Characteristics and Selection Techniques of Solar Energy Inverter

The working principle of solar energy inverter

The working principle of solar energy inverter lies in the inverter circuit, which is a core component of the inverter device, and completes the inverter function through the conduction and cutoff of power electronic switches. There are many methods for classifying solar energy inverters, such as according to the number of phases of the AC voltage output, they can be divided into single-phase inverters and three-phase inverters. According to their application in grid-connected systems or off-grid systems, they can be divided into grid-tied inverters and off-grid inverters.

Characteristics of solar energy inverter

• High efficiency is required. Due to the relatively high price of solar cells at present, in order to maximize the utilization of solar cells and improve system efficiency, it is necessary to find ways to improve the efficiency of the inverter.

• High reliability is required. Currently, PV power generation systems are mainly used in remote areas where many stations are unmanned and unattended. Therefore, it is necessary for solar electric inverter to have a reasonable circuit structure, strict component selection, and various protection functions, such as input DC polarity reverse protection, AC output short circuit protection, overheat and overload protection, etc.

• A wide range of input voltage adaptation is required. Due to the variation of the terminal voltage of solar cells with load and solar radiation intensity, especially when the battery ages, the range of variation of its terminal voltage is very large. For example, for a 12V battery, its terminal voltage may vary between 10V and 16V. This requires the inverter to ensure normal operation within a wider range of DC input voltages.

Tips for selecting solar energy inverter

When selecting an inverter, the rated capacity should first be considered to meet the power requirements of equipment under maximum load. For inverters with a single device load, the selection of the rated capacity is relatively simple. When the load equipment is purely resistive or has a power factor greater than 0.9, the rated capacity of the solar energy inverter is recommended to be 1.1 to 1.15 times the capacity of the load equipment. At the same time, the inverter should also have the ability to resist capacitive and inductive load impacts.

For general inductive loads such as motors, refrigerators, air conditioners, washing machines, and high-power water pumps, their instantaneous power may be 5 to 6 times their rated power during startup. At this time, the inverter will bear a large instantaneous surge. For such systems, the rated capacity of the inverter should have sufficient margin to ensure reliable startup. High-performance inverters can start up multiple times at full load without damaging the power devices. For small solar electric inverter, soft start or current limiting start may be required for their own safety.