Performance Comparison between Micro-inverter and String-inverter Photovoltaic Systems

This paper focuses on the analysis of the energy production of building integrated photovoltaic systems. All the PV systems are located in the south part of Italy - Sicily. A comparison has been made between two different conversion technologies: string-inverter versus micro-inverter. The two string-inverter systems analyzed have different azimuth angle, no shadowing, different peak power and different types of photovoltaic modules ( monocrystalline and polycrystalline silicon). The four micro-inverter systems have different shadowing percentage, different azimuth. All systems have fixed tilt angle and fixed azimuth angle. The experimental data were treated for almost one year. In order to analyze the performance of the systems, the most common Indexes (the Energy Yield Yf, the Reference Yield YR, the Performance Ratio PR and Efficiency K) have been used. This allowed to obtain a correct comparison even with different Irradiance values and different Peak Powers. The main goal of the analysis has been to evaluate the performances of the micro-inverter systems at different shadowing conditions. The results of the comparison have confirmed that micro-inverter systems present better performances both at shadowed and “not-shadowed” conditions. By comparing not-shadowed systems with the two different conversion technologies and similar azimuth and tilt angle it has been shown how, with almost the same values of Irradiance, micro-inverter systems maximize the energy production. Furthermore, the highest percentage of produced energy could justify the more expensive cost of this new conversion technology