DC-DC Converter Switching Control for Fault Current Isolation
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Solution Overview
Problem
In DC:DC power converters, faults in a DC network can lead to a high fault current being fed from the healthy side, potentially damaging the faulted network, and completely extinguishing this current can inhibit fault discrimination and isolation, causing the entire DC network to become isolated and non-operational.
Innovation Solution
The electrical power system includes a DC:DC power electronics converter with a DC:AC and AC:DC converter circuit, an AC link with a transformer, a DC power source, and a control system that monitors operating parameters to detect faults. The control system modifies the switching operation of transistors to supply a controlled amount of current from the DC power source to the DC electrical network, allowing for controlled fault current management and isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If all transistors are quickly switched off to extinguish fault current, then the fault current is prevented from becoming damagingly high, but the entire DC network becomes isolated and non-operational even if only a small part has a fault
Solution Approach 1:
The patent applies local quality by switching off transistors selectively based on their location relative to the fault. Transistors on the healthy side of the fault remain operational while only those on the faulted side are switched off. This allows the network to be divided into healthy and faulted zones, maintaining power supply to unaffected areas while isolating the fault locally.
Solution Approach 2:
The patent segments the DC network into healthy and faulted portions using the converter as a boundary. By controlling individual transistors on each side of the converter, the system creates distinct operational zones - allowing the healthy network segment to remain operational while the faulted segment is isolated, thus preventing total network shutdown.
2Reliability
If a zero or near-zero impedance is presented across the DC terminals facing the fault, then the fault current path is established, but the very low impedance results in a very large current that may damage the faulted DC network
Solution Approach 1:
The patent changes the impedance parameter dynamically by switching transistors on and off. During normal operation, the converter presents low impedance to allow efficient power transfer. Upon detecting a fault, the control system switches off transistors on the faulted side, thereby increasing the impedance to limit fault current magnitude while maintaining the protection function.
Solution Approach 2:
The patent implements dynamic impedance control by rapidly switching transistor states in response to fault conditions. The converter transitions from a low-impedance power transfer mode to a high-impedance fault limitation mode, with the impedance characteristic changing dynamically based on real-time fault detection and transistor switching actions.
3Reliability
If the switching operation is modified to supply a controlled amount of current during a fault, then fault discrimination and isolation are enabled, but the system complexity increases
Solution Approach 1:
The patent employs feedback by continuously monitoring operating parameters to detect faults and using this information to control transistor switching. The control system receives feedback about fault conditions and adjusts the switching operation accordingly, enabling automatic fault discrimination and isolation without requiring complex external control mechanisms.
Solution Approach 2:
The converter performs self-service by using its own transistor switching capability to accomplish fault isolation. Rather than requiring separate isolation devices or complex external control systems, the converter utilizes its inherent switching elements to discriminate and isolate faults, thereby limiting the increase in overall system complexity.
Data Source
Figure 1A
Figure 1B~1C
Figure 2
AI summary
There is provided an electrical power system 10, 20, 30, comprising: a DC:DC power electronics converter 100, 100a, 100b comprising: a DC:AC converter circuit 110 having a DC side and an AC side; an AC:DC converter circuit 120 having a DC side and an AC side; and an AC link 130 connecting the AC side of the DC:AC circuit and the AC side of the AC:DC converter circuit, the AC link including a transformer 135 having a first winding 135-i connected to the AC side of the DC:AC converter circuit and a second winding 135-ii connected to the AC side of the AC:DC converter; a DC power source connected to the DC side of the DC:AC converter circuit 110; a DC electrical network connected to the DC side of the AC:DC converter circuit 120; and a control system 150 configured to: control a switching operation of a first plurality of transistors 111-L, 111-H, 112-L, 112-H of the DC:AC converter circuit 110 and a second plurality of transistors 121-L, 121-H, 122-L, 122-H of the AC:DC converter circuit 120 monitor one or more operating parameters of the electrical power system and determine, based on the one or more parameters, whether there is a fault in the DC electrical network; and in response to determining there is a fault in the DC electrical network, modify a switching operation of the first plurality of transistors and/or the second plurality of transistors to supply a controlled amount of fault current from the DC power source to the DC electrical network via the DC:DC power electronics converter.