Photovoltaic String Disconnection Apparatus with Autonomous Power Supply
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Solution Overview
Problem
Existing solar installations with string inverters require additional lines for signal transmission and power supply, and retrofitting with protective circuits is cumbersome due to space constraints and integration issues, while existing switching units draw significant energy from control signals, reducing power transmission efficiency.
Innovation Solution
A disconnection apparatus for photovoltaic strings that integrates a circuit breaker, band-stop filter, and supply circuit in series, with a bandpass filter and reverse current diode to autonomously supply energy, reducing the need for additional lines and minimizing power draw from control signals, and includes a monitoring circuit for enhanced reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If switching elements are used to disconnect solar modules in hazard situations, then safety voltage limits are ensured, but additional lines for signal transmission and power supply are required
Solution Approach 1:
The string line serves multiple functions: it transmits DC current from solar modules to the inverter, transmits control signals for disconnection apparatus operation, and provides power supply to the disconnection apparatus through the built-in supply circuit. This eliminates the need for separate additional lines for control and power, reducing system complexity while maintaining safety functionality.
2Reliability
If protective circuits are integrated into connection boxes of solar modules, then safety standards are met, but space constraints and integration issues make retrofitting cumbersome
Solution Approach 1:
The disconnection apparatus is designed as a separate, modular unit that can be integrated into existing string configurations without modifying individual solar modules or their connection boxes. This segmentation allows easy retrofitting of existing installations while maintaining safety functionality.
Solution Approach 2:
The disconnection apparatus combines multiple functions including the circuit breaker, supply circuit, and control signal reception into a single integrated unit that interfaces with the existing string line, eliminating the need for separate protective circuits in each module's connection box.
3Extent of automation
If switching units draw energy from control signals, then autonomous operation is achieved, but power transmission efficiency is reduced due to significant energy draw
Solution Approach 1:
The disconnection apparatus includes a supply circuit that autonomously generates operating power by utilizing the voltage drop across the string line during normal operation. This self-service approach eliminates the need to draw significant energy from control signals, thereby maintaining power transmission efficiency while achieving autonomous operation.
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
Enables reliable and efficient disconnection of solar modules without additional lines, ensuring safe voltage limits and reducing power losses, while allowing for easy integration into existing installations and minimizing the impact on control signal strength.
Implementation Method 1
A bandpass filter for coupling out a high-frequency control signal from the electrical connection bridges the circuit breaker and the band-stop filter in parallel
Implementation Method 2
a diode that is oppositely polarized relative to an operating current flow direction, the diode being referred to hereinafter as reverse current diode, is connected in parallel with the circuit breaker. In this configuration, a reverse current can flow through the string even with the circuit breaker open
Implementation Method 3
the electrical power for supplying the disconnection apparatus and, if appropriate, the further electrical components is substantially drawn from a direct current flowing between the first and second terminals
Data Source
AI summary
A description is given of an apparatus for disconnecting a connection between solar modules of a photovoltaic string. A circuit breaker, a band-stop filter and a supply circuit are arranged in a series circuit between a first and second terminal. The series circuit is configured to conduct a current that includes a DC string current flowing through the photovoltaic string and a high-frequency control signal modulated onto the DC string current. The supply circuit is configured to generate energy to power the apparatus from the DC string current. An AC bypass circuit bridges the circuit breaker in parallel and is configured to conduct the high-frequency control signal. A control unit is configured to operate the apparatus based on the high-frequency control signal. A reverse current diode oppositely polarized relative to an operating current flow is connected in parallel with the circuit breaker or the circuit breaker and the band-stop filter.