In order to solve long-distance integration of photovoltaic (PV) power station to power grid, and improve the system stability of grid-connected PV power station, the PV power station is integrated with voltage source converter high voltage direct current (VSC-HVDC) system, a topology of direct-current connecting cascaded photovoltaic power station to power grid via VSC-HVDC system is proposed. The voltage characteristics of PV module and the control strategy for PV module and DC voltage control strategy for VSC station are analyzed, thus, an improved control strategy of DC voltage margin & droop is put forward. The system and proposed control strategy are simulated under PSCAD/EMDTC electromagnetic transient software by different irradiation conditions. Simulation results show the feasibility of the system, indicating that the proposed control strategy can effectively maintain the system voltage stability of PV power station.