Due to the lack of damping in the system, the power oscillation in the energy storage based grid-connected photovoltaic power generation system will threaten the dynamic stability of the system. In the paper, the control principle of active power and reactive power increasing system damping is analyzed firstly. Then on the basis of grid connected power control of photovoltaic energy storage system, a novel additional active and reactive power modulation was proposed, thus power oscillation is effectively suppressed. The proposed strategy can realize the control mode switching of the PV grid connected inverter and the battery energy storage system in the process of power oscillation by detecting DC voltage variation in the PV side. Meanwhile, it also can make the joint system have the ability to inject active and reactive power, so as to improve the damping characteristic of the system. Finally, a typical power system based on photovoltaic and storage system was used to validate the proposed control strategy. Simulation results demonstrate that the proposed control method damp the power oscillation sufficiently and it achieves the goal of improving the damping of power generation system with multi-power coordination.