Resonant Circuit Current Interruption for High Voltage DC
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Solution Overview
Problem
Current current interrupting technologies face challenges in efficiently interrupting direct current in power systems, particularly at high voltages, due to limited controllability and complexity, and lack of natural zero cross-over, which can lead to high fault currents and equipment damage.
Innovation Solution
A system comprising a mechanical main circuit breaker, an energy absorbing device, and a resonant circuit with a controllable voltage source, which injects energy to force a rapid increase in alternating current amplitude, achieving artificial zero cross-over and efficient current interruption by coordinating the opening of the mechanical breaker with the excitation of an oscillating current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a mechanical circuit breaker is used to interrupt current in DC power systems, then physical separation and safety are achieved, but the lack of natural zero cross-over leads to high fault currents and inability to interrupt quickly
Solution Approach 1:
The patent applies periodic action by introducing an AC oscillating current component into the DC circuit through a resonance circuit. This creates periodic zero-crossing points in the total current waveform, allowing the mechanical breaker to interrupt current at these zero-crossing moments rather than attempting to stop continuous DC flow, thereby achieving fast interruption without excessive fault currents.
Solution Approach 2:
The patent changes the parameter of current waveform from pure DC to a composite waveform containing AC oscillation superimposed on DC. By adjusting the resonance circuit parameters (inductance L and capacitance C), the oscillation frequency and amplitude are controlled to ensure zero-crossings occur at optimal moments for breaker operation, enabling fast current interruption.
2Speed
If a resonance circuit with auxiliary power supply is used to generate oscillating current, then zero cross-over is achieved, but the arrangement becomes complex and requires elaborate charging processes
Solution Approach 1:
The patent implements self-service by designing the resonance circuit to automatically charge its capacitor using the system's existing DC power source. The capacitor charges through the inductor during normal operation, and when a fault occurs, the stored energy is automatically discharged to generate the oscillating current needed for interruption, eliminating the need for separate auxiliary power supplies and complex charging control systems.
Solution Approach 2:
The resonance circuit components serve multiple functions: the inductor and capacitor form the oscillating circuit for generating zero-crossings, the capacitor also serves as an energy storage element that charges from the DC system, and the same components limit fault current magnitude. This multi-functionality reduces overall system complexity compared to dedicated auxiliary power supply arrangements.
3Speed
If the oscillating current is excited by arc voltage in the mechanical breaker, then zero cross-over can be achieved, but controllability is limited and optimal switching behavior is difficult to achieve
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor in the resonance circuit from the DC power source before the fault current reaches dangerous levels. When a fault is detected, the controller immediately activates the oscillating current generation, ensuring that zero-crossing opportunities are available at optimal moments for interruption, rather than waiting for arc voltage to naturally excite the oscillation after contact separation begins.
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 enables fast and controlled current interruption, reducing the risk of high fault currents and protecting equipment, with improved controllability and suitability for high voltage applications, by ensuring current zero-crossing occurs before peak current values are reached.
Implementation Method 1
the resonant circuit being made to generate a resonance current superposing current of any arc generated in the current interrupter
Implementation Method 2
When interrupting a current flowing in an electrical circuit by contact separation, an arc is in general generated between the contacts
Data Source
AI summary
An arrangement for interrupting current comprises a first and a second terminal. First, second, and third parallel circuit branches are arranged between the terminals to electrically connect two power networks. The first parallel circuit branch comprises a mechanical main circuit breaker, the second parallel circuit branch comprises an energy absorbing device, and the third parallel circuit branch comprises a resonant circuit and a voltage control means arranged in series. The voltage control means is controllable to inject energy into the resonant circuit to force a rapid increase of alternating current, wherein the alternating current flows in a loop containing the first and the third parallel circuit branches as the mechanical main circuit breaker is controlled to open to interrupt main current. Zero cross-over of the current through the mechanical main circuit breaker is thereby realized as the alternating current amplitude exceeds the main current amplitude.