Pandian's dc-dc Boost converters for Solar Panels using Twisted Multi wire Transmission Line Transformers: High gain up to 7.4, and no need for additional MPPT control circuits
A dc to dc Boost converter with a single inductor limits the voltage gain due to stray resistances in the inductor to about 1.5. This paper proposes dc to dc Boost converters by using twisted multiwire transmission line transformers specifically for solar panels. An output voltage of 225V in to 3260 ohms (dc voltage gain of about 7.4) was obtained by using a converter with a 5 wire transformer. The circuits work over a wide range of frequencies. Interestingly, the circuits exhibit a DCM mode of operation with good performance when the PWM ratio D is less than about 0.16. In this mode, the solar panel current charges the input capacitor for 84% of the PWM period and the energy in the capacitor is “converted” in the short 16% of the PWM period where the input current of the converter is many times the solar panel current. This results in a good performance of the solar panel without any need for additional MPPT control. The functioning of the converter is explained with waveforms and equations where it is shown that if the frequency of the converter is increased by a factor F, for optimum performance, the D value has to be increased by SQRT(F). The major feature of the proposed converters with solar panels is that no additional MPPT control is required. The efficiency of the converter was better than 81% when the 200W solar panel was tested in door at 12 Watts. The high dc gain possible with the proposed converters will reduce the wiring costs in solar panels and the copper loss in the solar panel wirings.