Adjustable Bandpass Filter for Stable Power Conversion
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Solution Overview
Problem
Existing frequency detectors for electric railroad vehicles require complex circuit configurations with multiple band-pass filters (BPFs) and envelope processing circuits to handle different overhead wire frequencies, leading to instability when there is a mismatch between the detected frequency and preset center frequencies.
Innovation Solution
A power conversion device with a simplified circuit configuration using a single BPF and multiple voltage thresholds, where the filter characteristics are adjusted based on detected frequencies, allowing for precise frequency detection and stable converter operation across varying overhead wire frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple band-pass filters (BPFs) are used to detect different overhead wire frequencies, then the frequency detection capability is improved, but the circuit complexity increases
Solution Approach 1:
The patent applies dynamics by making the BPF characteristics adjustable rather than fixed. The filter's center frequency and bandwidth are dynamically changed based on the detected overhead wire frequency, allowing a single BPF to adapt to different frequency conditions (16.7Hz, 25Hz, 50Hz, 60Hz) without requiring multiple fixed filters.
Solution Approach 2:
The patent changes the parameters of the BPF (center frequency and bandwidth) based on the detected overhead wire frequency. By adjusting these parameters dynamically, the system achieves frequency detection adaptability with a single filter, avoiding the need for multiple fixed-frequency BPFs and their associated envelope processing circuits.
2Adaptability or versatility
If multiple BPFs with different center frequencies are provided for different territories, then the adaptability to different overhead wire frequencies is improved, but the ease of manufacture deteriorates
Solution Approach 1:
The patent makes the BPF universal by enabling it to function at multiple frequency ranges through parameter adjustment. A single BPF circuit can handle all required frequency ranges (16.7Hz, 25Hz, 50Hz, 60Hz) by dynamically changing its characteristics, eliminating the need to manufacture and configure multiple territory-specific filter sets.
Solution Approach 2:
The BPF transitions from a static, territory-specific component to a dynamic, universally adaptable component. The filter characteristics are adjusted in real-time based on the detected frequency, allowing the same circuit to be deployed across all territories without reconfiguration or standardization issues.
3Device complexity
If the center frequency of BPF is fixed, then the circuit configuration is simplified, but the converter operation stability deteriorates when there is frequency mismatch
Solution Approach 1:
The patent implements feedback by detecting the overhead wire frequency and using this information to adjust the BPF characteristics. The frequency detection result feeds back to the BPF control, which dynamically adjusts the filter parameters to match the actual input frequency, ensuring stable converter operation across different frequency conditions.
Solution Approach 2:
The BPF characteristics are made dynamic rather than fixed. The center frequency and bandwidth are adjusted in real-time based on the detected overhead wire frequency, preventing frequency mismatch and ensuring stable converter operation while maintaining circuit configuration simplicity.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A transformer (2) steps down an input AC power, and supplies the AC power to a converter (3). The primary voltage of the transformer (2) detected by a voltage detector (8) is supplied to a converter controller (4) and a frequency detector (6) via a BPF (5). The converter controller (4) controls the converter (3) such that a power factor is equal to or greater than a predetermined value based on the primary voltage, and the converter (3) converts the AC power into DC power. The frequency detector (6) detects the frequency of the primary voltage based on an interval between time points at which the primary voltage via the BPF (5) exceeds a threshold. A filter adjuster (7) calculates a filter characteristic with the detected frequency as a center frequency of the BPF (5), and adjusts the BPF (5) based on the filter characteristic.