Semiconductor Protection Elements for Voltage Source Converter Short Circuits
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Solution Overview
Problem
Existing voltage source converters suffer from high fault currents during short circuits, which can damage power semiconductors and freewheeling diodes, and current solutions are costly and inefficient due to derating of components.
Innovation Solution
Incorporating semiconductor protection means, such as additional freewheeling diodes or thyristors in parallel with existing components, and inductances to limit current flow and detect short circuits, allowing the protection elements to handle fault currents and relieve the load on integrated diodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If freewheeling diodes are derated to withstand short-circuit currents, then reliability of power semiconductors is improved, but manufacturing cost increases and ease of manufacture deteriorates
Solution Approach 1:
The patent divides the fault current handling function between two separate components: the integrated freewheeling diode (which handles normal operation currents) and the separately provided protection diode (which handles short-circuit currents). This segmentation allows each component to be optimized for its specific function, with the protection diode being specifically derated for short-circuit conditions without affecting the integration of the main power semiconductor module.
Solution Approach 2:
The protection diode acts as an intermediary component that specifically handles the harmful short-circuit current, protecting the main power semiconductor and its integrated freewheeling diode from damage. This intermediary element absorbs the stress of fault conditions, allowing the main component to operate within its normal ratings.
2Reliability
If additional protection elements are added to handle fault currents, then reliability of power semiconductors is improved, but device complexity increases
Solution Approach 1:
The patent combines the protection diode with the power semiconductor module in a single integrated component package. The protection diode is provided in close association with the power semiconductor, allowing both components to share common packaging, mounting, and electrical connections. This merging reduces the overall system complexity compared to using completely separate protection components.
3Reliability
If inductances are used to limit fault currents, then reliability of power semiconductors is improved, but productivity decreases due to longer fault clearance time
Solution Approach 1:
The protection diode is pre-positioned in parallel with the integrated freewheeling diode before any fault occurs. When a short-circuit condition develops, the protection diode immediately begins handling the fault current without requiring any switching action or detection delay. This preliminary positioning allows instantaneous current redistribution, protecting the power semiconductor during the critical initial fault period.
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
The solution effectively manages high short-circuit currents, reducing the risk of component damage and operational costs by distributing the fault current through additional protection elements and inductances, enhancing the reliability and efficiency of the converter.
Implementation Method 1
The fault current that occurs in the case of the short circuit is driven by the power supply system voltage and is usually interrupted by the opening of a circuit-breaker that isolates the AC voltage from the converter
Implementation Method 2
the protection element accepts a significant proportion of the fault current in the event of a fault and thus relieves the load on the integrated freewheeling diode
Data Source
AI summary
A device for converting an electric current includes at least one phase module having an AC terminal and at least one DC terminal. Phase module branches, each of which is equipped with serially connected submodules, are respectively provided between each DC terminal and each AC terminal. Each submodule is provided with at least one power semiconductor. Semiconductor protecting means are connected in parallel or in series to at least one of the power semiconductors to enable the device to withstand even high short-circuit currents for a sufficient period of time. A method for protecting the power semiconductors of the device, is also provided.