# Flexible Simulation Platform for Generating Realistic Waveforms with Voltage Notches
## 1 Introduction  
Voltage notches are steady-state voltage changes with a duration much shorter than the AC period, caused by the normal operation of line-commutated power converters [1; 2; 3]. This phenomenon distorts the voltage waveform and may excite the natural frequencies of the system, creating considerable high-frequency oscillations and significantly impacting power quality in distribution networks [4]. For instance, voltage notches lead to damaged capacitor banks, parallel resonances, radio disturbances, and electronic equipment malfunction [4]. Electronic equipment at low-voltage (LV) levels is particularly susceptible to voltage notches because of the resulting signal interference in logic or communication circuits [5]. Other power converters face challenges, including thermal stress in snubbers and filters caused by harmonic currents and control circuit malfunctions and timing errors in phase-locked-loop systems, due to distorted supply voltage [2; 5]. Line-commutated power converters are extensively used in industrial applications such as electrochemical processes, motor drives, and controlled power supplies [6]. Consequently, voltage notch issues are particularly relevant to industrial LV networks [7; 8; 9]. Therefore, the analysis, monitoring, and mitigation of this disturbance are of paramount importance for the industrial sector. Despite the relevance of voltage notches, the current state of research reveals a lack of comprehensive studies and practical tools to address this power quality disturbance (PQD) [1; 7]. Previous efforts include formulating analytical expressions to model voltage and current waveforms during commutation notches [4; 5; 8], conducting measurement-based analyses at industrial installations [9; 10], developing algorithms for detection and classification [7; 11], and implementing mitigation measures [12]. While these works offer valuable insights, several aspects remain unexplored. For instance, though time-domain simulation of voltage notches has been developed for in-depth research, testing, and validation, many studies provide little detail on the simulation platform [4; 8; 12], limiting the wide application of these tools. Addressing this gap, [7] provides a simulation platform analyzing the impact of key parameters affecting the voltage notch waveform, such as firing angle, snubber circuit, and capacitor banks in the LV network. Moreover, the work in [7] adopts a systematic approach to generating synthetic datasets of voltage notches to test a classification algorithm. However, the dependence between the key parameters is not fully addressed in [7] for dataset generation, and the plausibility of simulations has not been validated. Moreover, influencing factors observed in real-world LV networks, such as background voltage unbalance and distortion, have not been considered. The IEEE 519 standard emphasizes the necessity of realistic voltage notch simulations, stating that detailed simulations are required when direct measurements are unavailable to confirm an installation's compliance with recommended limits [5]. However, this concern has not been fully addressed, as previously described. To bridge this research gap, a MATLAB/Simulink-based platform is introduced to generate realistic synthetic waveforms with voltage notches, offering the following key contributions:  
* To enable comprehensive analysis of voltage notches, a benchmark low-voltage (LV) installation model featuring a six-pulse controlled rectifier is introduced. This model allows for the examination of key parameters influencing voltage notch characteristics, such as short-circuit power at the point of common coupling (PCC), commutation reactance, firing angle, snubber circuit characteristics, rated power of the rectifier, and background voltage unbalance and distortion. The platform also facilitates simulations involving linear loads and capacitor banks in the LV network. While other factors like nonlinear loads can affect voltage waveforms, they are acknowledged but not included in this analysis.