Solar String Shut-Off Circuit for Stable Self-Powered Switching
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Solution Overview
Problem
The installation cost of shut-off devices in solar power generation systems is high, and the instability of power generation can lead to unstable operation due to the reliance on solar cell module power for driving switching devices, causing repeated switching between ON and OFF states when power is insufficient.
Innovation Solution
A solar power generation system with multiple solar cell module groups, each with a shut-off device comprising a semiconductor switching device and power supply unit that maintains the open-close unit in an ON state even when power is small or unstable, using a bypass device to transfer power from other groups when necessary, and communicating control signals via power line or wireless communication to reduce additional wiring and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shut-off device is installed for each solar cell module to improve firefighter safety, then the safety of firefighters is improved, but the installation cost of shut-off devices increases
Solution Approach 1:
The solar cell modules are divided into multiple groups (first group, second group, third group, etc.), and shut-off devices are installed at the group level rather than at each individual module level. This segmentation approach maintains safety by ensuring that each group has adequate voltage limitations while significantly reducing the number of shut-off devices required, thereby lowering installation costs.
Solution Approach 2:
A semiconductor switching device is introduced as an intermediary component between the solar cell groups and the mechanical contactor. The semiconductor switching device controls the power flow and enables the mechanical contactor to operate reliably, preventing contact welding issues while maintaining the reduced shut-off device configuration.
2Loss of time
If the switching device is driven by power from solar cell modules, then the system uses self-generated power, but the operation of the solar power generation system becomes unstable when power generation amount drops or fluctuates
Solution Approach 1:
The power supply unit is designed with sufficient power generation capability to handle not only the normal operation of the shut-off device but also to provide a power buffer during fluctuations in solar cell output. This ensures that the semiconductor switching device and mechanical contactor can operate reliably even when solar cell power generation drops or becomes unstable, preventing repeated switching of the contactor.
3Extent of automation
If the contactor is closed with power from solar cell modules, then the system operates with self-powered switching, but the contact opens immediately when power is insufficient, causing repeated closing and opening
Solution Approach 1:
The semiconductor switching device serves as an intermediary that mediates between the solar cell power output and the mechanical contactor. It provides precise control of the power flow, ensuring that sufficient and stable power is delivered to the contactor coil for reliable actuation, thereby preventing contact welding and repeated switching even when overall system power fluctuates.
Solution Approach 2:
The power supply unit is designed to dynamically adjust its power output parameters to match the specific requirements of the semiconductor switching device and mechanical contactor. By optimizing the voltage and current parameters, the system ensures stable actuation of the contactor while preventing contact welding, even during solar cell power fluctuations.
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 reduces installation costs and enhances system stability by ensuring continuous operation even with unstable power generation, maintaining the open-close units in an ON state and preventing frequent switching, thus providing a safer and more reliable solar power generation system.
Implementation Method 1
a plurality of solar cell modules 6 connected in series
Implementation Method 2
an inverter 3 connected to the string 2 for converting DC power output from the solar cell modules 6 to AC power
Data Source
AI summary
A solar power generation system includes a string, an inverter, and a plurality of shut-off devices. The string includes a plurality of solar cell module groups. The plurality of shut-off devices are configured to cut off a connection between the plurality of solar cell module groups. The plurality of solar cell module groups include a first group, a second group connected to the first group, and a third group connected to the second group. The plurality of shut-off devices includes a first open-close unit connected to the second group, a semiconductor switching device connected in series to the first open-close unit, and a power supply unit connected to the second group and configured to generate power to drive the first open-close unit. The semiconductor switching device enters an OFF state when an amount of power generated by second group is smaller than a predetermined threshold.