PROJECT TITLE :

DC-DC MMC for HVDC Grid Interface of Utility-Scale Photovoltaic Conversion Systems - 2017

ABSTRACT:

This paper explores a utility-scale photovoltaic (PV) plant configuration primarily based on a dc-dc stage interfaced directly to a modular multilevel converter (MMC) used for an HVdc power station. Since PV systems are dc by nature, the proposed solution has several blessings, such as full dc operation and step-up transformers avoidance with modular and reliable configuration. The contributions of this paper are the experimental validation of the proposed utility-scale configuration, whereas the conventional modulation stage has been further enhanced by including an adaptive phase-shifted modulation allowing improved voltage and current waveforms injected to dc grid beneath unbalanced power string operation. The enhanced performance is obtained by reducing the carrier frequency element of the converter voltage, generating an improved voltage ripple. Finally, experimental validation throughout steady-state and dynamic operation are presented to illustrate the behavior of the dc-dc MMC converter managed by the proposed modulation and management scheme.