Modelling and Simulation by Bond Graph Technique of a DC Motor FED from a Photovoltaic Source Via MPPT Boost Converter

Optimum matching of loads to Photovoltaic (PV) generator is most desirable for more accurate sizing. Because of the relatively high cost of the PV generator, the system designer is mainly interested in its full utilisation by optimum matching of the system components during the entire operating period. To achieve an optimum matching of the output characteristics of the PV source to the input characteristics of electromechanical loads, controlled converters are used. The converters topologies are function of optimal PV array and load parameters. Application of PV power to electromechanical loads requires an understanding of the dynamics of such systems. As a very convenient and powerful tool for dynamic modelling, bond graph technique was used. The application of bond graph technique for the modelling of PV systems is not yet widespread. The purpose of this work is to study the dynamic behaviour of a class of PV systems composed of a PV generator, a DC motor, and a boost DC-DC converter. The graphical approach based on bond graph methodology is used to formulate the dynamic model of this PV system. To develop that model, we take into account the non-linear device volt-ampere characteristic PV generator and we use averaged model DC-DC converter. Causality problems are discussed and a simplified model is deduced in order to give information from control loop point of view. Time responses are simulated and stability domain is computed. A performance comparison between buck and boost converters showed disadvantages of these latter topologies in such application. In fact, results showed the existence of non minimal phase responses caused by positive real roots in the transfer function velocity numerator. This situation leads to mechanical problems hardly bearable by electromechanical machines. IMACS/IEEE CSCC'99 Proceedings, Pages:2591-2599 KeysWord s : Bond graph, photovoltaic, modelling, simulation, boost converter, MPPT, Acronym s: photovoltaic:PV, direct current: DC