Novel High-Frequency Isolated Cascade PV Inverter Topology Based on Multibus DC Collection

This article proposes a novel single-stage isolated cascade photovoltaic (PV) inverter topology based on a multibus dc collection. The PV power plant can be divided into many arrays, each of which supplies power to three cascaded isolated inverter units through a dc bus. This isolated inverter unit is composed of cascade isolated bridge cells (I-BCs) connected in input-parallel output-series (IPOS). Compared with a conventional two-stage isolated cascade PV converter, the proposed PV topology can totally eliminate the individual dc-link capacitors at the high-voltage (HV) side, which leads to extremely reduced system volume and eliminated the voltage-balancing control between the dc-link capacitors. This article, first, describes the basic principle and the carrier phase shift pulse-width modulation (CPS-PWM) applied to this topology and, then, analyzes the power balance constraints between the cascade three-phase units for the PV grid-connected system. Finally, the effectiveness of the novel topology is verified by the simulation and experimental results.