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Small switch, big effect,

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  • Author:RNZE
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  • Release Time:2021-10-29
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In April 2016, after President Xi Jinping visited the photovoltaic poverty alleviation project in Jinzhai, Anhui, photovoltaic poverty alleviation became popular, and this new model combining new energy and poverty alleviation began to attract widespread attention. The total scale of photovoltaic poverty alleviation projects during the "13th Five-Year Plan" period of the national solar energy plan is 15GW, and the annual construction scale is about 3GW, accounting for 20% of the country's annual new photovoltaic power generation installed capacity.


Obviously, everyone realizes that photovoltaic poverty alleviation is a big cake, which not only drives the income of poor households, but also promotes the rapid development of the domestic photovoltaic industry. However, many problems are also exposed in the actual implementation of poverty alleviation projects.


It is not advisable to cut corners and replace pillars


Because poverty alleviation projects are generally led by the government to bid, usually adopt a low-price competition strategy, and the payment cycle is long, so many installers or contractors will directly omit the DC switch in the project in order to save costs.


Another "smart" approach is that some manufacturers use AC circuit breakers on the DC side in pursuit of low cost when selecting components for inverters, combiner boxes, etc. The arc extinguishing capacity, rated On-load cut-off power is far from enough, which can easily lead to overheating, leakage and sparks, and even a fire in the power station. AC systems, these also increase the risk of electric shock and fire accidents.


The big role of the DC switch


Let's talk about the protection functions of DC switches in photovoltaic power plants through examples.


(1) When installing the photovoltaic system, the installer generally isolates the input of the solar panel and the inverter by turning off the DC switch first. When such wiring and plugging and unplugging the DC terminal, the DC power is not connected.


Enter the DC side of the inverter to prevent personal electric shock and damage to the inverter and back-end equipment. Therefore, when the system is installed, we need a DC switch' to cut off the DC power between the inverter and the battery board.


(2) In a photovoltaic power station, the inverter is the core center. In order to ensure sufficient power generation time, the inverter does not have a start and stop button. As long as there is light (even in rainy weather), the solar panel can generate electricity, and the inverter can generate electricity. That is to work automatically. However, this also brings a problem, when the inverter is replaced or repaired, even if the AC side has been disconnected through the installed AC circuit breaker but the DC side has always been powered. In this case, if the inverter is Without a 'DC switch' to isolate the DC current from the panel, it is easy to cause electric shock and damage to the equipment.


(3) At present, most of the inverters on the market are TL series, that is, there is no internal electrical isolation, and there is a possibility of backflow from the AC side to the DC side. During maintenance, if the physical isolation between the AC switch and the DC switch is used, each segments can be more securely protected.


According to relevant methods, it is understood that the future photovoltaic poverty alleviation will be mainly village-level power stations of 100-300kW, and basically will use string inverter solutions, mainly using built-in DC switches embedded in the inverter, or external DC switches (battery panels) and the inverter installed independently). Therefore, the photovoltaic DC switch is the most important component of system security. The reliability and stability of the photovoltaic DC switch are directly related to the stable power generation and revenue of the photovoltaic system, and directly affect the safe and reliable operation of the photovoltaic system.


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