Graphic computational platform integrated with an electronic emulator dedicated to photovoltaic systems teaching

Abstract

This study deals with the development of a photovoltaic (PV) electronic emulator (PVEE), operating integrated with a graphic computing platform, for teaching topics related to PV systems in either undergraduate or postgraduate courses. The PVEE is deployed by a DC-DC buck converter to emulate on its output terminals several characteristic curves of a specific PV system, in which climate conditions such as solar irradiation and temperature are taken into account. Emulation of the PV module characteristic curves is embedded in a digital signal controller, which is based on a mathematical model that represents the electric circuit of the PV cell. The educational platform makes possible the following tasks: (i) define and change the PV cell model, (ii) define the number of PV modules, (iii) define and change the solar irradiation and temperature that the PV modules are subjected to, and (iv) visualise voltage and current quantities that are synthesised by the PVEE. From experimental tests, the PVEE is evaluated considering climatic variations involving solar irradiation, temperature, and load transients, whose purpose is to validate the theoretical development. Furthermore, the DC-DC boost converter is employed to perform the maximum power point tracking. Experimental results demonstrate the effectiveness of the proposed system.

Educational Experimental Platform for Emulation of Photovoltaic Modules

“…The mathematical model of the PV module is derived from well-known single-diode equivalent circuit of the PV cell, with parallel and series resistances, which is shown on Fig The circuit from Fig. 2 can be described with following equations, which are given in [5]: It is obvious from (1)-(5) that the PV model has three inputs: PV voltage vpv, solar insolation Iins and ambient temperature T, and one output: PV current ipv from (1). The model parameters, such as Isc, Voc and other, are the standard PV module data-sheet parameters.…”

“…However, these emulators have low power ratings and not so high precision. Most of the PV emulators known in literature are based on DC-DC power electronics converters, especially on buck converter [5]- [13]. Although their complexity is increased, they offer higher power ratings, typical for PV modules and arrays, and much better matching between the characteristics of real and emulated PV modules.…”

“…However, considering that the PV modules are current sources by their nature, it is better using current mode control (CMC), especially having in mind all the benefits of CMC over VMC. Majority of the mentioned PV emulators employ CMC [5]- [11]. Usually, the load voltage is measured and fed into the PV model.…”

“…Considering that the load current of the buck converter is equal to the average inductor current, the calculated PV reference current can be used as a reference inductor current, as it is proposed in [5], which means that the average current mode control (ACMC) can be applied. Also, in [11] is shown that both current regulators can be used at the same time: the outer load current PI regulator and the inner inductor current regulator, which is based on predictive ACMC.…”

“…Important issue in practical realization of the PV emulator is implementation of the PV mathematical nonlinear model. The PV model could be implemented on various digitals platforms, such as microcontrollers or digital signal processors [5], [7], [8], [11], [13], field programmable gate arrays [9], [14], etc. Especially interesting is using Matlab/Simulink environment for real time implementation of the PV emulators, by utilization of data acquisition boards [12], [15], [16].…”