Mitigation Of Oscillations Research Articles

Flow characteristics analysis and combustion oscillation mitigation of a hydrogen industrial burner

With the promotion of carbon neutrality policies, hydrogen burners are widely used in the industrial field, and exploring the combustion characteristics and stable combustion technology of hydrogen industrial burners has important engineering application significance. This study investigates the flow characteristics and combustion oscillation mitigation of a specific hydrogen industrial burner for heating thermal oil through experiments and numerical simulations. The oscillating combustion with a frequency of 100 Hz is discovered during the field test. The dynamic characteristics are reproduced via large eddy simulation (LES), and the pressure amplitude is reduced by 22% via the active control strategy. LES results show that corner recirculation zone and main recirculation zone occur in the flame holding chamber, with maximum recirculation velocity and maximum temperature of −20 m/s and 2110 K, respectively. The unstable modes and key elementary reactions are revealed by modal analysis and eigen-analysis. The clustered neural network with horizons (CNNH) controller is constructed to suppress the combustion instability. The CNNH controller can effectively suppress the pressure oscillation by perturbing the inlet mass flow rate of main H2, reducing the peak amplitude in the frequency domain by 67%. By optimizing the controller parameters, the CNNH controller can be further applied to different scenarios of hydrogen industrial burners.

The analysis of the models performance indicators by cloud and post-cloud computing paradigms

The work describes cloud and post-cloud computing paradigms, on the basis of which it is possible to model and build intelligent video surveillance systems. Based on the analysis of literary sources, it was concluded that performance indicators largely depend on the paradigm of the computational model, but the degree of importance of each performance indicator is different for different paradigms. Taking into account the peculiarities of different paradigms, the performance indicators characteristic of each of them are described. It has been found that the common indicators for evaluating all models developed on the basis of cloud and post-cloud computing paradigms (with varying degrees of importance) are: Throughput, Network Congestion, SLA Violation, Fault Tolerance, Statistical Analysis Measurements, The Number of Orchestration Decisions, The number of Contradictory Decisions, Time to Adaptation, Competition Ratio, Cache Hit Ratio, The number of Contradictory Actions, Oscillation Mitigation, Cost, Technique’s Overhead, Privacy. Based on the analysis of cloud and post-cloud computing simulators, it is established that the metrics of resource usage, energy, response time, and latency are those that can be used by researchers when conducting a comparative analysis of models built on the basis of the following paradigms: fog, edge, fog, and cloud computing. The practical significance of the conducted research is that, depending on the tasks that will be set before the future video surveillance system, researchers will be able to evaluate the effectiveness of using different architectures (Cloud, FOG, Mist, etc.) with the help of certain simulators. In the future, it is advisable to conduct a study of the degree of importance of common metrics for evaluating all models developed on the basis of cloud and post-cloud computing paradigms, and conduct their normalization for the possibility of conducting an adequate comparative analysis. It is also relevant in future research that it is advisable to conduct research using different types of sensor devices (surveillance cameras with different technical characteristics, unmanned aerial vehicles, etc.).

On the Departure from Monin–Obukhov Surface Similarity and Transition to the Convective Mixed Layer

Large-eddy simulations are used to evaluate mean profile similarity in the convective boundary layer (CBL). Particular care is taken regarding the grid sensitivity of the profiles and the mitigation of inertial oscillations in the simulation spin-up. The nondimensional gradients ϕ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\phi $$\\end{document} for wind speed and air temperature generally align with Monin–Obukhov similarity across cases but have a steeper slope than predicted within each profile. The same trend has been noted in several other recent studies. The Businger-Dyer relations are modified here with an exponential cutoff term to account for the decay in ϕ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\phi $$\\end{document} to first-order approximation, yielding improved similarity from approximately 0.05zi\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$z_i$$\\end{document} to above 0.3zi\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$z_i$$\\end{document}, where zi\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$z_i$$\\end{document} is the CBL depth. The necessity for the exponential correction is attributed to an extended transition from surface scaling to zero gradient in the mixed layer, where the departure from Monin–Obukhov similarity may be negligible at the surface but becomes substantial well below the conventional surface layer height of 0.1zi\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$z_i$$\\end{document}.

Optimizing power system stability: A hybrid approach using manta ray foraging and Salp swarm optimization algorithms for electromechanical oscillation mitigation in multi‐machine systems

AbstractThis paper emphasizes the significance of ensuring adequate damping of electromechanical oscillations in power systems to ensure stable operation. Power System Stabilizers (PSSs) are influential in enhancing system damping and refining dynamic characteristics during transient conditions. However, the efficacy of PSSs is notably contingent on parameter values, particularly in the case of lead‐lag PSSs. In response to this challenge, the paper introduces a Tilt‐Integral‐Derivative (TID)‐based PSS, optimized through a novel optimization algorithm called Hybrid Manta Ray Foraging and Salp Swarm Optimization Algorithms (MRFOSSA). The MRFOSSA algorithm demonstrates robustness and enhanced convergence, validated through benchmark function tests, and outperforms competing algorithms. These superior characteristics of MRFOSSA were employed in optimal tuning of TID‐PSSs to uphold the stability of multi‐machine power systems. The MRFOSSA algorithm demonstrates robustness and enhanced convergence, outperforms competing algorithms in the optimal tuning of TID‐PSS within the Western System Coordinating Council (WSCC)‐3‐machines 9‐bus test system. In summary, the proposed TID‐PSS, coupled with the MRFOSSA algorithm, presents a promising avenue for enhancing power system stability.

Gate Voltage Oscillation Mitigation in Solid-State Circuit Breakers With Single-Gate Driven Series-Connected Power Devices

Gate Voltage Oscillation Mitigation in Solid-State Circuit Breakers With Single-Gate Driven Series-Connected Power Devices

Impact of Synchronous Condensers’ Ratings on Mitigating Subsynchronous Oscillations in Wind Farms

Subsynchronous oscillations have occurred in wind farms due to the high penetration of converter-based technology in power systems and may potentially lead to grid instability. As an effective solution, synchronous condensers, with their ability to control voltage and inject reactive power in the power system, are increasingly being adopted, as they can lead to the mitigation of such oscillations in weak grid conditions. However, the impact of synchronous condensers’ power ratings on system stability is a topic that requires further investigation. In fact, an improper selection of a synchronous condenser’s rating will not extinguish existing subsynchronous oscillations and may even cause the emergence of new oscillatory phenomena. This paper presents a novel examination of the impact that the synchronous condenser’s power rating has on the small-signal stability of a wind farm with existing subsynchronous oscillations while being connected to a weak grid. The wind farm’s model is developed using state-space modeling, centering on grid interconnection and incorporating the state-space submodel of a synchronous condenser to show its impact on subsynchronous oscillation mitigation. The stability analysis determines the optimal synchronous condenser’s power ratings for suppressing these oscillations in the wind farm model. The findings are corroborated through time domain simulations and fast-Fourier transformation (FFT) analysis, which further validate the stability effects of a synchronous condenser’s rating.

Joule-class sub-nanosecond pulses produced by end-pumped direct bonded YAG/sapphire modular amplifier

A Joule-class room-temperature diode-pumped solid-state laser was developed. The energy scaling of the 100 mJ 1064 nm seed pulse was realized by a series of two diode-pumped amplifiers. The gain medium consists in free combinations of Nd:YAG ceramics bonded to sapphire transparent heat sinks, to relax the thermal load induced by the 34 kW pump power. At low repetition rate, parasitic lasing was the main limitation to energy scaling. By choosing a gain module combination producing a step-like gradual doping concentration profile, mitigation of parasitic oscillations was observed, and the system delivered 2.8 J, 800 ps pulses at 2 Hz.

Analysis and Mitigation of Electromechanical Oscillations in Drivetrain for Hybrid Synchronization Control of DFIG-Based Wind Turbines

Analysis and Mitigation of Electromechanical Oscillations in Drivetrain for Hybrid Synchronization Control of DFIG-Based Wind Turbines

Assessment and Mitigation of Multi-Mode Oscillations in Wind-Solar Hybrid Multi-Microgrids

Assessment and Mitigation of Multi-Mode Oscillations in Wind-Solar Hybrid Multi-Microgrids

An efficient energy management scheme using rule-based swarm intelligence approach to support pulsed load via solar-powered battery-ultracapacitor hybrid energy system

This work presents an energy management scheme (EMS) based on a rule-based grasshopper optimization algorithm (RB-GOA) for a solar-powered battery-ultracapacitor hybrid system. The main objective is to efficiently meet pulsed load (PL) demands and extract maximum energy from the photovoltaic (PV) array. The proposed approach establishes a simple IF-THEN set of rules to define the search space, including PV, battery bank (BB), and ultracapacitor (UC) constraints. GOA then dynamically allocates power shares among PV, BB, and UC to meet PL demand based on these rules and search space. A comprehensive study is conducted to evaluate and compare the performance of the proposed technique with other well-known swarm intelligence techniques (SITs) such as the cuckoo search algorithm (CSA), gray wolf optimization (GWO), and salp swarm algorithm (SSA). Evaluation is carried out for various cases, including PV alone without any energy storage device, variable PV with a constant load, variable PV with PL cases, and PV with maximum power point tracking (MPPT). Comparative analysis shows that the proposed technique outperforms the other SITs in terms of reducing power surges caused by PV power or load transition, oscillation mitigation, and MPP tracking. Specifically, for the variable PV with constant load case, it reduces the power surge by 26%, 22%, and 8% compared to CSA, GWO, and SSA, respectively. It also mitigates oscillations twice as fast as CSA and GWO and more than three times as fast as SSA. Moreover, it reduces the power surge by 9 times compared to CSA and GWO and by 6 times compared to SSA in variable PV with the PL case. Furthermore, its MPP tracking speed is approximately 29% to 61% faster than its counterparts, regardless of weather conditions. The results demonstrate that the proposed EMS is superior to other SITs in keeping a stable output across PL demand, reducing power surges, and minimizing oscillations while maximizing the usage of PV energy.

A Common Grounded Non-Isolated ASISC High Gain DC-DC Converter with Oscillation Mitigation across Switches

A Common Grounded Non-Isolated ASISC High Gain DC-DC Converter with Oscillation Mitigation across Switches

Mathematical Model-Based Analysis and Mitigation of GaN Switching Oscillations

Mathematical Model-Based Analysis and Mitigation of GaN Switching Oscillations

Data-driven optimization of a gas turbine combustor: A Bayesian approach addressing NO x emissions, lean extinction limits, and thermoacoustic stability

Abstract The design of gas turbine combustors for optimal operation at different power ratings is a multifaceted engineering task, as it requires the consideration of several objectives that must be evaluated under different test conditions. We address this challenge by presenting a data-driven approach that uses multiple probabilistic surrogate models derived from Gaussian process regression to automatically select optimal combustor designs from a large parameter space, requiring only a few experimental data points. We present two strategies for surrogate model training that differ in terms of required experimental and computational efforts. Depending on the measurement time and cost for a target, one of the strategies may be preferred. We apply the methodology to train three surrogate models under operating conditions where the corresponding design objectives are critical: reduction of NO x emissions, prevention of lean flame extinction, and mitigation of thermoacoustic oscillations. Once trained, the models can be flexibly used for different forms of a posteriori design optimization, as we demonstrate in this study.

Mitigation of Voltage and Frequency Oscillations of a Microgrid during Wind Gust by Using Fuzzy-Controlled Flywheel Energy Storage

Mitigation of Voltage and Frequency Oscillations of a Microgrid during Wind Gust by Using Fuzzy-Controlled Flywheel Energy Storage

Risk-informed longitudinal control in autonomous vehicles: A safety potential field modeling approach

The advent of autonomous vehicles (AVs) has complicated traffic flow and raised safety concerns, there is a pressing need to enhance traffic efficiency alongside ensuring robust safety. This paper proposes a dynamic longitudinal control strategy for AVs, based on real-time accident risk assessments. Data from traffic flow, road characteristics, and weather conditions are analyzed using a random forest algorithm, producing a real-time accident risk identification model through a support vector machine. In addition, the Perceived Risk Field Model (PRFM), a car-following model calibrated using the NGSIM dataset, considers vehicle distance, velocity, relative velocity, and acceleration. These models underpin our proposed longitudinal control strategies, tailored to variable accident risk levels. Under the normal risk control strategy, the PRFM outperforms the Intelligent Driver Model (IDM) and the Cooperative Adaptive Cruise Control Model (CACC) in stability and driving comfort. For high accident risk scenarios, our approach shows improved collision avoidance and traffic oscillation mitigation. Simulations indicate that the high accident risk control strategy offers better safety and stability than the normal risk strategy. Furthermore, traffic flow diagrams suggest an increase in road capacity as AV penetration rates rise, pointing to the promising efficiency of our proposed solution. This research provides a robust framework for AV operation, ensuring optimal traffic safety and efficiency.

Sub-synchronous oscillation mitigation of VSC-HVDC with doubly-fed induction generator-based wind farm integration

Sub-synchronous oscillation mitigation of VSC-HVDC with doubly-fed induction generator-based wind farm integration

Effect of diameter and inclination of steam injection pipe on chugging dynamics in direct contact condensation

Low mass flux of steam and high degree of subcooling are the prominent factors for occurrence of unstable direct contact condensation, commonly known as chugging, when steam is injected into a subcooled water pool. Such an arrangement is typically used in the pressure suppression pool of the primary containment vessel in a boiling water reactor. With an attempt to identify the conditions of minimum pressure oscillations during the chugging regime, the present study investigates the effect of internal diameter (0.5–1 in.) and inclination (8.75˚) of steam injection pipe on steam bubble dynamics, pressure transients and heat transfer characteristics at different steam mass flow rates (5–25 kg/hr) and submergence depths of steam pipe (1–13 cm) within the water pool. The study reveals that the condensation cycle time decreases with a decrease in the internal diameter of the pipe. Furthermore, the frequencies of fluctuations in the interfacial area of the steam bubble and pressure transients in the steam pipe exhibit an increasing trend with an increase in steam mass flow rate and a decrease in internal diameter of the steam injection pipe. The chugging frequencies in the inclined and vertical orientation of steam injection pipe lie within the range of 0.5–3 Hz. The average heat transfer coefficient increases with an increase in the internal diameter of pipe and steam mass flow rate. The amplitude of pressure oscillations has decreased significantly whereas heat transfer coefficient has increased marginally upon changing the orientation of steam injection pipe from vertical to inclined. Therefore, smaller diameter and inclined orientation of steam injection pipe are favourable for mitigation of pressure oscillations in applications of direct contact condensation.

Mitigation of power system oscillations in weak grids with battery energy storage systems: A real-world case study

Sub-synchronous oscillations are becoming commonplace in weak areas of power systems with high levels of renewable generation, affecting their operation. Moreover, there is a lack of methods and techniques that facilitate the understanding of such phenomena and the analysis of mitigation alternatives from a practical-knowledge point of view. In this manuscript, the combination of static and dynamic techniques is utilized and consolidated to derive general conclusions when mitigating sub-synchronous oscillations by means of grid-forming battery energy storage systems (GFM BESSs). The grid impedance shaping effect of GFM BESSs, which allows the mitigation of undesired oscillations, is demonstrated through small-signal (static) and frequency scanning (dynamic) analyses when studying an actual and extremely weak grid, the Australian West Murray Zone. These findings are further validated when performing detailed real-time EMT digital simulations of the grid. Furthermore, additional dynamic simulations demonstrate the ability of GFM BESSs to provide system strength and increment the hosting capacity of renewables in weak areas. The methods and techniques presented in this work can be applied to any power system, further supporting existing industry practices.

On mitigation of oscillations of a mechanical system with two degrees of freedom in the vicinity of external resonances

On mitigation of oscillations of a mechanical system with two degrees of freedom in the vicinity of external resonances

Adaptive frequency control in smart microgrid using controlled loads supported by real-time implementation.

The operation of the system's frequency can be strongly impacted by load change, solar irradiation, wind disturbance, and system parametric uncertainty. In this paper, the application of an adaptive controller based on a hybrid Jaya-Balloon optimizer (JBO) for frequency oscillation mitigation in a single area smart μG system is studied. The proposed adaptive control approach is applied to control the flexible loads such as HPs and EVs by using the JBO which efficiently controls the system frequency. The suggested technique uses the power balance equation to provide a dynamic output feedback controller. The main target is to regulate the frequency and power of an islanded single area μG powered by a PV and a diesel generator with integrations of smart bidirectional loads (HPs and EVs) that are controlled by the proposed adaptive controller in presence of electrical random loads. Moreover, the JBO is designed to minimize the effect of the system load disturbance and parameter variations. For a better assessment, the proposed controller using JBO technique is compared with two other methods which are the coefficient diagram method (CDM) and adaptive one using classical the Jaya technique. In the obtained results, the frequency deviation is found as 0.0015 Hz, which is fully acceptable and in the range of the IEEE standards. The MATLAB simulation results reveal that the suggested technique has a substantial advantage over other techniques in terms of frequency stability in the face of concurrent disturbances and parameter uncertainties. The real-time simulation tests are presented using a dSPACE DS1103 connected to another PC via QUARC pid_e data acquisition card and confirmed the MATLAB simulation results.