Impedance-Based Oscillatory Stability Analysis of High Power Electronics-Penetrated Power Systems—A Survey

Abstract

With increasing power electronics integrated into the power grids, the new types of oscillation issues have posed a critical threat to the secure operation of power grids. Apart from the conventional eigenvalue-based analysis, the impedance-based analysis becomes more attractive for the assessment of the oscillatory stability. This paper presents a systematic survey on the technical matters of the emerging impedance-based oscillatory stability analysis of power systems with high power electronics penetration. Firstly, the detailed derivation of impedance models of the power electronic converter-connected equipment are discussed. Then, common coordinate systems for the derivation of impedance models, as well as the characteristics of the impedance model in different coordinate systems are surveyed. On this basis, the aggregation of the individual impedance models is introduced to derive the lumped impedance model. Additionally, two typical impedance-based oscillatory stability criteria are demonstrated and discussed in details. Finally, the advantages as well as the limitations of the impedance-based oscillatory stability analysis, and the contributions as well as the challenges of the existing studies are summarized. A list of relevant literature is accommodated in the end.

Impedance-Based Method for Predictive Stability Assessment

“…The modeling of RES for determining impedances poses another challenge, and operating-point-dependent (OP-dependent) variations in RES impedance are still being overlooked [34,31,35]. In [36], a method is introduced that already considers the OP dependence of RES.…”

“…The implementation of the stability criterion for three-phase energy systems represents another focal point research [41,42,43,44]. Common transformations used for applying the impedance-based stability criterion are DQ-transformations and symmetrical components [34]. The choice of transformation method has so far depended on factors such as the background of the users and the intended application scenario.…”

“…However, a challenge with this method is still the analytical determination of the inverter impedance, which is assumed in this application. Alternatively, this monitoring approach can be complemented in advance using differential impedance spectroscopy [34]. However, long-term measurements conducted at the medium-voltage level indicate that the time dependency of the grid impedance up to 9 kHz is largely cyclically pronounced [33].…”

Application of energy flow analysis in investigating machine‐side oscillations of full converter‐based wind generation systems

“…The type configuration of FCWG is shown in Figure 1 [20,21]. The main components of FCWG are as follows: (i) a PMSG; (ii) the MSC and its controllers; (iii) the DC-link, the grid-side converter (GSC) and their controllers; and (iv) the phase-locked loop (PLL), etc.…”

Combination of Orthogonal Injections in Impedance Measurements of Grid-Connected Systems

“…The stability analysis of grid-connected devices is a common utilization for the impedance measurements [34], [35]. In this section, an impedance-based stability analysis is performed by applying the impedance measurements obtained with the COS and the MLBS.…”