PV Junction Output Layout for Lower-Cost DC Cable Transmission
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Solution Overview
Problem
In photovoltaic power stations, the skin effect reduces the withstand current per unit area of conducting wires, leading to high costs for cables when the current of electric energy output is high.
Innovation Solution
A photovoltaic system is designed with a junction device that transmits direct currents to an inverter through multiple outputs, reducing the current of each output and thereby reducing cable costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a junction device converges direct currents from multiple photovoltaic strings into a single high-current output, then the system achieves centralized power transmission, but the cable costs increase due to the skin effect reducing withstand current per unit area
Solution Approach 1:
The junction device divides the converged direct current into multiple output currents through multiple output terminals. Instead of transmitting one high-current stream, the system transmits multiple lower-current streams in parallel, reducing the skin effect impact and cable costs for each transmission path
Solution Approach 2:
The system transitions from a single-dimensional high-current transmission path to a multi-dimensional parallel transmission structure. By utilizing multiple output terminals simultaneously, the current distribution moves from a concentrated single path to a distributed multi-path configuration, effectively reducing the current burden on each individual cable
2Productivity
If DC-DC conversion circuits are added to each junction device for maximum power point tracking, then power generation efficiency is improved, but device complexity increases
Solution Approach 1:
The DC-DC conversion circuit is designed to perform multiple functions within a single integrated system: it enables maximum power point tracking to optimize power generation efficiency while simultaneously managing current conversion and distribution. This multi-functional approach consolidates what could be separate components into one unified device, managing complexity through functional integration
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
The system effectively reduces cable costs by minimizing the current through each output, while also improving power generation efficiency through DC-DC conversion and maximum power point tracking.
Implementation Method 1
Each photovoltaic string includes a first direct current output terminal, and is configured to generate a first direct current
Implementation Method 2
each junction device includes at least one direct current (direct current, DC)-DC conversion circuit, and each DC-DC conversion circuit performs DC-DC conversion on at least one first direct current
Data Source
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AI summary
This application provides a photovoltaic system, including a plurality of photovoltaic strings, at least one junction device, and at least one inverter. Each photovoltaic string includes a first direct current output terminal, and is configured to generate a first direct current. Each junction device is connected to the plurality of photovoltaic strings. Each junction device is configured to output second direct currents through second direct current output terminals of the junction device after converging a plurality of first direct currents. An ith junction device includes a plurality of second direct current output terminals. The ith junction device is configured to output a plurality of mutually independent second direct currents after converging a plurality of first direct currents, and i is a positive integer. A quantity of the plurality of second direct currents is less than a quantity of the plurality of first direct currents. The at least one inverter is configured to convert the plurality of second direct currents into an alternating current. The junction device outputs a plurality of direct currents, so that a current of each direct current can be reduced, thereby reducing costs of a cable used to transmit the direct currents output by the junction device.