Active Ripple Filter for DC Link Voltage Ripple Reduction
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Solution Overview
Problem
Single-phase power conversion systems face inefficiencies due to high-frequency harmonic currents causing voltage ripple on the DC link, which are typically filtered using bulky capacitors, leading to reduced power density and efficiency.
Innovation Solution
An active ripple filter is introduced, comprising a low-voltage full-bridge inverter and a coupled capacitor, which generates a cancelling ripple voltage opposite in phase to the voltage ripple, directing the ripple current to the DC link capacitor, thereby reducing capacitance requirements and maintaining high power conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a bulk capacitor is used to filter voltage ripple on the DC link, then the voltage ripple is reduced, but the power density and efficiency are reduced due to bulky capacitor size
Solution Approach 1:
An active ripple filter is introduced as an intermediary device between the rectifier and the load. This filter actively generates a cancelling ripple voltage that opposes the harmful voltage ripple on the DC link, thereby reducing the ripple without requiring large bulk capacitors. The active filter acts as a mediator that neutralizes the harmful effect while maintaining compact dimensions.
Solution Approach 2:
The invention converts the harmful voltage ripple into a beneficial effect by generating a cancelling ripple voltage that is opposite in phase to the original ripple. The active ripple filter utilizes the ripple frequency characteristics to create an equal and opposite voltage, effectively canceling the harmful ripple while improving power density and efficiency.
2Object-affected harmful factors
If conventional filtering methods are used, then voltage ripple is suppressed, but system efficiency and power density are compromised
Solution Approach 1:
The invention replaces passive mechanical filtering (bulk capacitors) with an active electronic system. The active ripple filter uses electronic switching and control circuitry to generate the cancelling voltage, substituting the bulky passive capacitor-based filtering mechanism with a more efficient active electronic approach that reduces energy losses.
Solution Approach 2:
The active ripple filter dynamically adjusts the amplitude and phase of the cancelling voltage to match the ripple characteristics. By changing the voltage parameters (amplitude, phase, frequency) in real-time, the system efficiently counteracts the harmonic current while maintaining high conversion efficiency and adapting to varying load conditions.
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 ripple filter achieves high power density, low reactive power processing, and high efficiency in kW-scale power conversion systems, with compact dimensions and simple control mechanisms, minimizing the impact of voltage ripple on system components.
Implementation Method 1
generates a cancelling ripple voltage opposite in phase to the voltage ripple
Implementation Method 2
directing the ripple current to the DC link capacitor
Data Source
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AI summary
According to one aspect, embodiments of the invention provide a power system including an input configured to be coupled to a power source and to receive input power from the power source, an output configured to be coupled to a load and to provide output power to the load, a power converter coupled between the input and the output, and an active ripple filter coupled to one of the output and the input including a DC link having at least one DC link capacitor and configured to generate a cancelling ripple voltage to cancel a ripple current associated with the power converter.