Photovoltaic Inverter Fault Isolation via Bypass Circuit
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Solution Overview
Problem
Photovoltaic inverters face challenges in preventing the further spread of faults, such as short-circuits and overvoltages, which can lead to continuous energy injection into faulty points, causing damage and increased costs due to high current surges and voltage imbalances.
Innovation Solution
The photovoltaic inverter incorporates a DC/AC converter, a drive control circuit, a bypass circuit, and an isolation circuit, where the drive control circuit disconnects the isolation circuit after connecting the bypass circuit to prevent energy flow to faulty points, ensuring low-current disconnection and reducing the risk of damage to the isolation circuit, thereby minimizing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the isolation circuit is directly disconnected without connecting the bypass circuit first, then the disconnection speed is fast, but high current surges will occur causing damage to the isolation circuit
Solution Approach 1:
The bypass circuit is connected before disconnecting the isolation circuit. This preliminary action creates an alternative current path that prevents high current surges when the isolation circuit is disconnected, protecting the isolation circuit from damage while maintaining fast disconnection capability.
Solution Approach 2:
The bypass circuit acts as a cushioning mechanism that absorbs and redirects current flow before the isolation circuit is disconnected. By establishing this protective pathway in advance, the system prevents harmful current surges from damaging the isolation circuit during the disconnection process.
2Productivity
If the photovoltaic module remains connected during bus faults, then continuous energy generation is maintained, but fault spread and system damage occur
Solution Approach 1:
The system segments the photovoltaic module connection from the faulty bus through the isolation circuit. This segmentation allows the module to be electrically separated from the fault while maintaining physical connection, enabling fault isolation without complete system shutdown and facilitating selective repair.
Solution Approach 2:
The isolation circuit and bypass circuit serve as intermediary components between the photovoltaic module and the bus system. These intermediaries enable controlled disconnection and protection, allowing the module to be isolated from faults while maintaining the ability to reconnect safely when the fault is resolved.
3Reliability
If complex protection circuits are added to prevent fault spread, then system safety is improved, but device complexity and cost increase
Solution Approach 1:
The bypass circuit serves multiple functions: it provides an alternative current path during isolation, protects against high current surges, and enables safe disconnection of the isolation circuit. This multi-functionality reduces the need for separate protection components, simplifying the overall circuit structure while maintaining comprehensive fault protection.
Solution Approach 2:
The system uses temporary bypass connections during fault conditions that can be discarded when the fault is resolved. The bypass circuit is activated only when needed for protection and can be deactivated or removed after the isolation circuit is safely disconnected, reducing permanent complexity in the system design.
Data Source
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AI summary
This application provides a photovoltaic inverter, including a DC/AC converter, a positive direct current bus, a negative direct current bus, a drive control circuit, and at least one first unit. A first end of the positive direct current bus and a first end of the negative direct current bus are electrically connected to the DC/AC converter respectively. The first unit includes a first bypass circuit and an isolation circuit. After the drive control circuit is configured to detect that the positive direct current bus and the negative direct current bus are faulty, the drive control circuit is configured to control a first end and a second end of the first bypass circuit to be connected and is configured to control a first end and a second end of the isolation circuit to be disconnected, so that the first photovoltaic module is disconnected from the positive direct current bus or the negative direct current bus, where a time point at which the isolation circuit is disconnected is later than a time point at which the first bypass circuit is connected.