Phase-Controlled Bridge FCLs for Precise Fault Current Limiting
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Solution Overview
Problem
Existing Fault Current Limiters (FCLs) face challenges in precisely limiting fault currents to desired values, especially under dynamic conditions, and often result in high power losses and increased costs due to the need for high-rated circuit breakers.
Innovation Solution
The development of phase-controlled IGBT and GTO bridge-type FCLs with bi-directional switches and a non-superconducting reactor, along with a precise phase control algorithm that calculates optimal turn-on and turn-off angles for switches to limit fault currents, allowing for accurate control and reduced power losses during normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional circuit breakers are used to eliminate fault currents, then fault currents can be eliminated, but the response time is limited and the price increases with the amplitude of fault currents
Solution Approach 1:
The FCL is pre-configured in the circuit before a fault occurs. When a fault happens, the FCL immediately begins limiting the fault current without waiting for detection and activation, as the limiting action is already in place through the pre-positioned reactor and semiconductor switches.
Solution Approach 2:
The FCL acts as an intermediary device between the power source and the fault, inserting a reactor with controllable impedance to limit the fault current. This mediator approach allows gradual current limitation rather than abrupt interruption, achieving faster effective response than traditional circuit breakers.
2Power
If FCLs are implemented to limit fault currents, then circuit breaker rated short circuit current can be reduced and price decreased, but power losses increase during fault operation
Solution Approach 1:
The semiconductor switches operate periodically, turning on and off in synchronization with the AC cycle to control current flow through the reactor. This periodic switching allows the FCL to limit fault currents while dissipating energy in controlled intervals, reducing continuous power losses compared to resistive FCL designs.
Solution Approach 2:
The impedance of the FCL is dynamically changed by controlling the switching angles of the semiconductor devices. By adjusting the conduction angle and switching timing, the effective impedance presented to the fault current varies, allowing optimization between current limitation effectiveness and power loss minimization.
3Ease of manufacture
If diode-based bridge type FCLs are used, then cost and control simplicity are improved, but manufacturing precision and control resolution decrease
Solution Approach 1:
The FCL transitions from a static diode-based design to a dynamic design with controllable semiconductor switches (IGBTs or GTOs). These switches can be precisely controlled through phase-angle modulation, allowing dynamic adjustment of the current waveform and precise limitation to desired values, while maintaining reasonable cost through efficient control algorithms.
4Measurement precision
If transistor-based FCLs are used, then flexibility and control resolution are improved for accurate fault current limitation, but device complexity and cost increase
Solution Approach 1:
The FCL design uses a unified controller that can operate with different types of semiconductor switches (IGBTs or GTOs) and adapt to various fault conditions. The control system provides multi-functionality by handling both normal operation bypassing and fault current limitation, as well as providing precise phase-angle control for accurate current limitation without requiring separate specialized circuits.
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 enables precise limitation of fault currents to desired values, maintaining constancy despite dynamic behavior, and reduces power losses to nearly zero during normal operation, while also lowering the cost of FCLs by optimizing control units and reducing the need for high-rated circuit breakers.
Implementation Method 1
a non-superconducting reactor being installed inside said bridge and having internal resistance RDC
Implementation Method 2
having internal resistance RDC with series connected dumping resistor RD
Implementation Method 3
parallel to bridge connected shunt capacitor Csh and resistor Rsh
Implementation Method 4
phase-controlled Insulated-Gate Bipolar Transistor (IGBT) bridge type, Gate Turn-off Thyristor (GTO) bridge type
Implementation Method 5
series connected dumping resistor RD
Data Source
AI summary
The present invention provides topologies of phase-controlled IGBT bridge type and GTO bridge type Fault Current Limiter (FCL), which allow the precise limitation of fault currents to the desired values and can keep these values constant despite variations (dynamic behavior) of the fault currents. According to an embodiment of the invention, the topologies enable to use a phase control approach for optimal firing angles calculation. This control approach can be used in the proposed FCL topologies and other controlled bridge topologies such as SCRs bridge, GTO bridge, and IGBT/IGCT/Mosfet bridge topologies.