Calculation of dynamic MPP-tracking efficiency of PV-inverter using recorded irradiance

The inverter is the key element in grid-connected photovoltaic systems. Measurements of inverter efficiency should take into account two phenomena: the DC/AC conversion and Maximum Power Point (MPP) tracking process. Since the solar energy flux is variable, the PV-inverter operates with a wide range of load levels and also must face rapid changes of the input power. For MPP-tracking both static and dynamic conditions introduce problems that must be solved at the level of MPPT control algorithm. The reaction of some inverters to rapid irradiance changes has already been studied by applying selected input test-patterns in laboratory conditions. This paper presents the opposite approach by taking the recorded real-life irradiance profile and simulating the tracking algorithm behavior. The results of calculation of dynamic MPP-tracking efficiency have been performed for basic Perturb & Observe algorithm, using irradiance data of a variable-cloudy day, recorded with 1 s resolution.