Hybrid DC Circuit Breaker Control for Sequential Fault Interruption
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Solution Overview
Problem
Hybrid DC circuit breakers face challenges in achieving fast and efficient fault isolation due to the limitations of mechanical switch operation time and high conduction losses from solid-state switches, leading to sustained arcing and rapid fault current rise in DC systems.
Innovation Solution
A progressive switching method for hybrid DC circuit breakers, where semiconductor switching stages are sequentially turned off based on dielectric strength across ultrafast mechanical switch contacts, dynamically controlling voltage potential and curtail fault current during mechanical switch opening, reducing fault isolation time and peak fault current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical switch contacts are opened to interrupt DC current, then circuit protection is achieved, but sustained arcing occurs due to lack of natural current zero crossing
Solution Approach 1:
Semiconductor switching stages are activated before the mechanical switch contacts fully open to preemptively establish alternative current paths and suppress arc formation, preventing sustained arcing before it can develop
2Speed
If semiconductor switching stages are used to interrupt current, then fast switching is achieved, but real power consumption increases
Solution Approach 1:
The semiconductor switching function is divided into multiple stages that operate sequentially, with each stage handling a portion of the current interruption task, allowing faster overall switching while distributing and reducing total power consumption across stages
Solution Approach 2:
Not all semiconductor switching stages need to operate at full capacity simultaneously; by using partial action where only necessary stages are fully activated, real power consumption is reduced while maintaining the required fast switching performance
3Reliability
If all semiconductor switching stages are turned off simultaneously, then current interruption is achieved, but voltage surge exceeds surge arrestor blocking voltage ratings
Solution Approach 1:
Semiconductor switching stages are turned off in a predetermined sequence before the mechanical contacts open, progressively building dielectric strength and limiting voltage surge to remain within surge arrestor blocking voltage ratings
Solution Approach 2:
The switching stages are dynamically controlled with different turn-off timings based on their position in the series connection, creating a progressive voltage distribution that adapts to the mechanical switch opening process and prevents excessive voltage spikes
4Reliability
If mechanical switch opening time is extended to establish dielectric strength, then arc extinction is facilitated, but fault isolation time increases
Solution Approach 1:
Semiconductor switching stages begin turning off before the mechanical switch contacts have fully opened, preemptively establishing dielectric strength through the semiconductor devices while the mechanical switch is still closing, thereby reducing the required mechanical opening time and overall fault isolation time
Solution Approach 2:
The semiconductor switching stages act as intermediary devices that assist the mechanical switch in establishing dielectric strength, providing a transition path that facilitates arc extinction without requiring the mechanical switch to remain closed for an extended 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
This approach reduces fault isolation time, limits peak fault current, and enhances system stability by allowing earlier current interruption and minimizing energy absorption by surge arrestors, thereby protecting connected electronics and prolonging the lifespan of protective devices.
Implementation Method 1
a dielectric strength is established across the contacts of the UFMS as the contacts open
Implementation Method 2
turning off the individual switching stages redirects current through corresponding surge arrestors connected across the individual switching stages
Data Source
AI summary
Various examples are provided related to direct current circuit breakers and their control methods. In one example, among others, a hybrid direct current circuit breaker (DCCB) includes an ultrafast mechanical switch (UFMS) connected in series with a commutating switch (CS) or auxiliary circuit breaker (ACB); a main breaker (MB) including a series of η semiconductor switching stages in parallel with the UFMS and CS or ACB; and control circuitry that can turn off individual switching stages in a defined order in response to opening contacts of the UFMS. The switching stages can be turned off based upon a dielectric strength across the contacts as they open. In another example, a method includes opening contacts of an UFMS connected in series with a CS or ACB; and turning off individual switching stages of a series of η semiconductor switching stages connected across the UFMS and the CS or ACB.