Current-Fed Switched Inverter based hybrid topology for DC Nanogrid application

Abstract

High boost DC to AC inverters are used in renewable energy systems like solar PV, fuel cell, wind farm etc and UPS systems to mention a few. High voltage boost, wide output ranges of operation, shoot-through immunity are some of the desired properties of an inverter for a reliable, versatile and low distortion AC inversion. This paper proposes a single-stage, high boost inverter with buck-boost capability which has several distinct advantages over conventional voltage source inverters (VSI) like better EMI noise immunity, wide input and output voltage range of operation, etc. The proposed inverter is named as Current-Fed Switched Inverter (CFSI). A hybrid converter structure of CFSI has been developed which supplies both AC and DC loads, simultaneously, from a single DC supply which makes it suitable for DC Nanogrid application. This paper proposes the operation and control of a CFSI based hybrid converter which regulates the AC and DC bus voltages at their reference values in steady-state or dynamic load change event. The development of the proposed converter from basic current-fed DC/DC topology is discussed. Steady-state analysis of the converter is outlined to establish the relation between DC input and AC output. Small-signal analysis of the converter is done to design the closed loop controller for the converter. An experimental prototype is built to validate the proposed converter with its DSP based closed loop control. The closed loop controller is verified through its low cross regulation and dynamic performance for a 20% step change in either DC or AC load.