DC Converter Current Control for Bus Capacitor Ripple Suppression

Solution Overview

Problem

The increased ripple current in the bus capacitor of new energy power generation systems due to higher system power leads to increased loss and reduced service life, affecting the long-term reliability of the system.

Innovation Solution

A power conversion system with a controller that adjusts the output or input currents of selected direct current conversion units to counteract the ripple current in the bus capacitor, using current superposition and cancellation techniques to reduce the amplitude of the ripple current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If system power is increased to meet higher energy demands, then power output is improved, but ripple current in the bus capacitor increases leading to reduced service life and reliability

Engineering Contradiction:

Improvesystem power outputVSAvoidbus capacitor service life

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The system divides the M direct current conversion units into two groups: N units configured to output ripple currents that cancel the bus capacitor ripple current, and the remaining M-N units configured to output ripple currents in the same direction as the bus capacitor ripple current. This segmentation allows selective control of ripple current contributions while maintaining total power output.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent creates an asymmetric distribution of ripple current functions among the direct current conversion units. Instead of all units contributing equally to ripple current, N units are assigned the asymmetric role of generating counter-phase ripple currents to suppress the bus capacitor ripple, while other units maintain normal power conversion functions.

Inventive Principle:

Principle #4Asymmetry

2Power

If system power is increased to meet higher energy demands, then power output is improved, but bus capacitor loss increases due to higher ripple current

Engineering Contradiction:

Improvesystem power outputVSAvoidbus capacitor loss

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The system divides the M direct current conversion units into two groups: N units configured to output ripple currents that cancel the bus capacitor ripple current, and the remaining M-N units configured to output ripple currents in the same direction as the bus capacitor ripple current. This segmentation allows selective control of ripple current contributions while maintaining total power output.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent converts the harmful ripple current effect into a beneficial suppression mechanism. By controlling N direct current conversion units to output ripple currents in the opposite direction to the bus capacitor ripple current, the system uses the ripple current phenomenon itself to cancel and reduce the overall ripple current, thereby reducing bus capacitor losses.

Inventive Principle:

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

3Power

If all direct current conversion units operate to maintain power output, then power output is maintained, but ripple current suppression is insufficient

Engineering Contradiction:

Improvepower outputVSAvoidripple current amplitude

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The system divides the M direct current conversion units into two groups: N units configured to output ripple currents that cancel the bus capacitor ripple current, and the remaining M-N units configured to output ripple currents in the same direction as the bus capacitor ripple current. This segmentation allows selective control of ripple current contributions while maintaining total power output.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the operational parameters of N direct current conversion units by adjusting their output current phases to be opposite to the bus capacitor ripple current. This parameter change enables these units to contribute to ripple current suppression rather than addition, reducing the overall ripple current amplitude while maintaining power output.

Inventive Principle:

Principle #35Parameter changes

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 solution effectively suppresses the ripple current, reducing losses in the bus capacitor and prolonging its service life while maintaining overall system power output, thereby enhancing the long-term reliability of the power conversion system.

Implementation Method 1

controlling N direct current conversion units in the M direct current conversion units to adjust output currents/input currents in response to an amplitude of a ripple current of the bus capacitor being greater than a first threshold, to decrease the amplitude of the ripple current of the bus capacitor

Methodology Applied

Scientific EffectCurrent superposition and cancellation:

Data Source

PatentUS20250246992A1Power conversion system and ripple current suppression method thereof

Publication Date: 2025.07.31 HUAWEI DIGITAL POWER TECH CO LTD

AI summary

A power conversion system includes a controller, M direct current conversion units, a bus capacitor, and an inverter unit. An input end of each of the M direct current conversion units is connected to one direct current power supply. Output ends of the M direct current conversion units are connected in parallel and then connected to an input end of the inverter unit. The bus capacitor is connected in parallel to the input end of the inverter unit. The controller is configured to control N direct current conversion units in the M direct current conversion units to adjust output currents/input currents in response to an amplitude of a ripple current of the bus capacitor being greater than a first threshold, to decrease the amplitude of the ripple current of the bus capacitor. M is greater than or equal to 2, and N is a positive integer less than M.