Static Transfer Switching Using Flux Prediction to Limit Inrush
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Solution Overview
Problem
Conventional power switching methods in static transfer switches can lead to high inrush currents and forced shutdowns due to magnetic flux saturation in transformers, causing system instability and potential power loss.
Innovation Solution
A dual power switching system with a controller that calculates the magnetic flux difference between predicted and residual flux in an inductive device, allowing for forced commutation to switch from the main to the backup power source, avoiding high inrush currents and maintaining stable output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the silicon-controlled rectifier of the backup power source is turned on after the current drops to zero, then excessive inrush current is avoided, but the waiting time is too long and output voltage drops, risking forced shutdown of critical equipment
Solution Approach 1:
The controller performs preliminary detection of the current waveform and calculates the optimal switching time point before the current actually drops to zero. By predicting the magnetic flux state and determining the precise switching moment in advance, the system can turn on the backup power source's silicon-controlled rectifier at the optimal time, avoiding both excessive inrush current and excessive waiting time. This resolves the contradiction by performing the switching action at the preliminarily determined optimal moment rather than waiting passively for current to reach zero.
2Speed
If switching occurs when current is still flowing, then switching speed is improved and output voltage is maintained, but excessive inrush current may be induced in the transformer
Solution Approach 1:
The controller continuously monitors the current waveform and provides feedback to determine the optimal switching time. By detecting the real-time current state and calculating the magnetic flux, the system receives feedback on whether switching at the current moment would cause excessive inrush current. This feedback mechanism allows the controller to select the precise switching moment that balances switching speed with inrush current prevention, resolving the contradiction between fast switching and inrush current control.
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 system effectively prevents high inrush currents and ensures continuous power supply by accurately timing the switch from the main to the backup power source, maintaining stable operation of critical loads.
Implementation Method 1
the controller detects a residual magnetic flux of the inductive device and calculates a magnetic flux difference between the predicted magnetic flux and the residual magnetic flux
Implementation Method 2
since the transformer is an inductive device 120, there is a problem of magnetic flux saturation
Data Source
AI summary
A dual power switching system includes a first STS, a second STS, an inductive device, and a controller. The first STS is electrically coupled to a main power source, and the second STS is electrically coupled to a backup power source. When detecting that the main power source is abnormal, the controller detects a residual magnetic flux of the inductive device and calculates a magnetic flux difference between the predicted magnetic flux and the residual magnetic flux. When determining that an absolute value of the magnetic flux difference is less than or equal to a magnetic flux deviation value, the controller determines whether the output power meets a forced commutation condition. When determining that the output power meets the forced commutation condition, the controller turns on the second STS so that the first STS is forcibly turned off by the backup power source through the second STS.