Novel grid connection interface for utility-scale PV power plants based on MMC

摘要

The ever-increasing integration of photovoltaic (PV) energy has led to the fast development of utility-scale PV power plants worldwide. A novel grid connection interface for utility-scale PV power plants based on the modular multi-level converter (MMC) is explored. The grid connection interface is a DC boost interface by nature. It adopts the multistring topology, employs DC/DC boost converters, utilises a centralised MMC, and integrates an energy storage system. Meanwhile, the two-level control system for the DC boost interface is also designed. Compared with the conventional AC boost interfaces, the proposed DC boost interface avoids problems regarding reactive power transmission, harmonic resonance, and synchronous stabilisation. It also improves the power quality, efficiency, and the integration capacity of the PV generation. A case study of a utility-scale PV power plant with the DC boost interface is carried out in PSCAD/EMTDC. The simulation results validate the effectiveness and the merits of the DC boost interface under different operation conditions. The proposed DC boost interface proves more suitable for utility-scale PV power plants in areas with high solar irradiance. It also lays a solid foundation for the future research regarding the control and protection of utility-scale PV power plants.