Five issues you must know about the DC parameters of photovoltaic inverters

Is the maximum input DC power as large as possible?

Maximum DC power: The peak power of the solar panels recommended for customers to connect. For example, Suntrio Plus 50K has a maximum DC power of 60500W, which means that it is recommended to connect solar panels with a maximum power of 60500Wp. This value is set at 1.1 times the maximum output power of the inverter.

At present, the general operating efficiency of photovoltaic power stations is about 80%, and the light resources in different places are also different. In the second and third categories, customers are recommended to connect solar panels at 1.1 times the maximum output power, which can achieve the peak power operation of the inverter, avoid the inverter from operating under light load for a long time, and also avoid the situation of the inverter power curve being clipped.

As long as the inverter reaches full load output, it will automatically limit the DC input power. Connecting too many panels will only waste resources and increase costs. Therefore, the maximum DC input power is not the larger the better.

2What is the maximum DC voltage set based on?

The maximum DC voltage is the maximum open circuit voltage of the solar panel string and the sum of the open circuit voltages of all solar panels in a single string.

For example, for the Suntrio Plus 50K inverter, in cold weather, the negative temperature characteristic of the open-circuit voltage of the components (the open-circuit voltage rises as the temperature decreases) means that the open-circuit voltage of a single string cannot exceed the inverter's maximum DC input voltage of 1000V.

3What is the difference between minimum input voltage and start-up voltage?

Minimum input voltage: The voltage at which the inverter screen lights up and the control circuit starts to work. For example, the screen of Suntrio Plus 50K lights up when the DC voltage reaches 250V.

Starting voltage: When the inverter DC voltage reaches the starting value, the inverter starts to connect to the grid for power generation. For example, Suntrio Plus 50K starts to connect to the grid when the DC voltage reaches 300V.

What does 4MPPT voltage range mean?

Is it enough to configure the string voltage within this range?

When the MPPT voltage of the string reaches the inverter MPPT voltage range (such as the Suntrio Plus 50K MPPT voltage range is 280V-900V), the inverter can track the maximum power point of the string.

However, it is recommended that the MPPT voltage be slightly higher than the rated voltage (600V) when configuring the string. Because in actual work, when the string operating voltage is lower than the rated voltage, the boost circuit starts to work, which will produce certain losses and reduce efficiency. Therefore, for 275Wp-300Wp crystalline silicon solar panels, it is recommended to configure 22 panels in a string.

5. What is the basis for setting the maximum input current? What are the requirements for DC wiring?

Maximum DC input current = maximum input current of a single string x number of strings.

A pair of DC terminals cannot bear the current after converging. Therefore, in actual construction, you must not connect the DC converging to a pair of DC terminals in order to save costs. Otherwise, it will not only affect the power generation of the machine, but also cause certain electrical safety hazards.