DC-DC Converter Ripple Control via DC-Link Voltage Adjustment
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Solution Overview
Problem
Existing DC-DC converters in electric energy storage systems face challenges in minimizing current ripple without increasing losses, size, or cost, which affects power efficiency and the lifespan of energy storage devices.
Innovation Solution
The method involves dynamically adjusting the DC-link voltage to optimize the ratio of energy storage voltage to DC-link voltage, thereby controlling the current ripple to a desired level, including zero or near-zero ripple, using techniques such as interleaved multi-phase converters and selective phase switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If stronger passive filtering is used to reduce current ripple, then current ripple is reduced, but the filter becomes bulky and expensive and introduces extra losses
Solution Approach 1:
The invention changes the operating parameters of the DC-DC converter, specifically the duty cycle and switching frequency, to minimize current ripple without requiring additional filtering components. By dynamically adjusting these parameters, the converter achieves optimal ripple reduction while maintaining high efficiency and avoiding the energy losses associated with traditional passive filters.
2Object-affected harmful factors
If inductance in output filter is increased to reduce current ripple, then current ripple is reduced, but the filter becomes bulky and expensive
Solution Approach 1:
The invention uses parameter optimization of the existing inductor and capacitor values, combined with dynamic duty cycle adjustment, to achieve ripple reduction without increasing the physical size of the filter components. The method finds optimal operating points where minimal filtering components are sufficient.
3Object-affected harmful factors
If switching frequency is increased to reduce inductance requirement, then current ripple is reduced, but switching losses and core losses increase drastically
Solution Approach 1:
The invention optimizes the switching frequency parameter to find the optimal balance between ripple reduction and loss minimization. Rather than simply increasing frequency, the method identifies specific frequency ranges and duty cycle values that achieve effective ripple suppression while keeping switching and core losses within acceptable limits.
4Object-affected harmful factors
If more phases are added to interleaved converter to reduce current ripple, then current ripple is reduced to 1/N, but complexity and switching losses increase
Solution Approach 1:
The invention segments the power conversion function into multiple phases with optimized phase shifting, where each phase operates independently but contributes to overall ripple reduction. This segmentation allows achieving ripple cancellation with fewer phases by optimizing the interaction between phases through controlled duty cycle variations.
Data Source
Figure 1A~1D
Figure 2~3
Figure 4~5
AI summary
An electric system comprises a DC-link (2), an energy storage (12), and a DC-DC converter (10) coupled between the DC-link and the energy storage. The DC-link has an adjustable DC-link voltage UDC and the energy storage has a DC energy storage voltage UES. A current ripple control (110) is provided to dynamically adjust the DC-link voltage UDC so that a voltage ratio UES/UDC is controlled to an optimal value or value range that causes a desired current ripple level at the energy storage.