An inverter is a device that converts direct current into alternating current, and a photovoltaic inverter is an inverter designed for photovoltaic power generation systems. Photovoltaic inverters are an important part of photovoltaic power generation systems. The core of photovoltaic power generation is to use photovoltaic modules to convert solar energy into electrical energy. However, since photovoltaic modules can only generate direct current, and its size is related to the intensity of sunlight, it is difficult to use it directly. Therefore, it is necessary to convert this direct current into our commonly used Alternating current, which facilitates the transmission and utilization of electric power.
Classification of photovoltaic inverters
Photovoltaic inverters can be 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 input into the national grid. Grid-connected inverters can be divided into four categories according to power and usage: micro inverters, string inverters, centralized inverters, and distributed inverters.
Micro inverters are also called component inverters, with a power rating of 180W to 1000W, suitable for small power generation systems.
String inverters are single-phase inverters with a power of 1KW to 10KW, suitable for household power generation systems, grid-connected voltage of 220V, and 4KW to 80KW three-phase inverters, 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 an independent off-grid photovoltaic system, and the converted current can be stored in the battery except for its own use.
3. Microgrid inverter
The micro-grid 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 the model and capacity, especially in solar power generation systems, the efficiency of the inverter is an important factor in determining the capacity of solar cells and storage batteries.
The selection of the inverter must first consider having sufficient rated capacity to meet the electrical power requirements of the equipment under the maximum load. For the inverter with a single equipment as the load, the selection of the rated capacity is relatively simple.
When the electrical equipment is a pure 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 impacts 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 the rated power. At this time, the inverter will bear a large instantaneous power surge. For this type of system, the rated capacity of the inverter should have a sufficient margin to ensure reliable start-up of the load. A high-performance inverter can be started at full load for many times without damaging the power device. Small inverters sometimes need soft start or current-limited start for their own safety.