Research On Multi-dimensional Evaluation Of Inertia Level Of Power System With High Proportion Of New Energy

In recent years,a large number of conventional units are gradually replaced by new energy units with a high proportion of new energy connected to the grid.The inertia of the system is constantly weakened,and the frequency problem under the impact of active power is more prominent.Due to the strong fluctuation and intermittency of the output of new energy units and the geographical difference in the distribution of natural scenery resources,the inertia of the system fluctuates greatly on the time scale,but presents a certain imbalance in the spatial distribution on the space scale.In order to effectively evaluate the inertia response and frequency disturbance rejection ability of the system with a high proportion of new energy,this paper carries out multidimensional evaluation research on the inertia level of the power system with a high proportion of new energy.The main work is as follows:(1)A method for evaluating the equivalent inertia of power system including the virtual inertia of new energy is proposed.Using the equivalent inertia time constant and equivalent damping coefficient,a linear model was established to describe the sag control strategy and VSG control strategy of grid-connected inverter.On this basis,combined with the motion equation of synchronous generator rotor,a controlled autoregressive identification model was established to solve the virtual inertia of new energy and the rotational inertia of synchronous generator,and the problem of solving the inertia was transformed into a parameter identification problem in the model.Then,the adaptive forgetting factor is introduced and the adaptive recursive least squares identification method is adopted to continuously identify the unknown parameters in the model and calculate the equivalent inertia of the power system with high proportion of new energy.(2)An estimation method of power system inertia spatial distribution based on multi-information identification is proposed.By analyzing the supporting effect of system inertia resources on node inertia,a node inertia representation model was constructed to describe the "active powerfrequency dynamic process" of each node under different disturbance scales.Based on the output error moving average model,the inertia spatial distribution estimation model was built.The multi-information identification method was adopted to expand the scalar information into the vector information,accelerate the convergence of the algorithm,solve the unknown parameters in the inertia identification model quickly and accurately,and then obtain the equivalent inertia of all nodes in the system.Combined with the geographical location information of each node,a visual interface is drawn to help operators timely perceive the inertia distribution of the power system with a high proportion of new energy and accurately locate the weak inertia nodes.(3)The monitoring and early warning system of power grid inertia is designed and implemented based on MATLAB/GUI.The system based on power system dynamic simulation data collected,unit/system inertia continuous tracking curve drawing,regional/node spatial distribution of moment of inertia color chart,synchronous display each moment each type of the output of generating unit,can quickly perceive new energy level high moment of inertia of electric power system as a whole and inertia space distribution,It can provide reference for dispatchers to coordinate and optimize system operation mode,unit switching state,new energy virtual inertia parameters and asynchronous power access scale,and realize the intelligent goal of "online evaluation and dynamic perception" of power grid inertia.