AC Train Controller Power Failure Detection via Frequency Extraction
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Solution Overview
Problem
Conventional AC electric train controllers experience delayed and erroneous power failure detection when multiple trains are connected, leading to hindered travel and potential device breakdowns due to overcurrents.
Innovation Solution
A controller with a converter, inverter, current detector, and control unit that extracts a specific-frequency current signal from the transformer output current, calculates current deviation, and compares it to a set value to swiftly and reliably detect power failures, stopping converter operation upon detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional wave detector is used to detect power failure by monitoring current signal frequency components, then the detection method is simple, but erroneous detection occurs when multiple trains are connected causing travel delays
Solution Approach 1:
The patent extracts the fundamental frequency component from the complex current signal using a specific-frequency-signal calculating unit. By isolating only the fundamental frequency component and comparing it with the total current, the system eliminates interference from harmonic frequencies generated by multiple trains, thereby resolving the contradiction between simple detection and accurate detection.
2Reliability
If the power-failure-detection set value is lowered to reduce erroneous detection, then false positives decrease, but detection delay increases and overcurrent may cause device breakdown
Solution Approach 1:
The patent implements a feedback mechanism by continuously comparing the fundamental frequency current component with the total current and using the deviation signal to control the converter operation. This feedback loop enables rapid detection and immediate response, resolving the contradiction between detection accuracy and response time by providing real-time monitoring and control.
3Productivity
If multiple electric trains are connected as loads of the substation, then system capacity increases, but current value of wave detector becomes high causing erroneous power failure detection
Solution Approach 1:
The patent applies local quality by focusing detection on the specific fundamental frequency component rather than the total current. This selective approach allows the system to maintain high detection reliability even when multiple trains are connected, as the fundamental frequency component remains distinct from the harmonic content generated by multiple loads.
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
Enables swift and reliable power failure detection in AC overhead wires, preventing erroneous delays and overcurrents, thus stabilizing train travel and preventing equipment failures.
Implementation Method 1
a converter (4) that converts an AC voltage input from an AC overhead wire (1) through a transformer (3), into a DC voltage
Implementation Method 2
an inverter (10) that converts a DC voltage of the converter (4) into an AC voltage and outputs the same to an AC motor (13)
Data Source
AI summary
In a controller for an AC electric train capable of power running and regenerative running, and capable of detecting a power failure in an AC overhead wire for supplying AC electric power, a power failure in the AC overhead wire is swiftly and reliably detected. A power failure detector provided in an electric-train control unit includes a specific-frequency-signal calculating unit that extracts a current component corresponding to a specific-frequency set value from a main-transformer output-current detection signal and outputs an extracted signal as a specific-frequency current signal, a subtracter that subtracts the main-transformer output-current detection signal from the specific-frequency current signal and outputs a result of the subtraction as a current deviation, and a power-failure detecting unit that compares the current deviation with a predetermined power-failure-detection set value, and outputs a power-failure detection signal when the current deviation is greater than the power-failure-detection set value.