PV String Trip Switch Control for Reverse Connection Faults
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Solution Overview
Problem
When multiple photovoltaic module strings are connected in parallel, a reverse connection in one or more strings can cause the current from correctly connected strings to be injected, leading to system failure and potential damage to battery cells due to large reverse currents.
Innovation Solution
A photovoltaic system with a power taking circuit that directly supplies power to a switching power supply and controller, allowing the controller to disconnect a trip switch when a reverse connection is detected, preventing the reversely connected module strings from burning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple photovoltaic module strings are connected in parallel to increase power output, then the power generation capacity is improved, but the risk of reverse connection causing system failure and component damage increases
Solution Approach 1:
The patent implements preliminary detection of reverse connection before the switch is closed. The controller detects whether any photovoltaic module string is reversely connected through voltage polarity detection. If reverse connection is detected, the controller prevents the switch from closing, thereby avoiding the harmful effect of reverse current injection and protecting the system from failure.
Solution Approach 2:
The patent employs feedback control by continuously monitoring the voltage polarity of each photovoltaic module string and providing feedback to the controller. Based on this feedback, the controller makes real-time decisions about whether to close or open the switch, ensuring system safety while maximizing power generation.
2Productivity
If the switch is closed to enable power generation, then the productivity is improved, but the harmful effect of reverse current injection occurs when reverse connection exists
Solution Approach 1:
The patent applies preliminary anti-action by detecting reverse connection conditions before closing the switch. When reverse connection is detected, the controller prevents switch closure, thereby counteracting the potential harmful effect of reverse current injection before it can occur. This ensures that productivity is maximized only when safe operating conditions are met.
3Ease of operation
If the switching power supply operates normally to control the trip switch, then the ease of operation is improved, but the system becomes unable to respond when reverse connection prevents normal operation
Solution Approach 1:
The patent implements preliminary detection of reverse connection conditions before the switching power supply operates. The controller detects reverse connection through voltage polarity detection and takes preliminary action to prevent switch closure or to open the trip switch if reverse connection is detected after closure. This ensures the system can respond to faults even when reverse connection prevents normal switching power supply operation.
Data Source
AI summary
Provided are a photovoltaic system and a control method. The system comprises: a conversion circuit, a power taking circuit, a trip switch, a switching power supply and a controller. The trip switch is connected between the conversion circuit and an input end of a converter. The power taking circuit is configured to take power from at least one photovoltaic module string and supply power to the switching power supply. The switching power supply is configured to supply power to the controller and the trip switch when the power taking circuit provides power normally. The controller is configured to, when a photovoltaic module string has a fault, at least disconnect the trip switch corresponding to the fault photovoltaic module string, to disconnect connection between the faulty photovoltaic string and the conversion circuit.