Energy conversion and control technology of building integrated photovoltaic

Building integrated photovoltaic (BIPV) is the important form using renewable energy in future city. In BIPV system, conventional building elements can be replaced by special PV modules to perform the same functions; therefore, its advantages include low installation cost, shortened energy payback time and pleasant architectural appearance. The structures of BIPV system can be mainly divided into centralized configuration, string, multi-string, AC module and DC module according to the different combinations of PV array and inverter (converter). AC and DC module configurations have good flexibility, plug-and-play and anti-mismatch performance for each module operates with separate MPPT. However, module configurations are complex, and haven´t popularization in market. The centralized and string configurations have more extensive application in practice, but MPPT mismatch is easy to appear especially under partial shadow condition (PSC). This paper proposes a novel MPPT algorithm based on analyzing the output characteristics of PV array under uniform irradiance and PSC in centralized and string configurations. The MPPT algorithm adds partial shadow judging conditions in variable step perturb and observe (P&O) method. The system runs the variable step P&O method to realize MPPT when PV array under uniform irradiance. Under PSC, the control method can eliminate the interference of local maximum power point (MPP) to make the PV array running at global MPP. Simulation and experimental results verify that the proposed algorithm have good effect in centralized and string configurations of BIPV system.