Measurements of power transfer efficiency in CPV cell-array models using individual DC–DC converters

• Non-uniform illumination is a major problem in parabolic dish CPV systems.
• A connection fitting each cell of the array with a DC–DC converter is used.
• The possibility of choosing the working point of each cell is the key advantage.
• An array using diodes is shown to increase the efficiency of this connection.
• Another experiment, using real solar cells, confirms the benefits.

The high degree of non-uniformity in the irradiance distribution over series-connected solar cells is the main obstacle to the development of concentration photovoltaic (CPV) systems using parabolic dishes. In order to overcome the power loss resulting from the current mismatch due to illumination inhomogeneity, we propose a new cell connection with individual DC–DC converters. The aim of this work is to present an experimental procedure to implement this new approach and to demonstrate its advantages with a basic CPV array prototype. Two separate experiments are carried out respectively with real and equivalent-circuit solar cells in order to study the I–V behavior of the connection under different irradiance distributions. The cells working points which yield the highest net power are determined by maximizing the array efficiency by means of a calculation algorithm. The effectiveness of the system is then proved by comparing the output power obtained by field measurement, with the maximum power that could be delivered by the cells array connected in series. In this study, a possible path towards the development of a more effective CPV receiver prototype is outlined.

Illumination non-homogeneity is the main problem which affects dense-array CPV systems. In a previous work we theoretically showed that connecting each cell in the array to a DC–DC converter module, leads to an increase of the power transfer efficiency with respect to classical series connection. This finding is here confirmed by two experiments making use of a cells’ array, one for a certain combination of shirt circuit currents and another for a typical illumination distribution produced by a parabolic reflector. Encouraging gains in the order of 10% are found.Figure optionsDownload as PowerPoint slide