Photovoltaic field connected to the grid via voltage source converter based high voltage direct current (VSC-HVDC ) transmission is an important trend in the future development of the power system,but there is a risk that the interaction between photovoltaic and VSC-HVDC system may trigger system oscillations and instabilities. So,the open-loop and closed-loop interconnection models of the photovoltaic field integrated into grid through VSC-HVDC are established. The dynamic interaction between the photovoltaic subsystem and the VSC-HVDC subsystem based on the open-loop mode resonance theory are analyzed. When a strong interaction between two subsystems occurs,it may cause the corresponding closed-loop oscillation mode to enter the right side of the complex plane and trigger system oscillation instability. The risk of interaction instability between the photovoltaic subsystem and the VSC-HVDC subsystem can be mitigated by adjusting the control parameters of the dominant link. If the control parameters can not be adjusted,an additional damping controller for the photovoltaic unit is proposed as an inhibitory measure,which destroys the mode resonance phenomenon by adjusting the open-loop oscillatory modes of the photovoltaic subsystem away from the open-loop oscillatory modes of the VSC-HVDC subsystem in the complex plane,so as to stabilise the closed-loop system. The correctness of the above theoretical analysis results and the superiority of the proposed damping controller are verified by the simulation examples.