Technical Post: In-depth Interpretation of Technical Parameters on the Input Side of Photovoltaic Inverters-EEWORLD

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I believe that when many friends are purchasing photovoltaic inverters, the most headache is looking at a lot of performance parameters and not knowing where to start. What is the impact of MPPT voltage range and MPPT number on inverter performance? Is there any relationship between the rated power and apparent power values and whether the inverter is easy to use? Anti-islanding protection, string fault detection, various protection functions in the inverter brochure, which protection functions are more suitable for your own photovoltaic system?

Don’t worry, Ai Luojun will take you to carefully understand the input parameters of the inverter, that is, the PV side input performance parameters, and directly tell you how to choose the matching PV components.

1. The maximum input DC power is the maximum power allowed to be input to the inverter, which determines the maximum number of PV modules connected. For example, for an inverter with a maximum DC power of 5200W, the power of a photovoltaic panel on the market is around 250W-300W. If 250W is selected, the maximum number of PV modules that can be connected to the inverter = 5200/250≈20.

2. Maximum input voltage/current, minimum operating voltage is the maximum voltage and current allowed to be input to the inverter, that is, the voltage and current of the selected PV components cannot exceed this value. The voltage input to the inverter must be greater than or equal to this value for the inverter to work properly.

3. Maximum input short-circuit current This value is the maximum current that the inverter allows to pass after the PV module connected to the inverter is short-circuited. If the current of the PV module short-circuit exceeds this value, the inverter will burn out.

The above are the limit parameters of the inverter input. However, in order to fully utilize the power generation of PV modules, people in the industry invented MPPT - Maximum Power Point Tracking. For example, in the IU diagram of PV modules, the power of PV modules is the largest only at point P. The MPPT function of the inverter is to continuously track the maximum power point of PV modules to maximize the power output of PV modules.

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1. MPPT voltage range

That is, when the input voltage of the inverter is within this range, the efficiency of the PV module is higher. Regarding this parameter, some people say that the larger the range, the better, but I do think that within a certain range, the larger the MPPT voltage range, the better. After all, the lower the MPPT voltage, the higher the requirements for the circuit, the higher the cost of the inverter, and the higher the price the customer buys.

2. Number of MPPT paths and number of strings allowed to be connected

The inverter has several MPPTs. For example, our inverter X3-30.0-T has 2 MPPTs. Each MPPT allows 4 strings to be connected. As shown in the following figure, the lighting conditions of the PV1 strings are the same. All PV1 components can use one MPPT to achieve the maximum power input of each PV component.

As mentioned above, the more MPPT paths there are, the higher the cost of the inverter, so it is recommended to select the number of MPPT paths according to the actual environment. If the PV panels are used in the desert, one MPPT path is enough.

Reference address：Technical Post: In-depth Interpretation of Technical Parameters on the Input Side of Photovoltaic Inverters

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