Transient response of single-phase photovoltaic inverters to step changes in supply voltage distortion

This paper presents an experimental study on the transient response of three commercially available photovoltaic (PV) inverters on step changes in the supply voltage distortion. Step changes of individual harmonics are applied to three different PV inverters varying in order, amplitude and phase angle. Moreover, different times of switching in terms of the fundamental frequency, i.e. points on wave, are considered. From the laboratory results presented, it can be seen that the inverters behave very different. To quantify the dynamic response characteristics, three parameters of interest are defined and evaluated: the overshoot of the grid-side current, the settling time and the eigenfrequencies of the transient response. The dependencies of these parameters on the above mentioned impact factors are analyzed, which can be used e.g. to develop dynamic models of PV inverters. The paper demonstrates the importance for assessing the transient response (dynamic behavior) of PV inverters and the individuality of their behavior, which requires inverter-make dependent models for grid-studies. A single model covering different makes of inverters is insufficient.