PV Array Group Switching for Rapid Voltage Shutdown
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Solution Overview
Problem
Photovoltaic systems pose a safety hazard during emergencies due to their continuous power generation, which can expose firefighters and personnel to high voltages, necessitating a rapid shutdown mechanism to limit output voltage within safety levels as per the 2017 National Electric Code (NEC) Section 690.12.
Innovation Solution
A photovoltaic system with a control circuit that switches groups of solar cells in and out of the system, either by disconnecting or shorting them, to lower the output voltage below safety levels during rapid shutdown and restore normal operation upon detection of a release trigger, using a switch device and bypass diodes to manage the voltage contributions of solar cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If photovoltaic systems operate continuously to generate power, then energy production is maintained, but safety hazards arise during emergencies due to high voltage exposure
Solution Approach 1:
The photovoltaic array is divided into multiple independently controllable groups of solar cells. During rapid shutdown, only specific groups are disconnected or shorted while others remain operational, allowing partial energy production to continue while eliminating voltage hazards in the shutdown sections.
Solution Approach 2:
The system dynamically adjusts its operational state by switching between normal operation and rapid shutdown modes. Switch devices controlled by the control circuit enable real-time reconfiguration of the photovoltaic system, transitioning from continuous power generation to safe voltage reduction within 30 seconds.
2Object-affected harmful factors
If rapid shutdown is implemented to reduce voltage below safety levels, then personnel safety is improved, but system complexity increases due to additional switch devices and control circuits
Solution Approach 1:
The control system is segmented into distributed control circuits that can independently manage switch devices for different solar cell groups. This modular approach simplifies the overall control architecture compared to a centralized system, as each control circuit only needs to manage its local section.
Solution Approach 2:
The control circuit automatically detects shutdown conditions and activates the switch devices without requiring external intervention. The system self-manages the rapid shutdown process, reducing the need for complex external control mechanisms.
3Object-affected harmful factors
If solar cells are switched out during rapid shutdown, then output voltage is reduced below safety levels, but productivity decreases due to loss of power generation
Solution Approach 1:
The photovoltaic array is divided into multiple independently controllable groups of solar cells. During rapid shutdown, only specific groups are disconnected or shorted while others remain operational, allowing partial energy production to continue while eliminating voltage hazards in the shutdown sections.
Solution Approach 2:
The system dynamically adjusts its operational state by switching between normal operation and rapid shutdown modes. Switch devices controlled by the control circuit enable real-time reconfiguration of the photovoltaic system, transitioning from continuous power generation to safe voltage reduction within 30 seconds.
4Object-affected harmful factors
If switch devices are used to disconnect solar cells, then voltage control is improved, but device complexity and potential failure points increase
Solution Approach 1:
Bypass diodes are introduced as intermediary components that provide alternative current paths. These diodes enable the switch devices to operate more reliably by preventing reverse current flow and reducing stress on the switching components, thereby improving overall system reliability during rapid shutdown operations.
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
Effectively reduces the output voltage of photovoltaic systems to safe levels during emergencies, ensuring personnel safety while allowing for seamless resumption of normal operation once the emergency is resolved, thereby complying with safety regulations.
Implementation Method 1
Solar cells are well known devices for converting solar radiation to electrical energy. Solar radiation impinging on the solar cell creates electrical charges that may be harnessed to power an external electrical circuit
Implementation Method 2
Solar cells may also be switched out by shorting them out of the photovoltaic system. A switch device, such as a transistor, may be used to short the solar cells out of the photovoltaic system
Data Source
AI summary
A photovoltaic system includes groups of solar cells that can be switched in and out of the photovoltaic system. In response to detecting initiation of rapid shutdown, a control circuit controls a switch device to switch out a group of solar cells to lower the output voltage of the photovoltaic system below a safety level. In response to detecting a release trigger that indicates resumption of normal operation, the control circuit controls the switch device to switch back the group of solar cells to restore the output voltage of the photovoltaic system to a normal operating level. Solar cells may be switched out by disconnecting them from the photovoltaic system and switched back by reconnecting them into the photovoltaic system. Solar cells may also be switched out by shorting them out of the photovoltaic system and switched back in by removing the short.