Active Flux Control for Output Transformer Saturation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional electric rail networks face challenges in accurately isolating fault sections during voltage dips, leading to non-linear behavior of output transformers, which causes distorted waveforms and incorrect fault detection, delaying power restoration.
Innovation Solution
A method for active flux control using a closed-loop estimator to inject a DC current component into the output transformer, derived from measurements of primary and secondary currents and converter voltage, to reduce saturation and maintain sinusoidal waveforms during faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active flux control is implemented by injecting DC current component into the output transformer, then transformer saturation is reduced and waveform distortion is minimized, but device complexity increases due to the need for closed-loop estimator and flux control system
Solution Approach 1:
The patent implements feedback control by using a closed-loop estimator that continuously monitors the magnetic flux state of the output transformer and adjusts the DC current injection accordingly. The estimator receives feedback signals from current transformers and voltage measurements, processes this information to determine the flux state, and generates control signals to maintain optimal flux levels during fault conditions, thereby improving fault detection accuracy while managing system complexity through intelligent control algorithms
Solution Approach 2:
The patent introduces a flux estimator as an intermediary component that mediates between the physical transformer and the control system. This estimator acts as a virtual sensor that indirectly measures the magnetic flux state by processing electrical measurements, enabling the control system to make informed decisions about DC current injection without requiring direct flux measurement, thus balancing improved reliability with acceptable device complexity
2Reliability
If DC current component is injected into the output transformer to control flux, then saturation during faults is reduced, but energy loss increases due to continuous current injection
Solution Approach 1:
The patent applies dynamic control by continuously adjusting the DC current injection level based on real-time flux measurements and fault conditions. The control system modulates the magnitude and duration of DC current injection to match the actual saturation risk, injecting current only when and where needed to prevent saturation during faults, thereby maintaining reliable transformer operation while minimizing unnecessary energy loss during normal operation or less severe fault conditions
3Reliability
If flux control is activated during voltage dips, then non-linear behavior is reduced and protection system operation is improved, but response time may be delayed due to detection and calculation requirements
Solution Approach 1:
The patent implements preliminary action by pre-configuring the closed-loop estimator with transformer parameters and saturation characteristics before faults occur. The system continuously monitors voltage and current measurements in real-time, maintaining readiness to detect flux saturation conditions. When voltage dips or faults occur, the pre-prepared estimation algorithms can immediately process the measurements and generate control signals, reducing the detection and calculation delay and improving protection system response time while maintaining reliable operation
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
Effectively reduces output transformer saturation and maintains sinusoidal waveforms, enhancing the accuracy of fault detection and reducing delays in power restoration by controlling the flux in the output transformer during network faults.
Implementation Method 1
A method for active flux control by controlling a power converter to inject a DC current component into an output transformer during a fault situation
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
An active flux control method is described. The active flux control method injects a DC current component into an output transformer (10) that is connected to a power converter in order to reduce the saturation of the output transformer during a network fault. The method includes using a flux controller (20) to derive an estimated magnetisation curve of the output transformer using a closed-loop estimator comprising a flux model (21) and a modelled magnetisation flux (22). A DC component of the estimated magnetisation flux is calculated. Current control is carried out using a current controller (30) that controls the power converter to inject a DC current component into the output transformer. The DC current component is calculated from the DC component of the estimated magnetisation flux.