Active DC Harmonic Filtering for Diode-Bridge Power Rectifiers
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Solution Overview
Problem
Existing aircraft electrical power systems face challenges in achieving high-quality DC output with reduced cost and complexity, as passive diode-bridge rectifiers produce lower quality DC voltage, while active devices increase system complexity and cost, and conventional filters are bulky and lossy, optimized for a narrow range of operating parameters.
Innovation Solution
An electrical power system incorporating a diode-bridge rectifier and an active filter circuit with a controller to control power semiconductor switches, which filters harmonics in the DC output by determining and adjusting the output voltage using a Fourier Transform or Goertzel Algorithm, and employing time-interleaved or synchronized switching of active bridge circuits to emulate an R-L-C filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a passive diode-bridge rectifier is used, then cost and complexity are reduced, but DC output quality deteriorates with higher harmonic content
Solution Approach 1:
The patent combines a passive diode-bridge rectifier with an active filter circuit into a hybrid rectification system. The diode-bridge provides basic rectification function while the active filter circuit, containing controllable power semiconductor switches, is merged in parallel to actively compensate for harmonics and improve DC output quality, thus resolving the contradiction between simplicity and output quality.
Solution Approach 2:
The active filter circuit acts as an intermediary component between the passive rectifier and the DC load. It processes the rectified output by actively filtering harmonics and regulating voltage, mediating the transition from low-quality passive rectification to high-quality DC output without requiring a complete active rectifier design.
2Manufacturing precision
If an active rectifier with controllable power semiconductor switches is used, then DC output quality is improved, but system cost and complexity increase
Solution Approach 1:
The patent segments the rectification function into two separate components: a passive diode-bridge rectifier that handles the basic AC-to-DC conversion, and an active filter circuit that handles only the harmonic filtering and voltage regulation. This segmentation allows the system to achieve high DC output quality while avoiding the full complexity of a completely active rectifier design.
Solution Approach 2:
Instead of using full active control for the entire rectification process, the patent applies partial active action only where needed - specifically in the filter circuit that compensates for harmonics and regulates voltage. This partial application of active devices reduces overall system complexity while maintaining DC output quality.
3Manufacturing precision
If conventional passive R-L-C filters are used to improve DC voltage quality, then harmonic filtering is achieved, but the filters become bulky and lossy with narrow operating range
Solution Approach 1:
The patent replaces conventional passive mechanical R-L-C filter components with an active filter circuit using controllable power semiconductor switches. This substitution eliminates the need for bulky inductors and capacitors, significantly reducing filter mass while maintaining harmonic filtering capability through electronic control mechanisms.
Solution Approach 2:
The active filter circuit provides dynamic harmonic filtering capability through controllable power semiconductor switches that can adapt to varying operating conditions. Unlike fixed passive filters optimized for narrow ranges, the active circuit can dynamically adjust its filtering characteristics to maintain effectiveness across wide operating parameter variations.
4Manufacturing precision
If conventional passive R-L-C filters are used, then harmonic filtering is provided, but energy losses increase
Solution Approach 1:
The patent replaces lossy passive R-L-C filter components with an active filter circuit using controllable power semiconductor switches. This substitution reduces energy losses by using electronic switching and control mechanisms instead of resistive and inductive elements that dissipate power, while maintaining effective harmonic filtering.
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
The system achieves improved DC output quality with reduced size and mass, allowing for flexible frequency response and harmonic filtering, thereby optimizing the electrical power system's efficiency and reducing the need for large capacitors and passive filters.
Implementation Method 1
an active filter circuit comprising a plurality of power semiconductor switches connected in a bridge configuration between first and second output terminals
Implementation Method 2
determining and adjusting the output voltage using a Fourier Transform or Goertzel Algorithm
Implementation Method 3
determining and adjusting the output voltage using a Fourier Transform or Goertzel Algorithm
Implementation Method 4
employing time-interleaved or synchronized switching of active bridge circuits to emulate an R-L-C filter
Data Source
AI summary
An electrical power system 10, comprising: a rotary electrical machine 12 configured to output AC; a diode-bridge rectifier 13 having an AC input connected to the electrical machine 12 and a DC output (DC+, DC−); an active filter circuit 14 comprising a plurality of power semiconductor switches 141L-H, 142L-H connected in a bridge configuration between first and second output terminals 14out, the first and second output terminals 14out connected to the DC output (DC+, DC−) of the diode-bridge rectifier 13; and a controller 15 configured to control a switching operation of the plurality of power semiconductor switches 141L-H, 142L-H of the 10 active filter circuit 14 to control an output voltage Vfilt across the first and second output terminals 14out of the active filter circuit 14.