DC Power Combiner Circuit for Shaded Photovoltaic Cell Strings
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Solution Overview
Problem
Photovoltaic systems face inefficiencies due to current variations in serially connected multi-junction cells, particularly during partial shading, leading to power losses from shorted cells and increased ohmic losses in parallel connections, which are not practically feasible due to differing MPP voltages across stacked pn junctions.
Innovation Solution
The implementation of a power combiner circuit using inductive elements like transformers and MOSFETs to combine multiple voltage inputs from serially connected photovoltaic cells, ensuring equal voltage ratios and maximizing power output by adjusting switching cycles to maintain optimal operating points across all cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple multi-junction cells are connected in series to form a photovoltaic panel, then the voltage output increases, but current variations due to partial shading cause power losses from shorted cells
Solution Approach 1:
The patent segments the series-connected photovoltaic cells into multiple parallel groups, where each group contains cells connected in series. This segmentation allows independent control of each group through separate inductive elements and switching circuits, enabling the system to bypass shaded cells in one group while maintaining power generation from other groups, thus resolving the power loss problem caused by series connection vulnerabilities to partial shading
Solution Approach 2:
The patent employs dynamic switching circuits with controllable switches (such as MOSFETs or IGBTs) that can rapidly change the connection configuration of photovoltaic cells based on real-time shading conditions. The inductive elements work with these dynamic switches to enable rapid reconfiguration, allowing the system to adapt to varying environmental conditions and maximize power extraction from unshaded cells while isolating shaded ones
2Reliability
If bypass diodes are used to prevent thermal failures in shaded cells, then cell breakdown is prevented, but power generation efficiency decreases due to the bypass path
Solution Approach 1:
The patent implements control circuits that monitor the operating conditions of each photovoltaic cell group and provide feedback to the switching circuits. This feedback mechanism enables the system to detect when a cell is shaded or malfunctioning and automatically adjust the switching configuration to bypass only the affected cells while maintaining optimal power extraction from healthy cells, thus preventing thermal failures without significantly reducing overall power generation efficiency
Solution Approach 2:
The patent employs dynamic switching circuits that can rapidly reconfigure the connection topology in response to real-time cell performance monitoring. Unlike static bypass diodes that permanently create alternative current paths, the dynamic switches enable temporary and selective bypassing of problematic cells only when needed, allowing the system to maintain high power generation efficiency by keeping all cells in the power-generating configuration under normal conditions while providing protection when abnormalities are detected
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 solution effectively compensates for current variations, maximizing power gain by avoiding losses from shorted cells and minimizing ohmic losses, thereby enhancing overall photovoltaic panel efficiency and practicality in varying environmental conditions.
Implementation Method 1
inductive elements like transformers and MOSFETs to combine multiple voltage inputs
Data Source
Figure 1~2
Figure 3
Figure 4~5b
AI summary
A circuit for combining direct current (DC) power including multiple direct current (DC) voltage inputs; multiple inductive elements. The inductive elements are adapted for operatively connecting respectively to the DC voltage inputs. Multiple switches connect respectively with the inductive elements. A controller is configured to periodically switch the switches. A direct current voltage output is connected across one of the DC voltage inputs and a common reference to both the inputs and the output.