Quasi-five-level inverter with bidirectional switch
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Solution Overview
Problem
Conventional five-level inverters used in uninterruptible power supplies (UPS) are complex, expensive, and have a large number of power switches, limiting their use due to high costs and complexity, while also experiencing high harmonic distortion.
Innovation Solution
A quasi-five-level inverter system that utilizes a bidirectional switch and diodes to switch between five voltage levels, reducing the number of power switches and complexity, while maintaining high efficiency and low harmonic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional five-level inverters are used, then voltage level control is achieved, but device complexity and cost increase due to large number of power switches
Solution Approach 1:
The inverter circuit is divided into multiple H-bridge modules, each capable of independent operation. By segmenting the overall circuit into modular units, the system achieves five-level voltage control through coordinated operation of simpler modular components rather than requiring a single complex circuit configuration with numerous switches.
Solution Approach 2:
Multiple H-bridge modules are combined in series to achieve the five-level voltage output. The merging of these modular units allows the system to generate multiple voltage levels (±Vdc, 0) by selectively activating and series-connecting the modules, thereby reducing the need for individual complex switching arrangements in each module.
2Adaptability or versatility
If conventional five-level inverters are used, then voltage level control is achieved, but manufacturing cost increases due to complexity
Solution Approach 1:
The inverter is segmented into identical or similar H-bridge modules that can be manufactured as standardized units. This segmentation enables mass production of modular components, reducing per-unit manufacturing costs through economies of scale and simplified assembly processes compared to custom-built complex five-level inverter circuits.
Solution Approach 2:
The system uses capacitor voltage balancing to dynamically adjust and maintain equal voltage levels across series-connected modules. By controlling the voltage parameters of individual module capacitors, the system ensures optimal operation and reduces the need for expensive precision matching during manufacturing.
3Power
If conventional five-level inverters are used, then power conversion is achieved, but harmonic distortion increases
Solution Approach 1:
The inverter uses periodic switching of the H-bridge modules to generate the five-level voltage waveform. By implementing controlled periodic switching sequences that alternate between different module configurations, the system synthesizes a stepped voltage waveform that closely approximates a sine wave, thereby reducing harmonic distortion while maintaining efficient power conversion.
Solution Approach 2:
The system incorporates feedback control through capacitor voltage balancing mechanisms that monitor and adjust the voltage levels of individual module capacitors. This feedback ensures equal voltage distribution across modules and maintains waveform quality, reducing harmonic distortion by compensating for deviations in real-time operation.
Data Source
AI summary
According to one aspect, embodiments of the invention provide an inverter comprising an input, an output, a plurality of DC busses, a mid-point bus, an LC filter, a common node coupled to the LC filter, a plurality of switches coupled to the plurality of DC busses and the common node, a bidirectional switch coupled between the mid-point bus and the common node, and a controller configured to operate the plurality of switches and the bidirectional switch in a first mode of operation to generate a voltage at the common node at a first positive DC voltage level, in a second mode of operation to generate the voltage at a second positive DC voltage level, in a third mode of operation to generate the voltage at a first negative DC voltage level, and in a fourth mode of operation to generate the voltage at a second negative DC voltage level.