DC Bus Ripple Detection Using Harmonic Bandpass Filters
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Solution Overview
Problem
Conventional power conversion systems face challenges in accurately and cost-effectively detecting excessive DC bus ripple voltage and input phase loss, which can stress capacitors and reduce system efficiency, due to complex and noisy detection methods.
Innovation Solution
The use of bandpass filters to monitor specific harmonics of the DC bus voltage, such as the second, fourth, and sixth harmonics, in conjunction with logic circuits to detect excessive ripple and phase loss, allowing for fast and accurate identification of adverse conditions without significant added cost or complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ripple detection approaches are used, then detection capability is provided, but system cost and complexity increase due to additional circuitry or computational requirements
Solution Approach 1:
The system uses the existing DC bus voltage signal that is already present in the power conversion system to detect ripple conditions. The detection apparatus processes the voltage signal through bandpass filters to extract harmonic components, eliminating the need for separate sensing circuitry. The controller utilizes its existing computational resources to perform the detection algorithm, making the system self-sufficient without additional hardware complexity.
Solution Approach 2:
The detection apparatus serves multiple functions: it monitors DC bus voltage, detects excessive ripple through harmonic analysis, identifies phase loss conditions, and provides early warning for capacitor stress. By making the detection system multi-functional, it replaces what would otherwise require multiple separate monitoring systems, thereby reducing overall system complexity while maintaining comprehensive detection capability.
2Device complexity
If simple detection techniques are used, then system cost is reduced, but detection accuracy and reliability deteriorate due to noise susceptibility and low accuracy
Solution Approach 1:
The bandpass filters act as intermediaries that selectively extract specific harmonic components (2nd, 4th, and 6th harmonics) from the DC bus voltage signal. These filters isolate the relevant frequency components while rejecting noise and unrelated signals. By using these intermediary filtering stages, the system achieves high detection accuracy without requiring complex signal processing algorithms or additional sensing hardware.
Solution Approach 2:
The system changes the parameter being monitored from the raw DC bus voltage to specific harmonic components of that voltage. By transforming the detection parameter from time-domain voltage levels to frequency-domain harmonic amplitudes, the system achieves noise immunity and high accuracy. The controller analyzes the amplitudes of specific harmonics to detect phase loss and ripple conditions, providing precise measurement without increased hardware complexity.
3Device complexity
If conventional phase loss detection is used, then basic detection is provided, but detection completeness deteriorates due to inability to detect all phase loss conditions
Solution Approach 1:
The detection method segments the analysis into multiple independent harmonic components (2nd, 4th, and 6th harmonics) rather than relying on a single detection parameter. Each harmonic provides independent information about different aspects of system health. By analyzing multiple segmented frequency components, the system achieves complete detection of all phase loss conditions while maintaining a relatively simple implementation using basic filtering and amplitude comparison.
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
This approach provides robust, accurate, and timely detection of ripple and phase loss, reducing the risk of capacitor stress and improving system reliability with minimal additional hardware or computational overhead.
Implementation Method 1
bandpass filters can be used as harmonic detectors to monitor and detect the amplitude of the sixth harmonic content in the DC bus voltage along with either or both of the second and fourth harmonics
Data Source
AI summary
Methods and apparatus are presented for detecting phase loss and/or excessive ripple in a power converter, in which bandpass filters are used to obtain harmonic voltage amplitudes associated with the power converter DC bus, and phase loss is detected if a ratio of the second harmonic to the sixth harmonic and/or a ratio of the fourth harmonic to the sixth harmonic exceed predetermined threshold values.