Photovoltaic Shutdown Circuit for Long-Distance PLC Signal Detection
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Solution Overview
Problem
Current photovoltaic shutdown systems face challenges in identifying controlling signals from generators more than 300 meters away due to interference from ripples in the DC busbar, particularly from inverters, leading to unstable operation.
Innovation Solution
A photovoltaic shutdown circuit comprising a signal receiving module, signal processing module, and controllable switch module, which includes a signal modulation unit, threshold comparison unit, amplification unit, and time delay unit to revert and amplify controlling signals, filter out interference, and control the switch module for reliable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PLC signal transmission is used for photovoltaic shutdown control, then the system can achieve automated shutdown function, but the signal becomes too weak beyond 300 meters and cannot resist interference from inverter ripples
Solution Approach 1:
The patent introduces an intermediary signal processing mechanism that mediates between the PLC control signal and the shutdown execution. The signal processing module acts as a mediator that receives the weak PLC signal, processes it through multiple stages (signal detection, amplification, filtering, modulation), and converts it into a robust control signal for the shutdown switch, thereby resolving the conflict between long-distance signal transmission and interference resistance.
Solution Approach 2:
The patent applies parameter changes by transforming the PLC signal through multiple processing stages that change its amplitude, frequency, and waveform characteristics. The signal amplification stage increases amplitude, the filtering stage modifies frequency content by removing ripple interference, and the modulation stage changes the signal waveform into a triangular wave pattern that is more resistant to interference during transmission over long distances.
2Length of moving object
If signal amplification is applied to strengthen the PLC signal, then the signal can be transmitted beyond 300 meters, but the inverter ripple interference is also amplified
Solution Approach 1:
The patent extracts the harmful ripple interference component from the amplified signal through the filtering module. After the signal amplification stage boosts both the useful PLC signal and the harmful inverter ripple, the filtering stage selectively removes the ripple frequency components while preserving the control signal, thereby achieving long-distance transmission without propagating the interference.
Solution Approach 2:
The patent converts the harmful ripple interference into a beneficial filtering opportunity. By intentionally amplifying the signal first (which also amplifies the ripple), the system creates a stronger signal-to-noise ratio that allows subsequent filtering stages to more effectively remove the ripple components, transforming the initially harmful amplification of interference into a useful step for achieving clean long-distance signal transmission.
3Reliability
If complex signal processing modules are added to filter interference, then the signal can resist ripple interference, but the device complexity increases
Solution Approach 1:
The patent merges multiple signal processing functions into an integrated signal processing module that combines signal detection, amplification, filtering, and modulation circuits in a unified structure. This consolidation approach reduces the overall device complexity compared to having separate independent modules for each function, while still providing comprehensive interference rejection capabilities through the coordinated operation of all processing stages within the single integrated module.
4Reliability
If standard PLC chips are used for shutdown control, then the system can achieve basic control function, but the cost is high due to capital and order requirements
Solution Approach 1:
The patent replaces expensive, high-reliability PLC chips with more economical signal processing components that can be manufactured at lower cost. The design uses standard electronic components for signal detection, amplification, and filtering that are widely available and inexpensive, sacrificing some of the advanced features of proprietary PLC chips while achieving the essential shutdown control function at a much lower manufacturing cost suitable for commercial photovoltaic applications.
Data Source
AI summary
Disclosed are a photovoltaic shutdown circuit and a photovoltaic system. The photovoltaic shutdown circuit comprises a shutdown power line, a signal receiving module, a signal processing module, and a controllable switch module. The signal processing module comprises a signal modulation unit and a threshold comparison unit. A switch end of the controllable switch module is connected in series to the shutdown power line. The signal receiving module is connected to the shutdown power line for receiving a first signal with a controlling signal; the signal modulation unit is for reverting the controlling signal; the threshold comparison unit is connected to the signal modulation unit to receive the reverted controlling signal and compare the reverted controlling signal with a set threshold to output a driving signal. The controllable switch module is connected to the threshold comparison unit to receive the driving signal and control an on/off of the controllable switch module.