Overseas customer feedback, said the inverter output is limited, can not be effective output. After in-depth communication, we understand that there are problems with their inverter and module configurations: the modules are over-matched too much, resulting in excessive working current some of the time, inverter current-limited operation, and some power-limited phenomena.

In fact, this situation also happens in China from time to time, and many owners have done a lot of things that are unpleasant without understanding the operation mechanism of the inverter.

(1) Make a “shield” for the inverter

Mistake: Previously, when I did research, I found that customers installed shields to protect the safety of the inverter, but this not only did not protect the machine, but also affected the heat dissipation of the machine. Especially in the hot summer, the installation of the shield will easily cause the surrounding working environment to be too hot, resulting in the overheating and derating of the inverter, which will limit the output power and affect the power generation revenue.

Correct: String inverters are all IP65 or above protection level, and do not need additional overall protection. Therefore, we only suggest two points here: first, when string inverters are installed, you can install some protective canopy on its upper part to avoid direct rainfall; in addition, when installing multiple string inverters, you should pay attention to the inverter spacing to ensure enough space for heat dissipation and follow the installation manual recommendations as much as possible.

(2) Configure too many components, thinking that the more they are equipped, the more electricity they generate

There is a saying in the north that “the spoon is big, but the bowl is accurate”, which means that the bowl is only so big, and it can’t hold more rice. In fact, the same is true for inverter module configuration. For example, the maximum output power of Shengnengjie SE-5kw inverter is 5.5KVA, even if 6kw of power is input on the input side, its output will not reach 6kw, but only 5.5kw at most, which means the output power is limited.

Considering the impact of system loss, we usually recommend different over-provisioning ratio in different areas. Because, if the inverter over allocation is too high, it will not only waste the system cost, but also make the inverter overload for a long time, resulting in lower service life.

(3) Use DC sink box for convergence

As we all know, centralized inverters will add a sink box on the DC side, mainly to connect the components of the square array in series and parallel, and add lightning protection, fuses, DC switches and other protection devices, and then unified to the DC cabinet side of the inverter.

For string inverter, the DC sink box is directly omitted, and the lightning protection and overcurrent protection units are placed inside the machine, which greatly reduces the workload of construction and maintenance. However, we also found that some users are still using the old thinking of centralized configuration.

Wrong: The number of DC terminals on the input side of the inverter directly determines how many power components can be configured. Some customers ignore the current limit conditions on the input side and parallel-connect the modules before connecting to the inverter, resulting in excessive input current and burned fuses, or even damaged terminals, which affects the power generation revenue.

Correct: The power on the input side of the inverter, i.e. the current limit, needs to be fully considered. Generally, the maximum input current of the module is around 9-10A, and the double-sided module is slightly larger, but only around 11-12A, while the DC input side current of the inverter is mostly around 12.5A, so extra attention is needed when configuring.