Ripple Injection Control in Power Converters for DC Link Protection

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Solution Overview

Problem

Traditional power conversion systems damage capacitors due to large voltage ripples and are prone to overvoltage protection issues, especially during power grid fluctuations, as they only consume the DC component of input power, leaving the AC component to cause capacitor damage and trigger protection mechanisms.

Innovation Solution

A power conversion system with ripple injection, comprising an AC-DC conversion unit, voltage regulation unit, DC-DC conversion units, and control units that adjust the ripple magnitude of output power to match the input power ripple, performing ripple injection operations to balance voltage and current, thereby protecting capacitors and optimizing three-phase current balance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If constant-current charging mode is used to consume only DC component of input power, then battery charging stability is improved, but capacitor voltage ripples increase causing capacitor damage and overvoltage protection issues

Engineering Contradiction:

Improvebattery charging stabilityVSAvoidcapacitor voltage ripples

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful ripple component of input power into a beneficial function by injecting it through DC-DC conversion units to the loads. Instead of allowing ripples to damage the capacitor, the system actively utilizes the ripple power to supply additional current to loads, transforming a harmful factor into a useful resource for improving charging efficiency and reducing capacitor stress

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent dynamically adjusts the ripple injection magnitude based on real-time detection of input power ripple characteristics. The control unit modifies operating parameters of DC-DC conversion units to match ripple injection levels with actual ripple conditions, optimizing the balance between capacitor protection and load supply while adapting to varying grid conditions

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If ripple component of input power flows into capacitor of DC link, then power conversion simplicity is maintained, but capacitor damage and overvoltage protection triggering occur

Engineering Contradiction:

Improvepower conversion simplicityVSAvoidcapacitor reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent segments the power conversion system into distinct functional modules: AC-DC conversion unit, voltage regulation unit with capacitor, and multiple DC-DC conversion units. This segmentation allows the ripple handling function to be isolated in dedicated DC-DC units that can process and redirect ripple energy away from the capacitor, protecting it while maintaining overall system functionality

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces DC-DC conversion units as intermediary devices between the capacitor and the loads. These intermediaries capture the ripple component that would otherwise damage the capacitor and transform it into useful power for load supply, acting as a buffer that protects the capacitor while utilizing the ripple energy constructively

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If power grid fluctuation occurs, then system adaptability to grid conditions is maintained, but excessive voltage ripple on DC link triggers overvoltage protection and causes tripping

Engineering Contradiction:

Improvesystem adaptability to grid conditionsVSAvoidsystem continuity (avoiding tripping)

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent implements a feedback control mechanism where the control unit continuously detects the ripple characteristics of input power and adjusts the operation of DC-DC conversion units accordingly. This feedback loop enables the system to adapt to grid fluctuations by dynamically modifying ripple injection levels, preventing excessive voltage ripple during grid abnormalities and avoiding overvoltage protection triggering

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent transforms the static constant-current charging mode into a dynamic system that can adapt its behavior based on real-time grid conditions. The DC-DC conversion units dynamically adjust their ripple injection magnitude in response to varying input power characteristics, enabling the system to maintain stable operation during grid fluctuations while utilizing available ripple energy

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS12184166B2Power conversion system with ripple injection and power conversion control method

Publication Date: 2024.12.31 DELTA ELECTRONICS INC(CN)

AI summary

A power conversion system with ripple injection includes an AC-DC conversion unit, a voltage regulation unit, at least one DC-DC conversion unit, at least one load, and a first control unit. The voltage regulation unit provides a DC link and receives one portion of an input power as an energy storage power. Each DC-DC conversion unit receives the other portion of the input power as an output power. The at least one load correspondingly receives the output power for being supplied power. The first control unit is coupled to the DC link, the at least one DC-DC conversion unit, and the at least one load. The first control unit controls the at least one DC-DC conversion unit to adjust a magnitude of a ripple of the output power to perform a ripple injection operation according to a magnitude of a ripple of the input power.