PV Rapid Shutdown Circuit With Transformer-Isolated Arc Sensing
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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 to implement, particularly in requiring multiple disconnect switches and arc detection mechanisms.
Innovation Solution
An isolation switch device using a transformer to isolate arc sensing circuitry from the PV DC bus, driven by an AC power source with passive circuitry providing gate signals to normally open switches, allowing remote shutdown of PV panels and compliance with safety standards without affecting the AC power source, and an arc-sensing method employing Local Mean Decomposition (LMD) and Windowed LMD to detect arcing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple disconnect switches and electronic controllers are provided to ensure rapid shutdown capability, then safety compliance is improved, but system cost and complexity increase
Solution Approach 1:
The patent combines the rapid shutdown switch with an integrated arc detection circuit and control electronics into a single unified device. This merging eliminates the need for separate disconnect switches and controllers, reducing system complexity while maintaining safety compliance through the combined functionality of arc detection, shutdown control, and isolation switching in one unit
Solution Approach 2:
The isolation switch device performs multiple functions simultaneously: it acts as a disconnect switch for rapid shutdown, an arc detection sensor, and a control unit. This multi-functionality allows a single device to replace multiple separate components, reducing overall system complexity while ensuring both rapid shutdown capability and arc fault protection
2Reliability
If multiple disconnect switches are installed at multiple locations in the PV string to reduce voltage levels, then voltage safety is improved, but system cost increases
Solution Approach 1:
The patent integrates arc detection, control electronics, and the disconnect switch into a single isolation switch device, eliminating the need for multiple separate switches and controllers throughout the PV string. This integration maintains voltage safety through proper isolation while significantly reducing the number of components required
Solution Approach 2:
The isolation switch device uses passive circuitry that automatically provides gate signals to control switches based on detected conditions, eliminating the need for expensive active electronic controllers at each location. The system serves itself by using the inherent electrical signals from the PV bus to control the shutdown mechanism
3Difficulty of detecting and measuring
If arc detection circuitry is directly connected to the PV DC bus, then arc detection capability is improved, but the system becomes vulnerable to high voltage and requires additional isolation components
Solution Approach 1:
The patent introduces a transformer as an intermediary component that couples the arc detection circuitry to the PV DC bus through magnetic coupling rather than direct electrical connection. This transformer isolation allows the detection circuit to sense arc conditions on the high-voltage bus while remaining electrically isolated, eliminating the need for additional isolation components and protecting the low-voltage control electronics
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 isolates the arc sensing circuitry, reduces the cost of safety systems by using shared transformer and passive circuitry, and quickly detects arcing to prevent damage, ensuring compliance with safety standards by rapidly disconnecting PV panels from the bus.
Implementation Method 1
an AC injector transformer for coupling the AC current to a DC bus of a PV panel array, the AC injector transformer having a first winding connected to the AC power supply, a second winding connected to the DC bus
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
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.