PV Panel Shut-Down Apparatus with Sequential Control Modules
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Solution Overview
Problem
Traditional shut-down apparatuses for photovoltaic plants cause high in-rush currents and incomplete de-energization of photovoltaic panels due to sudden discharge of capacitances, posing safety risks and inefficiencies.
Innovation Solution
A shut-down apparatus with a daisy chain configuration of control modules that sequentially receive and actuate shut-down signals with time delays to progressively de-energize photovoltaic panels, reducing in-rush currents and ensuring complete de-energization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional shut-down apparatus short-circuits the power terminals of photovoltaic panels, then the DC section is de-energized, but high in-rush currents occur due to sudden discharge of capacitances
Solution Approach 1:
The shut-down process is segmented into multiple sequential steps, with each control module de-energizing one photovoltaic panel at a time rather than all panels simultaneously. This segmentation of the de-energization process prevents sudden simultaneous discharge of all capacitances, thereby reducing in-rush currents while maintaining effective de-energization of the DC section
Solution Approach 2:
The control modules are configured to perform preliminary actions by sequentially short-circuiting photovoltaic panels in a controlled manner before complete system shutdown. Each module prepares the system for the next shutdown phase by progressively discharging capacitances in predetermined time intervals, preventing harmful in-rush currents
2Productivity
If traditional shut-down apparatus short-circuits power terminals, then shut-down is achieved, but some panels may remain energized due to connection interruptions creating safety issues
Solution Approach 1:
Each control module incorporates feedback mechanisms to monitor the actual de-energization status of photovoltaic panels. The control modules detect whether panels are properly de-energized and can identify connection interruptions, ensuring complete shutdown and alerting operators to safety issues, thereby eliminating residual safety risks
Solution Approach 2:
The control modules perform preliminary verification actions to ensure complete de-energization before considering the shut-down process complete. By checking each panel's status and detecting connection interruptions, the system ensures no panels remain energized, preventing safety issues for operators
3Object-generated harmful factors
If control modules are configured to sequentially de-energize panels with time delays, then in-rush currents are reduced, but shut-down process duration increases
Solution Approach 1:
The control modules use optimized time delays that are sufficient to reduce in-rush currents but not excessively long. By applying the minimum necessary time intervals between sequential panel de-energization, the system achieves current reduction while minimizing the overall shut-down duration, avoiding unnecessary time loss
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 solution effectively minimizes in-rush currents and ensures complete de-energization of photovoltaic panels, enhancing safety and operational efficiency while allowing for lower impedance designs and cost-effective manufacturing.
Implementation Method 1
Such in-rush currents are due to the sudden discharge of capacitances present in the system, namely the parasitic capacitances of the photovoltaic panels and the input capacitance at the DC side of the inverter
Implementation Method 2
The switching circuit SC is configured to short-circuit the power terminals T1, T2 of the photovoltaic panel SLi in response to a trip signal Cs received from the controller U
Data Source
Figure 1
Figure 2
Figure 2A
AI summary
A shut-down apparatus (1) for a string (100) of photovoltaic panels (SL1, SL2, SLN-1, SLN) electrically connected in series characterized in that it comprises a plurality of control modules (MD1, MD2, MDN-1, MDN) comprising: - an initial control module (MD1) operatively associated to a corresponding photovoltaic panel (SL1); - one or more intermediate control modules (MD2, MDN-1), each operatively associated to a corresponding photovoltaic panel (SL2, SLN-1); - a final control module (MDN) operatively associated to a corresponding photovoltaic panel (SLN). Each control module is adapted to cause the shut-down of a corresponding photovoltaic panel in response to a received input shut-down signal (C1, C2, CN-1, CN), said control modules sequentially receiving said input shut-down signals at subsequent shut-down instants, each pair of subsequent shut-down instants being separated by a corresponding time delay (Td).