Equipment for the analysis of the maximum energy of real photovoltaic systems

This paper proposes the use of an electronic equipment for the analysis of the maximum available energy of photovoltaic generators as a function of the number of MPPT's implemented on the system. The equipment measures and stores systematically the real evolution of the I-V characteristic curves of photovoltaic modules or generators (group of modules). The equipment consists of a current-controlled converter, a microcontroller and a data storage unit. The microcontroller is a DSP that drives the converter by means of generating the proper current reference. It also organizes the measured characteristic curves from the arrays and generators to be stored in the data storage unit. Both the DSP and the data storage unit are placed in a PC. The equipment can measure three times per second the complete I-V characteristic curves of up to seven different arrays or photovoltaic generators. Software has been developed and implemented to deal with the measured curves in such a way as to decrease the number of points per curve, reduce the number of curves depending on the irradiance variation, code the curves, and store them in a database. Finally, another software makes possible to analyse off line the stored data and calculate the energy of the photovoltaic generator in different working conditions. As an example, a 2 kW photovoltaic generator is analysed in different weather conditions as a function of the number or MPPTs used.