DC Link Shutdown Circuit for Multi-Inverter Short-Circuit Protection
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Solution Overview
Problem
Existing DC networks with multiple inverters and rectifiers face challenges in efficiently and economically protecting against short circuits, particularly in high-voltage frequency converters, where electrolytic capacitors can burst due to overvoltage, leading to potential explosions, and existing protective circuits are complex and costly to implement.
Innovation Solution
A circuit arrangement with multiple protective circuits, each with a switch-off device that includes a first switching device on the rectifier side and a second switching device on the inverter side, allowing for immediate interruption of current flow in all intermediate circuits upon detection of a fault, eliminating the need for additional fuses or circuit breakers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protective circuits are provided for each intermediate circuit in a DC link, then reliability of protection against short circuits is improved, but device complexity increases due to requiring fuses or fast-switching elements for each intermediate circuit
Solution Approach 1:
The patent combines multiple protective functions into a single shutdown device with switching elements that can interrupt current flow to multiple intermediate circuits simultaneously. Instead of providing separate fuses or protective devices for each intermediate circuit, one shutdown device with plurality of switching elements serves all intermediate circuits, reducing overall device complexity while maintaining comprehensive protection.
Solution Approach 2:
The shutdown device is designed as a universal protective unit that can protect multiple intermediate circuits through its plurality of switching elements. This multi-functional device replaces the need for dedicated protective devices for each intermediate circuit, achieving both reliability and simplicity by making one device serve multiple protective functions.
2Ease of manufacture
If electrolytic capacitors are used as intermediate circuit capacitors, then ease of manufacture is improved, but harmful factors increase due to risk of explosive bursting from overvoltage
Solution Approach 1:
The protective circuit with switching elements is activated before the overvoltage condition can cause capacitor bursting. When a short circuit or fault is detected in any intermediate circuit, the switching elements immediately interrupt the current flow, preventing the voltage from rising to dangerous levels that would cause electrolytic capacitor bursting. This preliminary protective action eliminates the harmful effect before it can manifest.
Solution Approach 2:
The shutdown device provides beforehand cushioning by having switching elements ready to interrupt current flow immediately upon fault detection. This prior protective measure cushions against the potential harmful effect of overvoltage by preventing the voltage surge from reaching levels that would damage the electrolytic capacitors, thus protecting them before damage can occur.
3Speed
If fuses or fast-switching elements are provided for each intermediate circuit, then protection speed is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges the protective functions of multiple fuses or fast-switching elements into a single shutdown device with plurality of switching elements. This consolidated approach maintains fast protection speed by using electronically controllable switching elements that can interrupt current flow rapidly, while simultaneously reducing device complexity by eliminating the need for separate protective devices for each intermediate circuit.
Data Source
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AI summary
The invention relates to a circuit arrangement for a DC system with several inverters (3, 47) and one or more rectifiers (2), wherein each inverter (3, 47) is assigned an intermediate circuit (4, 48), with a plurality of protection circuits (13), wherein a protection circuit (13) is provided for each intermediate circuit (4, 48), and with a disconnect device (36) configured to interrupt a current flow into the intermediate circuits (4, 48), wherein the disconnect device (36) has a first switching device (37) on the rectifier side and a second switching device (41) on the inverter side, wherein the second switching device (41) is configured to actuate the first switching device (37), and wherein the first switching device (37) is configured to interrupt a current flow into the intermediate circuits (4, 48).