PV Rapid Shutdown Circuit Using AC Injection and LMD Arc Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High voltage solar panel systems face issues with electrical arcs due to poor connections, leading to potential circuit damage and fires, and existing safety systems are costly and complex, requiring multiple disconnect switches and arc detection mechanisms.
Innovation Solution
An isolation switch device using an AC coupler and bandpass filter, driven by a remote AC power source, isolates arc sensing circuitry from the PV DC bus, allowing for efficient shutdown and arc detection without affecting the AC power source, and employing Local Mean Decomposition (LMD) and Windowed LMD methods to detect arcs and interrupt the DC bus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple disconnect switches and electronic controllers are installed to achieve rapid shutdown and arc detection, then safety compliance is improved, but system cost and complexity increase
Solution Approach 1:
The patent combines multiple safety functions (arc detection, rapid shutdown control, and disconnect switch actuation) into a single integrated controller unit. This consolidation eliminates the need for separate electronic controllers at each panel while maintaining compliance with UL 1741 and ANSI/UL 1699 standards through centralized monitoring and control of the DC bus system.
Solution Approach 2:
The controller is designed as a multi-functional device that performs arc fault detection, rapid shutdown initiation, and coordinated control of multiple disconnect switches. This universal approach allows one device to replace multiple specialized components, reducing overall system complexity while achieving comprehensive safety coverage across the PV array.
2Reliability
If disconnect switches are installed at multiple locations in the PV string to limit voltage during shutdown, then safety compliance is improved, but system cost increases
Solution Approach 1:
The PV array is divided into multiple segments or strings, each equipped with its own disconnect switch controlled by the centralized controller. This segmentation allows independent control of each segment during shutdown, ensuring that voltage at any point on the DC bus remains within safe limits (30V outside PV boundaries, 80V within boundaries) while using fewer total switches than a fully distributed approach.
Solution Approach 2:
The centralized controller acts as an intermediary between the arc detection function and the disconnect switches. It receives arc fault signals, processes the information, and coordinates the actuation of multiple disconnect switches to achieve proper voltage segmentation and isolation, eliminating the need for complex local control electronics at each switch location.
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 reduces the cost and complexity of safety systems by enabling remote shutdown and arc detection, ensuring safe operation while complying with safety standards, such as limiting voltage within 30 seconds and preventing fire risks.
Implementation Method 1
an AC coupler (which can be a transformer) and a bandpass filter connected in series between an input and an output of the device
Implementation Method 2
a bandpass filter connected in series between an input and an output of the device; the bandpass filter of the isolation switch may be operative to pass an AC current within a range of 200 kHz and 300 KHz
Implementation Method 3
a rectifier gate signal circuit connected to the AC coupler and providing a switch gate signal
Implementation Method 4
at least one normally open switch connected in parallel to the bandpass filter, a gate of the at least one normally open switch being connected to the switch gate signal
Data Source
AI summary
The present disclosure provides a system, apparatus and method for providing rapid shutdown for photovoltaic power systems and provides a system, apparatus and method for providing arc sensing for photovoltaic power systems. An AC current can be put on the DC bus to control PV panel shutdown. Local mean decomposition can be used to sense arcing on the DC bus.