ripple current; when it falls below the threshold, second two-phase modulation is used to ensure accurate current detection, thus adaptively optimizing performance based on operating conditions
Solution Approach 2:
The patent changes the modulation parameter (phase difference between carrier waves) based on the voltage command differential value. By adjusting the differential value threshold and switching between different modulation strategies, the system optimizes the balance between ripple current suppression and current detection accuracy under varying operating conditions
2Loss of energy
If phase difference in PWM command signal is set to 180° for ripple current suppression, then capacitor ripple current is reduced, but switching occurs during current detection periods causing noise
Solution Approach 1:
The control unit calculates the differential value between medium and minimum phase voltage commands in advance and uses this information to determine the appropriate modulation strategy before current detection occurs, preventing noise contamination of detection values
Solution Approach 2:
The system continuously monitors the differential value between phase voltage commands and adjusts the modulation strategy accordingly, creating a feedback mechanism that maintains optimal performance by switching between ripple suppression and detection accuracy modes based on real-time operating conditions
Data Source
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AI summary
When a first medium phase voltage command and a first minimum phase voltage command are close to each other in a first three-phase voltage command, then a first three-phase application voltage is calculated from the first three-phase voltage command by switching from a first calculation process, which corresponds to first two-phase modulation, to a second calculation process, and when a second medium phase voltage command and a second minimum phase voltage command are close to each other in a second three-phase voltage command, a second three-phase application voltage is calculated from the second three-phase voltage command by switching from a third calculation process, which corresponds to first two-phase modulation, to fourth calculation process.