Pantograph Separation Detection Using Dynamic Voltage Thresholds
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Solution Overview
Problem
The existing power conversion system for railway vehicles inaccurately determines whether a current collector is separate from a power line due to fixed thresholds that do not account for variations in voltage decreasing rates caused by changes in motor power consumption, leading to potential errors in determining separation.
Innovation Solution
A control device equipped with a changing rate calculator, a first threshold calculator, and a separation determiner that calculates a dynamic first threshold based on a physical quantity correlated with output power, allowing for accurate determination of current collector separation from the power line by comparing the voltage changing rate with the calculated threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fixed thresholds are used for separation determination, then the control system is simple to implement, but the determination accuracy is insufficient due to variations in voltage decreasing rate
Solution Approach 1:
The patent applies dynamics by transitioning from fixed thresholds to dynamic thresholds that are calculated in real-time based on the physical quantity (motor torque or output power). The threshold calculation unit continuously updates the threshold values according to current operating conditions, making the separation determination system adaptive to varying voltage decreasing rates while maintaining reasonable computational complexity through formula-based calculations.
Solution Approach 2:
The patent changes the parameter of the threshold from a constant value to a variable value that depends on physical quantity (motor torque or output power). By establishing a correlation between the threshold and the physical quantity, the system adapts to different operating conditions and voltage decreasing rates, thereby improving separation determination accuracy without requiring complex algorithms.
2Reliability
If a large difference between first and second thresholds is used, then separation can be certainly detected, but determination errors increase due to insufficient accuracy
Solution Approach 1:
The patent resolves this contradiction by making the threshold parameter dynamic rather than fixed. The first and second thresholds are calculated based on the physical quantity (motor torque or output power), allowing the system to maintain appropriate threshold differences for reliable detection while adapting to specific operating conditions to minimize determination errors.
Solution Approach 2:
By implementing dynamic threshold calculation, the system can adjust the threshold values according to real-time operating conditions. This allows the thresholds to maintain an appropriate difference for reliable separation detection while being adapted to the current voltage decreasing rate, thereby preventing determination errors that would occur with fixed large differences.
3Measurement precision
If the voltage decreasing rate varies with motor power consumption, then the fixed threshold system cannot accurately detect separation, but increasing threshold adaptability increases system complexity
Solution Approach 1:
The patent changes the threshold parameter to be dependent on the physical quantity (motor torque or output power), which correlates with the voltage decreasing rate. This approach provides accurate separation detection by adapting to varying motor power consumption while maintaining relatively simple formula-based calculation methods, avoiding excessive system complexity.
Solution Approach 2:
The patent introduces the physical quantity (motor torque or output power) as an intermediary parameter that mediates between the voltage decreasing rate and the threshold. This intermediary allows the system to accurately reflect voltage changing characteristics without directly measuring complex voltage rates, simplifying the overall system while improving measurement accuracy.
Data Source
AI summary
A control device includes a changing rate calculator, a first threshold calculator, and a separation determiner. The control device determines whether a current collector is separate from a power line, in a power conversion system in which a power converter converts power supplied from the current collector to the primary side of the power converter into alternating-current (AC) power and supplies the AC power to a motor connected to the secondary side of the power converter. The changing rate calculator calculates a changing rate of the voltage at the primary side of the power converter. The first threshold calculator calculates a first threshold having the absolute value positively correlated with an output power from the power converter. The separation determiner compares the changing rate with the first threshold and determines whether the current collector is separate from the power line.