ABSTRACT
This paper presents design of DC interface unit for PV -grid connected roof top system. The proposed design takes care of safety standard given by Electro-Tecnical Commission in IEC-364 together with reliability and efficiency aspects. The DC interface unit is based on H-bridge topology and is operated at 100 KHz frequency. The reliability of the system is high due to use of embedded controller 80196 chip. Conventional pulse width modulation (PWM) technique can not be used because it results in poor efficiency at light load condition due to cross modulation and electro magnetic interferences. In addtion it is very difficult to operate the system at maximum power point (MPP) due non-availability of enough steps to provide effective modulation. These problems are overcome by using new technique i.e. Time Division Modulation. The design is very relevant because it enables the software control to implement MPP operation at very high frequency which resulted in 1KW power from 8 cubic inch transformer. In addition the energy conversion of DC interface module is 90% from quarter load to full load.
