As a new energy, aluminum electrolytic capacitor solar energy can provide clean and pollution-free energy for our lives. Because the current generated by photovoltaic power generation system is DC, but civil power is mainly supplied by AC, and solar power generation will eventually run in the grid, which means that solar power generation must convert DC into AC through inverter to drive loads such as household appliances. Therefore, inverter plays an important role in solar power generation system. The main function of inverter is to convert the variable DC voltage input of power supply into undisturbed AC sine wave output, which can be used by equipment and fed back to power grid.
Requirements of solar power generation for photovoltaic inverter For engineers who are familiar with power management, what points should be paid extra attention to when designing the inverter of solar power generation system? First of all, as far as the use of inverters in existing photovoltaic systems is concerned, they can only be used for 5 to 10 years, while the service life of photovoltaic panels is as long as 25 years, and inverters have become the least reliable components in photovoltaic systems. AlbertoGuerra of IR suggested that designers must consider the service life of inverters in photovoltaic systems. The solar inverter technology industry has high expectations for the product life, which can generally guarantee the service life of 20 to 25 years, so it pays special attention to the reliability of each component.
The key to improve the life of photovoltaic inverter is the reliability of its components. Although semiconductor components usually reach this level of reliability, it may be a challenge for passive components, especially electrolytic capacitors. Improving the reliability of electrolytic capacitor has become one of the keys to improve the reliability of photovoltaic inverter.
The role of electrolytic capacitor in photovoltaic inverter can be regarded as a special purpose inverter powered by DC power supply, with an output frequency of 50Hz or 50Hz synchronized with the power grid. There is no current pulse of the rectifier circuit generated by the rectifier, so the capacitor on the DC bus functions as a DC bus capacitor or as a "DC-Link" capacitor, and its function is to absorb the switching frequency extremely high harmonic current and the output frequency triple harmonic current generated by the inverter.
Requirements of photovoltaic inverter for electrolytic capacitor
1. The high-voltage and high-power photovoltaic inverter directly merges the converted alternating current into the high-voltage power grid. However, from the perspective of safety, the output voltage of the photovoltaic battery pack is generally not higher than 900V, so two 450V electrolytic capacitors can be selected in series, but in order to improve safety, two 500V electrolytic capacitors can be selected in series. Therefore, capacitors with high voltage level are needed to reduce the series connection of capacitors and improve reliability.
2. High ripple resistance. Generally, the current flowing through the capacitor of photovoltaic inverter is 0.44 times of the effective value of the inverter output current. For example, the output voltage of photovoltaic inverter is 250V, the output current corresponding to each output of 1kW power is about 2.54A, and the current flowing through DC bus capacitor is 1.12A. The DC bus capacitor of 100kW photovoltaic inverter needs to flow with an effective current of 112A, and the rated current of the selected capacitor should not be lower than this value. If the rated current of one electrolytic capacitor cannot meet the requirements, multiple electrolytic capacitors should be connected in parallel to obtain the required current value. Therefore, a single electrolytic capacitor with high ripple resistance is required to reduce the number of parallel electrolytic capacitors and improve the overall reliability.
3. Long life In the solar power generation system, the service life of the photovoltaic panel is as long as 25 years, and the inverter can only be used for 5 to 10 years, so the solar power generation system requires the service life of the photovoltaic inverter system to be 25 years. For passive electrolytic capacitor, its negative electrode is electrolyte, which will slowly dry up and fail with the increase of service time. This will inevitably require the electrolytic capacitor industry to manufacture electrolytic capacitors with longer life to meet the requirements of photovoltaic inverters.
The progress of life-span components such as aluminum electrolytic capacitors makes it possible for photovoltaic inverters to have a long life. With the continuous development of reliability of lifetime components, the lifetime of photovoltaic inverter will meet the requirements of solar power generation system. The future solar power generation system will become a highly reliable and maintenance-free power generation system; Solar energy will also become clean, pollution-free and cheap energy and enter thousands of households.
