should be mentioned that the corresponding power p in fig2 is defined by the rectangles which bound the individual points of these rectangles only the rectangle associated with p 4 is emphasized by hatching the characteristic curve s 1 in fig2 continuously changes depending on the incident solar radiation intensity and or the temperature if a change occurs the dotted curve s 2 may be obtained this produces a new peak power point for example the value mpp 2 with the afore described control method the dc voltage u is adjusted so that the solar generator is operated at the new peak power point mpp 2 fig4 shows a photovoltaic system 1 with a solar generator 3 having a plurality of photovoltaic modules 5 each module 5 in turn includes a plurality of photovoltaic cells the modules 5 are connected in a conventional manner in series and have terminals 7 at their respective ends at which the generated dc voltage u and the resulting dc current i can be obtained depending on the dc current i consumed by the load connected to terminals 7 a dc voltage u corresponding for example to the voltage depicted in the curves s 1 and s 2 of fig2 can be supplied a dc motor 9 is connected to terminals 7 the dc motor is implemented as an externally excited dc machine with an excitation winding 11 the shaft 13 of the dc motor 9 drives a three phase ac generator 15 in particular a three phase generator with a higher output voltage the generator 15 is connected to a three.