In the technical specifications of the PV inverter, the MPPT efficiency indicator will be marked. MPPT efficiency is the most critical factor in determining the amount of PV inverter power generation, and its importance greatly exceeds the efficiency of the PV inverter itself. At present, domestic and foreign PV inverters can compare the power generation under the same conditions, and the difference may be as high as 20%. The main reason for this difference is MPPT efficiency. The calculation method and source of MPPT efficiency are introduced below.

The efficiency of MPPT is equal to the hardware efficiency multiplied by the software efficiency. The hardware efficiency is mainly determined by the accuracy of the current sensor and the accuracy of the sampling circuit. The software efficiency is mainly determined by the sampling frequency. MPPT implements a variety of methods, but whether it is adopted That method must first measure the change in component power and then react to the change. This involves a key component, the current sensor, its accuracy and linearity will directly determine the hardware efficiency, and the sampling frequency of the software is also determined by the accuracy of the hardware.

At present, the current sensor has two kinds of open loop and closed loop. The open loop current sensor has a measurement accuracy of 99%, a linear accuracy of 99%, a total measurement error of 2%, a closed loop current sensor measurement accuracy of 99.6%, a linear accuracy of 99.9%, and a total measurement error of 0.5. %. What does this mean? For example, if an open-loop current sensor is used, the component power will change by 2%, and the inverter will not be detected. Because the error of the open-loop current sensor is large, the sampling frequency is also reduced, otherwise oscillation will occur, so the efficiency of the software. It can only reach 99%, that is to say, the inverter with open-loop current sensor has an MPPT limit efficiency of only 97%, while the PV inverter with closed-loop current sensor has an MPPT limit efficiency of 99.5%.



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