Small Disturbance Relationship with Internal-Voltage Amplitude/Frequency Excitation and Active/reactive Current Response and Its Linearization Method of AC Network for AC Power System Dynamic Analysis

With the high penetration of renewable generations, increasingly serious impact of dynamics of AC network as an important part of power systems on system dynamic behaviors urgently asks for constructing corresponding small disturbance linearization relationship of AC network to achieve dynamic analysis for today's new system by applying mature linear system mathematics. However, due to the existence of AC signals in the network, relevant DC state variables and operating points required for establishing and linearizing small disturbance relationship are not intuitive. But existing researches almost have not yet understood appropriate state variables and operating points from the perspective of AC power systems' basic operation principle and physical connotation of system dynamics, causing there is still a lack of a universal construction idea and a general linearization method of the small disturbance relationship of AC network suitable for system dynamic analysis. Thus, system operation principle and physical dynamics are first concerned by taking a simplified converter interfaced power system as an example in this paper, and internal-voltage amplitude/frequency (A/F) and active/reactive (A/R) current are revealed as state variables and operating points of AC power systems. A universal construction idea of small disturbance relationship with internal-voltage A/F excitation and A/R current response of AC network and relevant linearization method are then proposed. Finally, small disturbance linearization relationship of a typical inductive transmission line is established and is validated by simulation.

I. Introduction

With the increasing of renewable generations, power electronic interfaced power devices are replacing electro-magnetic power devices (e.g. synchronous generators) [1]–[2]. Due to the existence of energy storage elements with various energy storage levels and relevant multi-timescale controls, fast dynamics that close to the time scale of AC network dynamics have been occurring in the internal-voltage amplitude/frequency (A/F) at the port of power devices, which causes the increasingly significant impact of dynamic characteristics of AC network on system dynamic behaviors. Growing occurrences of related oscillations in power systems are seriously endangering the system safe and normal operation [3]–[5]. Therefore, it is urgent to realize a universal system dynamic analysis considering dynamic characteristics of AC network, in which small disturbance relationship and its linearization of AC network as fundaments should be concerned at first.