Interleaved Converter Assembly With Integrated EMC Filtering
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Solution Overview
Problem
Converter assemblies for converting DC to AC voltage in high-power applications, such as test stands, face challenges with high-frequency interference and large EMC line filters, which hinder compact design and compliance with electromagnetic compatibility standards.
Innovation Solution
A converter assembly with electronically controllable half bridges and a control unit for phase- or time-offset activation, combined with interleaving chokes and common-mode chokes, forms two LC filter stages to reduce interference, eliminating the need for separate EMC filters by efficiently dissipating high-frequency interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional EMC line filters with LC components are used to reduce high-frequency interference, then electromagnetic compatibility is improved, but the device size and complexity increase
Solution Approach 1:
The patent combines the EMC filter functionality with the existing converter assembly components. The inverter unit and its switching elements are integrated directly into the converter assembly structure, eliminating the need for separate external EMC filters. This merging approach reduces overall device size while maintaining electromagnetic compatibility through careful layout and integrated filtering of high-frequency interference.
Solution Approach 2:
The patent introduces an intermediary DC voltage intermediate circuit between the DC voltage source and the inverter unit. This intermediate circuit serves as a buffer that reduces high-frequency interference propagation while allowing the converter assembly to maintain a compact design. The intermediate circuit acts as a mediator that filters interference without requiring large external EMC filter components.
2Adaptability or versatility
If the converter assembly is designed for high power applications with bidirectional operation, then versatility and power capability are improved, but the device size increases making it difficult to arrange directly on electrical load machines
Solution Approach 1:
The converter assembly is segmented into functional modules: a DC voltage source interface, a DC voltage intermediate circuit, an inverter unit with multiple half bridges, and control electronics. This modular segmentation allows the high-power bidirectional converter to be compact enough for direct mounting on electrical load machines while maintaining full functionality. Each module is optimized for its specific function, reducing overall volume.
Solution Approach 2:
The inverter unit is designed with multiple half bridges that enable bidirectional power flow and multiple operating modes (rectification, inversion, regenerative braking). This multi-functionality is achieved within a compact structure by sharing common components such as the DC voltage intermediate circuit and control electronics, thereby reducing the overall volume required for high-power versatile operation.
3Productivity
If high-frequency switching processes are used for pulse width modulation, then conversion efficiency and power density are improved, but high-frequency interference and ripple currents increase causing EMC violations and ripple torques
Solution Approach 1:
The patent employs periodic pulse width modulation with carefully selected switching frequencies that balance conversion efficiency with interference reduction. The inverter unit uses periodic switching of half bridges to synthesize AC output, while the DC voltage intermediate circuit provides periodic energy buffering that reduces ripple currents. This periodic action maintains high conversion efficiency while minimizing high-frequency interference through optimized switching patterns.
Solution Approach 2:
The patent converts the harmful high-frequency switching ripple into a beneficial filtering function. The DC voltage intermediate circuit, with its capacitance, naturally filters high-frequency ripple currents generated by the switching process. Additionally, the inductor elements in the circuit topology convert high-frequency interference into magnetic energy that is dissipated or redirected, transforming the harmful switching effects into useful filtering action that maintains EMC compliance.
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 achieves a compact, interference-free converter assembly that meets EMC standards without additional filters, ensuring smooth sinusoidal signal replication and reduced ripple currents, thus preventing electromagnetic compatibility violations and ripple torques in electrical machines.
Implementation Method 1
The semiconductor switches switch the DC voltage on and off with high frequency; the mean value of the high-frequency, pulse-width-modulated switching frequency is the output AC voltage.
Implementation Method 2
interleaving chokes and common-mode chokes, forms two LC filter stages to reduce interference
Data Source
AI summary
The invention relates to a converter assembly for converting a DC voltage from a DC voltage source, e.g. a battery, a fuel cell or a DC voltage intermediate circuit, into an N-phase AC voltage, e.g. for supplying an N-phase electric machine, comprising a connected inverter unit (1) having a number M of electronically controllable half bridges (2, 2′, 2a, 2a′, 2b, 2b′) for each of the N phases, wherein M is greater than one, a control unit (3) controlling the half bridges (2, 2′, 2a, 2a′, 2b, 2b′) which is designed to activate the half bridges (2, 2′, 2a, 2a′, 2b, 2b′) in a phase-offset manner with a switching frequency fT, wherein the phases are connected to a respective winding (5, 5′, 5″) of a common-mode choke (10) with a common magnetic core for damping electrical common-mode interference, and wherein the outputs of the half bridges (2, 2′, 2a, 2a′, 2b, 2b′), supplying said phases, are interconnected via interleaving chokes (4, 4′, 4a, 4a′, 4b, 4b′), wherein a first resistance-damped capacitor circuit (6) is provided at the output of the interleaving chokes (4, 4′, 4a, 4a′, 4b, 4b′) forming a first LC filter stage (8), and a second resistance-damped capacitor circuit (7) is provided at the output of the common-mode choke (5, 5′, 5″) forming a second LC filter stage (9).