DC Solid-State Circuit Breaker With DC-Link Pre-Charging
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Solution Overview
Problem
Existing solid-state circuit breakers (SSCBs) face inefficiencies due to high power losses and slow fault current clearance in direct current (DC) systems, particularly in low-voltage and medium-voltage grids, which can lead to catastrophic failures and increased system costs.
Innovation Solution
A DC solid-state circuit breaker (SSCB) design incorporating a power module with controlled semiconductors, a DC-Link capacitor, and a pre-charging system to minimize current flow during normal operation and rapidly interrupt fault currents by charging the DC-Link before operation, using a controlled semiconductor to open the connection between terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional mechanical circuit breakers are used in DC systems, then the structure is simple and cost is low, but the fault clearance speed is slow leading to catastrophic failures
Solution Approach 1:
The patent replaces the mechanical switching system with a solid-state power semiconductor module that can open and close connections electronically. This substitution enables rapid fault clearance (microsecond to millisecond range) compared to mechanical breakers, while the modular semiconductor design keeps the overall system complexity manageable through standardized components.
Solution Approach 2:
The circuit breaker employs dynamic control of the power semiconductor module through a control unit that responds to fault detection. The system transitions from static mechanical contact closure to dynamic electronic switching, allowing adaptive response to different fault conditions and enabling rapid interruption of fault currents.
2Productivity
If solid-state circuit breakers with high power transistors are used to handle high currents, then the fault clearance speed increases, but the power losses and thermal design complexity increase
Solution Approach 1:
The patent incorporates a pre-charging system with a pre-charging transistor and capacitor that charges the DC-Link capacitor before the main power transistor operates. This preliminary action reduces the voltage stress and power losses during the main switching operation, as the pre-charged capacitor can immediately supply or absorb current without requiring the main transistor to handle the full power surge.
Solution Approach 2:
The DC-Link capacitor acts as an intermediary energy storage element between the DC source and the load. It mediates the power transfer by being charged through the pre-charging system and then discharging through the main power transistor during operation, reducing the instantaneous power handling requirements and losses of the main transistor.
3Loss of energy
If the DC-Link capacitor is charged before operation through a pre-charging system, then the power losses are reduced, but the device complexity increases
Solution Approach 1:
The patent segments the power transistor operation into two distinct phases: a pre-charging phase handled by a dedicated pre-charging transistor and capacitor, and a main operation phase handled by the main power transistor. This segmentation allows each component to be optimized for its specific function, reducing overall power losses while distributing the complexity across modular, manageable subsystems.
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 proposed SSCB effectively reduces fault current by minimizing power losses and quickly interrupting fault currents, enhancing system efficiency and preventing damage to DC sources and loads.
Implementation Method 1
at least a semiconductor configured to restrict the current flow to a specific direction
Implementation Method 2
The DC-Link comprises one capacitor or more capacitors connected to one another in series and/or parallel
Data Source
AI summary
A DC solid state circuit breaker (SSCB) and DC circuit breaker system, the SSCB having a power module (40) with a first controlled power semiconductor (41), a DC-Link (50), a semiconductor (61) and a pre-charging system (70) with an impedance (71). The power module (40) connected between a first power terminal (31) and a second power terminal (32); the DC-Link (50) connected between the first power terminal (31) and an intermediate node (34); the semiconductor (61) connected between the intermediate node (34) and the second power terminal (32); the pre-charging system (70) connected between the intermediate node (34) and a third power terminal (33). During normal operation current can flow freely between the first (31) and second (32) power terminals without producing any additional losses due to the pre-charging system (70). No varistors or similar devices are required. Several SSCBs (30) may be combined for additional features.