Active DC Link Absorption Circuit for Rail Traction Harmonics
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Solution Overview
Problem
Existing absorption circuits in traction converters for rail vehicles are heavy, voluminous, and cost-intensive due to the use of passive components, which are inefficient in filtering higher-frequency harmonics and require additional components for frequency adaptation.
Innovation Solution
An active absorption circuit arrangement using switching units, inductances, and capacitive energy stores, controlled by a facility to dynamically adjust to mains frequency and filter harmonics, reducing the need for additional components and enabling smaller, lighter designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passive resonant circuit with inductance and capacitance is used for absorption, then the circuit can filter harmonics at the resonance frequency, but the components become heavy, voluminous, and cost-intensive
Solution Approach 1:
The patent replaces the passive mechanical resonant circuit (inductance and capacitance components) with an active electronic absorption circuit using power semiconductor switches (IGBTs, MOSFETs, or thyristors) controlled by a control facility. This substitution eliminates the need for heavy passive components while maintaining the harmonic filtering function through active switching and control mechanisms.
Solution Approach 2:
The invention changes the operating parameters of the absorption circuit by using controllable power semiconductor switches that can dynamically adjust their switching characteristics. The control facility modifies the switching frequency and duty cycle to adapt to different mains frequencies (16.7 Hz or 50 Hz) and filter harmonics effectively, replacing the fixed parameter passive resonant circuit.
2Device complexity
If a passive resonant circuit is used for absorption, then the circuit structure is simple, but additional components are needed for frequency adaptation and the circuit is inefficient at filtering higher-frequency harmonics
Solution Approach 1:
The patent introduces dynamic control through a control facility that actively manages the power semiconductor switches. This allows the absorption circuit to dynamically adapt its switching frequency and timing to match different mains frequencies (16.7 Hz or 50 Hz) and effectively filter harmonics, replacing the static passive resonant circuit that requires physical component changes for frequency adaptation.
Solution Approach 2:
The active absorption circuit with controllable power semiconductor switches serves multiple functions: it can adapt to different mains frequencies, filter harmonics at the fundamental frequency and higher frequencies, and provide dynamic response to varying load conditions. This multi-functionality replaces the need for separate components for frequency adaptation that would be required with a passive resonant circuit.
3Ease of manufacture
If passive components are used in the absorption circuit, then the circuit is simple to implement, but losses are higher and efficiency is reduced
Solution Approach 1:
The patent replaces passive energy-dissipating components (resistors, inductors, capacitors) with active power semiconductor switches that can recover and recycle energy. The controlled switching of IGBTs, MOSFETs, or thyristors enables energy to be returned to the DC link or reused, significantly reducing energy losses compared to passive dissipation methods while maintaining implementation feasibility through standard power electronics components.
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 active absorption circuit reduces losses, weight, and volume while effectively filtering harmonics and adapting to different mains frequencies, eliminating the need for additional frequency adaptation components.
Implementation Method 1
Each switching unit contains two terminals, at least two controllable power semiconductor switches and at least one switching unit capacitance and is configured, dependent upon switching settings of the power semiconductor switches, to provide at least two different voltages at the terminals
Implementation Method 2
the at least one inductance is connected in series with at least one switching unit, at least one capacitive energy store
Implementation Method 3
at least one capacitive energy store. The at least one capacitive energy store is connected in series with the at least one switching arrangement
Implementation Method 4
A resonance frequency of the absorption circuit is adjusted to twice the mains frequency, corresponding to 33.4 Hz for the aforementioned 15 kV, 16.7 Hz supply network and/or 100 Hz for the 25 kV, 50 Hz supply network, so that the portions at this frequency are almost completely removed via the absorption circuit
Data Source
AI summary
An absorption circuit arrangement is for a traction converter of a rail vehicle. The traction converter has a first power converter, a second power converter, a DC link circuit connecting the first power converter and the second power converter with a first and a second voltage potential and a link circuit capacitance arranged in the DC link circuit. The absorption circuit arrangement is arranged in the DC link circuit and is connected in parallel with the link circuit capacitance and contains a switching arrangement having a switching unit and an inductance. Each switching unit contains two terminals, two controllable power semiconductor switches and a switching unit capacitance and is configured, dependent upon switching settings of the power semiconductor switches, to provide at least two different voltages at the terminals.