PV Branch Protection Switching for Low-Loss Fault Isolation
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Solution Overview
Problem
Existing photovoltaic power generation systems face inefficiencies in protecting photovoltaic units and lines from short-circuit currents due to high fuse currents and large resistance, leading to ineffective protection and increased power loss.
Innovation Solution
A protection apparatus and method that utilizes protection switches to connect a maximum of three photovoltaic units in parallel, with a controller determining fault conditions to open the switches, reducing reliance on fuses and minimizing resistance and power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a photovoltaic unit or line is faulty, then the system needs to disconnect the faulty unit to protect the system, but this causes power loss from healthy units
Solution Approach 1:
The direct current side is segmented into multiple independent branches, each with its own protection switch. When a fault occurs in one branch, only the protection switch of that specific branch opens, isolating the faulty unit while keeping other branches connected and operational, thus protecting the system while minimizing power loss from healthy units
Solution Approach 2:
The protection switch is designed to dynamically adjust the connection state based on fault detection. The controller monitors parameters in real-time and controls the protection switch to open or close accordingly, enabling the system to adaptively respond to faults and maintain optimal power generation from healthy units
2Power
If series connection is used to increase output voltage, then the output voltage increases, but a single fault causes the entire string to stop working
Solution Approach 1:
The series-connected string is divided into multiple parallel branches, each capable of independent operation. This segmentation allows the system to maintain output voltage through parallel configuration while ensuring that a fault in one branch does not affect other branches, thus improving system continuity and reliability
Solution Approach 2:
The system changes the connection configuration parameter from pure series to parallel combination of branches. By adjusting the connection topology, the system achieves both high output voltage (through series connection within branches) and high reliability (through parallel branching that isolates faults)
3Power
If parallel connection is used to increase output current, then the output current increases, but the system becomes more complex
Solution Approach 1:
The parallel connection is implemented through segmented branches rather than a complex mesh network. Each branch is an independent series connection of photovoltaic units, making the parallel structure systematic and manageable. This segmentation approach increases output current while keeping the system structure clear and complexity controlled
Solution Approach 2:
Each branch is designed with universal characteristics - same series connection structure and independent protection capability. This universality allows the system to scale by simply adding identical branches, increasing output current without proportionally increasing system complexity, as each branch serves multiple functions including voltage generation, current contribution, and independent fault isolation
Data Source
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Figure 6A
AI summary
This application discloses a protection apparatus and a protection method for a photovoltaic power generation system and a photovoltaic power generation system, and relates to the field of photovoltaic power generation technologies. The 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 by using 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. The controller is configured to: when determining, based on a parameter detection value of the branch or a parameter detection value of the direct current bus, that the photovoltaic power generation system is faulty, control the protection switch to be open. According to the apparatus, a photovoltaic unit and a line can be effectively protected with a low power loss when the photovoltaic power generation system is faulty.