The photovoltaic inverter is the core equipment of the photovoltaic power generation system. Its main function is to convert the direct current generated by the photovoltaic power generation system into alternating current, and to track the maximum output power of the photovoltaic module array, so as to convert its energy with the smallest conversion loss and the best energy. Power quality is used for electrical equipment applications or feeding into the grid. Since photovoltaics have become an important member of the new energy track, inverters have become one of the sub-tracks that the market pays attention to.
The photovoltaic inverter is mainly composed of input filter circuit, DC/DC MPPT circuit, DC/AC inverter circuit, output filter circuit and core control unit circuit. Photovoltaic inverters can be divided into single-phase inverters and three-phase inverters according to the number of phases of the output AC voltage; according to whether they are used in grid-connected power generation systems or off-grid power generation systems, they can be divided into grid-connected inverters and off-grid inverters; according to the type of photovoltaic power generation applied, it can be divided into centralized photovoltaic power generation inverters and distributed photovoltaic power generation inverters; according to whether energy is stored, it can be divided into grid-connected inverters and energy storage inverters. Inverter; according to different technical routes, it can be divided into centralized inverter, string inverter, distributed inverter and micro inverter.
Figure: A brief schematic diagram of the inverter (source: Hemai's prospectus)
At present, the market is mainly dominated by centralized inverters and string inverters. With the rapid growth of the distributed photovoltaic market and the continuous increase in the proportion of string inverters in centralized photovoltaic power plants. According to public data, in 2021, in the photovoltaic inverter market, string inverters will account for 69.6%, centralized inverters will account for 27.7%, and distributed inverters and micro inverters will account for about 2.7%. %. But in general, the current development trend of Chinese inverter companies is very good, and the main market is overseas, and the overseas market is expected to account for between 60% and 70%. Coupled with the current shortage of energy in overseas markets, the willingness of the public to purchase photovoltaics and energy storage has greatly increased, and more and more countries and cities have introduced corresponding subsidy policies. The photovoltaic market has a lot of room for development in the next few years.
While shipments have grown significantly, the PV inverter manufacturing side is facing many problems such as rising component prices and chip supply bottlenecks. The supply chain of PV inverters is receiving more and more attention. Among them, according to their different characteristics, they correspond to different application scenarios, and the types and package sizes of crystal oscillators used by various inverters also vary widely, which is worthy of attention. So how to choose the crystal oscillator in the photovoltaic inverter?
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How to choose a crystal oscillator
In the selection of crystal oscillators, it is necessary to meet these two technical characteristics of photovoltaic inverters: ① The designed service life of long-life photovoltaic power generation systems is generally about 20 years, so the aging rate of crystal oscillators must be low, so as to ensure the design of photovoltaic inverters Longevity needs to be at a high level. ② The failure of the high-reliability photovoltaic inverter will lead to the shutdown of the photovoltaic system, which will directly lead to the loss of power generation. The high reliability of the crystal oscillator is a key factor affecting the normal operation of the photovoltaic inverter. At present, the commonly used package size of photovoltaic inverters is mostly 3225, and the commonly used frequency points are 20MHz, 16MHz, 32.768KHz, etc. What are the types of crystal oscillators used in photovoltaic inverters? The following are commonly used crystal oscillator solutions for photovoltaic inverter products.
01 In terms of passive crystals, it is recommended to use YSX321SL (3225). This crystal oscillator has the characteristics of -40~+85℃ industrial temperature, anti-interference and high reliability, so as to avoid the occurrence of photovoltaic inverter failures.
02In terms of active crystal oscillator, YSO110TR (3225) is recommended, which is resistant to high temperature, can reach -40~+125℃ automotive temperature and has high precision, especially suitable for photovoltaic inverters used in extremely harsh environments.
03 For the timing function, it is recommended to use the YST310S (3215) clock crystal, which has high stability, low aging rate, accurate timing and is not easy to deviate, which can effectively prolong the service life of the photovoltaic inverter.