Converter Sub-Module Bypass Switch for Overvoltage Protection
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Solution Overview
Problem
Conventional electric power converters face challenges in quickly and effectively bypassing a failing sub-module, leading to potential overvoltage and overcurrent issues, which can cause component failure and reduce system reliability, especially when using slow-operating bypass switches.
Innovation Solution
The electric power converter employs a bidirectional bypass switch unit with a semiconductor switch and a mechanical switch in parallel, allowing current to bypass a failing sub-module through a combination of a diode and a first switch element, reducing overall bypass operation time by using a fast semiconductor element and a relatively slow mechanical switch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional bypass switch is used to short a failing sub-module, then the system can continue operating, but the bypass operation time is too long causing overvoltage and overcurrent that may lead to component failure
Solution Approach 1:
The bypass switch is segmented into two independent switch elements (first and second switch elements) that operate at different speeds. The first switch element provides fast initial bypass action, while the second provides sustained bypass capability, thereby reducing overall bypass operation time and preventing overvoltage/overcurrent damage.
Solution Approach 2:
The bypass switch transitions from a static single-switch design to a dynamic multi-element design where switch elements are activated in sequence. The control unit dynamically manages the switching timing, first activating the first switch element for rapid response, then activating the second switch element to maintain the bypass state, optimizing both speed and reliability.
2Loss of time
If a fast-operating bypass switch is used to reduce bypass operation time, then overvoltage and overcurrent are prevented, but the cost of the bypass switch increases significantly
Solution Approach 1:
The bypass function is divided between two switch elements with different performance characteristics and cost levels. The first switch element provides fast operation at moderate cost, while the second switch element provides sustained operation at lower cost, achieving overall fast bypass performance without the prohibitive cost of a completely fast switch.
Solution Approach 2:
The system changes the operational parameters of the bypass switch by using two switch elements with different operating speeds and cost characteristics. The control unit adjusts the timing and sequence of switch activation to achieve fast overall bypass operation while utilizing lower-cost switch elements, thereby reducing total system cost.
3Device complexity
If a single bypass switch is used in the conventional configuration, then the circuit is simple, but the bypass operation is ineffective and cannot quickly short the failing sub-module
Solution Approach 1:
The bypass circuit is segmented into two switch elements connected in parallel, each serving a specific functional purpose. This segmentation enables the circuit to perform both fast initial bypass and sustained bypass operations, significantly improving bypass effectiveness while maintaining reasonable circuit complexity through systematic design.
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 configuration enables stable operation by quickly bypassing current through the sub-module, reducing the risk of overvoltage and overcurrent, and lowering costs while maintaining effective bypass functionality even with slower bypass switches.
Implementation Method 1
the current flows through the diode (132) and the first switch element (131) when the sub-module (10) fails
Data Source
AI summary
The present invention relates to a converter for electric power having multiple sub-modules connected in series, the sub-modules having an energy storage unit and multiple power semiconductor circuits connected in parallel to the energy storage unit, and which causes an electric current to bypass a sub-module in case the breakdown of the sub-module occurs. To this end, the converter for electric power according to the present invention has multiple sub-modules connected to each other in series, the sub-modules having an energy storage unit and at least one power semiconductor circuit that is connected in parallel to the energy storage unit and comprises multiple power semiconductor switches and freewheeling diodes, wherein each of the sub-modules comprises a bypass switching unit, which is connected in parallel to any one of said at least one power semiconductor circuit, and bypasses an electric current via the bypass switching unit.