Analysis Method Of Voltage-frequency Distribution Characteristics Of Transmission Lines Based On Vector With Time-varying Amplitude And Frequency

In the dynamic process of power system,the state of the system changes with time,and the internal potential generated by the power supply has time-varying amplitude and frequency.Under the excitation of such voltage signal,even in linear network,the relationship between node voltage vector and current vector no longer satisfies the simple algebraic relationship,which brings great trouble to network modeling.Quasi-steady-state hypothesis is often introduced in power systems dominated by traditional synchronous machines,ignoring the effect of voltage-frequency variation on current and spatial distribution of frequency.Under the background of the increasing trend of power electronization in power system,a lot of research focuses on the change of equipment's own characteristics while ignoring the change of network's characteristics.The network is often modeled by harmonic linearization in static coordinate system or based on the linearization of DC working point in dq coordinate system..However all of them greatly increase the complexity of the whole model and is not suitable for the analysis of large-scale systems.In addition,both harmonic linearization and dq coordinate linearization are concerned the relationship between the projection values of time-varying amplitude-frequency vectors,which is not conducive to intuitive understanding of the role of the network in power transmission and process of maintaining voltage and frequency.Based on the modeling method of amplitude-phase motion equation,a new network model is proposed by studying the relationship between instantaneous amplitude and frequency of voltage signal and current signal in the network.The rationality of the model is verified by simulation.On this basis,the voltage-frequency distribution in a simple system in dynamic process is analyzed.Compared with the quasi-steady state model,this method considers the frequency variation and spatial distribution,and is closer to the actual system.Compared with the linearization in dq coordinate system,it is beneficial to reduce the order of the system model.