Variable DC-Link Converter for Wide Voltage Range Battery Charging

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Solution Overview

Problem

Conventional AC/DC power converters face challenges in achieving lightweight, compact, efficient, and low-cost designs, particularly in battery chargers that require a wide output voltage range and struggle with parasitic control in transformer windings, and existing methods for adjusting leakage inductance are inefficient and difficult to implement.

Innovation Solution

A variable DC-link voltage structure in power converters, combined with advanced control strategies and a new transformer design with adjustable leakage inductance, allows for efficient operation across a wide voltage range and reduces AC winding loss, enabling better parasitic control and efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional fixed DC-link voltage structure is used in power converters, then the design is simpler, but the efficiency varies significantly across wide output voltage range and AC winding loss increases

Engineering Contradiction:

Improvedesign simplicityVSAvoidAC winding loss

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent applies dynamics by transitioning from a fixed DC-link voltage to a variable DC-link voltage that can be adjusted according to the output voltage requirements. The controller dynamically modifies the DC-link voltage to maintain optimal operating conditions across the wide output voltage range, thereby reducing AC winding loss while maintaining design feasibility.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements parameter changes by varying the DC-link voltage parameter in response to output voltage conditions. The controller detects the output voltage and adjusts the DC-link voltage parameter accordingly, optimizing the transformer operating point to minimize AC winding loss throughout the wide output voltage range.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If conventional fixed DC-link voltage structure is used, then the control system is simpler, but efficiency cannot be maintained constant across wide battery charging voltage range

Engineering Contradiction:

Improvecontrol system complexityVSAvoidefficiency variation

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The controller dynamically adjusts the DC-link voltage based on the detected output voltage and charging current conditions. This dynamic adjustment maintains constant efficiency across the wide battery charging voltage range by keeping the power converter operating at optimal points, despite the increased control complexity.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements feedback control by continuously detecting the output voltage and charging current, comparing them with reference values, and adjusting the DC-link voltage accordingly. This closed-loop feedback mechanism ensures constant efficiency maintenance across the wide operating range.

Inventive Principle:

Principle #23Feedback

3Adaptability or versatility

If leakage inductance is adjusted using conventional methods, then the transformer design is more flexible, but the implementation is difficult and inefficient

Engineering Contradiction:

Improveleakage inductance adjustabilityVSAvoidimplementation difficulty

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent replaces mechanical or physical leakage inductance adjustment methods with an electrical control approach. Instead of physically modifying the transformer structure to change leakage inductance, the controller electronically adjusts the effective leakage inductance through PWM control and DC-link voltage modulation, making implementation easier and more efficient.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 proposed solution maintains constant efficiency across a wide battery charging voltage range, reduces AC winding loss, and allows for adjustable leakage inductance, enhancing the overall performance and cost-effectiveness of power converters.

Implementation Method 1

A transformer is one example of a power converter

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS10454381B2Variable DC link converter and transformer for wide output voltage range applications

Publication Date: 2019.10.22 VIRGINIA TECH INTELLECTUAL PROPERTIES INC

AI summary

A variable direct current (DC) link power converter is described. In one example, the power converter includes a first converter stage configured to convert power from a power source to power at an intermediate link voltage and a second converter stage configured to convert the power at the intermediate link voltage to power for charging a battery. The power converter further includes a control system having an intermediate link voltage regulation control loop configured, in a first mode of operation, to regulate the intermediate link voltage through the first converter stage based on a voltage of the battery, and a ripple regulation control loop configured to sense a charging current for the battery and regulate a gain of the second converter stage based on the charging current to reduce ripple in the charging current. A new configuration of transformer suitable for use with the power converter is also described.