Stability Analysis And Control Research Of PV/HESS Grid-connected Power System Based On Synchronous Torque Coupling

VSG expands the energy storage device as a new inertia source,which effectively makes up for the lack of inertia existing in the photovoltaic grid-connected system,but its access makes the frequency stability of the system face new challenges.The processing level of VSG is limited by the operation mode,and its control effect is closely related to virtual inertia and damping.Improper parameter configuration will make the system face the risk of instability.To play VSG flexibility,and improve the stability of photovoltaic storage grid-connected system,this paper deeply analysis the virtual synchronous transient stability mechanism of the grid system,the main research results are as follows:(1)Firstly,the transformation relationship between the rotating kinetic energy of the generator and HESD is established,and the small-signal model of the photovoltaic storage system is derived.Combined with the characteristic root trajectory,the analysis results are as follows: In the synchronous operation state,the power between the generator and VSG is decoupled,and there is a natural design contradiction between the virtual inertia and damping.(2)Secondly,based on the analysis results,the torque coupling r elationship between VSG and the synchronous generator is established.Combined with the equal area rule,the conclusion is drawn that the power response level of the VSG is improved,the transient energy in the system is reduced,and the transient stabilit y margin of the system is improved.(3)Thirdly,based on the complex variable averaging method,the Hamilton energy function of the system with synchronous torque coupling is established.By analyzing the mechanism of transient energy transfer of the syst em,a design scheme of inertia and torque coupling coefficient is proposed to maximize the absorption of transient energy of the system by VSG,to improve the dynamic characteristics of the system.(4)Finally,a high permeability test system with photovoltaic and HESD is built on MATLAB/Simulink to verify the effectiveness of the proposed strategy.The results show that under the proposed synchronous torque coupling control strategy,the VSG can efficiently transfer the transient energy in the system,provide inertia support to the system,and suppress the frequency and power oscillation characteristics of the system.