PV String Trip Switch Control for Reverse Wiring Protection
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Solution Overview
Problem
When multiple photovoltaic module strings are connected in parallel, a reverse connection in one or more module strings can cause the switching power supply to fail, leading to the injection of current from correctly connected strings into the reverse-connected ones, potentially damaging the battery cells.
Innovation Solution
A photovoltaic system is designed with a power taking circuit, a trip switch, a switching power supply, and a controller. The power taking circuit directly supplies power to the switching power supply, which in turn powers the controller and trip switch. The controller can disconnect the trip switch if a wiring fault, such as a reverse connection, is detected.
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 current injection and battery cell damage increases
Solution Approach 1:
The trip switch is configured to automatically disconnect the photovoltaic module strings from the power taking circuit when reverse connection is detected, preventing reverse current from flowing into the battery cells. This preliminary protective action occurs before damage can occur, resolving the contradiction by enabling parallel connection for increased power while mitigating the reverse current hazard through automated detection and disconnection
Solution Approach 2:
The trip switch serves as an intermediary protective device between the photovoltaic module strings and the battery cells. It monitors the connection status and interrupts the circuit when reverse connection is detected, thereby protecting the battery cells from reverse current damage while allowing the system to operate at higher power levels when properly connected
2Device complexity
If the switching power supply is used to power the controller and trip switch, then the system integration is improved, but the system fails to operate when reverse connection occurs because the switching power supply cannot function
Solution Approach 1:
The system uses the power taking circuit to directly supply power to the switching power supply, which in turn powers the controller and trip switch. When reverse connection is detected, the trip switch disconnects the faulty strings, allowing the power taking circuit to continue operating and maintaining power supply to the control system. This self-service approach resolves the contradiction by enabling the system to maintain operation under fault conditions while keeping the design integrated
3Loss of energy
If the trip switch is closed to enable current flow, then the power transmission efficiency is improved, but the reverse-connected strings will burn when reverse connection exists
Solution Approach 1:
The controller continuously monitors the connection status of photovoltaic module strings and provides feedback to the trip switch. When reverse connection is detected, the controller signals the trip switch to open, preventing reverse current damage. When proper connection is confirmed, the trip switch closes to enable efficient power transmission. This feedback mechanism resolves the contradiction by dynamically controlling the trip switch state based on real-time connection status
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration prevents the reverse-connected photovoltaic module strings from burning by ensuring the trip switch remains open when a reverse connection is detected, thereby avoiding the flow of reverse current and protecting the battery cells.
Implementation Method 1
each photovoltaic module includes a plurality of battery cells connected in series
Data Source
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AI summary
The present application discloses a photovoltaic system and a control method. The photovoltaic system comprises at least two photovoltaic strings, a power acquisition loop, a trip switch, a switch mode power supply, and a controller. The at least two photovoltaic strings are connected in series or in parallel; the trip switch is connected between the photovoltaic strings and an input end of a converter; the power acquisition loop is used for acquiring power from at least one photovoltaic string and supplying power to the switch mode power supply; the switch mode power supply is used for supplying power to the controller and the trip switch when the power acquisition loop supplies power normally; and the controller is used for controlling, when a wiring fault occurs to the at least two photovoltaic strings connected in parallel, the trip switch to be switched off. The power acquisition loop is specially provided, and the power acquisition loop can directly acquire power from the photovoltaic strings and supply power to the switch mode power supply. When the photovoltaic strings connected to the power acquisition loop are reversely connected, the switch mode power supply does not work, and the trip switch is not switched off, so that the reversely connected photovoltaic strings are not burnt out.