PV Branch Protection Switch for Low-Loss Short-Circuit Isolation
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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 sum of short-circuit currents from multiple photovoltaic units, leading to inadequate 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 the resistance is too large causing power loss
Solution Approach 1:
The patent changes the current rating parameter of the protection device from high (fuse) to matched (protection switch rated at sum of individual unit currents), and changes the resistance parameter from large (fuse) to small (protection switch), thereby achieving both effective protection and low power loss
Solution Approach 2:
The patent uses a protection switch that replicates the protection function of fuses but with improved characteristics - the protection switch can be controlled to open at precise current thresholds and has lower resistance, copying the protective function while eliminating the drawbacks of fuses
2Power
If multiple photovoltaic units are connected in parallel to improve power generation, then output power increases, but short-circuit current sum exceeds protection capability
Solution Approach 1:
The patent implements dynamic protection by using a controllable protection switch that can adjust its operation based on real-time current conditions, allowing the system to safely accommodate multiple parallel units while maintaining protection capability through active control rather than static fuse ratings
Solution Approach 2:
The patent employs feedback control where the controller monitors the current through the protection switch and the controller opens the switch when short-circuit current is detected, creating a closed-loop protection system that adapts to the actual operating conditions of multiple parallel photovoltaic units
3Adaptability or versatility
If fuse current rating is increased to handle multiple photovoltaic units, then protection coverage expands, but protection effectiveness decreases
Solution Approach 1:
The patent creates a universal protection solution where a single protection switch can protect multiple photovoltaic units in parallel by rating it at the sum of their individual currents, making the protection device adaptable to different system configurations while maintaining effectiveness through controlled opening action
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.