Over-voltage Protection System Using Segmented Detection
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Solution Overview
Problem
In high-voltage subsea power transmission systems, existing technologies face challenges in quickly detecting and bypassing over-voltages to prevent damage during faults, particularly due to the need for fast isolation and reliable protection in harsh marine environments with high operating voltages.
Innovation Solution
An over-voltage protection system utilizing an electronic valve with series-connected semiconductor devices, an over-voltage detection circuit including a voltage divider and optocoupler, and self-powered gate drive circuits to rapidly bypass the circuit during over-voltage conditions, ensuring simultaneous activation of semiconductor devices and coordinated operation with mechanical switches for long-duration fault clearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional over-voltage detection methods are used in high-voltage subsea power transmission systems, then the system can detect over-voltage conditions, but the detection delay time is too long (greater than 1 microsecond) to provide timely protection
Solution Approach 1:
The high-voltage detection circuit is segmented into multiple series-connected semiconductor devices (e.g., 5 thyristors rated at 10 kV each for a 50 kV system). Each device has its own detection circuit, allowing the system to detect over-voltage conditions at specific segments rather than requiring a single high-voltage detection point, thereby reducing detection delay and improving response time.
Solution Approach 2:
A voltage divider circuit is introduced as an intermediary between the high-voltage circuit and the detection electronics. The voltage divider scales down the high voltage to a lower level that can be safely and quickly detected by electronic circuits, enabling fast detection without exposing sensitive electronics to high voltage stress.
2Strength
If series connection of multiple semiconductor devices is used to achieve high voltage handling capability, then the voltage handling capacity is improved, but the complexity of the protection system increases
Solution Approach 1:
The semiconductor devices (thyristors) serve multiple functions: they are part of the power conversion circuitry and simultaneously form the protection bypass path. The same series-connected devices that handle normal power transmission are used to bypass over-voltage conditions, eliminating the need for separate protection devices and reducing overall system complexity.
Solution Approach 2:
The detection circuit is designed to directly trigger the gate drive circuits of the semiconductor devices without requiring external control systems. When over-voltage is detected, the system automatically triggers the bypass path through self-contained gate drive circuits, reducing the need for complex external control and coordination systems.
3Speed
If fast over-voltage detection and bypass is implemented, then the protection speed is improved, but the isolation requirements for high-voltage components become more challenging
Solution Approach 1:
The voltage divider circuit acts as an isolation intermediary, providing galvanic isolation between the high-voltage detection point and the low-voltage electronics. This allows fast electronic detection while maintaining proper isolation, as the voltage divider can be designed with appropriate creepage and clearance distances without compromising detection speed.
4Reliability
If parallel connection of protecting devices is used to bypass modules during fault conditions, then the protection capability is improved, but the device complexity and isolation requirements increase
Solution Approach 1:
The semiconductor devices are configured to provide both normal power transmission functionality and fault protection bypass capability through the same physical components. During normal operation, they conduct power; during over-voltage faults, they automatically switch to bypass mode, eliminating the need for separate protection devices and reducing overall system complexity.
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 fast and reliable bypassing of over-voltages with minimal detection delay, ensuring continuous power flow and reduced DC voltage during faults, while meeting high isolation requirements and improving system reliability through synchronized semiconductor device activation and reduced voltage unbalance.
Implementation Method 1
The over-voltage detection circuit includes a voltage divider circuit connected to a break-over diode in a way to provide a representative low voltage to the break-over diode, the representative low voltage representing a voltage across the one semiconductor device
Implementation Method 2
an optocoupler configured to receive a current from the break-over diode when the representative low voltage exceeds a threshold voltage of the break-over diode indicating an over-voltage condition
Implementation Method 3
The over-voltage detection circuit further includes an optocoupler configured to receive a current from the break-over diode when the representative low voltage exceeds a threshold voltage of the break-over diode
Implementation Method 4
a plurality of self-powered gate drive circuits connected to the plurality of semiconductor devices, wherein the plurality of self-powered gate drive circuits receive over-voltage triggering pulses from the optocoupler during the over-voltage condition and switch on the plurality of semiconductor devices to bypass the circuit
Data Source
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AI summary
An over-voltage protection system (60) includes an electronic valve (62) connected across two terminals (N, P) of a circuit and an over-voltage detection circuit (64) connected across one of the plurality of semiconductor devices for detecting an over-voltage across the circuit. The electronic valve (62) includes a plurality of semiconductor devices connected in series. The over-voltage detection circuit (64) includes a voltage divider circuit (65) connected to a break-over diode (B1) and an optocoupler (U1) configured to receive a current from the break-over diode (B1) when a representative low voltage that is provided to the break-over diode (B1) exceeds a threshold voltage of the break-over diode (B1), thereby indicating an over-voltage condition. The representative low voltage provided to the break-over diode (B1) represents a voltage across the one semiconductor device. A plurality of self-powered gate drive circuits (80) are connected to the plurality of semiconductor devices. The plurality of self-powered gate drive circuits (80) receive over-voltage triggering pulses from the optocoupler (U1) during the over-voltage condition and switch on the plurality of semiconductor devices to bypass the circuit.