Photovoltaic Module String Layout for Localized Shading Bypass
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Solution Overview
Problem
Conventional photovoltaic modules experience significant power generation efficiency loss due to shading of a part of the photovoltaic cells, which activates bypass diodes and reduces power output in multiple connected strings, leading to hot spots and potential cell damage.
Innovation Solution
The photovoltaic module is configured with photovoltaic cell connection units connected in series and turn-back portions, where each unit is connected in parallel with bypass diodes, allowing shaded units to be bypassed without affecting the entire string, and output wiring members are sealed or drawn out to the terminal box.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bypass diodes are provided inside a terminal box for the entire photovoltaic string, then power generation continuity is maintained when a string fails, but shading of a part of the photovoltaic cells causes significant power loss in multiple connected strings
Solution Approach 1:
The photovoltaic string is divided into multiple photovoltaic cell connection units, each with its own bypass diode. This segmentation allows individual units to be bypassed independently when shaded, preventing the entire string from losing power. The patent applies this by creating separate connection units (e.g., 21a, 21b, 21c) that can operate independently, so shading in one unit does not affect others.
Solution Approach 2:
Bypass diodes are introduced as intermediary components between the photovoltaic cell connection units and the terminal box. These diodes act as mediators that redirect current flow around shaded units, preventing them from becoming bottlenecks. The patent shows bypass diodes (e.g., 43a, 43b, 43c) connected in parallel with each connection unit, allowing current to bypass shaded cells while maintaining overall string operation.
2Power
If photovoltaic cells are connected in series to form multiple lines, then power generation capacity is increased, but shading in one cell causes activation of bypass diodes and reduces power output in connected strings
Solution Approach 1:
The series-connected photovoltaic cells are segmented into smaller connection units, each capable of independent bypass operation. This allows the system to maintain high power capacity through series connection while limiting the impact of shading to only the affected segment. The patent implements this by dividing the string into units like 21a, 21b, 21c, where each unit has its own bypass path.
Solution Approach 2:
The electrical configuration parameters are changed by introducing parallel bypass paths for each connection unit. This modifies the circuit topology from a simple series connection to a more complex arrangement where each unit can independently switch between series and bypass modes. The patent shows this parameter change through the connection of bypass diodes in parallel with each photovoltaic cell connection unit, allowing dynamic adjustment of current flow paths.
3Ease of operation
If bypass diodes are activated due to shading, then current can flow around shaded cells, but power generation efficiency deteriorates significantly as the entire string output is reduced
Solution Approach 1:
The photovoltaic string is segmented into independent connection units, each with its own bypass diode. This segmentation ensures that when a bypass is activated, only the affected unit is bypassed rather than the entire string. The patent applies this by creating separate units (21a, 21b, 21c) that can be independently bypassed, maintaining power generation in unaffected units.
Solution Approach 2:
Each photovoltaic cell connection unit is given the local quality of having its own bypass diode, allowing localized bypass operation. This means that bypass action is confined to the specific unit experiencing shading, rather than affecting the entire string. The patent demonstrates this local quality by equipping each unit with dedicated bypass components, enabling selective bypassing based on local conditions.
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 configuration minimizes the impact of shading on power generation efficiency by isolating affected units, preventing hot spots and maintaining overall power output by bypassing shaded cells, thus enhancing power generation efficiency.
Implementation Method 1
The bypass diodes are electrically connected in parallel with the respective photovoltaic strings. When a trouble occurs in a part of the photovoltaic strings, an electric current is allowed to flow without passing the troubled photovoltaic string(s).
Implementation Method 2
A photovoltaic module includes photovoltaic strings in which a plurality of photovoltaic cells as power generating elements is electrically connected in series.
Data Source
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AI summary
A photovoltaic module includes a plurality of photovoltaic cell connection units in each of which a plurality of photovoltaic cells adjacent to each other in a first direction is connected in series with each other. Two of the photovoltaic cell connection units, the two being adjacent in a second direction orthogonal to the first direction, are connected in series with each other by bus bars to constitute a photovoltaic string. An end of an output wiring member is connected to a starting end or a terminating end of the photovoltaic cell connection unit, and another end of the output wiring member establishes electrical continuity with a terminal box. The terminal box includes bypass diodes, and each of the plurality of photovoltaic cell connection units is connected in parallel with corresponding one of the bypass diodes.