Power Converter Pulse-Width Modulation CM Voltage Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current power converters produce large common mode (CM) voltage components, leading to expensive and voluminous CM filters, which generate heat and increase costs due to the need for large inductance chokes.
Innovation Solution
A method for pulse-width modulation of power converters that selects between different modulation techniques based on a modulation index, such as SVPWM, DPWMMIN, and DPWMSYM, to reduce CM voltage, allowing for smaller and less expensive CM filters by adjusting null vector times and using techniques like DPWMMIN at lower modulation indices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If typical modulation methods (e.g., SVPWM) are used, then the power converter operates effectively, but a very large CM voltage is produced leading to expensive and voluminous filters
Solution Approach 1:
The patent applies dynamics by making the modulation technique selectable and adjustable based on operating conditions. The control system dynamically switches between different modulation techniques (SVPWM, DPWMMIN, DPWMMAX, DPWMSYM) depending on the modulation index and operational requirements, allowing optimization of CM voltage characteristics in real-time while maintaining effective power converter operation
Solution Approach 2:
The patent changes the modulation technique parameter based on the modulation index. By selecting different modulation techniques (SVPWM, DPWMMIN, DPWMMAX, DPWMSYM) according to the modulation index range, the system alters the CM voltage characteristics. Specifically, DPWMMIN and DPWMMAX techniques are used at lower modulation indices to reduce CM voltage amplitude, thereby reducing the required CM filter size while maintaining effective operation
2Reliability
If a CM filter with large inductance is used to filter large CM voltage, then filtering performance is improved, but the filter becomes bigger in volume, generates more heat and increases cost
Solution Approach 1:
The patent converts the harmful large CM voltage produced by typical modulation methods into a benefit by using this voltage characteristic information to select optimal modulation techniques. By utilizing DPWMMIN and DPWMMAX techniques at lower modulation indices, the system transforms what would be a harmful high CM voltage condition into an opportunity to actively reduce CM voltage, thereby improving filtering performance while reducing filter volume and heat generation
Solution Approach 2:
The patent changes the modulation technique parameter based on the modulation index to control CM voltage characteristics. By selecting DPWMMIN or DPWMMAX techniques when the modulation index is below a threshold value, the system reduces the CM voltage amplitude that needs to be filtered, thereby allowing for smaller inductance values in the CM filter while maintaining adequate filtering performance
3Reliability
If modulation techniques are selected based on modulation index, then CM voltage characteristics can be optimized, but control complexity increases
Solution Approach 1:
The patent segments the modulation index range into different regions and assigns specific modulation techniques to each region. By dividing the control strategy into discrete segments (e.g., modulation index below threshold uses DPWMMIN/DPWMMAX, above threshold uses SVPWM), the system optimizes CM voltage characteristics in each operating region while keeping the control logic structured and manageable through clear segmentation boundaries
Data Source
AI summary
A method for pulse-width modulation of a power converter (10) and a power converter (10) are presented. The method comprises determining (110) a modulation index, selecting (120), based on the modulation index, a modulation technique from a plurality of pre-deter-mined modulation techniques, and modulating (130) an output (16) of the power converter (10) by utilizing the selected modulation technique.