Multi-level Voltage Converter Sub-modules with High-Frequency Switching

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Solution Overview

Problem

Multi-level voltage converters face limitations in dynamic response and incur significant additional costs due to the integration of additional energy storage functionality, which restricts their distribution in high voltage direct current networks interconnected with alternating current networks.

Innovation Solution

The design incorporates improved sub-modules with DC/DC converters and switching circuits that selectively control electrical energy storage devices, allowing for reduced voltage constraints and lower current requirements, enabling efficient power management and cost reduction by using high-frequency switching circuits with MOSFET or semiconductor transistors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If additional energy storage devices with DC-DC converters are integrated into each sub-module, then the converter can provide additional energy storage capacity to respond to overload and absorb excess power, but the device complexity and cost increase significantly

Engineering Contradiction:

Improveenergy storage capacityVSAvoidconverter structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The converter is divided into multiple sub-modules connected in series, with each sub-module containing a capacitive element. This segmentation allows the system to provide energy storage capacity through the collective capacitance of multiple elements rather than requiring a single large energy storage device in each module, thereby reducing individual device complexity while maintaining overall adaptability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The capacitive elements in the sub-modules serve dual functions: they act as energy storage devices for responding to overload and absorbing excess power, while also functioning as voltage stabilization components for the DC link. This multi-functionality eliminates the need for separate dedicated energy storage devices, reducing device complexity and cost.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If traditional additional energy storage devices are used, then the converter can respond to power fluctuations, but the dynamic response is limited

Engineering Contradiction:

Improvepower managementVSAvoiddynamic response

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The invention replaces traditional mechanical or electrochemical energy storage systems with electronic switching circuits that can rapidly connect or disconnect capacitive elements. This substitution enables much faster dynamic response to power fluctuations, as electronic switching occurs on microsecond timescales compared to the slower response of mechanical or chemical energy storage systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The switching circuits operate by periodically connecting or disconnecting capacitive elements based on real-time power conditions. This periodic switching action allows the system to dynamically respond to power fluctuations by adjusting the effective capacitance of the DC link, thereby improving reliability in power management while maintaining fast response times.

Inventive Principle:

Principle #19Periodic action

3Reliability

If additional energy storage functionality is integrated, then the converter can reinforce safety by responding to overload and absorbing excess power, but significant additional cost is incurred

Engineering Contradiction:

ImprovesafetyVSAvoidcost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The existing capacitive elements in the converter sub-modules are utilized for energy storage purposes, allowing the system to serve itself rather than requiring additional external energy storage devices. This self-service approach maintains safety and reliability functions while avoiding the additional costs associated with separate energy storage systems.

Inventive Principle:

Principle #25Self-service

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

This configuration enhances the dynamic response and reduces costs by minimizing switching losses and component sizing, making the solution more viable for high voltage direct current networks.

Implementation Method 1

a capacitive element (6), configured to store electrical energy

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

The DC-DC converter has an interface connected to the terminals of the capacitive element of the sub-module

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentEP3966922B1Multi-level voltage converter with optimised additional energy storage

Publication Date: 2023.06.07 SUPERGRID INSTITUTE SAS

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AI summary

The invention concerns a multi-level voltage converter (2) for converting a DC voltage into an AC voltage, comprising: - an arm, comprising an upper half-arm and a lower half-arm (257), each including several sub-modules in series (51, 52, 53), each comprising a capacitive energy storage element (6) and a circuit (4) for selectively bypassing the capacitive element or connecting it in series with the other sub-modules of the half-arm; - an improved sub-module includes several electrical energy exchange devices (7), each comprising: -an electrical energy storage device (81); -a DC/DC converter (71) having a second interface (713, 714) connected to the terminals of the storage device (81), comprising a switching circuit (721, 722) for selectively controlling the discharging or recharging of the storage device (81) via the first interface, the switching circuit (721, 722) including switches having a switching frequency higher than 10 kHz.