Power Converter Surge Mode for DC Link Voltage Relief
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Power converter arrangements connected to a power grid face challenges with voltage surges, such as those caused by lightning strikes, which lead to high voltage stress on electronic switches and increased conduction losses due to the need for higher voltage blocking capabilities.
Innovation Solution
The power converter arrangement operates in a surge mode when the DC link voltage reaches a certain threshold, by deactivating the second power converter and temporarily operating the first power converter in reverse mode to transfer energy from the DC link capacitor to the input, thereby reducing the DC link voltage and mitigating stress on the second power converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electronic switches are designed with higher voltage blocking capability to withstand surge voltages, then robustness against voltage surges is improved, but conduction losses increase
Solution Approach 1:
The first power converter is operated in reverse mode during surge conditions, transferring energy from the DC link capacitor back to the power grid input. This inversion of the normal power flow direction allows the system to actively reduce DC link voltage during surges rather than merely withstanding them, protecting the second power converter without requiring higher voltage blocking capability in its switches
Solution Approach 2:
The system dynamically changes the operating parameters of the first power converter based on DC link voltage conditions. When surge voltage is detected, the converter switches from normal forward conversion mode to reverse conversion mode, changing the direction of energy flow and the operating state of its electronic switches, thereby adapting to the surge condition without requiring permanently higher voltage ratings
2Object-affected harmful factors
If the DC link voltage is allowed to increase to surge levels, then the power converter can withstand lightning strikes, but voltage stress on electronic switches increases
Solution Approach 1:
The control system detects the onset of voltage surges and activates the reverse conversion mode of the first power converter before the DC link voltage reaches dangerous levels. This preliminary anti-action prevents the voltage from rising to harmful levels in the first place, rather than merely reacting after the surge occurs
Solution Approach 2:
The first power converter acting in reverse mode serves as an intermediary mechanism between the DC link capacitor and the power grid input. It actively manages the energy flow to prevent excessive voltage buildup on the DC link, thereby protecting the second power converter's electronic switches from voltage stress during surge conditions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively reduces the DC link voltage to a safe level, protecting the second power converter and minimizing conduction losses, while maintaining the stability of the power converter arrangement during voltage surges.
Implementation Method 1
operating the first power converter in a reverse mode to transfer energy from the DC link capacitor circuit to the input of the first power converter
Data Source
AI summary
A method for operating a power converter arrangement and a corresponding controller are disclosed. The method includes operating the power converter arrangement in a surge mode, when a DC link voltage of the power converter arrangement reaches a first voltage threshold. The power converter includes a first power converter having an input and an output; a second power converter having an input and an output; and a DC link capacitor circuit coupled to the output of the first power converter and the input of the second power converter and providing the DC link voltage. Operating the power converter arrangement in the surge mode includes: deactivating the second power converter; and operating, at least temporarily, the first power converter in a reverse mode to transfer energy from the DC link capacitor circuit to the input of the first power converter.