A New 0.8Voc Model Technique to Estimate the Peak Global Voltage for Medium Voltage Megawatt Photovoltaic System Integration

Abstract

The paper proposes a new 0.8Voc model technique for medium voltage megawatt photovoltaic (PV) system integration. The power-voltage characteristic of photovoltaic (PV) modules shows multiple of local maximum power point when the modules are exposed to different irradiance levels. It is predicted that the local peaks are located near the multiples of 0.8 Voc, where Voc is .the open circuit voltage of the PV module. However, this prediction is not necessary correct especially with long string of PV modules exposed to lower irradiance level. It is most likely that the algorithm will deviate from the original peak locations and unnecessary scanning will be essential. Therefore, a new 0.8Voc model is proposed, which estimates the voltage at global maximum power point. By scanning the PV current on I-V characteristic curve to map out solar irradiance pattern, peak voltage and related deviation correction expressions are calculated. Afterwards, the position of the global peak voltage is estimated. The proposed algorithm is capable of exploiting the advantages of conventional 0.8Voc model, while improving its performance. The principles of design and theoretical analysis of the proposed algorithm are presented and its feasibility also validated by simulation for medium voltage megawatt photovoltaic (PV) system integration.