Ground Fault Detection Device for Photovoltaic Strings
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing ground fault detection devices for photovoltaic strings face challenges when detecting faults while the power conditioner is operational, as high currents may flow through the switching section, requiring components resistant to high currents, which are costly and oversized.
Innovation Solution
A ground fault detection device that includes a stop determination unit to assess when the power converter is in stoppage, allowing electrical disconnection between the solar battery and power converter, and using a disconnection unit with relays to detect faults based on voltage and current conditions, eliminating the need for high-current-resistant components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ground fault detection is performed while the power converter is in operation, then ground fault detection capability is maintained, but high current flows through the switching section requiring expensive high-current-resistant components
Solution Approach 1:
The patent applies dynamics by making the switching section state-variable: it switches between connected and disconnected states based on operational conditions. The control unit determines when to disconnect based on voltage and current thresholds, allowing ground fault detection during low-current stoppage periods while maintaining system connectivity during normal operation. This dynamic switching resolves the contradiction by ensuring high current flows only when necessary for power conversion, not during detection phases.
Solution Approach 2:
The patent implements periodic action by performing ground fault detection during periodic stoppage intervals of the power converter. The control unit monitors voltage and current values over time, disconnecting the switching section during stoppage periods when current is low, and reconnecting during operation periods. This periodic disconnection enables ground fault detection without requiring continuous high-current capability, thus reducing component specifications and costs.
2Productivity
If the switching section remains connected during operation, then power conversion continues uninterrupted, but ground fault detection cannot be performed without causing system interruption
Solution Approach 1:
The patent applies preliminary action by performing ground fault detection during stoppage intervals before the next operation cycle begins. The control unit detects ground faults by measuring voltage and current when the switching section is disconnected, ensuring detection accuracy without interrupting overall system productivity. This preliminary detection during low-current periods allows the system to resume operation with confirmed safety, resolving the contradiction between continuous productivity and detection accuracy.
3Power
If components resistant to great current are used for the switching section, then the system can handle operational currents, but the device size and cost increase
Solution Approach 1:
The patent applies parameter changes by altering the current flow conditions through temporal switching. Instead of designing the switching section to continuously handle high current, the system changes the operational parameter of current flow by disconnecting during detection phases. This allows the use of smaller, less expensive components that only need to handle high current during brief operation intervals, rather than continuously, thus reducing volume and cost while maintaining required power handling capability.
Data Source
AI summary
When a ground fault detection device detects a ground fault of a photovoltaic string, for example, while a power conditioner is in operation, a great current may be flowing in a switching section from the photovoltaic string, so that components resistant to a great current have been used for the switching section. A ground fault detection device includes a stop determination unit configured to determine whether a power converter for converting electric power from a solar battery is in stoppage, and a ground fault detector configured to detect a ground fault of the solar battery in a state where the solar battery and the power converter are electrically disconnected from each other by a disconnection unit arranged between the solar battery and the power converter when the stop determination unit determines that the power converter is in stoppage.