Improving the Impedance-Based Stability Criterion by Using the Vector Fitting Method

Abstract

In this paper, some issues related to the impedance based stability criterion such as RHP poles in the minor loop gain, how to specify source and load impedances, and nodedependent stability margins are discussed and the vector fitting method is used to improve the method. This results in an eigenvalue analysis of the system instead of using the Nyquist diagram, and leads to obtain more information about the system. Furthermore, a participation factor analysis can be used to identify the problematic subsystem. The proposed method is examined in the assessment of a stable and an unstable system and simulation results are used for verification.

Electromagnetic Oscillation Origin Location in Multiple-Inverter-Based Power Systems Using Components Impedance Frequency Responses

“…are needed for calculation of P (I g ), and Z right N K and Y lef t N K are needed for calculation of P (I K ), respectively. The derivation procedure of these impedance/admittance models in the conventional IBSCs can be explained as follows [14], [17], [19], [23].…”

“…First, the system planner can theoretically derive the impedance models of the GCIs if internal control structures and parameters are provided by the vendors [3], [8], [10], [16], [17], [19]. Second, when detailed information of the GCIs is confidential for the system planner due to the industry secrecy and intellectual property protection, the vendors tend to deliver lookup tables which provide discrete impedance/admittance frequency responses of the GCIs [18], [22], [23]. Third, when black-box simulation models are provided by the manufactures, the system planner can perform frequency scanning in commercial softwares, e.g., PSCAD/EMTDC and Matlab/Simulink [26], [27], [39], [41].…”

“…The vector fitting (VF) and matrix fitting (MF) algorithms initially proposed in [20], [21] can fit a set of discrete frequency responses by continuous transfer function and transfer matrix, respectively, which have been employed in [18], [22]- [25] to facilitate the stability assessment of power electronic-dominated power systems. Specifically, the VF algorithm is used in [18], [23] to fit discrete load impedance and source admittance frequency responses as continuous transfer functions, so that extraction of the RHP poles from the analytically-derived transfer functions can be avoided. Discrete loop impedance models (LIMs) are established in [26]- [28] by further aggregating the impedance frequency responses of the load and source sub-modules, based on which the MF algorithm is used to generate continuous LIMs, and zeros of the determinant of the fitted LIMs are identified.…”

Decoupled Multi-Port Impedance Modelling Method of Transmission Network in Inverter-Fed Power Plant

“…The impedance formulas in this model are in interest for stability analysis. Therefore, the formulas are listed as (12) and (13), which are in a similar form of (8).…”

“…Most of existing works always simplify or ignore transmission lines (TLs)/power cables impedance. For example, only the TL impedance between point of common connection (PCC) and grid is considered in [7]- [10], [12], [15]. The TLs impedance between the GCIs are considered in [13], [14], [17].…”