T-Type DC Circuit Breaker Using Half-Controlled Components
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Solution Overview
Problem
Current DC circuit breakers face challenges in achieving rapid and cost-effective DC interruption due to limitations in mechanical, hybrid, and solid-state designs, including high conduction losses and high costs associated with the use of fully-controlled power electronic components.
Innovation Solution
A T-type DC circuit breaker combines fully-controlled and half-controlled power electronic components, utilizing a main branch, commutation switches, and a bypass branch with a bypass capacitor and diode to generate a reverse voltage for forced turn-off, allowing for controlled and rapid DC interruption while minimizing losses and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If mechanical switches are used to interrupt DC, then the device structure is simple, but the interruption speed is slow and arc extinction is difficult
Solution Approach 1:
The patent replaces the mechanical switch interruption mechanism with a power electronic component (IGBT)-based commutation circuit. The IGBT Q1 is turned off to initiate current transfer, and the capacitor C1 discharges through the commutation inductor L1 and anti-parallel diode D1 to generate a commutation current that forces the main switch S1 to turn off, achieving rapid non-mechanical interruption.
Solution Approach 2:
The patent introduces a commutation circuit consisting of capacitor C1, inductor L1, and diode D1 as an intermediary mechanism. This commutation circuit generates the necessary commutation current to force the main switch S1 to turn off, acting as a mediator between the control signal and the main switch interruption.
2Extent of automation
If fully-controlled power electronic components are used to interrupt DC, then the interruption process is fully controllable, but the cost is high
Solution Approach 1:
The patent applies different control qualities to different parts of the circuit. The commutation switch Q1 uses a fully-controlled IGBT for precise control of the commutation process, while the main switch S1 uses a half-controlled IGCT that can be turned on by gate signal but turns off naturally when current reverses, reducing cost while maintaining overall controllability.
Solution Approach 2:
The patent applies full control only where necessary (the commutation switch Q1) and accepts partial control (the main switch S1) where the natural current zero-crossing can be utilized. This partial control approach reduces the number of fully-controlled components needed while still achieving complete interruption control.
3Speed
If fully-controlled power electronic components are used to transmit and interrupt DC, then the interruption is rapid and controllable, but the conduction loss is high
Solution Approach 1:
The patent pre-charges capacitor C1 to the DC link voltage before interruption is needed. When interruption is required, the already-charged capacitor can immediately discharge through the commutation circuit, enabling rapid current transfer and switch turn-off without waiting for energy accumulation, thus achieving fast interruption with minimal energy loss.
Solution Approach 2:
The commutation capacitor C1 is periodically recharged during normal operation and then discharged during interruption events. This periodic charge-discharge cycle allows the circuit to maintain readiness for rapid interruption while keeping conduction losses low during normal power transmission through the main switch.
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 T-type DC circuit breaker achieves low loss and low cost while ensuring complete controllability and rapidity in the DC interruption process, effectively addressing the limitations of existing technologies.
Implementation Method 1
the bypass branch is charged by the DC power supply during the turn-off process of the T-type DC circuit breaker to generate a reverse voltage to forcibly turn off the main branch
Data Source
AI summary
A T-type DC circuit breaker includes a main branch, a first commutation switch, a second commutation switch, and a bypass branch. The first commutation switch and the second commutation switch are arranged at both ends of the main branch, respectively. The bypass branch is connected in parallel with the main branch. The main branch includes at least one half-controlled power electronic component. The bypass branch includes a bypass capacitor and a bypass diode connected in series. Each of the first commutation switch and the second commutation switch includes at least one fully-controlled power electronic component. The first commutation switch is connected in parallel with a first surge arrester, and the second commutation switch is connected in parallel with a second surge arrester. The grounded branch is arranged between the main branch and the second commutation switch and is grounded or connected to the negative terminal of the load.