Hybrid DC Link System for Regenerative Drive Ripple Control
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Solution Overview
Problem
Regenerative drive systems face challenges in managing energy variations and ripple currents on DC buses during transient conditions, leading to potential component failure and reduced lifespan due to oversized designs and limitations in existing capacitor technologies.
Innovation Solution
A hybrid DC link system is introduced, incorporating a ripple current control branch with a film capacitor and an energy buffering branch with electrolytic capacitors, along with an impedance element and damping resistive elements, to actively control DC voltage and buffer energy spikes, while a controller monitors and manages system imbalances to prevent failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single capacitor technology is used in the DC link, then the design is simpler, but it cannot simultaneously handle ripple current suppression and energy buffering effectively
Solution Approach 1:
The DC link capacitor is segmented into two distinct branches: a film capacitor branch for ripple current suppression and an electrolytic capacitor branch for energy buffering. This segmentation allows each capacitor type to be optimized for its specific function, with the film capacitor handling high-frequency ripple currents and the electrolytic capacitor handling low-frequency energy variations, thereby extending component lifespan while maintaining system reliability
Solution Approach 2:
The patent employs a composite capacitor configuration combining two different capacitor technologies (film and electrolytic) in parallel. This composite approach leverages the complementary strengths of each capacitor type - the film capacitor's low ESR and high ripple current capability combined with the electrolytic capacitor's high energy storage density - to achieve superior overall performance in both ripple suppression and energy buffering
2Reliability
If the DC link is oversized to handle energy variations, then energy buffering capability is improved, but the system becomes less efficient and more costly
Solution Approach 1:
The DC link is segmented into functional branches with specific capacitance values optimized for their roles. The electrolytic capacitor branch is sized specifically for energy buffering (e.g., 2000 µF) while the film capacitor branch is sized for ripple suppression (e.g., 47 µF), allowing the system to handle energy variations efficiently without requiring an excessively large overall capacitance that would reduce system efficiency
Solution Approach 2:
The patent optimizes the capacitance parameters of each branch to achieve the desired energy buffering capability while maintaining system efficiency. By carefully selecting the capacitance values and ESR characteristics of each capacitor type, the system can buffer energy variations effectively without requiring an oversized DC link that would increase cost and reduce productivity
3Reliability
If only film capacitors are used, then ripple current handling is improved, but energy buffering capacity is insufficient
Solution Approach 1:
The capacitor system is segmented into two branches with distinct functions: the film capacitor branch (e.g., 47 µF) is optimized for ripple current handling with low ESR, while the electrolytic capacitor branch (e.g., 2000 µF) is optimized for energy buffering with high capacitance. This segmentation allows each component to excel at its specific function without compromise
Solution Approach 2:
The patent creates a composite capacitor system combining film and electrolytic capacitors in parallel. The film capacitor provides excellent ripple current handling due to its low ESR and high frequency response, while the electrolytic capacitor provides substantial energy storage capacity. Together, they deliver both superior ripple current handling and adequate energy buffering capacity
4Quantity of substance
If only electrolytic capacitors are used, then energy buffering is improved, but ripple current handling capability is reduced
Solution Approach 1:
The DC link capacitor is segmented into two functional branches: the electrolytic capacitor branch provides high energy storage capacity (e.g., 2000 µF) for buffering energy variations, while the separate film capacitor branch provides low ESR ripple current handling (e.g., 47 µF). This segmentation allows the electrolytic capacitor to focus on energy buffering without being overwhelmed by ripple currents
Solution Approach 2:
The patent employs a composite configuration where electrolytic and film capacitors work in parallel. The electrolytic capacitor handles the bulk energy storage and buffering function with its high capacitance, while the film capacitor handles the high-frequency ripple current with its low ESR. This composite approach ensures both adequate energy buffering and superior ripple current handling 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 hybrid DC link system effectively suppresses ripple currents and buffers energy variations, extending component lifespan and preventing failures by actively managing voltage and current, ensuring reliable operation during transient conditions.
Implementation Method 1
A hybrid DC link system is introduced, incorporating a ripple current control branch with a film capacitor
Implementation Method 2
an energy buffering branch with electrolytic capacitors, along with an impedance element and damping resistive elements, to actively control DC voltage and buffer energy spikes
Implementation Method 3
damping resistive elements, to actively control DC voltage and buffer energy spikes
Data Source
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AI summary
A system includes a converter operatively connected to an alternating current (AC) power source and a direct current (DC) bus, an inverter operatively connected to a motor and the DC bus, and a hybrid DC link system operatively connected between a high side and a low side of the DC bus. The converter includes a first plurality of switching devices in selective communication with each phase of the AC power source and the DC bus. The inverter includes a second plurality of switching devices in selective communication with each phase of the motor and the DC bus. The hybrid DC link system includes a ripple current control branch in parallel with an energy buffering branch.