Research On Local Frequency Transient Drop Characteristics Of Power Grid With Wind And Solar Power

Affected by the energy crisis and environmental pollution,China’s renewable energy power generation has developed rapidly.The continuous increase in the installed capacity of new energy has reduced the society’s dependence on fossil energy to a certain extent,and has promoted the consumption of new energy in the power system.However,it has also brought a series of new problems.When new energy power sources are connected to the grid,the proportion of traditional power sources is reduced,the inertia of the power system is reduced,and the frequency stability of the power system is weakened.After a high-power disturbance occurs in the power grid,the local frequency of the disturbance center will drop significantly,and the frequency drop of the transient process is the largest,which has the greatest impact on the stable operation of the entire system.In the early stage of the disturbance,how the frequency of different locations and different types of power sources will respond,and how much support is provided to the disturbance center,urgently need to carry out research on related issues.To this end,this paper simulates and analyzes the power-frequency electromagnetic transient characteristics of a typical power unit under the electromagnetic transient time scale,and proposes a frequency transient drop degree(Frequency Transient Drop Degree,which is based on the identification of power-frequency transient characteristics).FTDD)evaluation method.First,using PSCAD simulation software,the electromagnetic transient model of multiple typical power units such as synchronous generators,wind generators,photovoltaic power generation systems,and 3-machine 9-node system transient models were built.Based on the transient model of the system,it simulates a large disturbance in the power grid,that is,a large sudden change in power,and studies and analyzes the frequency change characteristics and response of power units of different types and locations.Secondly,the power and frequency change data of typical generator sets or generating units are collected from the offline simulation results when the power grid is subjected to different degrees of disturbance,and the power-frequency transient characteristic models of different generator sets or units are fitted by function approximation,and the foundation is built Model library.Finally,for the power grid to be monitored,after local power imbalance disturbances occur,the initial maximum power mutations sensed by different units or units are quickly collected,and the power-frequency transient characteristics relationship in the basic model library is called to quickly evaluate the power grid.Partial FTDD.The calculation example of an IEEE 3-machine 9-node system shows that the proposed method can quickly and accurately predict the local FTDD of the power grid for different wind power penetration conditions.