Static Transfer Switch Flux-Based Disconnection Control
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Solution Overview
Problem
Existing static transfer switches (STSs) in mission critical environments face challenges in reducing transfer time between power sources without causing inrush current, which can trip protection devices and damage downstream equipment, making them a single point of failure and costly for mission critical facilities.
Innovation Solution
The implementation of a static transfer switch with a controller that monitors voltage waveforms and flux differences between power sources, using thyristor current interrupters with an auxiliary turn-off unit to accelerate the disconnection of the primary power source from the load, reducing transfer time and preventing inrush current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the transfer time is reduced by accelerating disconnection of the primary power source, then the productivity of power transfer is improved, but inrush current may occur which can trip protection devices and damage downstream equipment
Solution Approach 1:
The controller calculates flux for each phase of both power sources in advance and determines the optimal disconnection sequence before transfer occurs. By pre-calculating flux differences and identifying which phase should be disconnected first, the system prepares the transfer path ahead of time, enabling faster transfer without causing inrush current.
Solution Approach 2:
The patent replaces traditional mechanical transfer switches with solid-state switches controlled by a controller that uses flux-based calculations. This electronic control system substitutes the mechanical switching mechanism, allowing for precise control of switch disconnection timing based on real-time flux measurements, thereby eliminating the inrush current problem associated with mechanical switching while achieving faster transfer times.
2Speed
If solid-state switches are used to enable faster transfer, then the speed of transfer is improved, but the complexity of the device increases due to additional control requirements
Solution Approach 1:
The controller automatically monitors voltage waveforms, calculates flux in real-time, and determines the optimal disconnection sequence without external intervention. The system self-regulates the transfer process by using its own measurements and calculations to control the solid-state switches, eliminating the need for complex external control systems while maintaining high transfer speed.
Solution Approach 2:
The controller dynamically changes operational parameters (voltage waveform monitoring, flux calculations, disconnection timing) based on real-time system conditions. By adjusting these parameters adaptively rather than using fixed control logic, the system achieves fast transfer speeds while keeping the control mechanism relatively simple and responsive to actual system state.
3Reliability
If flux-based control is implemented to prevent inrush current, then the reliability of power transfer is improved, but the measurement precision requirements increase
Solution Approach 1:
The controller continuously monitors voltage waveforms and calculates flux in real-time, using this feedback to adjust the disconnection timing of solid-state switches. By implementing closed-loop feedback control based on actual flux measurements, the system achieves reliable transfer that prevents inrush current while managing measurement precision requirements through adaptive control rather than demanding ultra-precise fixed thresholds.
Data Source
AI summary
A method of operating a static transfer switch is provided. The method includes monitoring a voltage waveform for each phase of first and second power sources, and calculating flux for each phase of the power sources. The method also includes determining (i) a first flux difference between the respective flux of the first phases of the first and second power sources, (ii) a second flux difference between the respective flux of the second phases of the first and second power sources, and (iii) a third flux difference between the respective flux of the third phases of the first and second power sources. The method further includes turning off a third solid-state switch to disconnect the third phase of the first power source from a load, in response to the controller determining that the third flux difference is greater the first and second flux differences.