In order to ensure the safe and stable operation of energy storage power station

the stability of multi-parallel energy storage power converter system（PCS） under PI control was studied.First

a fully decoupled control strategy was proposed in the dq coordinate system.Through the equivalent transformation

a single PCS control model based on virtual resistance was established.Then the multi-parallel PCS model with grid impedance was established by the Norton equivalent circuit

the distribution of its poles was analyzed

and the stability interval of the virtual resistance was given by the Routh criterion.The results show that when the virtual resistance of the control parameters is within the stable range

multi-parallel PCS can operate stably

and if the virtual resistance is outside the limited range

resonance occurs.Finally

a multi-parallel PCS simulation model is built on the simulink platform

and the correctness of the theory is verified by the simulation results.