Analyses and comparison of direct maximum power point tracking (MPPT) algorithms has resulted in this valuable paper. Three direct maximum power point tracking (MPPT) algorithms with non-adaptive voltage step were evaluated in the light of their performance for photovoltaic systems under dynamic conditions for a resistive load. A microcontroller-based buck–boost DC–DC converter platform is used to implement and compare the algorithms. Dynamic test procedures from a new standard for inverter efficiency determination EN 50530 were implemented to evaluate dynamic MPPT algorithms’ efficiency and their dependence. Experimental results showed that MPPT algorithms’ regulating frequency and regulating voltage step play a crucial role in the dynamic performance of direct algorithms. A range of regulating frequencies and voltage steps were examined. If proper parameter values are chosen, all algorithms perform well and close to each other. Detailed evaluation was performed with determining partial MPPT efficiency under different irradiance slopes. Results showed that at least 10 Hz should be used to satisfy the 99% tracking efficiency over all slopes in the range from 0.5 to 100 W/m2/s as specified by EN 50530 standard. Further increase of regulating frequency would result in higher slope efficiency only at dynamic conditions.

COBISS.SI-ID: 8505172

The energy yield of photovoltaic (PV) systems with fixed free-standing PV arrays is affected also by the self-shading effects. The rows of PV modules in arrays may partially shade the PV modules in the rows behind. In this paper the effects of the row distance on the PV system’s energy yield were valuated. The estimation of the self-shading losses by the irradiation losses simply overestimates the losses; therefore we developed an accurate simulation model to simulate the real energy loss due to shading of the preceding row in a PV system. The model demonstrates that the self-shading energy losses are at commonly used distances between rows from 20 to 40% lower than the irradiation losses at the modules’ bottom considering the shading conditions. The self-shading energy loss is studied in the case of Ljubljana, Slovenia which may refer to the whole Central Europe. To estimate the self-shading losses a technology and with parameter modifications also location-independent empirical equation based on module-to-cell width ratio was derived and validated.

COBISS.SI-ID: 8374868

Long-term measured meteorological values should be used to obtain reliable results on PV yield. Only then it is possible to dimension the PV system for yield optimization. We showed that the measured irradiation values are the most important parameter in photovoltaics. If only measurements of global irradiation are available, the diffuse part of irradiation can be simulated. Temperature measurements have merely a small effect on optimal orientation of PV system. Accurate albedo values are also irrelevant for the system orientation during the summer as albedo is usually low and optimal tilt angles are small. However in regions, where the albedo changes significantly during the year, is its accuracy important especially during winter, as the ground covered by snow is often even brighter than the sky.

COBISS.SI-ID: 8560468