Comparison of power converter technologies in photovoltaic applications

The different basic topologies of DC/DC converters (buck, boost, and buck-boost) are compared with a view to their use in PV (photovoltaic) systems, where maximum power tracking of the PV array is required as climatic conditions and load vary, in order to optimize the efficiency of the conversion chain. The existence of dissipative elements in a real converter is taken into account in order to assess the efficiency obtainable with varying modulation parameters. Efficiency expressions are found for the three basic converter types used in such applications. It is found that the nature of the load plays a decisive role in the choice of topology. Where the load it inductive, as is the case for motors, the most suitable converter appears to be the buck type. In the other cases the choice is more complex and a careful analysis is required in order to find the optimum solution. The frequency ranges and semiconductor devices most suited to the different applications are briefly discussed. The possibility of using resonant and quasi-resonant conversion techniques for particular applications with high operating frequencies and lightweight equipment is examined