Power Converter Segmentation for Reduced Conduction Losses

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Solution Overview

Problem

Existing power-converting devices for direct current to alternate current conversion, such as those used with photovoltaic generators and fuel cells, suffer from high conduction losses due to the large number of switching elements required, leading to inefficiencies in power conversion.

Innovation Solution

A power-converting device configuration with two conversion circuits and bidirectional switches, where the first and second conversion circuits are connected in parallel, reducing the number of switching elements through which current passes, thereby minimizing conduction losses and improving efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a five-level inverter configuration with two direct current capacitors, two flying capacitors, and ten switching elements is used to output voltages at five levels, then the voltage switching capability is improved, but the sum of conduction losses of the switching elements increases

Engineering Contradiction:

Improvevoltage switching capabilityVSAvoidconduction losses

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The power conversion device is divided into a first conversion circuit and a second conversion circuit, each handling specific voltage levels. The first conversion circuit outputs voltages at two levels (first and second levels), while the second conversion circuit outputs voltages at three levels (second, third, and fourth levels). This segmentation allows each circuit to use fewer switching elements, reducing total conduction losses while maintaining five-level voltage switching capability through combination.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention introduces a hierarchical structure where the first and second conversion circuits operate at different voltage level dimensions. The first conversion circuit operates with coarser voltage steps (two levels), while the second conversion circuit operates with finer voltage steps (three levels). By combining these different dimensional approaches, the system achieves five-level output with reduced switching element count.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If ten switching elements are used in the five-level inverter, then the voltage levels are achieved, but the device complexity and heat generation increase

Engineering Contradiction:

Improvevoltage levelsVSAvoidnumber of switching elements

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The inverter is segmented into two independent conversion circuits with different functions. The first conversion circuit uses four switching elements to generate two voltage levels, while the second conversion circuit uses five switching elements to generate three voltage levels. This segmentation reduces the total switching element count from ten to nine while maintaining five-level voltage capability through the combination of both circuits' outputs.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second conversion circuit is designed to be multi-functional, serving both as a voltage generator for the third and fourth levels and as a buffer for the second level voltage. This multi-functionality allows the system to achieve five-level output with fewer total switching elements by having the second conversion circuit perform multiple roles in the voltage hierarchy.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Power

If six switching elements are used in the conventional five-level inverter current path, then the voltage conversion is achieved, but the conduction losses increase

Engineering Contradiction:

Improvevoltage conversionVSAvoidconduction losses

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The current path is segmented into two separate conversion circuits instead of flowing through six switching elements in sequence. The first conversion circuit handles current through at most two switching elements for its two voltage levels, while the second conversion circuit handles current through at most three switching elements for its three voltage levels. This segmentation reduces the maximum switching elements in any current path from six to three, significantly reducing conduction losses.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses partial action by having each conversion circuit handle only the voltage levels it is optimized for. The first conversion circuit partially handles the voltage conversion for levels one and two, while the second conversion circuit partially handles levels two through four. This partial division of labor reduces the number of switching elements any single current must pass through, minimizing conduction losses.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS9866147B2Power-converting device and power conditioner using the same

Publication Date: 2018.01.09 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A first bidirectional switch is electrically connected between a first connection point which is a connection point of a first switching element and a second switching element and a second connection point which is a connection point of a seventh switching element and an eighth switching element. A second bidirectional switch is electrically connected between a third connection point which is a connection point of a third switching element and a fourth switching element and a fourth connection point which is a connection point of a fifth switching element and a sixth switching element. A power-converting device is configured to generate an output voltage between a first output point and a second output point.