PLC Interface Circuit Using Magnetic Ring Isolation in PV Strings
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Solution Overview
Problem
Current power line communication systems in solar power generation systems face challenges due to the strict requirements for capacitor selection, particularly in handling high voltages and ensuring safety specifications, which increase costs and complexity.
Innovation Solution
The implementation of a magnetic ring coupling manner for power line communication, where the power lines connected to the optimizer groups pass through a magnetic ring, allowing only the PLC signal to enter the inverter, thereby reducing the specification requirements for capacitors and enhancing safety performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct capacitor coupling manner is used to transmit PLC signal, then the PLC signal can be transmitted from inverter to power line, but the capacitor needs to meet strict impedance and voltage requirements, increasing device complexity and cost
Solution Approach 1:
The patent introduces a magnetic ring as an intermediary component between the power lines and the inverter's modulation circuit. The magnetic ring couples the PLC signals from multiple optimizers while isolating the high voltage DC components, allowing signal transmission without directly coupling the high voltage lines to the modulation circuit. This mediator approach resolves the contradiction by enabling reliable signal transmission while reducing capacitor requirements.
Solution Approach 2:
The patent extracts the PLC signal from the high voltage power line by using the magnetic ring to separate the signal component from the high voltage DC component. The capacitor is used only for signal coupling after the high voltage has been isolated by the magnetic ring, rather than needing to block both high voltage and signal simultaneously. This extraction approach reduces the capacitor's specification requirements.
2Adaptability or versatility
If direct capacitor coupling is used, then PLC communication can be implemented, but high voltage between power lines (up to 1500V) must be handled by capacitors, increasing safety requirements and cost
Solution Approach 1:
The magnetic ring serves as a safety intermediary that couples the PLC signals while blocking the transmission of high voltage DC components to the inverter's modulation circuit. The capacitor then only needs to handle the isolated signal voltage, not the full 1500V line voltage, significantly reducing safety requirements and cost.
Solution Approach 2:
The patent converts the potentially harmful high voltage DC component into a beneficial isolated signal transmission. By using the magnetic ring to couple only the AC signal components while isolating the DC high voltage, the harmful high voltage is effectively filtered out, and the same infrastructure is used to achieve safe signal transmission.
3Productivity
If multiple optimizers are connected in series to photovoltaic modules, then power generation efficiency is improved, but the high voltage generated on optimizer group increases the requirements for capacitor specifications
Solution Approach 1:
The magnetic ring acts as an intermediary that allows multiple optimizers to be connected in series for improved power generation while isolating the resulting high voltage from the modulation circuit. The capacitor only needs to handle the coupled signal voltage rather than the full series voltage of multiple optimizers, maintaining productivity while reducing component specifications.
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
This solution reduces the specification requirements for capacitors, improves safety performance, and lowers the overall costs of the solar power generation system by eliminating the need for strict capacitor selection and handling high voltages within the inverter's modulation circuit.
Implementation Method 1
The power line connected to either end of the at least one capacitor passes through the magnetic ring... A high voltage generated on an optimizer group connected to the interface circuit and between direct current positive and negative electrodes is not introduced into a modulation circuit inside an inverter
Data Source
AI summary
An interface circuit, a string, and a system that are applied to power line communication, to lower device specifications, includes: an inverter, an optimizer group, a capacitor, a magnetic ring, power lines, and a signal line. An optimizer in the optimizer group is configured to adjust a size of a direct current output by a photovoltaic module connected to the optimizer. Two ends of the signal line passing through the magnetic ring are connected to the inverter. Two ends of a power line passing through the magnetic ring are respectively connected to the capacitor and the optimizer group. By using the foregoing interface circuit, a high voltage of a direct current output by the optimizer group is prevented from being introduced into the inverter, thereby reducing a specification requirement of a device such as a capacitor.