Converter Input Impedance Control for Variable Frequency Rail Networks
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Solution Overview
Problem
Existing on-board network converters for rail vehicles face challenges in minimizing current extraction impacts on railway networks, particularly in regulating AC voltage signals without disturbing frequency-selective systems, as basic frequencies used by track vacancy detection systems are constant but vary by route, requiring a highly sensitive frequency-selective controller that is difficult to design and set.
Innovation Solution
A method that actively increases input impedance by high-pass filtering the current drawn, bandpass filtering it to the network frequency, and selectively integrating it to generate a control signal that compensates for undesirable current variations, allowing the converter to adapt to variable frequencies and minimize disruptions to AC voltage signals, using a generalized integrator and phase-locked loop for frequency determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a frequency-selective controller is designed to regulate AC voltage signals at a fixed frequency, then the controller can be highly sensitive and effective at that frequency, but it cannot adapt to frequency variations from route to route
Solution Approach 1:
The patent applies dynamics by making the controller's operating frequency variable rather than fixed. The controller continuously adapts its frequency setting based on real-time detection of the AC voltage signal frequency on the railway network, allowing it to maintain high sensitivity across different routes while adapting to frequency variations.
Solution Approach 2:
The patent uses feedback by detecting the actual frequency of AC voltage signals on the network and using this information to adjust the controller's frequency setting. This closed-loop approach ensures the controller remains tuned to the correct frequency regardless of route-specific variations.
2Power
If the converter draws large current from the network, then the power consumption increases, but it disturbs the AC voltage signals modulated onto the network
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the converter's input impedance based on the detected AC signal frequency. By changing the impedance parameter to match the network conditions, the converter can draw required power while minimizing harmonic distortion and signal interference.
Solution Approach 2:
The patent converts the potentially harmful effect of current drawing into a beneficial outcome by using active impedance control to shape the current waveform. This ensures that while the converter draws sufficient power, it simultaneously suppresses harmful harmonics and protects AC voltage signals from distortion.
3Object-affected harmful factors
If the input impedance of the converter is increased to minimize current extraction impacts, then the converter does not disturb AC voltage signals, but the converter may not be able to draw sufficient current for large power consumption
Solution Approach 1:
The patent applies dynamics by making the input impedance variable rather than fixed. The controller dynamically adjusts the impedance based on the detected AC signal frequency and power requirements, allowing the converter to maintain high impedance for signal protection while drawing sufficient current when needed.
Solution Approach 2:
The patent uses parameter changes to adjust the input impedance characteristic in response to network conditions. By changing the impedance parameter dynamically, the converter optimizes both signal transmission quality and power consumption capability according to real-time requirements.
Data Source
Figure 1~2
AI summary
To actively increase the input impedance of a current converter (2) drawing current from a grid, the current (2) drawn by the converter is regulated towards zero at a variable frequency specified by the grid by high-pass filtering the current (2) to remove its DC component, by band-pass filtering the high-pass filtered current (4) with a band-pass filter (5) tuned to the frequency specified by the grid, by selectively integrating the band-pass filtered current (9) at a specific frequency to generate a control signal (1) for the current (2) drawn by the converter, and by determining the frequency at which the band-pass filtered current (9) is integrated from the control signal (1).