Analysis of casecaded cuk converters and a PWM inverter for use in a PV system

Abstract

Conventional Photovoltaic system use low voltage appliances of 12 or 24 volt rating. Normally available 230VAC, 50Hz lamps, fans and electronics goods cannot be used in these system. In this thesis, attempt to made to design and analyze a dc-dc-ac converter to provide a 230VAC at 50 Hz from PV modules and energy storage batteries used in PV systems. DC converters are used as DC transformers to step up or step down DC voltages. Harmonics are generated at the input and load side of the converter, and these harmonics can be reduced by input and output filter. A Cilk converter increases and decreases the output voltage. In this thesis work a 12V DC to 300V boost is required. A two stages or cascaded Cilk converter is step up the DC voltage to 340V from 12V battery. Cascaded Cilk converter is used for stepping battery voltage up, which can then be converted to AC by a PWM inverter and filtered to have sinusoidal 230VAC at 50Hz. The output AC thus obtained can be regulated precisely, either by controlling the duty cycle of the cascaded Cilk converter or by controlling modulation index of the PWM inverter. The required 230VAC, 50Hz is obtained by a conventional single phase PWM inverter followed by low pass LC filter. The complete circuit has been studied by simulation in this work so as to obtain the design procedures of an integrated switch mode DC-DC-AC power converter. The study provides an integrated switching mode conversion of 12VDC to 230VAC at 50 Hz which will allow conventional appliances of 50 Hz, 230VAC to be used in domestic photovoltaic system.