Single phase 9 level grid connected inverter for photovoltaic applications

Abstract

Two power conversion stages are generally used when low voltage unregulated PV voltage is conditioned to generate AC power. This paper proposes a novel 9 level inverter topology to generate high voltage AC by using low voltage PV modules. To realize high voltage AC at the output, the proposed circuit configuration can accommodate dual PV inputs. Further, this inverter is capable of boosting the input voltage by two times and obviates the need for a step up transformer on the output side. Proposed system can feed high quality power into the grid from both the PV modules operating at their respective MPPs. The multi-level inverter uses a total of 10 power switches among which two work at twice the output frequency (i.e. 2 × 50Hz) with required voltage withstanding capability equal to the total DC voltage applied to the input. 4 switches operate at high frequency with required voltage withstanding capability equal to half the total input DC voltage. Remaining 4 of the switches and 2 of the power diodes with required voltage withstanding capability of one fourth of the total input DC voltage. Due to more number of levels in the synthesized output voltage, the output filter requirements are significantly reduced. All the results of this work are presented.