High Voltage DC Bus Tie Switching with Series-Connected Semiconductor Units
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Solution Overview
Problem
High voltage DC power systems in offshore platforms and vessels lack effective static switching solutions to prevent fault propagation, as existing low voltage bus tie switches are not capable of operating at voltages above 1000V, particularly in marine and offshore systems requiring fast disconnection to maintain critical system functionality.
Innovation Solution
A DC power supply system with a power switching assembly comprising series connected power switching units, current limiters, and symmetrical sub-units with semiconductor devices, diodes, and capacitors, which disconnect DC bus sections upon fault detection to prevent fault propagation, and can operate within the range of 1kV to 15kV, using inductance as current limiters and damping circuits to manage oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low voltage bus tie switches are used to disconnect DC bus sections, then fault propagation can be prevented, but the system cannot operate at voltages above 1000V
Solution Approach 1:
The power switching assembly is divided into multiple series-connected power switching units, where each unit can be independently controlled to block or conduct current. This segmentation allows the system to handle high voltages by distributing the voltage across multiple units while maintaining the ability to isolate faults in individual sections of the DC bus.
Solution Approach 2:
A current limiter is introduced as an intermediary component between the power source and the power switching units. This current limiter prevents excessive current from damaging the semiconductor devices during fault conditions or switching transitions, enabling the system to operate safely at high voltages above 1000V while maintaining fault isolation capability.
2Adaptability or versatility
If mechanical breakers are used for high voltage systems, then the system can operate above 1000V, but the disconnection speed is insufficient for fast fault isolation
Solution Approach 1:
The patent replaces mechanical breakers with a static switching assembly based on semiconductor devices (such as IGBTs or MOSFETs). These solid-state switches can open and close in microseconds, providing extremely fast disconnection speed for fault isolation while maintaining the ability to operate at high voltages through series connection of multiple units.
3Adaptability or versatility
If series connected power switching units are used to achieve high voltage operation, then the system can operate at 1kV to 15kV, but the complexity of the switching assembly increases
Solution Approach 1:
The power switching assembly is divided into identical, modular power switching units that can be series-connected to achieve the desired high voltage rating. Each unit contains the same semiconductor device, diode, and capacitor configuration, making the system scalable and easier to design, manufacture, and maintain despite the high overall complexity.
Solution Approach 2:
Each power switching unit is designed as a universal module that can handle both normal operating conditions and fault conditions. The symmetrical configuration with diodes and capacitors in each unit allows the same hardware to perform multiple functions: voltage blocking, current switching, and fault protection, reducing the need for additional specialized components.
4Reliability
If current limiters are provided between terminals and power switching units, then protection from short circuits is improved, but the device complexity increases
Solution Approach 1:
The current limiter is integrated as part of the modular power switching unit structure, where each unit includes its own current limiting capability through the series connection of diodes and capacitors. This segmentation distributes the current limiting function across multiple units rather than requiring a single complex external current limiter.
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 provides reliable fault isolation in high voltage DC systems, ensuring continuous power supply to critical equipment by rapidly disconnecting faulty sections and preventing fault propagation, while managing system oscillations and voltage spikes, thus meeting regulatory requirements for safe operation.
Implementation Method 1
each power switching sub-unit comprises a semiconductor device for controlling current flow between the first terminal and the second terminal
Implementation Method 2
in parallel with the semiconductor device, a series connected diode and capacitor
Implementation Method 3
the current limiter comprises an inductance
Implementation Method 4
one or each of the sub-units further comprise a damping circuit in series with the capacitor
Data Source
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AI summary
A DC power supply system comprises first and second DC power distribution bus sections and a DC power switching assembly (122) comprises a plurality of series connected power switching units (121) and a current limiter (100). Each power switching unit comprises a first power switching unit terminal (123) and a second power switching unit terminal (123) and two symmetrical power switching sub-units (146) to control current flow between the first terminal and the second terminal. Each sub-unit (146) is electrically connected on one side to one of the first and second power switching unit terminals (23, 24) and on the other side to the other sub-unit (146). The power switching sub-units (146) each comprise a semiconductor device (Q1,Q2) and in parallel with the semiconductor device, a series connected diode (D1,D2) and capacitor (C1,C2). A first terminal (28) of the assembly (122) is electrically coupled to the first bus section (30) of the power distribution bus and the second terminal (29) is electrically coupled to the second bus section (31) of the power distribution bus. The voltage at one side of the power switching assembly (122) is greater than or equal to 1kV.