PV Branch Protection Switching for Low-Loss Short-Circuit Isolation
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Solution Overview
Problem
Conventional photovoltaic power generation systems face challenges in effectively protecting photovoltaic units and lines from short-circuit faults due to high fuse currents and large resistance losses, leading to inadequate protection and increased power losses.
Innovation Solution
A protection apparatus with a controller and protection switches is introduced, which connects photovoltaic units in parallel to manage short-circuit currents within tolerable ranges, reducing the need for fuses and minimizing power losses by using a protection switch with lower resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fuses are connected in series with photovoltaic units to protect against short-circuit faults, then protection capability is improved, but power loss increases due to large fuse resistance
Solution Approach 1:
The patent changes the resistance parameter by replacing fuses with protection switches that have significantly lower resistance. This allows the system to maintain protection capability while reducing power loss from resistance heating.
Solution Approach 2:
The patent substitutes the mechanical fuse (which relies on thermal melting) with an electronically controlled protection switch. This substitution enables active control of current interruption while maintaining lower resistance during normal operation.
2Power
If multiple photovoltaic units are connected in parallel to increase output power, then power generation capacity is improved, but short-circuit current increases making protection more difficult
Solution Approach 1:
The patent segments the parallel-connected photovoltaic units by introducing individual protection switches for each unit. This segmentation allows independent control and isolation of faulty units while maintaining operation of healthy units.
Solution Approach 2:
The patent introduces protection switches as intermediary devices between photovoltaic units and the electrical system. These switches act as mediators that can rapidly interrupt fault currents while allowing normal power transmission.
3Power
If fuses with high current ratings are used to accommodate multiple parallel photovoltaic units, then system capacity is improved, but protection sensitivity decreases because short-circuit current rarely reaches fuse rating
Solution Approach 1:
The patent introduces dynamic control capability through electronically controlled protection switches that can respond rapidly to fault conditions. This dynamic response enables effective protection at various current levels unlike static fuses.
Solution Approach 2:
The patent implements feedback control by using controllers that monitor system conditions and actively control the protection switches. This feedback mechanism enables sensitive detection and response to fault conditions while maintaining high system capacity.
Data Source
AI summary
A protection apparatus includes an interface, a protection switch, a direct current bus, and a controller. The apparatus is connected to at least two photovoltaic units via the interface, the at least two photovoltaic units are coupled to the direct current bus inside the apparatus to form at least two branches, and each branch is connected to at least one photovoltaic unit. The protection switch is configured to disconnect all or some of the photovoltaic units from the direct current bus, to enable a maximum of three photovoltaic units to be directly connected in parallel. According to the apparatus, a photovoltaic unit and a line are protected with a low power loss when a photovoltaic power generation system is faulty.