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　　String inverter solution: for rooftop photovoltaic power plants

　　In recent years, national policies have shifted from initial investment subsidies to kilowatt-hour subsidies. How to reduce power station operation and maintenance costs, increase power generation, and improve the overall profitability of power stations has become a new topic we are facing, and we need to explore in-depth in the form of power station construction.

　　Disadvantages of traditional centralized solutions

　　After actual project research and discussions with EPCs, design institutes and photovoltaic experts, we analyzed and summarized the problems encountered in the centralized inverter networking solution during the design, construction and operation and maintenance of rooftop power stations. The more prominent ones are the following 6 types of questions:

　　1. The most important issue in power station construction is safety. The centralized solution uses a DC combiner box. Due to the built-in DC branch fuse, there is a risk of continuous fire because the solar panels will be in working condition as long as there is light.

　　For distributed rooftop factories, it brings serious safety risks. Not only will the economic benefits of the power station itself be affected, but more importantly, it will affect other equipment in the factory. Bringing very heavy losses to the owners.

　　2. For irregular roofs, a single 500KW inverter cannot make full use of the roof area. The inverter is often overloaded or underloaded, or overmatched or undermatched.

　　3. On roofs with multiple orientations, the panel is partially shaded, resulting in inconsistency in the strings. Single-channel MPPT results in relatively low power generation; at the same time, the mismatch loss of each string will also lead to a loss of power generation;

　　4. The inverter requires maintenance by professional engineers. A single inverter failure has a great impact on power generation and poses a huge challenge to the safety of maintenance personnel. At the same time, there are many types of spare parts, and it takes more than 3 days to locate and repair the fault, which has a serious impact. Customer power generation revenue. The DC combiner box has a high failure rate and cannot monitor each string, which increases fault location time. Due to the volatilization of fuses, the failure rate and maintenance costs are high, requiring regular replacement and maintenance. The lines are complex and there are many joints processed on site, so the failure rate is high. After some projects have been in operation for 1 to 2 years, the effective power generation rate is lower than 90%; the picture below shows a burnt DC combiner box in a power station.

　　5. The centralized solution requires an inverter room and corresponding civil engineering works, as well as corresponding fans, air ducts, smoke sensors, temperature sensors and other equipment, which increases construction complexity, initial investment and operation and maintenance costs;

　　6. Centralized inverters require forced air cooling, and the computer room consumes a lot of power, with an average of at least 300W. It requires regular dust sweeping, fan maintenance and dust filter replacement;

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