Static Transfer Switching Using Flux-Based Forced Commutation
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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 when switching between main and backup power sources.
Innovation Solution
A dual power switching system with a controller that calculates the magnetic flux difference in real-time, allowing for forced commutation to switch from the main to the backup power source before the freewheeling current reaches zero, thereby avoiding high inrush currents and maintaining stable output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the conventional switching method waits for current to drop to zero before switching, then high inrush current is avoided, but the waiting time is too long and output voltage drops, risking forced shutdown
Solution Approach 1:
The patent applies preliminary action by detecting the magnetic flux state of the transformer before switching occurs. The controller predicts whether magnetic flux saturation will occur and proactively initiates the switching sequence accordingly. By calculating the relationship between primary and secondary winding fluxes in advance, the system determines the optimal switching moment before the current naturally drops to zero, thus avoiding both the high inrush current of conventional methods and the excessive waiting time that causes voltage droop.
2Reliability
If the backup power source is switched on immediately when main power source fails, then power continuity is improved, but magnetic flux saturation causes high inrush current
Solution Approach 1:
The patent implements feedback by continuously monitoring the magnetic flux state of the transformer through voltage integration on the primary and secondary windings. The controller uses this real-time flux information to determine the precise switching moment. The feedback mechanism allows the system to switch to the backup power source immediately when main power fails (maintaining power continuity) while simultaneously ensuring the magnetic flux conditions are favorable (avoiding high inrush current by switching when flux difference is within acceptable range).
Solution Approach 2:
The patent applies parameter changes by transforming the switching decision from a time-based parameter (waiting for current to zero) to a magnetic flux-based parameter. The controller calculates the magnetic flux in both primary and secondary windings and determines switching timing based on the flux difference being within a predetermined range. This parameter transformation enables immediate switching when power failure occurs while avoiding magnetic flux saturation, thus resolving the contradiction between power continuity and inrush current prevention.
3Object-affected harmful factors
If the switching waits for current to reach zero, then inrush current is prevented, but output voltage drops too low causing forced shutdown
Solution Approach 1:
The patent changes the controlling parameter from current magnitude to magnetic flux state. Instead of waiting for current to reach zero (which causes voltage droop), the controller integrates voltage to calculate magnetic flux and switches when the flux difference between primary and secondary windings is within a predetermined range. This parameter change allows switching to occur at an optimal moment that maintains output voltage while preventing inrush current, as the flux-based timing ensures the transformer core is not saturated.
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 ensures continuous power supply to critical loads by preventing high inrush currents and maintaining stable output voltage, reducing the risk of system failure and equipment shutdown.
Implementation Method 1
the controller is configured to integrate a voltage of the primary winding to calculate a first magnetic flux and integrate a voltage of the secondary winding to calculate a second magnetic flux
Implementation Method 2
the controller turns on the second static transfer switch so that the first static transfer switch is forcibly turned off by the backup power source through the second static transfer switch
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A dual power switching system (100) includes a first STS (130), a second STS (131), an inductive device (120), and a controller (134). The first STS (130) is electrically coupled to a main power source (110), and the second STS (131) is electrically coupled to a backup power source (111). When detecting that the main power source (110) is abnormal, the controller (134) detects a residual magnetic flux of the inductive device and calculates a magnetic flux difference between the predicted magnetic flux (fp) 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 (134) determines whether the output power meets a forced commutation condition. When determining that the output power meets the forced commutation condition, the controller (134) turns on the second STS (131) so that the first STS (130) is forcibly turned off by the backup power source (111) through the second STS (131).