Harmonics assessment and mathematical modeling of power quality parameters for low voltage grid connected photovoltaic systems

Since the penetration of photovoltaic (PV) systems in the Low Voltage (LV) distribution network is increasing, the need to characterize and model the effect of these systems on power quality parameters is an up-to-date issue. Also, the reactive power capability of PV inverter should be defined and discussed. This research presents and investigates the experimental measurements of power quality parameters in-field on 8 kWp PV system connected to the LV distribution network in Electronics Research Institute, Egypt. This research aims to investigate unity power factor and constant reactive power functions as two different operation modes of PV inverter based on the measurements at PV inverter output and the grid point without local loads at off days of the governmental building in order to avoid load effects on the PV inverter parameters. Field measurement data were recorded using the power quality analyzer CA8335. Statistical analysis of each harmonic, power factor and total harmonic distortion are analyzed and presented under different loading conditions and two different functions of the PV inverter. The focus is set on the characterization of the relationship between current harmonics of PV inverter and voltage harmonics prevailing in LV system. It is found that the PV inverter presents high current total harmonic distortion levels at power levels below its rated value. This paper proposes mathematical models in order to characterize the current total harmonic distortion and the power factor at two different operation modes. The accuracy of the proposed empirical models was compared with previous research studies and presented the highest accurate results. The presented results are useful for the manufacturer of the tested PV inverter.