ABSTRACT
This research studied a circuit topology of a solar based Single Ended Primary Inductance Converter (SEPIC) system and a battery furnishing a permanent magnet dc motor with current via a dc grid. The complete model equations of the entire system were derived. Harmonic balance technique was used to determine the converter steady state and ripple quantities. Analyses investigating the relationship of the converter state variables as a function of its duty ratio were developed. Results show that operating the converter between 0 - 0.4 duty ratio give best system performances. On the other hand, results show that operating the converter above this range limits the converter optimal performance. The consequence of operating the system with duty ratios above 0.4 is that the ripples in the voltage and current waveforms increase. More so, results also show that for a steady state current of 12 A, for the permanent magnet dc motor in a period of low solar insolation, operating a Bi-directional converter at specific values of duty ratio causes the battery to discharge much faster compare to operating at duty ratio of 0.78. Two solar insolation data for Zaria (Lat 11.0670N Long 7.70E) was obtained from National Aeronautics and Space Administration (NASA) for a period of January to December 2013 and another ground level captured from Electrical & Computer Engineering Department using the data acquisition module (model TQ 140876-002) from August 17 to September 24, 2014. These insolation data from both stations were used to validate the efficiency of the proposed design. The targeted load demand of approximately 2441.43W was achieved. This represents 97.66 % of the load demand designed for in this research. The designed solar energy system contributed 70% of the power to the load, while the battery supplied 30% of the load demand power. An effective hybrid storage system based on solar and battery was achieved, which met the designed objective of this research.