Load Frequency Research Articles

Effects of the Dynamic Loading Frequency on Performance of the Proton Exchange Membrane Water Electrolysis.

Green hydrogen production via PEM water electrolysis is challenged by fluctuating input power when coupled with renewable energy sources. This study investigates the effects of dynamic loading frequencies on membrane electrode assembly (MEA) performance and durability. We found that higher loading frequencies facilitate the growth of the oxide layer of Ti porous transport layer (Ti-PTL) due to increased duration in the voltage spike region. These thicker and coarser oxide layers directly induce cracks and delamination in the anodic catalyst layers by spontaneously adsorbing an ionomer. These changes negatively impact the interface contact quality and anodic electrochemical active area, ultimately reducing the performance of the MEA, with higher frequencies accelerating this degradation. Additionally, applying a Pt coating to PTL effectively mitigates these adverse effects. This work highlights the importance of dynamic loading studies and reveals that effective management of the Ti-PTL and catalyst/PTL interface is necessary to achieve long-term operational durability of PEM water electrolysis.

Towards load frequency management in thermal power systems using an improved open-source development model algorithm

Towards load frequency management in thermal power systems using an improved open-source development model algorithm

Quantitative benefits of geocells in controlling liquefaction in sands

Geocells have become an integral part of many geosystems like road and railway embankments, retaining walls and foundations, attributed to their multiple merits in terms of stability and strength, but their contributions towards liquefaction mitigation are unknown. The present study aims to understand the role of geocell reinforcement on the liquefaction and post-liquefaction shear response of saturated sands through monotonic and cyclic triaxial tests. Low-strength geocells of required physical and mechanical properties were fabricated through ultrasonic welding of 3D printed polypropylene (PP) sheets. The liquefaction benefits of including a single geocell in sand were quantified in terms of the reduction in pore water pressure, retardation in stiffness degradation and delay in the retardation of effective stress. In general, the inclusion of geocells delayed liquefaction, with higher beneficial effects at lower initial confining pressure, higher cyclic strain amplitude and higher cyclic loading frequency. The maximum benefit measured in terms of percentage rise in the number of cycles needed to liquefy was calculated to be about 230 %. Geocell reinforcement also helped in the quick regain of post-liquefaction shear strength and stiffness.

Suppression Limit Cycles in 2x2 Nonlinear Systems with Memory Type Nonlinearities

For several decades, the importance and weight-age of prediction of nonlinear self-sustained oscillations or Limit Cycles (LC) and their quenching by signal stabilization have been discussed, which is confined to Single Input and Single Output (SISO) systems. However, for the last five to six decades, the analysis of 2x2 Multi Input and Multi Output (MIMO) Nonlinear Systems gained importance in which a lot of literature available. In recent days’ people have started discussing suppression of LC which limits the performance of most of the physical systems in the world. It is a formidable task to suppress the limit cycles for 2x2 systems with memory type nonlinearity in particular. Backlash is one of the nonlinearities commonly occurring in physical systems that limit the performance of speed and position control in robotics, automation industry and other occasions like Load Frequency Control (LFC) in multi area power systems. The feasibility of suppression of such nonlinear self-oscillations has been explored in case of the memory type nonlinearities. Backlash is a common memory type nonlinearity which is an inherent Characteristic of a Governor, used for usual load frequency control of an inter-connected power system and elsewhere. Suppression LC using pole placement technique through arbitrary selection and optimal selection of feedback Gain Matrix K with complete state controllability condition and Riccati Equation respectively and is done through state feedback. The Governing equation is d/dt [X(t)] =(A-BK) X: which facilitates the determination of feedback gain matrix K for close loop Poles / Eigen values placement where the limit cycles are suppressed/eliminated in the general multi variable systems. The complexity involved in implicit non-memory type or memory type nonlinearities, it is extremely difficult to formulate the problem for 2x2 systems. Under this circumstance, the harmonic linearization/harmonic balance reduces the complexity considerably. Still the analytical expressions are so complex which loses the insight into the problem particularly for memory type nonlinearity in 2x2 system and the method is made further simpler assuming a 2x2 system exhibits the LC predominately at a single frequency. Hence in the proposed work an alternative attempt has been made to develop a graphical method for the prediction of Limit Cycling Oscillations in 2x2 memory type Nonlinear systems which not only reduces the complexity of formulations but also facilitates clear insight into the problem and its solution. The present techniques are well illustrated with an example and validated / substantiated by digital simulation (developed program using MATLAB codes) and use of SIMULINK Tool Box of MATLAB software. The present work has the brighter future scope of: Adapting the Techniques like Signal Stabilization and Suppression LC for 3x3 or higher dimensional nonlinear systems through an exhaustive analysis. Analytical/Mathematical methods may also be developed for signal stabilization using both deterministic and random signals based on Dual Input Describing function (DIDF) and Random Input Describing Function (RIDF) respectively. The phenomena of Synchronization and De-synchronization can be observed/identified analytically using Incremental Input Describing Function (IDF), which can also be validated by digital simulations.

Quenching and Suppression of Limit Cycles in 3x3 Nonlinear Systems

For several decades, the importance and weight-age of prediction of nonlinear self-sustained oscillations or Limit Cycles (LC) and their quenching by signal stabilization have been discussed which is confined to Single Input and Single Output (SISO) system. However, for the last five to six decades, the analysis of 2x2 Multi Input and Multi Output (MIMO) Nonlinear Systems gained importance in which a lot of literature available. In recent days few literatures are available which addresses the exhibition of LC and their quenching/suppression in 3x3 MIMO Nonlinear systems. Poor performances in many cases like Load Frequency Control (LFC) in multi area power system, speed and position control in robotics, automation industry and other occasions have been observed which draws attention of Researchers. The complexity involved, in implicit nonmemory type and memory type nonlinearities, it is extremely difficult to formulate the problem in particular for 3x3 systems. Under this circumstance, the harmonic linearization/ harmonic balance reduces the complexity considerably. Still the analytical expressions are so complex which loses the insight into the problem particularly for memory type nonlinearity in 3x3 system. Hence in the present work a novel graphical method has been developed for prediction of limit cycling oscillations in a 3x3 nonlinear system. The quenching of such LC using signal stabilization technique using deterministic (Sinusoidal) and random (Gaussian) signals has been explored. Suppression LC using pole placement technique through arbitrary selection and optimal selection of feedback Gain Matrix K with complete state controllability condition and Riccati Equation respectively. The method is made further simpler assuming a 3x3 system exhibits the LC predominantly at a single frequency, which facilitates clear insight into the problem and its solution. The proposed techniques are well illustrated with example and validated/substantiated by digital simulation (a developed program using MATLAB codes) and use of SIMULINK Tool Box of MATLAB software. The Signal stabilization with Random (Gaussian) Signals and Suppression LC with optimal selection of state feedback matrix K using Riccati Equation for 3x3 nonlinear systems have never been discussed elsewhere and hence it claims originality and novelty. The present work has the brighter future scope of: i. Adapting the Techniques like Signal Stabilization and Suppression LC for 3x3 or higher dimensional nonlinear systems through an exhaustive analysis. ii. Analytical/Mathematical method may also be developed for signal stabilization using both deterministic and random signals based on Dual Input Describing function (DIDF) and Random Input Describing Function (RIDF) respectively. iii. The phenomena of Synchronization and De-synchronization can be observed/identified analytically using Incremental Input Describing Function (IDF), which can also be validated by digital simulations.

Predictive control of interconnected fractional‐order systems with communication delays: An application for load frequency control of power system

AbstractThis research focuses on constrained model predictive control (CMPC) problem for interconnected fractional‐order systems (IFOS). Communication delays and imposed disturbances are considered in the design procedure of the control system. The dynamic equations of the IFOS are reformulated to handle the interaction delays and to obtain a model for the overall system. Then, a constrained model predictive controller is designed for the input and output (I/O) oriented model of the IFOS. To solve this control problem, a quadratic programming algorithm is utilized to obtain the optimal solution. Since most of the power systems exhibit an interconnected structure and consist of several subsystems, this study considers the load frequency control (LFC) problem for an interconnected fractional‐order power system in the presence of communication delays to evaluate the proposed technique. Numerical simulations are provided for two different cases, and the results are reported.

Influence of the Loading Frequency on Very High Cycle Fatigue Behavior of Structural Steels

ABSTRACTIn ultrasonic fatigue tests, the VHCF properties can be determined in a reasonable time. Nevertheless, the high frequency can affect the fatigue behavior for some materials. This study investigated the fatigue capability of 34CrNiMo6 and 42CrMo4 steels, both of which find widespread applications in several mechanical components. These steels were carried out for conventional and ultrasonic fatigue tests under fully reversed testing conditions. A microplasticity strain amplitude was calculated, indicating an order of magnitude decreases around 10–100, when compared with the experimental results from low‐frequency tests. Cyclic strain rates were estimated for each steel and correlated with the number of cycles to failure. A conversion constant was obtained by fitting a curve to convert the high frequency results into theoretical results at low frequency. The experimental and predicted results were evaluated. The results proved the relevance of the strain rate in frequency effect. The converted results showed strong agreement with the experimental results in low‐frequency tests for the steels being studied.

Enhancing load frequency control and automatic voltage regulation in Interconnected power systems using the Walrus optimization algorithm

This paper introduces the Walrus Optimization Algorithm (WaOA) to address load frequency control and automatic voltage regulation in a two-area interconnected power systems. The load frequency control and automatic voltage regulation are critical for maintaining power quality by ensuring stable frequency and voltage levels. The parameters of fractional order Proportional-Integral-Derivative (FO-PID) controller are optimized using WaOA, inspired by the social and foraging behaviors of walruses, which inhabit the arctic and sub-arctic regions. The proposed method demonstrates faster convergence in frequency and voltage regulation and improved tie-line power stabilization compared to recent optimization algorithms such as salp swarm, whale optimization, crayfish optimization, secretary bird optimization, hippopotamus optimization, brown bear optimization, teaching learning optimization, artificial gorilla troop optimization, and wild horse optimization. MATLAB simulations show that the WaOA-tuned FO-PID controller improves frequency regulation by approximately 25%, and exhibits a considerable faster settling time. Bode plot analyses confirm the stability with gain margins of 5.83 dB and 9.61 dB, and phase margins of 10.8 degrees and 28.6 degrees for the two areas respectively. The system modeling and validation in MATLAB showcases the superior performance and reliability of the WaOA-tuned FO-PID controller in enhancing power system stability and quality under step, random step load disturbance, with nonlinearities like GDC and GDB, and system parameter variations.

Review of load frequency control in modern power systems: a state-of-the-art review and future trends

Review of load frequency control in modern power systems: a state-of-the-art review and future trends

Dust resuspension from contaminated fabrics subjected to force-induced vibrations

A parametric study inspired by daily human activities (e.g., shaking clothes) is presented in this paper. Dust resuspension from contaminated fabrics (with four levels of initial dust load: 1, 10, 20, and 30 g/m2) subjected to force-induced vibrations (with low frequencies ranging from 0 to 6 Hz) was experimentally investigated. It was found that different settings of vibration duration, vibration frequency, and initial dust load can lead to significant differences in the resuspension results. Flexible fabric motion and multilayer dust motion were demonstrated as major contributors through visualization experiments. The observed phenomena of acceleration amplification effect along the fabric and various particle-particle interactions provided a crucial basis for our reasonable assumptions in the mathematical description. A set of empirical correlations was therefore developed whose form was proposed to be applicable in a wide range of scenarios involving moving surfaces. This paper not only reveals an everyday event that can trigger particulate matter emissions, but also helps enrich the understanding of particle dynamics.

Load frequency and virtual inertia control for power system using fuzzy self-tuned PID controller with high penetration of renewable energy

Reliance on renewable energy is increasing, and generating units are being added to the network. Since renewable power fluctuates greatly, the frequency deviation of the grid becomes a crucial problem with access to renewable power generation. The fluctuation of the renewable power output of the system puts forward a higher demand for load frequency control of the power grid to increase the penetration of renewable power in the system. PID controller has proven its effectiveness for the LFC due to its simple structure and clear concept. In this article, the virtual synchronous generator is introduced and a fuzzy self-tuned PID controller is proposed for inertia control. The proposed controller is implemented in light of the significant integration of renewable energy and virtual inertia. The efficacy of the suggested controller is evaluated against the traditional PID controller for the Egyptian Power System as a case study under various load disturbance scenarios. The control technique is employed for variable loads with photovoltaic and wind turbine generation systems. Three instances of load changes are studied and the controller design is performed based on grey wolf optimizer in each case. The overshot and integral time absolute error are considered as comparison measures. The new contribution is applied to the proposed controller for the grid and virtual inertia. In the case of many load variations imposed, the disturbances of residential and industrial loads varied from 0.05, 0.01, 0.15, and 0.02 pu. The maximum overshoot is 0.005 for the proposed controller and 0.0078 for the classic PID controller. The integral time absolute error is 0.06429 for the proposed controller and 0.11481 for the classic PID controller. The results demonstrate the efficacy of the proposed controller for inertia control with high penetration of renewable energy. The results show that the proposed fuzzy self-tuned PID controller has an overshot less than the classical PID controller by 25% and integral time absolute error by 45%. These results show that the use of the proposed fuzzy self-tune controller for the grid and inertia gave a better performance in terms of the overshot value and the integral time absolute error.

Modified and Improved TID Controller for Automatic Voltage Regulator Systems

This paper proposes a fractional order integral-derivative plus second-order derivative with low-pass filters and a tilt controller called IλDND2N2-T to improve the control performance of an automatic voltage regulator (AVR). In this study, equilibrium optimisation (EO), multiverse optimisation (MVO), and particle swarm optimisation (PSO) algorithms are used to optimise the parameters of the proposed controller and statistical tests are performed with the data obtained from the application of these three algorithms to the AVR problem. Afterwards, the performance of the IλDND2N2-T controller is demonstrated by comparing the transient responses with the results obtained in recently published papers. In addition, extra disturbances such as frequency deviation, load variation, and short circuit faults in the generator are applied to the AVR system. The proposed controller has outperformed the compared controller against these disturbances. Finally, a robustness test is performed in terms of deterioration in the system parameters. The results show that the IλDND2N2-T controller outperforms the compared controllers under all conditions and exhibits a robust effect on the perturbed system parameters.

Cascaded Integral Minus Tilt Integral Derivative With Filter for Frequency Stabilization of V2G/G2V Enabled Hybrid Microgrid

ABSTRACTRenewable generation plays an important part in today's power system. With the inclusion of the inverter interfaced renewable energy sources (RESs) into a microgrid, the total system inertia decreases and it leads to increased frequency deviation in presence of a disturbance. This paper proposes a cascaded Integral Minus Tilt Integral Derivative with Filter (I–TDN)‐Proportional‐Integral (PI), [(I‐TDN)‐PI] controller for frequency stabilization of a hybrid microgrid in presence of electric vehicles (EV). The microgrid model includes reheated thermal power plant with high degree of non‐linear system such as inverter based RESs like photovoltaic and wind generation systems. A diesel engine generator is incorporated for load frequency control during perturbation in the system frequency. Virtual inertia controller (VIC) with inverter based energy storage system (ESS) is commonly used to improve system inertia and frequency stability of the microgrid. In addition to the ESS, this paper proposes inclusion of the EVs in this VIC. The optimal gains of the proposed cascaded I‐TDN‐PI controller are determined using Mountain Gazelle Optimizer (MGO), a modern metaheuristic optimization algorithm. Sensitivity of the proposed controller is investigated in presence of system nonlinearities, load perturbations, time delay, system parameter variation and RES power fluctuations. The simulation results justify the robustness of the proposed control structure for frequency stabilization of the microgrid.

Memory State‐Feedback Control for a Linear System With Time‐Varying Delay Based on the Tuning Matrix Search Algorithm

ABSTRACTA multiple augmented Lyapunov function (MALF) is a function that includes more than one augmented matrix, allowing for a more precise evaluation of the relationships between different states within a system and facilitating the analysis of system stability. However, employing multiple augmented matrices can complicate the process of designing controllers. For this issue, this article proposes a controller synthesis algorithm to address the complexity of controller design resulting from multiple augmentation matrices. First, a memory state‐feedback control criterion with tuning matrices is derived by constructing an MALF. Second, a tuning matrix search algorithm is proposed to provide appropriate tuning matrices for the memory state‐feedback control criterion, leading to the determination of optimal controller gains. Finally, the effectiveness and advantage are verified by simulation of load frequency control for in the power system and control for a linear singular time‐delay system.

Impact of triaxial stress state at various pavement depths on the dynamic modulus of asphalt mixture

The mechanical characteristics of asphalt mixture are closely related with its stress state, temperature, and loading rate, therefore, the loading condition of the asphalt mixture's dynamic modulus test should be consistent with the actual temperature, loading frequency, and stress state that are applied to the mixture in actual pavement, thus can the test produce an objective result that can accurately reflect the actual stress-strain relationship for the asphalt mixture. However, due to limitations in the loading capacity of current dynamic modulus test equipment, the present modulus tester cannot yet set such a loading condition whose stress state is consistent with that of asphalt mixture in actual pavement. As a result, the modulus testing results of the current test may not accurately reflect the actual stress-strain characteristics of an asphalt mixture under real traffic loads. Therefore, this paper aims to figure out the impact of stress state on asphalt mixture’s dynamic modulus, and firstly conducts a numerical analysis to ascertain asphalt pavement’s triaxial stress state at different depth, then, utilizing the nonlinear elasticity theory of Soil Plasticity, proposes a theoretical model that can reflect triaxial stress state’s effect on asphalt mixture’s dynamic modulus, and then, arranges a series of triaxial dynamic modulus tests for asphalt mixture in different stress state to verify the model’s effectiveness, and meantime analyzes stress state’s influencing rule to asphalt mixture’s dynamic modulus. Their results indicate, the asphalt mixture of the actual pavement is in an obvious triaxial stress state, and that the higher the triaxial stress state, the larger the dynamic modulus, particularly for the mixture near the surface, whose high stress state will lead to their dynamic modulus to be significantly larger than that of the underlying course, while the model proposed in this paper can to a large extent reflect this impact.

Robust Distributed Load Frequency Control for Multi-Area Power Systems with Photovoltaic and Battery Energy Storage System

The intermittent power generation of renewable energy sources (RESs) interrupts the balance between power generation and demand load due to the increased frequency fluctuation, which challenges the frequency stability analysis and control synthesis of power generation systems. This paper proposes a robust distributed load frequency control (DLFC) scheme for multi-area power systems. Firstly, a multi-area power system is constructed by integrating photovoltaic (PV) and battery energy storage systems (BESSs). Then, by employing the linear matrix inequality (LMI) technique, the sufficient condition capable of ensuring that the proposed controller satisfies H∞ robust performance in the sense of asymptotic stability is derived. Finally, testing is conducted on a four-area renewable power system, and results verify the strong robustness of the proposed controller against load disturbance and intermittence of RESs.

An accelerated corrosion-fatigue testing method for marine high-strength steel based on equivalence principle of fatigue crack growth

The corrosion-fatigue test is widely used to assess marine equipment. However, due to the low-frequency and high-cycle loading of marine equipment in service, conventional test methods require long cycle times and high costs. This makes it challenging to meet the rapid evaluation demands associated with equipment development effectively. In this study, an accelerated corrosion test method was proposed for steel by adjusting the composition, temperature, pH and H2O2 concentration of environment. Fatigue crack growth tests were conducted under various corrosion environments and load frequencies. The matching relationships between corrosion fatigue acceleration multiplier, corrosion environment parameters and load parameters were established. Additionally, a corrosion fatigue acceleration test method was proposed based on the equivalent principle of fatigue crack growth. The results show that effective coupling between corrosion and fatigue can be achieved by gradually reducing the load frequency as the stress intensity factor amplitude increases throughout the crack growth process. It is consistent with the trend of fatigue crack growth rate in the seawater environment. The 4.85% fatigue life deviation and the 15.68 times corrosion fatigue acceleration can be achieved by our method. This work improves the accuracy and reliability of fatigue performance evaluation for offshore equipment.

Free Vibration and Buckling Analyses of Functionally Graded Plates With Graphene Platelets Reinforcement

Abstract While existing research has focused on using graphene platelets (GPLs) as reinforcement for homogeneous matrices, this study proposes a new nanocomposite for plate structures consisting of GPLs incorporated into a conventional functionally graded matrix with the aim of enhancing their overall stiffness. The performance of such plates is evaluated via free vibration and buckling analyses in the present study. Note that the matrix phase is graded continuously with the power law distribution across the plate's thickness, whereas various GPL dispersion patterns along the thickness are studied. The material properties of the typical functionally graded matrix are determined by the rule of mixture, and then those of the composite are estimated by the modified Halpin–Tsai model as well as the rule of mixture. Based on Hamilton's principle and the novel four-unknown refined plate theory (RPT4), the governing equations of the plate are developed. The Navier-type solution scheme is then adopted to get the critical buckling load and natural frequency of the nanocomposite plate. Numerical findings are examined to evaluate the novel nanocomposite plate model, and a parametric study is also conducted. In addition, high-accurate results are provided via the Navier-type solution here as benchmark solutions for further studies on functionally graded material structures reinforced by GPLs.

Enhanced Frequency/Voltage Control in Multi-Source Power System Using CES and SSA-Optimized Cascade TID-FOPTID Controller

The stability and reliability of modern power systems, especially those with several renewable energy sources, strongly rely on load frequency control (LFC) and automatic voltage regulation (AVR) for frequency and voltage control under inconstant load demands. In this study, a new cascade tilt integral derivative-fractional order proportional tilt integral derivative (TID-FOPTID) controller is presented that is polished through the salp swarm algorithm (SSA) for LFC of a multi-area power system with AVR in all control areas. The system integrates capacitive energy storage (CES) and deals with governor dead-band and generation rate constraint nonlinear effects in a thermal-hydro-gas three-area multi-source power system (TAMSPS). The analysis of results, due to the SSA-based TID-FOPTID controller compared to TID-FOTID and TID-FOTID + 1 shows a positive outcome. Integrating CES brings additional improvement in the system performance, the overshoot/undershoot, and settling time are minimized. Finally, the sensitivity analysis reveals that the suggested controller will be effective and reliable for enhancing the frequency stability of the complex power system with a high RES integration level.

Experimental characterization and numerical modeling of a frequency-independent viscoelastic damper

Conventional viscoelastic dampers (VED) exhibit significant frequency dependency, leading to variability in stiffness and damping properties at different excitation frequencies, which introduces uncertainties in their design and application in practical engineering. This study addresses this issue by developing a frequency-independent VED through comprehensive experimental characterization and numerical modeling. Four full-scale VEDs were designed and manufactured to explore its mechanical behavior. Cyclic loading tests were carried out under various loading conditions, including different strain amplitudes, loading frequencies, ambient temperatures, and low-cycle fatigue tests. Then, a frequency-independent mechanical model is proposed by combining an energy dissipation element with a nonlinear stiffness element in parallel. Finally, nonlinear dynamic time-history analyses were conducted on a steel frame with and without the VEDs at various ambient temperatures. The experimental results show that the developed VEDs maintain consistent hysteretic behavior across a range of frequencies, exhibit high mechanical stability under varying strain amplitudes and temperatures, and possess excellent recoverability after low-cycle fatigue test. The frequency-independent mechanical model developed in this study accurately simulates the hysteretic response of the developed VEDs, validating its applicability through experimental data. Seismic response analyses demonstrate considerable mitigations in inter-story drift ratios and residual inter-story drift ratios compared to the frame without dampers. These findings highlight the reliability and effectiveness of frequency-independent VEDs in structural vibration control, offering a promising solution for seismic performance enhancement.