Photovoltaic power conversion with efficiency weight optimisation

Abstract

Photovoltaic power conversion systems for power rating of about 2.5 kW consist generally of a step-up converter, a DC-AC inverter for 5 Hz and the transformer coupling to the grid. Potential separation is required between the modules and grid. A standard 5 Hz transformer can accomplish this separation. Heavy in weight, loud in noises and exhibiting high temperatures through the transformer make the whole system large in volume and expensive. By discussing optimisation facts, new ideas in the conversion structure have been found in a two-inverter conversion concept and will be evaluated in this synopsis. The main idea of this new concept is to make the necessary separation also with a transformer but with a ferrite core and an operating frequency of 2 kHz. Optimised for these 2 kHz the above-mentioned problematic facts will be minimised. The first converter is used for the DC-AC conversion to the base of 2 kHz. The second inverter, supplied after the transformer and a stabilised rectifying system, makes the DC-AC conversion to the 5 Hz grid. Further on, component costs will be reduced through using the same kind of inverter. Also the control management is more modular and effective.