PV Inverter Protection Switch for Short-Circuit Current Limiting
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Solution Overview
Problem
Existing photovoltaic power generation systems face challenges in effectively protecting photovoltaic units and lines from short-circuit currents, as fuses used for protection have high current ratings that are rarely exceeded by the combined output currents of multiple photovoltaic units, leading to ineffective protection and significant power losses.
Innovation Solution
A protection apparatus is introduced that includes an interface, a protection switch, a direct current bus, and a controller. This apparatus connects to at least two photovoltaic units, forming branches that are connected in parallel, allowing for a maximum of three photovoltaic units to be directly connected in parallel. The controller detects faults based on parameter detection values and controls the protection switch to open, ensuring that short-circuit currents remain within tolerable limits for the faulty photovoltaic unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fuses are used to protect photovoltaic units and lines from short-circuit currents, then protection is provided, but the fuse current rating is too high to effectively blow and protect, and power losses increase due to fuse resistance
Solution Approach 1:
The patent divides the protection function into two parts: a protection switch that limits short-circuit current to tolerable levels, and a fuse that operates at lower current ratings. This segmentation allows the fuse to actually blow and protect effectively while the protection switch prevents excessive current from overwhelming the system.
Solution Approach 2:
The protection switch performs preliminary action by detecting faults and opening the circuit before excessive short-circuit current can damage the photovoltaic units or lines. This preliminary protection action prevents the need for high-rated fuses and reduces power losses during normal operation.
2Power
If multiple photovoltaic units are connected in parallel to improve power generation capacity, then output power increases, but short-circuit current increases making effective fuse protection more difficult
Solution Approach 1:
The patent segments the protection function between a protection switch that handles high current limiting and a fuse that provides backup protection. This allows multiple photovoltaic units to be connected in parallel to increase power output while maintaining effective protection through the coordinated action of both components.
Solution Approach 2:
The protection switch acts as an intermediary between multiple photovoltaic units and the fuse. It detects faults and opens the circuit before excessive current reaches the fuse, allowing the fuse to operate at lower current ratings even when multiple units are connected in parallel.
3Reliability
If fuses are installed in series with photovoltaic units, then protection is provided, but cable costs increase due to the need for Y harness
Solution Approach 1:
The protection switch provides multi-functionality by serving both as a protection device and as a circuit configuration element. It can be installed in a single location to protect multiple photovoltaic units, eliminating the need for separate fuses and Y harness connections for each unit, thus reducing cable costs while maintaining comprehensive protection coverage.
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 inverter is faulty.