Power Converter Offset Voltage Control for Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power converters using three-phase modulation suffer from voltage saturation issues, leading to increased distortion, noise, and vibration, particularly due to constant switching to two-phase modulation based on amplitude or modulation factor, which results in discontinuous voltage changes and inefficient noise reduction.
Innovation Solution
A power converter that computes a first offset voltage by subtracting a DC voltage multiplied by a constant from the maximum phase of three-phase voltage commands and sets it to zero when negative, and uses this offset to correct the voltage commands, ensuring the inverter outputs reduced distortion and noise by maintaining the maximum phase within detectable limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two-phase modulation is constantly switched based on amplitude or modulation factor, then voltage saturation is prevented, but distortion factors of output voltages increase and noise and vibration increase
Solution Approach 1:
The patent changes the parameter for modulation switching from amplitude-based to phase-angle-based. By calculating the phase angle of the voltage vector and comparing it with predetermined thresholds, the system determines when to switch between three-phase and two-phase modulation. This parameter change allows for more precise control of the switching timing, preventing constant unnecessary switching while maintaining voltage saturation prevention.
Solution Approach 2:
The patent implements dynamic switching between three-phase and two-phase modulation based on real-time phase angle calculations. The system continuously monitors the phase angle of the voltage vector and dynamically adjusts the modulation type accordingly, rather than using fixed amplitude-based switching. This dynamic approach optimizes the balance between preventing voltage saturation and minimizing distortion and noise.
2Reliability
If modulation system is switched based on amplitude, then voltage saturation is avoided, but discontinuous voltage change occurs causing increased noise and vibration
Solution Approach 1:
The patent changes the switching criterion from amplitude-based to phase-angle-based parameters. By using the phase angle of the voltage vector as the switching parameter, the system achieves smoother transitions between modulation types. The phase angle provides a continuous parameter that varies smoothly with operating conditions, avoiding the discontinuous voltage changes that occur with amplitude-based switching.
3Power
If three-phase modulation is used, then output voltage amplitude is maintained, but voltage saturation occurs leading to increased distortion and noise
Solution Approach 1:
The patent implements dynamic switching between three-phase and two-phase modulation based on real-time phase angle calculations. The system continuously monitors the phase angle of the voltage vector and dynamically adjusts the modulation type accordingly, rather than using fixed amplitude-based switching. This dynamic approach optimizes the balance between maintaining output voltage amplitude and preventing voltage saturation.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Provided is a power converter, which is configured to convert a DC voltage into three-phase voltages based on three-phase voltage commands each being a sine wave to output the three-phase voltages, the power converter comprising: a third offset voltage computing section, which is configured to determine the three-phase voltage commands are determined as a maximum phase, an intermediate phase, and a minimum phase in descending order, to calculate fourth DC voltage by multiplying the DC voltage by a fourth constant to the minimum phase, to compute a third offset voltage by adding the fourth DC voltage to the minimum phase, to determine a sign of the third offset voltage and to set the third offset voltage to zero when a sign of the third offset voltage is positive; a corrected three-phase voltage command computing section, which is configured to output corrected three-phase voltage commands obtained by subtracting the third offset voltage from each phase of the three-phase voltage commands; and an inverter, which is configured to output the three-phase voltages based on the corrected three-phase voltage commands, wherein the inverter includes a current detector, which is configured to detect currents flowing through phases of the inverter based on a voltage drop in current detection resistive elements connected in series to upper arm switching elements, and wherein the third offset voltage computing section is configured to set the fourth constant so that energization time of the upper arm switching elements becomes equal to a lower limit value that enables detection of the currents in the current detection resistive elements.