Inverter is a device that converts direct current into alternating current. Photovoltaic inverter is an inverter designed for photovoltaic power generation system. Photovoltaic inverter is an important part of photovoltaic power generation system. The core of photovoltaic power generation is to use photovoltaic modules to convert solar energy into electrical energy. However, because photovoltaic modules can only generate direct current, and the size is related to the intensity of sunlight, it is difficult to use directly. Therefore, it is necessary to convert this direct current through photovoltaic inverters into our commonly used electricity. Alternating current, facilitates the transmission and utilization of electricity.

Photovoltaic inverters can be mainly divided into grid-connected inverters, off-grid inverters and micro inverters according to their functions.

1. Grid-connected inverter

Grid-connected inverters are mainly used in grid-connected photovoltaic systems, and the converted current is usually fed into the national grid. Grid-connected inverters can be divided into four categories according to power and use: micro inverters, string inverters, centralized inverters, and distributed inverters.

Micro inverters, also known as component inverters, have a power rating of 180W to 1000W and are suitable for small power generation systems.

String inverters are single-phase inverters with power from 1KW to 10KW, suitable for household power generation systems, grid-connected voltages of 220V, and three-phase inverters from 4KW to 80KW, suitable for industrial and commercial power generation systems.

Centralized inverters and distributed inverters, with power from 500KW to 1500KW, are generally used in large ground power stations.

2. Off-grid inverter

The off-grid inverter is suitable for independent off-grid photovoltaic systems, and the converted current can be stored in the battery except for self-use.

3. Microgrid inverter

The microgrid inverter will be connected to the battery panel separately to better improve the conversion efficiency.

Selection of photovoltaic inverters

There are many types of inverters, so special attention should be paid when selecting models and capacities. Especially in solar power generation systems, the efficiency of inverters is an important factor in determining the capacity of solar cells and batteries.

The selection of the inverter must first consider having enough rated capacity to meet the electrical power requirements of the equipment under the maximum load. For the inverter with a single device as the load, the selection of the rated capacity is relatively simple.

When the electrical equipment is a purely resistive load or the power factor is greater than 0.9, the rated capacity of the inverter should be 1.1-1.15 times the capacity of the electrical equipment, and the inverter should also be resistant to capacitive and inductive load shocks Ability.

For general inductive loads, such as motors, refrigerators, air conditioners, washing machines, high-power water pumps, etc., when starting, the instantaneous power may be 5-6 times its rated power. At this time, the inverter will withstand a large instantaneous power. surge. For this type of system, the rated capacity of the inverter should have sufficient margin to ensure reliable starting of the load. High-performance inverters can be started at full load for many times in a row without damaging the power device. For its own safety, small inverters sometimes need to use soft start or current limit start.