Is inverter suitable for capacity reduction?

At present, there are many types of inverters on the market. In order to simplify the management and explore the advantages of centralized purchasing, many EPC manufacturers often use limited types of inverters to design as many cases as possible, which will inevitably involve the use of inverter capacity reduction. Small scale capacity reduction is not a big problem. However, the use of large-scale capacity reduction, not only will cause a waste of inverter costs, but also can not get the desired power generation.

1.Waste of resources
For a simple example, the original 10kW inverter used to carry 6kW photovoltaic components, equivalent to the inverter used only 60% of the workload, time will inevitably lead to waste of resources, not conducive to the LCOE optimization. Of course, the small case is good, if it is a MW large case, waste can not be ignored.
2.Shorten the string length and reduce overall power generation.
(a)Not conducive to string optimization design
For some power level inverter, the number of DC input terminals is closely related to the rated power of MPPT module. If the power of 10 kW MPPT module is reduced to 6 kW, the length of the module string will be reduced to 60%, while the open circuit and working voltage of the series will be reduced to 60%. Obviously, this is not the optimal design.
(b)Not conducive to efficient inverter operation
As mentioned above, with the series open circuit and working voltage reduced to 60% of the original, the use of reduced capacity will have a significant impact on the operation behavior of the inverter.

Influence on Start-up and Shut-down Time of Inverter: After the voltage in series is reduced, the start-up time in the morning is delayed, the shut-down time in the evening is advanced, the daily power generation time is shortened, and the power generation capacity is reduced.

The influence on the working mode of inverter: the series inverter consists of two power conversion units, the former DC / DC realizes MPPT function and the latter DC / AC realizes inverter function. The former DC / DC is implemented by boost topology. Its working time is determined by the input voltage of the series. It works when the input voltage is lower than the set value, and stops when the input voltage is higher than the set value. With the decrease of series voltage, the working time of DC / DC module increases, and the average conversion efficiency of inverter decreases, resulting in the reduction of overall power generation.

It can be seen that the use of inverter capacity reduction is achieved at the cost of shortening the string length and reducing the input voltage. Its advantage is to reduce the use of inverter model, while the inverter long-term operation in light-load state, its life will be extended to a certain extent; The disadvantage is that the use of capacity reduction will not only waste the inverter resources, but also is not conducive to the inverter more efficient work, resulting in a reduction in overall power generation.

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