DC-DC Converter DC-Link Voltage Control for Low Current Ripple
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing DC-DC converters in electric energy storage systems face challenges in minimizing current ripple without increasing losses, size, or cost.
Innovation Solution
The method involves dynamically adjusting the DC-link voltage to control the ratio of energy storage voltage to DC-link voltage, optimizing it to achieve a desired current ripple level, which can be minimized to zero or close to zero.
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 device size and cost increase due to larger inductors and capacitors
Solution Approach 1:
The patent changes the operating parameters of the DC-DC converter by dynamically adjusting the switching frequency and duty cycle to minimize current ripple. By optimizing these parameters in real-time based on load conditions, the system achieves low current ripple without requiring oversized passive filters, thus resolving the contradiction between ripple reduction and filter size.
2Object-affected harmful factors
If switching frequency is increased to reduce inductance requirement, then current ripple is reduced, but power losses increase due to higher switching losses
Solution Approach 1:
The patent implements dynamic switching frequency adjustment where the switching frequency is varied based on operating conditions. During light load conditions, the frequency is reduced to minimize switching losses, while during heavy load conditions, the frequency is increased to reduce current ripple. This dynamic adaptation resolves the contradiction between ripple reduction and energy loss.
Solution Approach 2:
The system dynamically changes the switching frequency parameter in response to load variations, optimizing the trade-off between current ripple and switching losses. By adjusting this critical parameter rather than maintaining a fixed high frequency, the system achieves low ripple only when necessary while minimizing overall energy losses.
3Object-affected harmful factors
If multiple phases are added to reduce current ripple, then current ripple is reduced, but device complexity increases
Solution Approach 1:
The patent employs a multi-phase converter topology where the power conversion is divided into multiple parallel phases. Each phase operates with a phase-shifted switching pattern, and the combined output achieves reduced current ripple through phase cancellation effects. This segmentation approach reduces ripple while distributing the complexity across modular units.
Solution Approach 2:
The patent utilizes periodic switching with phase shifts between multiple converters. By coordinating the switching periods and phases of individual converters, the system achieves ripple cancellation through constructive and destructive interference of the periodic current waveforms, reducing overall ripple without requiring excessive filtering components.
Data Source
AI summary
An electric system includes a DC-link, an energy storage, and a DC-DC converter 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 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.