PV Inverter Anti-Backflow Circuit With Capacitive Signal Coupling
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Solution Overview
Problem
Current photovoltaic power generation systems face issues with backflow currents that can damage photovoltaic panels, and existing solutions are either complex or inefficient in preventing such damage.
Innovation Solution
A photovoltaic power generation system incorporating a single-stage inverter, anti-backflow circuits, and coupling capacitors to detect and control backflow currents, utilizing power line communication signals to manage bus voltage and optimizer output, thereby forming dual protection for the photovoltaic strings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a boost circuit, buck circuit, and DC/AC inversion circuit are used to adjust and control voltage output, then voltage control capability is improved, but device complexity increases and backflow current damage risk worsens
Solution Approach 1:
The patent extracts the backflow prevention function from the complex multi-circuit system and implements it through a dedicated anti-backflow circuit with diode and capacitor. This separates the voltage control function (handled by buck/boost circuits) from the backflow protection function, allowing each to be optimized independently while reducing overall system complexity and backflow damage risk.
2Reliability
If anti-backflow circuit is added to prevent backflow current, then photovoltaic panel protection is improved, but device complexity increases
Solution Approach 1:
The patent introduces an intermediary anti-backflow circuit consisting of a diode and capacitor that mediates between the photovoltaic panel and the inverter system. This intermediary component blocks backflow current while allowing forward current to pass, providing protection without requiring complex control mechanisms or significantly increasing system complexity.
3Reliability
If coupling capacitor is used to transmit control signals, then reliability is improved through dual protection, but device complexity increases
Solution Approach 1:
The coupling capacitor serves multiple functions: it blocks DC voltage while allowing AC control signals to pass, provides capacitance for voltage stabilization, and enables bidirectional communication between optimizers and inverter. By making this single component multi-functional, the patent achieves dual protection and improved reliability without adding numerous separate components, thus limiting the increase in device complexity.
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 system effectively reduces and prevents backflow currents, protecting photovoltaic panels by simplifying the circuit structure, reducing costs, and enhancing reliability through dual protection mechanisms.
Implementation Method 1
The coupling capacitor is connected in parallel to two ends of the anti-backflow circuit, and is configured to transmit a signal between each buck optimizer in the at least one photovoltaic string and the single-stage inverter
Implementation Method 2
The anti-backflow circuit is configured to prevent a backflow current from flowing back to one or more of the at least one photovoltaic string
Implementation Method 3
Each photovoltaic string includes a plurality of photovoltaic string units, each of the plurality of photovoltaic string units includes a buck optimizer and one or more photovoltaic panels
Data Source
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Figure 3~4(b)
AI summary
Embodiments of this application provide a photovoltaic power generation system. The system includes a single-stage inverter, an anti-backflow circuit, a photovoltaic string, and a coupling capacitor. The anti-backflow circuit is connected to one input end of the single-stage inverter, one output end of the photovoltaic string is connected to the other input end of the single-stage inverter, and the other output end of the photovoltaic string is connected to the anti-backflow circuit. The photovoltaic string includes a buck optimizer and a photovoltaic panel. The anti-backflow circuit is configured to prevent a backflow current from flowing back to the photovoltaic string. The coupling capacitor is connected in parallel to two ends of the anti-backflow circuit, and is configured to transmit a signal between each buck optimizer in the photovoltaic string and the single-stage inverter, to control backflow of the backflow current when the anti-backflow circuit fails. Based on this, a bus voltage is reduced by using the single-stage inverter to reduce the backflow current, to reduce damage caused by the backflow current to the photovoltaic panel. In addition, the photovoltaic power generation system is formed by using the buck optimizer and the single-stage inverter, and therefore has a simple structure.