Non-Isolated DCM/DCD Operated Step-Up Inverter Derived Novel CCM Operated Five Switch Step-Up/Down Inverter for Renewable Energy Applications

Abstract

A new non-isolated single stage DC/AC inverter namely five switch step-up/down inverter derived from a discontinuous conduction mode (DCM)/discontinuous-continuous- discontinuous (DCD) operated five switch step-up inverter for efficient utilization of renewable energy is introduced in this paper. The five switch step-up inverter enables stepping up of renewable energy output voltage and direct AC conversion as well. In cases of wide inverter input voltage variation which occurs in most of the renewable energy sources, which cannot be handled by this DCM/DCD operated step-up topology, continuous conduction mode (CCM) operated five switch step- up/down inverter is required. A novel sinusoidal pulse width modulation (SPWM) based control strategy is implemented for CCM operation of this inverter. With the help of this step- up/down topology, a DC input voltage greater than instantaneous AC output voltage is subjected to step-down operation and a DC input voltage less than instantaneous AC output voltage is subjected to step-up operation. With the implementation of this control strategy, a high voltage gain is attainable with reduced step-up/down inductor current ripple which in turn enhances efficiency. Additional benefit of this five switch step- up/down inverter topology is that only one switch operates at high frequency throughout line cycle, the remaining switches operates at low frequency. Since only a single switch is responsible for both step-up as well as step-down operation attainment, the switching stress on the remaining switches is much reduced, thus improving inverter efficiency. The CCM operated inverter behaviour is studied and its topological structure simulated using MATLAB/SIMULINK. Results of open loop control is discussed and theoretically verified.