Damping Torque Analysis And Power Angle Stabilization Mechanism Of Virtual Synchronous Machine With Network Structure

At present,China is in a new period of new energy revolution,large-scale renewable energy is gradually replacing traditional fossil energy,and new energy generation will become the main source of final energy demand in the future.On the one hand,the continuous access of new energy and power electronic equipment deepens the degree of electric power electronization in the power system,which causes the interaction between power electronic equipment and the power grid to cause broadband oscillation,which poses a great threat to the safe and stable operation of the power system.At present,broadband oscillation has become one of the important problems that hinder the continuous access of new energy.On the other hand,new energy has obvious randomness and volatility.The operation points of the power system are frequent and variable in a large range,the probability of wide-band oscillation instability is greatly increased,and the failure scenarios of traditional control methods are increasing.Under these factors,the grid connection of new energy power system is difficult in modeling and stability analysis,lack of effective mathematical model and analysis methods,and can not fully explain the physical nature of broadband oscillation.The large-scale grid connection of new energy has given rise to the control technology of virtual synchronous machine(VSM),which can effectively make up for the lack of inertia and insufficient voltage and frequency support caused by a large number of synchronous generators.However,the virtual synchronous machine control system has complex structure and strong coupling.The traditional stability analysis method cannot analyze the interaction mechanism among the interaction loops in the system.In order to solve the above problems,the multi-loop structure preserving modeling method and the chimeric torque analysis method are proposed.Firstly,the mathematical model of single virtual synchronous machine connected to the network is established,and the multi-loop interactive protection structure model of VSM connected to the network is established based on the idea of modularization and module reconstruction.Secondly,the principle and implementation process of the chimeric torque analysis method are introduced.Based on the chimeric torque method,the loop damping torque between each interaction loop is established to form the corresponding relation of analytic-structure connection.Then,the accurate traceability method of key loops and key parameters in VSM multi-loop system is analyzed in detail,and the laws of damping competition and damping mutual excitation among various links in VSM system are deeply analyzed,and the loop stability mechanism is analyzed according to the situation of negative excitation between multiple loops.Finally,a single machine infinite system under VSM control is taken as an example for simulation verification.The results show that the direct axis component and the cross axis component of voltage control loop and current control loop in VSM control system interact.The vicious competition of damping torque between the interactive circuits and negative excitation lead to the instability of the electromechanical oscillation mode of the system.This method can not only capture the instability mechanism of the system,but also provide reference for the actual parameter configuration optimization,which has certain application value.