Modular Static Transfer Switches for Fast Hot-Swappable Power Transfer
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Solution Overview
Problem
Conventional static transfer switches using thyristors face issues with overcurrent protection, slow switching speeds due to zero-crossing current requirements, and single-point failure modes, leading to potential disruptions and maintenance challenges.
Innovation Solution
A modular static transfer switch design featuring solid-state switch modules operating in parallel, allowing for hot swapping and redundancy, and utilizing non-thyristor based solid-state switching elements that can switch during non-zero current conditions, improving transfer speed and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thyristors are used as solid-state switching devices, then overcurrent protection is provided through additional protection devices, but the device complexity increases and the thyristors must be over-specified for current handling
Solution Approach 1:
The patent replaces thyristor-based mechanical switching with solid-state switches (MOSFETs or IGBTs) that can electronically interrupt current flow. This substitution eliminates the need for additional protection devices like fuses and circuit breakers, as the solid-state switches inherently provide overcurrent protection through their ability to turn off during fault conditions, thereby reducing device complexity while maintaining reliability
Solution Approach 2:
The patent changes the current handling parameters of the switching devices by using solid-state switches with lower current ratings compared to over-specified thyristors. The solid-state switches operate within their rated current capabilities by utilizing their turn-off capability during overcurrent events, eliminating the need to over-specify current handling capacity and reducing overall device complexity
2Reliability
If thyristors are used for switching, then the transfer can be implemented, but the transfer speed is slow due to zero-crossing current requirement causing up to half-waveform delay
Solution Approach 1:
The patent replaces thyristor-based switching with solid-state switch technology that does not require zero-crossing current conditions. Solid-state switches (MOSFETs or IGBTs) can interrupt current flow at any point in the AC waveform, enabling instantaneous transfer between power sources without the half-waveform delay inherent in thyristor operation, thereby significantly improving transfer speed while maintaining reliable transfer capability
Solution Approach 2:
The patent implements preliminary action by pre-positioning multiple solid-state switch modules in parallel configurations before transfer is needed. The control system can immediately activate the appropriate solid-state switches when transfer is required, without waiting for current zero-crossings, thus achieving rapid transfer response through advance preparation of the switching configuration
3Reliability
If thyristors are used in the static transfer switch, then the switching function is provided, but single point failure modes require the switch to be de-energized for service causing disruptions
Solution Approach 1:
The patent segments the static transfer switch into multiple independent solid-state switch modules that can operate independently. This modular segmentation allows individual modules to be serviced or replaced without taking down the entire system, as other modules can continue to provide switching functions, thereby maintaining operational continuity during maintenance while preserving the essential switching capability
Solution Approach 2:
The patent implements beforehand cushioning by configuring redundant solid-state switch modules in parallel arrangements before failures occur. When one module fails or requires maintenance, the pre-configured redundant modules are already in position to immediately take over the switching function, cushioning against service disruptions and maintaining system operation during maintenance activities
Data Source
AI summary
In one aspect, a modular static transfer switch is provided. The module static transfer switch includes an output configured to couple to a load, a first input configured to couple to a first power source, and a second input configured to couple to a second power source. The modular static transfer switch further includes a plurality of sold-state switch modules each comprising at least one solid-state switch. A first plurality of the solid-state switch modules are coupled in parallel between the first input and the output, each configured to selectively couple the first power source to the output using the at least one solid-state switch. A second plurality of the solid-state switch modules are coupled in parallel between the second input and the output, each configured to selectively couple the second power source to the output using the at least one solid-state switch.