PV Rapid Shutdown Isolation Circuit With LMD Arc Detection
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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 by normally open switches, and an arc-sensing method employing Local Mean Decomposition (LMD) and Windowed LMD to detect arcing and interrupt the PV circuit.
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 unified monitoring and control of the PV string.
Solution Approach 2:
The controller is designed as a multi-functional device that performs arc fault detection, rapid shutdown initiation, and disconnect switch control simultaneously. This universal approach allows one device to replace multiple specialized components, reducing overall system complexity while achieving all required safety functions.
2Reliability
If multiple disconnect switches are installed along the PV string to reduce voltage levels, then voltage safety is improved, but system cost increases
Solution Approach 1:
The PV string is divided into segments with disconnect switches positioned at strategic locations rather than at every panel. The controller monitors voltage levels and activates specific disconnect switches to segment the string, creating multiple lower-voltage sections that meet safety requirements while minimizing the total number of switches required.
Solution Approach 2:
The system pre-positions disconnect switches at optimal locations along the PV string during installation. The controller is pre-programmed with the string configuration and switch locations, enabling it to rapidly activate the appropriate disconnect switches when voltage reduction is needed, without requiring switches at every possible location.
3Measurement precision
If arc detection circuitry is directly connected to the PV DC bus, then arc detection accuracy is improved, but system complexity and cost increase
Solution Approach 1:
The patent introduces an intermediary coupling mechanism (such as a transformer or capacitive coupling circuit) between the arc detection circuitry and the PV DC bus. This intermediary allows the detection circuit to sense arc faults through electromagnetic induction or capacitive coupling without direct galvanic connection, maintaining detection accuracy while simplifying the circuit design and reducing component requirements.
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 using remote AC power to disconnect PV panels from the bus and accurately detects arcing, ensuring rapid shutdown and compliance with safety standards, thereby preventing fires and circuit damage.
Implementation Method 1
an AC coupler and a bandpass filter connected in series between an input and an output of the device; a rectifier gate signal circuit connected to the AC coupler
Implementation Method 2
the bandpass filter of the isolation switch may be operative to pass an AC current within a range of 200 kHz and 300 kHz
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.