Inverter Circuit Segmentation for Switch Element Reduction
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Solution Overview
Problem
Existing power-system-interconnected inverter devices require a large number of switch elements, leading to increased cost and complexity, particularly for household applications.
Innovation Solution
A power-system-interconnected inverter device is designed with a configuration that includes two three-level circuits and a bridge clamping circuit, utilizing a smaller number of switch elements to achieve a five-level circuit, along with a detection unit, amplification unit, voltage correction unit, and PWM-modulating unit to drive the switch elements and control the bridge clamping circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a multilevel circuit with n levels is configured to generate substantially sinusoidal voltage for system connection, then the output voltage quality is improved, but the number of switch elements increases to 2(n-1) leading to increased cost and device complexity
Solution Approach 1:
The inverter circuit is segmented into a first three-level circuit and a second three-level circuit that are connected in series. Each three-level circuit independently generates voltage with three levels, and their series connection produces five-level output voltage. This segmentation allows achieving five-level output without requiring 2(5-1)=8 switch elements in a conventional multilevel circuit, thereby reducing device complexity while maintaining output voltage quality.
2Manufacturing precision
If the number of levels is increased to n levels for better power quality, then the sinusoidal current injection capability is improved, but the cost of semiconductor elements and passive components increases significantly
Solution Approach 1:
The first three-level circuit and second three-level circuit are merged in series connection to achieve five-level output voltage. This merging strategy allows the inverter to achieve better sinusoidal current injection capability (equivalent to five-level performance) while using only 4 switch elements per three-level circuit, significantly reducing the total number of semiconductor elements compared to conventional approaches and thereby lowering manufacturing cost.
3Productivity
If more switch elements are used to achieve higher voltage levels, then the power conversion efficiency is improved, but the device size and cost increase
Solution Approach 1:
The inverter is segmented into two independent three-level circuits connected in series. Each circuit uses only 4 switch elements but contributes to the overall five-level voltage generation. This segmentation achieves high power conversion efficiency through multilevel voltage output while keeping the device size compact, as the total number of switch elements is reduced compared to conventional five-level inverters.
Data Source
AI summary
In a power-system-interconnected inverter device, PI control circuits obtain voltage correction values in directions reducing the current errors on the basis of current errors serving as differences between target current values and detection values. Multiplexers provide modulation circuits with voltage target values corrected by the voltage correction values being added to voltage detection values. The modulation circuits provide gate signals for switch elements in multilevel circuits. In addition, a sign circuit provides gate signals for switch elements in a bridge clamping circuit.