Research On The Identification Method For Inertia Constant And Inertial Temporal-spatial Characteristics Of Power System

Inertia is the inherent property of power system and the basis to ensure the safe and stable operation of the system.With the increasing share of power electronic converter interfaced renewable energy sources(RESs)such as wind power and photovoltaic,the power system inertia continues to decline,which seriously threatens the frequency stability of the system.In this case,the power system inertia can be improved by the virtual inertia control and the energy storage devices,and the frequency stability can be improved by the reserve capacity.In order to appropriately allocate the virtual inertia,the energy storage devices as well as the reserve capacity,it is necessary to clarify the characteristics of power system inertia and perceive power system inertia in real time,thus improving the frequency stability and reduce the system operating cost.Therefore,focused on power system inertia identification,this paper analyzes the characteristics of power system inertia firstly;then proposes the identification methods for power system inertia constant at different hierarchies,the analysis and identification methods for temporal-spatial characteristics of power system inertia,respectively.The main research is as follows:1)The characteristics of power system inertia are studied.Based on the inherent property of inertia to resist energy fluctuations,the nature of power system inertia is expounded.The sources of power system inertial energy are analyzed,then the difference and relationship between inertia and inertial energy of power system are clarified.The inertial response of the traditional power system and the high RESs penetrated power system is analyzed and tested.The research above is the theoretical basis for the following power system inertia identification.2)An identification method for power system inertia constant at different hierarchies based on ambient signal is proposed.By taking Laplace transformation on the swing equation under ambient conditions,the dynamic model of the synchronous machine is established,then the dynamic model is identified using the stochastic subspace method.As the order reduction of the identified model in the frequency domain will lead to large error in the identified results,a method to extract the inertia constant from the time domain response of the identified model is proposed.The sliding window method and the exponential smoothing method are used to track the inertia constant in real time.3)Furthermore,based on ambient signal,a recursive identification method for power system inertia constant at different hierarchies is proposed.The ambient signal is modeled using the ARMAX model,and the parameters of the ARMAX model are estimated using the recursive weighted least square algorithm.The performance of the recursive method and the nonrecursive method is tested.The recursive method is more efficient in calculation and more stable in the inertia constant identification,which is more suitable for real-time online application.In addition,the robustness of the recursive identification method is tested by considering the measurement noise,outliers and missing data.4)The analysis,modeling and identification methods for the inertial temporal-spatial characteristics of power system are proposed.Based on the inherent property of inertia to resist energy fluctuations,the node inertia of the power system is defined and its representation method is given.Based on the dynamic characteristics of node frequencies under large and small fluctuations,a method to analyze the temporal-spatial characteristics of power system inertia is presented.A representation model of the temporal-spatial characteristics of power system inertia is derived and an identification method for the temporal-spatial characteristics of power system inertia based on ambient signal is proposed.