Efficiency of solar inverter

The efficiency of solar inverters means that the market for solar inverters (photoelectric inverters) is growing due to the demand for renewable energy. These inverters require high efficiency and reliability. The power circuits used in these inverters are investigated, and the best choice for switch and rectifier devices is recommended. The general structure of the photoelectric inverter is shown in Figure 1, and three different inverters are available for selection. The sunlight shines on the solar modules connected in series, and each module contains a group of solar cell cells in series. The DC voltage generated by the solar module is in the order of several hundred volts. The specific value depends on the lighting conditions of the module array, the temperature of the battery and the number of modules in series.

The primary function of this type of inverter is to convert the input DC voltage into a stable value. This function is realized by a boost converter, which requires a boost switch and a boost diode. In the first structure, the boost stage is followed by an isolated full bridge converter. The function of the full bridge transformer is to provide isolation. The second full bridge converter on the output is used to convert the DC of the first stage full bridge converter to the AC voltage. Its output is filtered before being connected to the AC power grid through additional double contact relay switch, so as to provide safe isolation during fault events and isolation from the power grid at night. The second structure is the non isolation scheme. Among them, the AC voltage is directly generated by the DC voltage output from the voltage rise stage. The third structure uses the innovative topology of power switch and power diode to integrate the functions of boost and AC generation in a dedicated topology. Although the conversion efficiency of the solar panel is very low, it is very important to make the efficiency of the inverter as close to 100% as possible. In Germany, the 3kW series module installed on the roof facing south is expected to generate 2550 kWh per year. If the inverter efficiency increases from 95% to 96%, it can generate more 25kWh every year. The cost of using additional solar modules to generate this 25kWh is equivalent to adding an inverter. Since the increase in efficiency from 95% to 96% will not double the cost of the inverter, it is inevitable to invest in more efficient inverters. For the emerging design, the key design criterion is to improve the inverter efficiency most cost effectively. The reliability and cost of inverter are the other two design criteria. Higher efficiency can reduce the temperature fluctuation on the load cycle, thus improving the reliability. Therefore, these criteria are actually related. The use of modules will also improve reliability.