Single phase grid connected current source inverter: Mitigation of oscillating power effect on the grid current

Abstract

Although voltage source inverters (VSIs) are the most common DC-AC grid-tied converters, current source inverters (CSIs) are considered to be promising candidate, thanks to their low THD voltages/currents and inherent short-circuit proof. The natural oscillating power at the DC-link creates the main CSI's single phase application challenge. Hardware based solutions to this problem exhibits additional cost, components and size. Traditional software based solutions detect the oscillating power effect from a second harmonic component in the DC-link current; hence modify the carrier signal to mitigate the oscillation effect on the grid current. Those solutions are characterised mainly by excessive computational burden in addition to poor tracking. In this paper, a Proportional Resonant (PR) controller, tuned at the third harmonic, is utilized to minimize the oscillating power effect from the grid side, and hence acts as a harmonic cancellator (HC). The proposed technique features: (i) simple implementation, (ii) easy tuning, and (iii) superior steadystate elimination. In addition to simulation, experimental setup is implemented to validate the proposed technique effectiveness.