Frequency Dynamic Analysis Of Large Scale Interconnected Power System

The frequency is one of the key parameters in the power system operation.At present,China's power system has formed a national interconnected power grid.Regional grid interconnection improves the frequency stability of system.At the same time,it also increases the dangers of a malignant chain accident.When the frequency instability occurs,the influence can be expanded through the contact line,which may cause a large area of power outages.Power system frequency dynamic analysis is the basis of frequency stability analysis and control.The frequency analysis method of power system and the dynamic characteristics of regional frequency are analyzed and studied in this paper.In this paper,a model to calculate the regional frequency for two area power grid is summarized.The model combines the characteristics of single machine equivalent model and linearization method.And the model makes the original complex power system simplified into a two area system with three nodes by means of the equivalent and the network contraction.Finally,the model calculates the region frequency by solving the frequency algebraic equation of the simplified system.It has a clear principle and a small amount of calculation.In this paper,a new method based on the DC load-flow model for the analysis of power system dynamic frequency is provided.Based on the characteristics that active power is the main factor of frequency dynamics,the DC load-flow model is used to describe the system network and the influence of the turbine-governor dynamics and the load's frequency characteristics are considered in the method.The method preserves some analytic properties and does not need to be solved step by step.The analytic solution separates the oscillating and steady-state components of the dynamic frequency.The oscillation part gives the parameters such as frequency,amplitude,phase angle,attenuation factor and so on.In addition,the steady-state frequency can be determined directly by the steady state component.Compared with the simulation results of PSS/E,the algorithm can describe the power system frequency dynamic accurately.The paper studies the dynamic characteristics of the regional frequency of interconnected power system.Based on the improved IEEE 118 bus system,the space-time distribution features and the factors impacting power-frequency characteristics of the regional frequency are analyzed.In addition,the mutual influence phenomenon of the regional frequencies in different regions is studied.