Configuration of a photovoltaic (PV) power generator has influence on the operation of the generator, especially if it is prone to partial shading. In this paper, the mismatch losses and the power losses due to failure in tracking of the global maximum power point of a long string of 18 series-connected PV modules and three short strings of six series-connected PV modules connected in parallel are investigated under different partial shading conditions by using a MATLAB Simulink simulation model. The generators with parallel-connected short strings are studied in case when they have the same operating voltage and when they operate as separate strings. The results show that long series connection of modules and parallel connections of strings via a single inverter to the electrical grid should be minimized to avoid losses in case of partial shading conditions. Under partial shading conditions, short strings operating separately have the lowest power losses.

A photovoltaic (PV) generator is internally a power-limited nonlinear current source having both constant-current- and constant-voltage-like properties depending on the operating point. This paper investigates the dynamic properties of a PV generator and demonstrates that it has a profound effect on the operation of the interfacing converter. The most important properties an input source should have in order to emulate a real PV generator are defined. These properties are important, since a power electronic substitute is often used in the validation process instead of a real PV generator. This paper also qualifies two commercial solar array simulators as an example in terms of the defined properties. Investigations are based on extensive practical measurements of real PV generators and the two commercial solar array simulators interfaced with dc-dc as well as three- and single-phase dc-ac converters.

Unsupported nanometer-sized copper particles in a molecular beam of inert carrier gas have been studied using electron diffraction. A distinct separation in the size distributions of fcc and icosahedral particles is observed: Icosahedra occur at sizes well below a diameter limit of 3.8 nm predicted for copper by molecular dynamics simulations, while fcc particles occur close to this limit or above. Molecular dynamics simulations have also provided information about particle temperature via thermal expansion and atomic dynamics.