Switched String Converter Topology for DC-AC Conversion
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Solution Overview
Problem
Existing electric converters for DC to AC conversion from photovoltaic elements are complex, bulky, and inefficient, requiring multiple stages and lacking integration with energy storage elements.
Innovation Solution
A compact electric converter topology using multiple DC power banks with controllable switching circuits and energy storage elements, allowing for efficient energy transfer and versatile output configurations, including AC to AC or DC to AC conversion without additional stages, and enabling straightforward integration with energy storage systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a two-stage conversion (DC-DC boost stage followed by DC-AC conversion) is used for DC to AC conversion from photovoltaic elements, then the conversion function is achieved, but the design becomes complex and bulky
Solution Approach 1:
The patent combines the DC-DC boost stage and DC-AC conversion stage into a single integrated converter topology. The circuit uses a resonant tank circuit with inductor L1 and capacitor C1 that simultaneously performs voltage boosting and AC waveform generation, eliminating the need for separate conversion stages while maintaining reliable conversion function.
Solution Approach 2:
The converter circuit is designed to perform multiple functions simultaneously: the switching circuit controls both the boosting operation and the AC output generation, while the resonant tank circuit provides both voltage transformation and waveform shaping. This multi-functional design reduces overall system complexity while ensuring reliable conversion.
2Weight of moving object
If multiple conversion stages are used for DC to AC conversion, then the conversion function is achieved, but the converter size and weight increase
Solution Approach 1:
The patent merges the DC-DC boost stage and DC-AC conversion stage into a single integrated converter topology. The circuit uses a resonant tank circuit with inductor L1 and capacitor C1 that simultaneously performs voltage boosting and AC waveform generation, eliminating the need for separate conversion stages while maintaining reliable conversion function.
3Loss of energy
If conventional converter topology is used for DC to AC conversion, then the conversion function is achieved, but energy efficiency is reduced
Solution Approach 1:
The patent employs periodic switching of the controllable switches S1 and S2 in conjunction with the resonant tank circuit to achieve efficient energy transfer. The periodic switching allows the circuit to operate in resonant modes that minimize energy losses while maintaining reliable DC to AC conversion function.
Data Source
AI summary
The application relates to an electric converter for converting AC or DC input into an electric AC or DC output. A swap circuit with controllable electric switches serves to selectively swap connection of a plurality of DC power banks (DCBs) between an input terminal and an output terminal, thus selectively connecting the DCBs to an electric source or an electric load. The DCBs are formed as series of interconnected submodules (SMs) each having electric energy storage elements (ESEs) and a switching circuit for selectively by-passing or connecting the ESEs. By properly controlling the swap circuit and the switching of the SMs, the converter can be used for DC-AC, DC-DC, AC-DC, or AC-AC conversion, allowing multilevel output.