Active EMC Filter for Low-Frequency Harmonic Suppression
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Solution Overview
Problem
Existing EMC filters for power supplies are bulky and inefficient in filtering low-frequency current harmonics, particularly those above 100mA, due to their large size and mass, and often require internal intervention in current and voltage loops which is not always feasible.
Innovation Solution
A filtering device positioned upstream of a system to be filtered, comprising a network current sampling module, a bidirectional DC-DC power conversion module, and a correction module that uses pulse width modulation to manage energy storage in a capacitive reserve, allowing for single current measurement to vary energy levels and eliminate direct current components, thereby reducing filter size and mass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If passive filters are used to filter low-frequency current harmonics, then filtering effectiveness is improved, but filter size and mass increase significantly
Solution Approach 1:
The patent replaces the traditional passive mechanical filter system with an active filtering system using bidirectional DC-DC conversion. Instead of relying on large inductors and capacitors to passively attenuate harmonics, the system uses controlled power conversion with pulse width modulation to actively compensate for current harmonics, achieving effective filtering with significantly reduced mass and size.
Solution Approach 2:
The invention changes the operating parameters by using variable voltage control through bidirectional DC-DC conversion. By dynamically adjusting the voltage across the energy reserve capacitor and using pulse width modulation, the system adapts to different operating conditions and maintains effective harmonic filtering across varying power levels without requiring oversized fixed components.
2Object-affected harmful factors
If passive filters are used to filter low-frequency current harmonics, then filtering effectiveness is improved, but filter volume increases significantly
Solution Approach 1:
The patent replaces the traditional passive mechanical filter system with an active filtering system using bidirectional DC-DC conversion. Instead of relying on large inductors and capacitors to passively attenuate harmonics, the system uses controlled power conversion with pulse width modulation to actively compensate for current harmonics, achieving effective filtering with significantly reduced mass and size.
Solution Approach 2:
The invention transitions from a purely passive spatial filtering approach to an active temporal control approach. By using pulse width modulation and dynamic voltage control, the system achieves filtering in the time domain through controlled energy transfer, rather than relying solely on spatial arrangement of large passive components.
3Measurement precision
If internal intervention in current and voltage loops is implemented, then filtering precision is improved, but device complexity increases
Solution Approach 1:
The bidirectional DC-DC converter serves multiple functions simultaneously: it provides power conversion, active harmonic filtering, and energy management. By integrating these functions into a single control architecture, the system achieves precise filtering without requiring separate complex control loops for each function, thereby reducing overall system complexity while maintaining high filtering precision.
4Volume of stationary object
If energy reserve capacity is optimized for voltage rather than capacity, then space efficiency is improved, but energy storage capability is reduced
Solution Approach 1:
The system employs dynamic voltage control through bidirectional DC-DC conversion with pulse width modulation. The energy reserve capacitor operates with variable voltage levels rather than a fixed nominal voltage, allowing the system to optimize the trade-off between volume and storage capacity based on real-time power demands. This dynamic operation enables efficient use of the energy reserve with reduced volume while maintaining adequate storage capability.
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 solution effectively filters low-frequency emissions in the range of 10Hz to 3KHz with reduced size and mass, achieving 45% volume reduction and 65% weight reduction while maintaining compliance with EMC standards, and is adaptable to various DC-DC controllers.
Implementation Method 1
A bidirectional DC-DC power conversion module
Implementation Method 2
Optimization of the energy stored per capacitive battery volume with the capacity value (C)/charging voltage (V) pair
Data Source
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AI summary
Device and method for filtering emissions on a current-supplied network, positioned upstream of equipment, comprising: A current sampling module for the current flowing in the network, configured to transmit a sampled current IC to a bandpass filter (12) adapted to eliminate the DC component of the sampled current; A subtractor (13) configured to receive the remaining AC component of the sampled current and a given reference current value Iref, and adapted to generate an error signal Se; A correction module (14) adapted to process the error signal Se and to generate a corresponding voltage value Ve.to transmit the error voltage value Ve to a summing junction (15) adapted to receive a reference voltage value and a charging voltage value from the energy reserve and to weight these three values before transmitting them to a bidirectional DC-DC conversion manager (8) adapted to generate a voltage across the terminals of the energy reserve capacity so that the latter supplies energy to the network or, conversely, draws energy from the network.