Solar inverter efficiency

- Sep 12, 2018-

The efficiency of solar inverters means that the market for solar inverters (photovoltaic inverters) is growing due to the demand for renewable energy. These inverters require extremely high efficiency and reliability. The power circuits used in these inverters were examined and the best choice for switching and rectifying devices was recommended. The general structure of the photoelectric inverter is shown in Figure 1. There are three different inverters to choose from. Sunlight illuminates the solar modules connected in series, each module containing a set of solar cells in series. The direct current (DC) voltage generated by the solar module is on the order of hundreds of volts, depending on the lighting conditions of the module array, the temperature of the battery, and the number of series modules.

The primary function of this type of inverter is to convert the input DC voltage to a stable value. This function is implemented by a boost converter and requires a boost switch and a boost diode. In the first configuration, the boost stage is followed by an isolated full bridge converter. The role of a full bridge transformer is to provide isolation. The second full bridge converter on the output is used to convert the DC DC from the first stage full bridge converter to an alternating current (AC) voltage. The output is filtered before being connected to the AC grid network via an additional two-contact relay switch to provide safe isolation during fault events and isolation from the supply grid at night. The second structure is a non-isolated scheme. Wherein, the AC alternating voltage is directly generated by the DC voltage outputted by the boosting stage. The third architecture utilizes an innovative topology of power switches and power diodes to integrate the functions of the boost and AC-AC generation in a dedicated topology. Although the conversion efficiency of the solar panel is very low, the efficiency of the inverter is as high as possible. Close to 100% is very important. InGermany, a 3kW series module mounted on a south-facing roof is expected to generate 2,550 kWh per year. If the efficiency of the inverter increases from 95% to 96%, it can generate 25kWh more per year. The use of additional solar modules to generate this 25kWh is equivalent to adding an inverter. Since efficiency increases from 95% to 96% does not double the cost of the inverter, investing in more efficient inverters is an inevitable choice. For emerging designs, the most cost-effective way to increase inverter efficiency is the key design criteria. As for the reliability and cost of the inverter, there are two other design criteria. Higher efficiency can reduce temperature fluctuations over the load cycle, thereby increasing reliability, so these criteria are actually related. The use of modules also increases reliability.