First, the working principle and characteristics of photovoltaic inverter
Working principle: The core of the inverter device is the inverter switch circuit, referred to as the inverter circuit. The circuit completes the inverter function by turning on and off the power electronic switch.
1. High efficiency is required.
Due to the high price of solar cells at present, in order to maximize the utilization of solar cells and improve the system efficiency, we must try to improve the efficiency of the inverter.
2. High reliability is required.
At present, the photovoltaic power station system is mainly used in remote areas, and many power stations are unattended and maintained, which requires the inverter to have a reasonable circuit structure, strict component selection, and requires the inverter to have various protection functions, such as: input DC polarity reverse protection, AC output short circuit protection, overheating, overload protection, etc.
3. The input voltage is required to have a wider range of adaptation.
Because the terminal voltage of the solar cell varies with the load and the sunlight intensity. Especially when the battery is aging, its terminal voltage varies widely. For example, for a 12V battery, its terminal voltage may vary between 10V and 16V, which requires the inverter to work normally within a large DC input voltage range. .
2. Types of photovoltaic inverters
Photovoltaic inverters should be selected according to the environment. The photovoltaic inverters on the market are divided into three types: centralized inverters, string inverters, and micro inverters:
1. The centralized inverter is mainly used in large-scale ground power stations, with a voltage level of 315V, suitable for high-voltage grid connection;
2. String inverters, also known as distributed inverters, are mainly used in various barren hills, industrial and commercial or household roofs. The scale of the power station is generally small, and it is integrated into the national grid through the full amount of electricity or surplus electricity.
3. Micro-inverter, mainly used for direct integration on the battery board, suitable for small household power stations.
1. The grid-connected inverter with 220V output voltage is generally used in household photovoltaic power stations. Most of these power stations are integrated into the national grid in the form of self-generated and self-consumption surplus electricity.
2. The grid-connected inverter with 380V output voltage is mainly used in the construction of various industrial and commercial rooftop power stations and small centralized power stations with villages as units in many places in China. Such power stations are mostly integrated into the national grid in the form of full grid connection.
3. Grid-connected inverter with 480V output voltage, this type of inverter is mainly used in barren hills and tidal flat power stations with 10KV medium voltage grid-connected.