A New Snubber-less Soft-Switching Based Push-Pull DC-DC Converter for Grid-Connected Renewable Energy Application

Abstract

A bidirectional current-fed three-phase push-pull dc/dc converter is proposed for DC micro-grid application. The proposed converter is analyzed and designed to interface two dc buses of 48 V and 380 V in a micro grid. An innovative novel modulation technique is proposed to clamp the device voltage spike across primary side current-fed devices at turn-off solving traditional problem. The proposed modulation helps achieve natural zero current commutation of low voltage side (LVS) devices and zero voltage switching (ZVS) turn-on of high voltage side (HVS) devices. This eliminates the use of passive/active snubbersless in conventional current-fed topologies to mitigate the voltage-spike across the devices. The steady-state operation, analysis, and design of the converter with proposed modulation are explained. Soft-switching conditions are derived. It eliminates the use of passive/active clamp circuits to mitigate the turnoff voltage spike across the devices, a traditional problem associated with current-fed topologies. Additionally, the higher ripple frequency reduces the volume of the transformer and the input inductor, making it suitable for high-power applications. The micro grid on the other hand, although not a replacement of the national grid, aids the grid by decentralized generation incorporating environmental friendly distributed energy resources. Also, the bidirectional functionality makes the grid structure smart and interactive where traditional central control is shifted to decentralized control and energy storage plays a vital role in grid support. The proposed converter fed with an inverter and integrated with AC grid.