Multi-Level Power Converter Multiple Deadtime Control
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Solution Overview
Problem
Multi-level power converters in wind turbines face issues with voltage overshoots due to parasitic inductance, leading to device damage and increased losses, and require multiple deadtimes to manage switching speeds, causing harmonic distortion and increased costs.
Innovation Solution
Implementing multiple deadtimes for switching devices in a multi-level power converter, allowing inner devices to switch slower with longer deadtimes for safe operation and outer devices to switch faster to minimize distortion, thereby optimizing switching properties and reducing the need for filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single deadtime is used for all switching devices in a multi-level power converter, then the control is simplified, but the harmonic distortion increases and filtering requirements become more expensive
Solution Approach 1:
The patent divides the switching devices into multiple groups (inner and outer switching devices) and assigns different deadtime values to each group. This segmentation allows each group to be optimized independently, reducing overall harmonic distortion while maintaining manageable control complexity.
Solution Approach 2:
Different deadtime values are assigned to different locations in the circuit (inner vs. outer switching devices) based on their specific electrical characteristics and parasitic inductance levels. This local optimization reduces harmonic distortion generated by each switching event.
2Reliability
If inner switching devices switch slower to meet safe operating requirements, then device damage from voltage overshoots is prevented, but the switching losses increase and efficiency decreases
Solution Approach 1:
The switching devices are segmented into inner and outer groups with different switching speed requirements. Inner devices use longer deadtimes for slower switching to ensure safety, while outer devices use shorter deadtimes for faster switching to minimize losses.
Solution Approach 2:
The deadtime parameter is varied depending on the switching device location and operational requirements. By changing the deadtime parameter selectively, the system achieves both reliable operation and efficient energy conversion.
3Loss of energy
If outer switching devices maintain fast switching speeds, then switching losses are minimized and efficiency is improved, but the risk of device damage from voltage overshoots increases
Solution Approach 1:
Outer switching devices are separated from inner devices and assigned different deadtime values. This allows outer devices to switch faster with shorter deadtimes, minimizing losses while inner devices use longer deadtimes for protection.
Solution Approach 2:
The deadtime characteristic is tailored to the local requirements of each switching device group. Outer devices receive optimized deadtimes that balance fast switching with adequate protection, rather than applying a conservative uniform deadtime to all devices.
4Reliability
If longer deadtimes are used for inner switching devices, then voltage overshoots are reduced and device safety is ensured, but the harmonic distortion of the output signal increases
Solution Approach 1:
The patent segments the deadtime application by device group, applying longer deadtimes only to inner switching devices where safety is critical, while using shorter deadtimes for outer devices to minimize harmonic distortion.
Solution Approach 2:
Different deadtime durations are applied locally to different switching device groups based on their specific risk profiles. Inner devices receive longer deadtimes for protection, while outer devices receive shorter deadtimes to reduce distortion.
Data Source
AI summary
A method for operating a multi-level bridge power converter includes providing a plurality of switching devices of the power converter in one of a neutral point clamped topology or an active neutral point clamped topology. The method also includes providing a plurality of deadtimes for the switching devices. Further, the method includes selecting one of the deadtimes for each of the switching devices such that at least two of the switching devices operate according to different deadtimes. Moreover, the method includes operating the switching devices at the selected deadtimes to allow a first group of the switching devices to switch slower than a second group of the switching devices such that the first group of the switching devices satisfy safe operating requirements while the second group of the switching devices switch faster than the first group.