Mitigation of Oscillating Power Effect on PV Power and Grid Current in Single-phase Single-stage PV Grid-tied Systems

摘要

A photovoltaic system connected to single-phase utility, via a single-stage voltage source inverter, is considered in this paper. The inverter DC-side capacitor is reduced to almost one tenth its value to improve system reliability and life time. However, this decreases its buffering effect against single-phase grid power oscillations, resulting in high DC-link even harmonics which inject low-order harmonics in utility current. To overcome the latter, a resonant filter is added at PV output to decouple it from the rippled DC-link. This filter removes harmonic components, of second and fourth order, from PV power. Thus, the tracking performance of the array maximum power is greatly enhanced. Moreover, the inverter outer voltage loop is modified to measure the clean PV voltage rather the rippled DC-link voltage which in turn eliminates grid current harmonics. Simulation results verified the effectiveness of the applied filter and voltage loop modification.