Active DC-Link Resonant Buffer for High-Density Power Converters
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Solution Overview
Problem
Conventional power converters for electric vehicles rely on bulky and costly electrolytic capacitors, which reduce power density and increase manufacturing costs while having a limited lifespan.
Innovation Solution
Incorporating an active DC-link with semiconductor switching devices and a resonant tank to replace traditional passive DC-links, reducing component count and enhancing power converter efficiency and longevity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional passive DC-link with electrolytic capacitors is used, then filtering capability is provided, but size and manufacturing cost increase while lifespan is limited
Solution Approach 1:
The patent transforms the static passive DC-link into a dynamic active DC-link by introducing semiconductor switching devices (MOSFETs or IGBTs) that can actively control power flow. This dynamic structure replaces the static filtering function of electrolytic capacitors with an active control mechanism, enabling the system to maintain reliability without relying on degraded capacitor components.
Solution Approach 2:
The patent substitutes the mechanical/electrical passive filtering system (electrolytic capacitors) with an electronic active control system. The active DC-link uses switching devices and control circuitry to achieve power buffering and ripple filtering, replacing the physical capacitor-based approach with an electronically controlled alternative that eliminates the lifespan limitations of electrolytic capacitors.
2Power
If electrolytic capacitors are used in the DC-link, then power conversion function is achieved, but power density is reduced
Solution Approach 1:
The patent extracts and removes the bulky electrolytic capacitors from the DC-link structure. By eliminating these large-volume components, the system achieves higher power density without sacrificing the power conversion function. The active switching devices and resonant tank components occupy significantly less space while maintaining or improving performance.
Solution Approach 2:
The patent changes the operating parameters and structure of the DC-link by introducing high-frequency switching operation. This enables the use of smaller magnetic and electric components (resonant tank with smaller inductors and capacitors) that operate at higher frequencies, thereby reducing the overall volume of the power converter while maintaining the required power handling capability.
3Ease of manufacture
If passive DC-link with capacitors is used, then filtering is provided, but manufacturing cost increases
Solution Approach 1:
The active DC-link structure serves multiple functions simultaneously: power buffering, ripple filtering, and active power factor correction. The semiconductor switching devices and resonant tank not only filter the DC-link ripple but also enable active control of the input current waveform, providing power factor correction without requiring separate components. This multi-functionality reduces the overall component count and manufacturing cost while maintaining or improving filtering capability.
Solution Approach 2:
The patent merges the filtering function with the power conversion function by integrating the active DC-link control into the existing power converter topology. The same switching devices used for power conversion are also utilized for active filtering and power factor correction, eliminating the need for separate passive filtering components and reducing manufacturing complexity and cost.
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 DC-link provides a compact, cost-effective power converter with improved power density and extended lifespan, ensuring smooth power delivery and ripple reduction.
Implementation Method 1
a resonant tank preferably formed by a first capacitor and an inductor connected in series between the interconnection line between the top switch and the bottom switch and the second line of the DC bus
Data Source
Figure 1~2
Figure 3
Figure 4A~4B
AI summary
The invention refers to a power converter system (1) comprising: an input converter (3) adapted to provide an output signal, an output converter (4) adapted to convert a DC input signal into an AC or a DC output signal, and a DC bus connecting the output signal of the input converter (3) to the input signal of the output converter (4). The system (1) includes: an active DC-link (2) with two switching devices connected in series between first and second lines (L+, L-) of the DC bus, and a resonant tank connected in series between the interconnection between the two switching devices and the second line (L-). A controller operates the two switching devices, in a first mode of operation, in which the active DC-link (2) receives current from the input converter (3) to store energy in the resonant tank, and in a second mode of operation, in which the active DC-link (2) supplies energy stored in the resonant tank to the output converter (4).