Bidirectional DC Circuit Breaker Bridge Topology
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Solution Overview
Problem
Conventional high-voltage DC circuit breakers are inefficient in quickly isolating fault currents in multi-end DC power transmission systems, leading to high costs and complexity due to the need for directional power semiconductor devices, which results in suboptimal utilization and increased maintenance difficulties.
Innovation Solution
An apparatus comprising a current breaking branch with solid-state DC circuit breakers and non-linear resistances, along with bidirectional power semiconductor switches and high-speed isolation switches, allows for efficient current breaking in both directions by commutating currents through a bridge branch structure, reducing conduction losses and breaking times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional high-voltage DC circuit breaker structure is used with power semiconductor devices connected in anti-series or anti-parallel for bidirectional current breaking, then the circuit breaker can break currents in two directions, but the number of power semiconductor devices is doubled and costs greatly increase
Solution Approach 1:
The circuit breaker is divided into two independent single-direction breaking units: a first circuit breaker for breaking current in the first direction and a second circuit breaker for breaking current in the second direction. Each unit contains power semiconductor devices connected only in the same direction, avoiding the need for anti-series or anti-parallel configurations. This segmentation allows each breaker to operate independently for its designated direction, reducing overall device complexity while maintaining bidirectional breaking capability.
Solution Approach 2:
The first and second circuit breakers are combined in parallel connection to form a unified bidirectional circuit breaker system. The first circuit breaker handles current breaking in the first direction, while the second circuit breaker handles current breaking in the second direction. This merging approach allows both breakers to work together as an integrated system, achieving bidirectional current breaking without requiring each individual breaker to handle both directions, thus reducing the total number of power semiconductor devices needed.
2Adaptability or versatility
If power semiconductor devices are arranged in anti-parallel manner for bidirectional current breaking, then current can be broken in both directions, but over-voltage generated when current is turned off in one direction causes damage to devices in the other direction
Solution Approach 1:
The circuit breaker system is segmented into two independent units with dedicated current direction handling. The first circuit breaker is responsible exclusively for breaking current in the first direction, and the second circuit breaker is responsible exclusively for breaking current in the second direction. This segmentation ensures that over-voltage generated during current interruption in one direction does not affect the power semiconductor devices in the other direction, as each breaker operates independently with its own protective measures.
Solution Approach 2:
Control switches serve as intermediaries that selectively connect or disconnect the first and second circuit breakers based on current direction. When current flows in the first direction, the control switch connects the first circuit breaker while disconnecting the second circuit breaker, and vice versa. This intermediary control mechanism ensures that only the appropriate breaker is active during current interruption, preventing over-voltage from affecting inactive devices and enhancing system reliability.
3Reliability
If conventional circuit breaker structure with LC oscillation loop is used, then DC current can be cancelled completely with zero-crossing point, but arc-extinguishing time is long (tens of milliseconds) and cannot meet quick fault isolation requirement
Solution Approach 1:
The invention replaces the mechanical arc-extinguishing process with solid-state power semiconductor devices that can interrupt current electronically. Instead of relying on LC oscillation and natural zero-crossing points that take tens of milliseconds, the power semiconductor devices can turn off current within microseconds. This substitution of mechanical/physical arc extinction with electronic switching dramatically reduces the breaking time while maintaining complete current cancellation, meeting the quick fault isolation requirements of modern power systems.
4Speed
If high-speed mechanical switch is connected in parallel to primary circuit breaker for quick fault isolation, then breaking speed is improved, but the switch cannot completely isolate the apparatus and protection of primary circuit breaker is insufficient
Solution Approach 1:
The circuit breaker system is segmented into two independent circuit breakers (first and second breakers) that can operate independently. Each breaker is equipped with its own control switch and power semiconductor devices, allowing one breaker to handle fault isolation while the other remains protected and available for backup. This segmentation ensures that when one breaker is operating at high speed to isolate a fault, the other breaker provides complete isolation capability and protection, eliminating the insufficiency of single-breaker designs.
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 achieves low conduction losses, rapid breaking times (3-5 ms), and reduced costs by optimizing power semiconductor device utilization, while ensuring safe and reliable isolation and maintenance, thus addressing the inefficiencies of existing technologies.
Implementation Method 1
the current is switched to the primary circuit breaker, and is finally absorbed by the power-consuming element, thereby breaking the current
Implementation Method 2
bidirectional power semiconductor switches and high-speed isolation switches, allows for efficient current breaking in both directions by commutating currents through a bridge branch structure
Data Source
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AI summary
An apparatus for limiting a current of a circuit or breaking a current, and a control method thereof are disclosed. The apparatus includes a current breaking branch (29) and a bridge branch. The bridge branch includes two bridge arms formed by four identical current commutation branches. Every two of the four current commutation branches are connected in series, and the formed two bridge arms are then connected in parallel. The two bridge arms are both connected in parallel to the current breaking branch, and middle points of the two bridge arms are separately connected to two ends of a circuit. Each current commutation branch includes at least one high-speed isolation switch (6) and at least one bidirectional power semiconductor switch (10) that are connected in series. The apparatus can turn off currents in two directions.