The photovoltaic inverter is one of the main devices in solar power generation systems. Its primary function is to convert the direct current (DC) produced by photovoltaic panels into alternating current (AC), which can be used for household or industrial purposes or fed into the electrical grid. Understanding the operating principle and protection functions of the photovoltaic inverter helps in better utilizing and maintaining solar systems.
1. Operating Principle
DC Conversion
Photovoltaic panels generate direct current when exposed to sunlight. The main task of the photovoltaic inverter is to convert this direct current into alternating current with suitable frequency and voltage for the electrical grid. The conversion process typically involves the following steps:
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MPPT (Maximum Power Point Tracking): The inverter uses the MPPT algorithm to monitor the voltage and current output from the photovoltaic panels in real-time, ensuring that the maximum power is always extracted from the panels under varying lighting conditions.
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DC/DC Conversion: Through a DC/DC conversion circuit, the voltage of the direct current is adjusted to facilitate the subsequent conversion into alternating current.
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Inversion: In the inversion circuitry, power switches (such as MOSFETs or IGBTs) are used to convert the direct current into alternating current. The inverter generates alternating current at a specific frequency (usually 50Hz or 60Hz) depending on the requirements.
AC Output
Once the conversion is complete, the photovoltaic inverter sends the alternating current to the electrical grid or the household electrical system. The inverter continuously monitors the output current and voltage, ensuring stability and quality.
2. Protection Functions
The photovoltaic inverter not only handles the energy conversion but is also equipped with several protection functions to ensure the safety and stability of the system:
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Overload Protection: When the load exceeds the inverter's rated power, it automatically disconnects the output to avoid damage to the devices. This function effectively protects the inverter and connected devices.
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Short Circuit Protection: In the event of a short circuit, the inverter can quickly detect the situation and disconnect the power supply, preventing damage to devices and fire risks.
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Overheating Protection: When the internal temperature of the inverter exceeds a certain limit, the system automatically reduces the output power or, if necessary, shuts down the device to prevent failure due to overheating.
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Reverse Current Protection: This function prevents anomalies in the grid (such as power outages) from causing reverse current flow, protecting the photovoltaic system and grid devices.
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Ground Fault Protection: By monitoring the insulation status of the electrical system, the inverter can detect ground faults and automatically disconnect the power supply in case of malfunction, ensuring the safety of personnel.
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Island Protection: In the event of a power grid outage, the inverter can automatically detect the situation and disconnect from the grid, preventing the "islanding" phenomenon and ensuring the safety of maintenance personnel.
