Design of Dc-Dc Converter for Integration of Sources Snehal Pachpor Research Scholar, Electrical Engineering Department Visveswaraya National Institute of Technology, Nagpur Maharashtra, India pachporsnehal2@gmail.com H.M.Suryawanshi Professor, Dean (R&C), Electrical Engineering Department Visveswaraya National Institute of Technology, Nagpur Maharashtra, India Email: hms_1963@rediffmail.com Abstract— This paper presents practical design aspects of a high-power DC-DC converter which is applicable to renewable sources for dc grid. The output voltage of a dc-dc resonant converter can be varied by adjusting the switching frequency. In order to maintain output voltage constant from full load to no load using conventional frequency control, the range of switching frequency variation is very high. This consequently increases switching losses, electromagnetic interference which deteriorates the system performance especially for light loads. This paper proposes an algorithm to maintain output voltage constant by variable switching frequency and duty cycle with combined effect. The response using proposed algorithm is tested with 250 W, 110/480V dc-dc resonant converter and performance is analyzed using PSIM simulation. Keywords—Resonant converter,combined frequency duty ratio control I. INTRODUCTION With increasing interest in the area of resonant converters, a number of second and third order resonant converter topologies have been developed [5]. These topologies do not help in obtaining tight voltage regulation at light load conditions. The higher-order resonant converter possesses more desirable characteristics than second and third order resonant converter topologies.The full-bridge modified LCLC-type series resonant converter makes use of higher-order tank circuit. Therefore the designer has a choice to utilize non-idealities of the circuit. II. MODIFIED SERIES RESONANT CONVERTER Fig. 1. Modified series resonant converter and its equi.circuit The main power circuit and its equivalent circuit suitable for operation above resonance are shown in fig.1. The power switches (MOSFETs) S 1 , S 2 , S 3 and S 4 must be capable of withstanding the full supply voltage and must switch on/off at high frequency. D 1 , D 2 , D 3 and D 4 are the feedback diodes and need not be of fast recovery type. It is preferable if these diodes are integrated inside the switch in order to reduce the wiring inductance. The capacitor C n across each switch is a lossless snubber. The resonating components used are L s , C s , L p and C p . The diode bridge rectifier connected across the secondary of high- frequency transformer is of the fast recovery type. The parallel branch (L p ,C p ) of the tank circuit is placed in parallel with tertiary winding of the HF-transformer. The leakage inductance of the HF transformer can be used as part of the resonating inductor (L s ) and inductor (L p ). Thus, this configuration is best suited for higher output voltage, giving better performance in terms of efficiency and voltage regulation. Fig. 2. Idealized waveforms of inverter output voltage and current. 2014 IEEE International Conference on Power Electronics, Drives and Energy Systems (PEDES) 978-1-4799-6373-7/14/$31.00 ©2014 IEEE