Operating Area Investigation for Wind-Photovoltaic-Conventional Power Bundled MMC-HVDC Transmission System

The wind-photovoltaic-conventional power bundle modular multilevel converter based high voltage direct current (MMC-HVDC) transmission system has the promising application prospects. To investigate the impact on the system operation of different wind-photovoltaic-conventional power ratio conditions, this paper proposes a method to obtain the operating area for wind-photovoltaic-conventional power bundled MMC-HVDC transmission system, by considering the safe and stable operation constraints under steady-state conditions. Based on the proposed method, the impact of conventional power output proportion and power ratio of wind and photovoltaic on the system operating area of MMC-HVDC are analyzed. The results show that, the system active power operating area is mainly limited by the MMC overcurrent constraint and is almost unaffected by wind-photovoltaic-conventional power ratio. While the system reactive power operating area is restricted by the voltage deviation constraints for wind/photovoltaic grid-connected points and the PCC voltage deviation constraint, and which shifts towards delivering more reactive power, with the decrease of the conventional power output and the increase of imbalance between wind and photovoltaic active power.