Multi-voltage DC Grid Current Limiting Resistor Bypass Switch
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Solution Overview
Problem
Direct current grids face reliability issues due to rapid increases in short-circuit current, which can damage power electronics and destabilize bus voltages, necessitating effective current limiting and voltage stabilization during faults.
Innovation Solution
A multi-voltage level direct current grid system with current-limiting resistor units and bypass switches, where resistor units are activated during faults to limit fault currents and maintain voltage stability, preventing over-currents and ensuring rapid system recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If power electronic converters are introduced to enable flexible operation in direct current grids, then operational flexibility is improved, but system complexity and reliability risks increase due to limited over-current capacity
Solution Approach 1:
The patent applies preliminary action by pre-configuring current-limiting resistor units and bypass switches in the direct current grid system before faults occur. When a short-circuit fault happens, the bypass switch rapidly transitions the circuit from normal operation mode to fault protection mode, activating the current-limiting resistor unit in advance-prepared configuration to immediately limit fault current and protect power electronic converters, thus maintaining reliability while preserving operational flexibility.
2Loss of energy
If line impedance is kept small for efficient power transmission, then transmission efficiency is improved, but short-circuit current increases extremely quickly during faults causing damage to power electronics
Solution Approach 1:
The patent introduces current-limiting resistor units as intermediary elements that can be rapidly inserted into the circuit during faults. These resistor units act as mediators between the low-impedance transmission line and the fault point, providing controlled impedance to limit short-circuit current magnitude while preserving the originally low line impedance for normal efficient power transmission. The bypass switch controls the insertion and removal of this intermediary resistance.
3Object-affected harmful factors
If short-circuit current is limited by increasing line impedance, then fault current is reduced, but voltage drop increases and impacts all devices and loads on the direct current bus
Solution Approach 1:
The patent applies local quality by placing current-limiting resistor units specifically at locations where short-circuit faults occur (at lead-out wires and transformer connections) rather than uniformly throughout the entire direct current grid. This localized resistance insertion limits fault current at the specific fault point while minimizing voltage drop impact on the broader bus and other connected devices, as the resistance is only active locally during fault conditions.
4Loss of time
If bypass switches are used for rapid fault response, then fault elimination speed is improved, but device complexity increases due to additional switching components
Solution Approach 1:
The patent applies universality by designing the bypass switch to perform multiple functions: normally it provides a low-impedance bypass path for efficient power transmission, and during faults it rapidly transitions to insert the current-limiting resistor unit. This multi-functional switch reduces the need for separate dedicated fault-protection components, managing system complexity while achieving rapid fault response through its dual operational modes.
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 effectively limits fault currents, stabilizes bus voltages, and enhances the reliability of direct current grids by preventing damage to power electronics and enabling rapid fault recovery.
Implementation Method 1
a first current-limiting unit comprising a group of direct current switches, and a first bypass switch and a first current-limiting resistor unit which are connected in parallel
Implementation Method 2
a first bypass switch and a first current-limiting resistor unit which are connected in parallel
Data Source
AI summary
A multi-voltage level direct current grid system and a control protection method, the direct current grid system comprising: at least two direct current buses; at least one direct current transformer, one end of which is connected to a first direct current bus while another end is connected to a second direct current bus or a lead-out wire, which may achieve direct current voltage conversion; and at least one lead-out wire current limiter, one end of the lead-out wire current limiter being connected to the second direct current bus while another end is connected to the lead-out wire; the lead-out wire current limiter comprises a first current-limiting unit, and the first current limiting unit comprises a group of direct current switches, as well as a first bypass switch and a first current-limiting resistor unit that are connected in parallel.