Dual-Band Reduced-Order Model of an HVDC Link Embedded Into a Power Network for EMT Studies

Abstract

This paper presents an approach to obtain reducedorder models for power networks involving power electronic converters (PEC) via the frequency-domain balanced realizations (FDBR) technique. PECs play an essential role in power processing and energy conversion in modern electrical networks, such as the interconnection of renewable generators, HVDC links, and active filters. Integration of PECs into dynamic equivalents needs model-order reduction (MOR) in both low-and highfrequency ranges to account for both slow and fast dynamics due to the network and switching natures. The objective of the FDBR technique is to obtain an internally balanced system, i.e., an equally controllable/observable system, that can be reduced according to its dominant dynamics within the limited frequency bandwidths. This allows accounting for specific band-limited phenomena, such as those generated within a power network caused by PECs, which is the focus of this paper. The results show that faster yet accurate simulations are achieved by reduced-order models through FDBR compared to their full-order counterparts.

Extrapolation of Band-Limited Frequency Responses for Out-of-Band Modal Synthesis

“…The largest discrepancy occurring at 1100 Hz is 10 Hz and relatively small, indicating the feasibility of the derived sensitivity index. Based on (16), Fig. 4(c) plots the identified f 12 and f 13 (i.e., f 12 and f 13 ) using f 21 , indicating that f 12 (VF) and f 13 (VF) gradually decreases to 1200 Hz and increases to 1300 Hz, respectively, as f u increases.…”

“…In addition, it has high robustness when fitting noisy or contaminated frequency samples [11]- [14]. Due to its high accuracy and robustness, the VF has been widely utilized in power electronic [11], electromagnetic compatibility [13], microwave [14], and power system [15], [16] communities in the last two decades.…”

Insight into Frequency-Domain Extrapolations of Least-Squares-Based Curve Fitting Algorithms

“…Among the aforementioned literature, many efforts have been made in order to improve the VF performance in situations where several frequency ranges were involved, e.g., poles relocation [2], [13], model order reduction [3]- [6], [10], and passivity enforcement [7], [8]. More accurate and faster convergence property of poles relocation was obtained by a "hard relocating" procedure in [13] and by replacing the highfrequency asymptotic constraint of the scaling function with a milder summation requirement in [2].…”

“…[3]- [6], [10] in order to apply the VF on each narrow subinterval and obtain a reduced-order state-space model (SSM) for each subinterval. The frequency responses of each fitted reduced-order SSM located in neighboring subintervals were simply overlooked in [3], [10].…”

Model Reduction of Power System by Modified Balanced Truncation Method

“…Both regional frequency and tie-line exchange variations in such interconnected power systems networks are often induced by unforeseen demand only for power loads, uncertain system parameters, modelling error and disturbances due to various environmental conditions [3] [4]. Thus, during transient disturbances such as faults, line travel or any overload, the reliability of the power system is necessary to maintain the specified synchronism and voltage levels [5] [6] [7]. It is therefore capable of minimising the model of the power system so that simulation and controller design can be simplified [8].…”