Abstract
AC distribution grid is prone to instability due to negative impedance and constant power nature of the load if it is dominant with power electronics-based components. There are various time-domain and frequency-domain modelling methods which use various methodologies and analytical tools. Also, there are many small-signal stability analysis (SSSA) methods and their different variants for different specific conditions and situation. This paper presents a review of SSSA methods in AC distribution grid using impedance-based models in a synchronous reference frame (SRF). By simplifying and converting the system into load and source subsystem, the impedances of both subsystems are determined by perturbation method. For a single-phase system, Hilbert transform can be used to derive the equivalent SRF model. Afterwards, the Nyquist stability criterion can be used for stability analysis.
Highlights
Electric power was generated in bulk by large generation units depending upon location and availability of resources
The resulting system is prone to harmonics and instability due to negative impedance of constant power loads [9,10,11,12,13,14,15,16,17,18]
Stability analysis of a distribution grid (DG) dominated by non-linear loads can be evaluated by an impedance-based model
Summary
Electric power was generated in bulk by large generation units depending upon location and availability of resources. The dynamic behavior of PCs and their interaction with active loads in power systems may lead to oscillations and even instability of the system [21,22,23] This has increased the importance and need for system modelling for stability analysis. There are various SSSA methods for system modelling and small signal stability analysis of AC DG dominated by active loads These methods include impedance-based modelling in frequency-domain and state-space modelling in time domain [27,28]. One of the advantages of this method is that unknown impedance can be found through simulations or experiments This method works well with generators, transformers, and other conventional machine models, and with modern nonconventional converters based on power electronics.
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