Solar String Shut-Off Circuit for Low-Power Switching Stability
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Solution Overview
Problem
The operational stability of solar power generation systems is hindered by unstable power generation from solar cell modules, leading to repeated switching between ON and OFF states in shut-off devices, which can prevent system activation and reduce safety during emergencies.
Innovation Solution
A solar power generation system incorporating a primary shut-off device and secondary shut-off devices with semiconductor switching units that cut off power paths based on predetermined thresholds, ensuring stable operation even with low power generation, and including a bypass mechanism to transfer power from one solar cell module group to the inverter when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If power from solar cell modules is used to drive the switching device, then the switching device can be operated without external power supply, but the switching device may repeatedly switch between ON and OFF states when power generation is insufficient or unstable
Solution Approach 1:
A capacitor is introduced as an intermediary energy storage element between the solar cell modules and the switching device. The capacitor accumulates energy during periods of sufficient power generation and releases it during periods of insufficient generation, mediating the power supply to prevent unstable switching operations while maintaining system independence from external power supplies.
2Ease of operation
If mechanical contact switching devices are used to cut off electric paths, then the shut-off function can be achieved, but the devices are susceptible to repeated switching and operational instability
Solution Approach 1:
The patent replaces mechanical contact switching devices with semiconductor switching devices. This substitution eliminates the mechanical wear and contact bounce issues inherent in mechanical switches, providing more reliable and stable switching operations while maintaining the shut-off function. The semiconductor devices offer faster response times and greater durability.
3Device complexity
If a single shut-off device is used to protect against emergencies, then the system structure remains simple, but the protection coverage is limited and operational stability cannot be ensured
Solution Approach 1:
The patent divides the shut-off protection function into multiple independent shut-off devices distributed at different locations in the system. Each shut-off device independently monitors and protects its local section, providing redundant protection coverage. This segmentation approach enhances overall system reliability and emergency protection capability while maintaining relatively simple individual device structures.
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
The system maintains stable operation by ensuring the shut-off devices remain in a closed state even with low power generation, preventing unstable switching and enhancing safety by reliably disconnecting power during emergencies.
Implementation Method 1
The semiconductor switching device is configured to enter an OFF state when an amount of power generated by the associated solar cell module group falls below a predetermined threshold
Implementation Method 2
The power to drive the switching device is supplied from solar cell modules of the solar power generation system. That is, the power generated by the solar cell modules is used to drive an external device
Data Source
AI summary
The solar power generation system includes a string, an inverter, and primary and secondary shut-off devices. The primary shut-off device cuts off the string and the inverter in response to a first control signal. The secondary shut-off device cuts off a solar cell module group and another solar cell module or the inverter in response to a second control signal from the primary shut-off device. The secondary shut-off device includes a first secondary-device open-close unit in a first electric pathway, a semiconductor switching device disposed between the first secondary-device open-close unit and a solar cell module group, and a power supply unit having an anode-side terminal connected between a solar cell module group and the semiconductor switching device, which generates power to drive the third open-close unit. The semiconductor switching device enters an OFF state when power generated by the solar cell module groups falls below a predetermined threshold.