Dynamic Frequency Response Research Articles

Modeling Dynamic Frequency Response on Slab Track of Shinkansen Railway Based on Finite Element Method

The use of slab tracks in lieu of ballast tracks has introduced new dimensions in track dynamics in high‐speed railways. To improve the performance of slab tracks under dynamic frequency responses caused by loads on the Shinkansen railway, the present study aimed to investigate the effect of mechanical properties of track components, including the elasticity modulus and thickness on the resonance frequency of the vertical dynamic responses using the finite element method. Such responses included receptance and decay rate in the asphalt bearing layer (ABL), hydraulically bonded layer (HBL), and concrete bearing layer (CBL). In addition, the study sought to select the optimal layer as an effective layer in the view of reducing the resonance frequency of dynamic responses in comparison with the general model. Based on the data regarding the effects of elasticity modulus and thickness of slab track layers on the resonance of the dynamic frequency responses under the amplitude loads, by changing the load from 20 to 25 tons over the slab track, the receptance under the modulus and thickness change increased up to 34 and 29%. Moreover, the decay rate under the modulus and thickness change increased up to 31 and 37%. Accordingly, by increasing the load amplitude, the CBL and HBL showed lower dynamic responses than other layers. Thus, CBL and HBL were selected as the optimum layers for improving the performance of the slab track of the Shinkansen railway.

Research on the Impacts of the Inertia and Droop Control Gains from a Variable-Speed Wind Turbine Generator on the Frequency Response

System frequency must be kept very close to its nominal range to ensure the stability of an electric power grid. Excessive system frequency variations are able to result in load shedding, frequency instability, and even generator damage. With increasing wind power penetration, there is rising concern about the reduction in inertia response and primary frequency control in the electric power grid. Converter-based wind generation is capable of providing inertia response and primary frequency response; nevertheless, the primary frequency and inertia responses of wind generation are different from those of conventional synchronous fleets; it is not completely understood how the primary frequency and inertia responses affect the given system under various disturbances and available kinetic energy levels. Simulations are used to investigate the influences of inertia and droop control strategies on the dynamic frequency responses, particularly the index of the second frequency drop under various disturbance and wind conditions. A quantitative analysis provides insight into setting of inertia and droop control coefficients for various wind and disturbance conditions to facilitate adequate dynamic frequency responses during frequency events.

Study of the Inertia Support Potential From HVDC Cables in Power Systems With High Renewable Energy Source Penetration

Stimulated from the de-carbonization targets which was set up by governments worldwide, more and more conventional generation has been decommissioned. Lack of power system inertia support has gradually emerged as a major challenge for system operators around the world. It is especially the case for weak power systems with higher renewable energy source penetration. Existing research in providing inertial support relies on the installation of super capacitors onto the existing high voltage direct current (HVDC) systems. This technique imposes additional cost and reliability concerns. This article proposed a novel strategy which unlocked the potential from HVDC cables to provide inertia support. A comprehensive feasibility study has been performed on a prototype system in which the dynamic frequency response is analyzed. The results showed that for a feasible control strategy, the released energy from HVDC cables is sufficient to replace the vast majority of synchronous machines within a typical power system. This demonstrated the feasibility of utilizing existing HVDC cables for inertia support which significantly reduces the economic costs and improves the system reliabilities.

An Improved Dynamic Control and Resonance Damping for Voltage Source Inverters in Microgrids Through a Novel Active Damping Technique

Microgrids have the potential to provide customers with improved power quality and reliability. However, there are technical challenges related to the operation and control of microgrids and the distributed energy source (DERs) that constitute them. Resonance caused by the low-pass filters connected to the voltage source inverters of the DERs is one of those issues in the operation of microgrids. This paper proposes a novel technique of Active Damping Algorithm (ADA) for resonance damping and improving the dynamic stability of a microgrid composed of multiple converter-interfaced DERs. The paper considers two cases; one is where the resistor and the filter capacitor are connected in parallel, and the other is where they are connected in series. The proposed active damping method is based on output current feedback with automatically calculated and adjusted damping coefficients to suppress resonance. The proposed method was verified through simulation and experimental tests carried out using PSCAD/EMTDS and an operational microgrid in Beijing, China. The results from both the experiment and simulation analysis showed that the devised method was able to achieve the intended target; where the filter resonance is effectively surpassed and the voltage and frequency dynamic responses are quite stable and within the acceptable range during large power changes in the microgrid system.

A High-sensitivity FBG Accelerometer Based on a Bearing

We present the modelling, design, and characterization of a novel fiber Bragg grating (FBG) accelerometer based on a bearing. A cantilevered mechanical structure with bearings can effectively decrease energy loss during vibration and enhance sensitivity. The principle of the accelerometer is analysed by a simplified model. The influence of the structural parameters of the proposed sensor on its sensitivity and resonance frequency is further analysed for structural optimization. Meanwhile, its dynamic behaviour and frequency response characteristics are analysed by numerical simulations. In addition, dual-FBG not only enables temperature compensation but also enhances sensitivity. Experimental results indicate that the FBG accelerometer provides a linear response over a broad frequency range from 0.5 Hz to 40 Hz, with a high sensitivity of 575.8 pm/g. This FBG accelerometer with low frequency and high sensitivity provides effective support for the design of sensors of the same type.

Experimental Investigation on Dynamic Performance of Micro-Pile with Predrilled Oversize Hole on Shaking Table Test

For the situation of lacking research on micro-pile with predrilled oversize hole, the key part of semi-integral abutment bridge, the micro-pile-soil interaction shaking table test is carried out by considering the reaming pore diameter, depth, packing and other parameters in the end of the micro-pile to obtain the acceleration, pile moment, displacement and pile-system response frequency and other basic dynamic response and dynamic interaction law. Results show that: 1) the change of predrilled-hole parameters has litter effect on the dynamic properties of soil outside oversize hole; 2) The change of predrilled-hole parameters can cause the change of structural frequency, so led to the change of inertia force of pile head; 3) Inertial interaction has an important influence on the response of the upside part of pile and little influence in the downside part (lower than 15D). These conclusions will provide reference for dynamic response of interaction between pile with predrilled oversize hole and soil and make contribution to the practical application and designing of micro-pile with predrilled oversize hole.

Improving the Power Quality of Island Microgrid With Voltage and Frequency Control Based on a Hybrid Genetic Algorithm and PSO

An efficient power control technique for inverter-based distributed generation (DG) in an islanded microgrid is investigated in this work. The objective is to raise the caliber of the electricity pumped from network-connected DGs. The characteristics that are taken into consideration include voltage and frequency control, dynamic response, and steady-state response, particularly when the microgrid is operating in island mode or when there is a load change. The control method consists of an internal current control loop and an external power control loop based on a synchronous reference frame and a conventional PI controller. The power controller is designed based on voltage-frequency (VF) control. In addition, an intelligent search technique that combines Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) is utilized to automatically modify power controller parameters. The control technique in this research is that the DG modifies its control mode to modify the system voltage and frequency when the microgrid is islanded or load conditions change. The simulation results in MATLAB/SIMULINK software show that the proposed control system has been able to improve the power quality well.

Low Frequency Dynamic Response of Diaphragm-Encapsulated Fiber Laser Hydrophone

Low Frequency Dynamic Response of Diaphragm-Encapsulated Fiber Laser Hydrophone

Bending-torsional-axial-pendular nonlinear dynamic modeling and frequency response analysis of a marine double-helical gear drive system considering backlash

The double-helical gear system was widely used in ship transmission. In order to study the influence of backlash on the nonlinear frequency response characteristics of marine double-helical gear system, according to the structural characteristics of double-helical gear transmission, considering the time-varying meshing stiffness, backlash, damping, comprehensive transmission error, external load excitation, and other factors, a three-dimensional bending-torsional-axial-pendular coupling nonlinear dynamic modeling and dynamic differential equation of 24-DOF double-helical gear transmission system were established. The Runge–Kutta numerical method was used to analyze the influence of backlash, time-varying meshing stiffness, damping, error and external load excitation on the amplitude frequency characteristics. The results show that the backlash can cause the runout of the double-helical gear system, and the system has first harmonic and second harmonic response. With the increase of backlash, the amplitude of the system increases and the jumping phenomenon remains unchanged. The amplitude frequency response of the system is stimulated by time-varying meshing stiffness and comprehensive transmission error, and restrained by damping and external load excitation. The vibration displacement amplitude of the system increases with the increase of vibration displacement and has little effect on the state change of the system. The vibration test of double-helical gear is carried out. The frequency response components obtained by numerical simulation are basically consistent with the experimental results, which proves the correctness of the theoretical calculation. It provides a technical basis for the study of vibration and noise reduction performance of double-helical gear.

Optimization of synchronized frequency and voltage control for a distributed generation system using the Black Widow Optimization algorithm

Abstract A distributed generation network could be a hybrid power system that includes wind–diesel power generation based on induction generators (IGs) and synchronous generators (SGs). The main advantage of these systems is the possibility of using renewable energy in their structures. The most important challenge is to design the voltage-control loop with the frequency-control loop to obtain optimal responses for voltage and frequency deviations. In this work, the voltage-control loop is designed by an automatic voltage regulator. A linear model of the hybrid system has also been developed with coordinated voltage and frequency control. Dynamic frequency response and voltage deviations are compared for different load disturbances and different reactive loads. The gains of the SG and the static volt-ampere reactive compensator (SVC) controllers in the IG terminal are calculated using the Black Widow Optimization (BWO) algorithm to insure low frequency and voltage deviations. The BWO optimization algorithm is one of the newest and most powerful optimization methods to have been introduced so far. The results showed that the BWO algorithm has a good speed in solving the proposed objective function. A 22% improvement in time adjustment was observed in the use of an optimal SVC. Also, an 18% improvement was observed in the transitory values.

Vibration and nonlinear dynamic response of temperature-dependent FG-CNTRC laminated double curved shallow shell with positive and negative Poisson’s ratio

This paper reports a study on natural frequency, nonlinear dynamic response and frequency amplitude relation of temperature-dependent FG-CNTRC laminated double curved shallow shell with positive and negative Poisson’s ratio. The nonlinear motion equations and the compatibility equation are retrieved from first order shear deformation theory including the effect of von Karman nonlinearity terms, elastic foundations and initial imperfection. The system of dynamic governing equations is obtained by utilizing the Airy stress function and Bubnov–Galerkin procedure. The nonlinear dynamic response is also obtained by applying the 4th-order Runge–Kutta method. The frequency–amplitude relations of the shell is determined by using the assumption of inertia caused by a rotation. Besides, the analytical method and the finite element method are proposed to calculate the vibrational frequencies. Five types of FG-CNTRC laminate shell, three types of the structures and different thermal environments with the shell’s material properties depending on the temperature are also considered in this study. The numerical results are presented, verified with available studies in the literature. Finally, the effects of elastic foundations, initial imperfection, and temperature-dependence, typing double curved shallow shell, angle of lamination against the shell x-axis on the natural frequency and nonlinear dynamic response of FG-CNTRC laminated double curved shallow shell with positive and negative Poisson’s ratio are discussed.

An adaptive under-frequency optimal control strategy for power system combined pumped storage and under-frequency load shedding.

With the construction and development of ultra-high voltage (UHV) power grids, large-scale, long-distance power transmission has become common. A failure of the connecting line between the sending-end power grid and the receiving-end power grid will cause a large-scale power shortage and a frequency drop in the receiving-end power grid, which can result in the frequency collapse. Presently, under-frequency load shedding (UFLS) is adopted for solving the frequency control problem in emergency under-frequency conditions, which can easily cause large load losses. In this context, a frequency coordination optimal control strategy is proposed, which combines the mode transition of pumped storage units with UFLS to deal with emergency under-frequency problems. First, a mathematical model of the frequency dynamic response is established, which combines the mode transition of pumped storage units with UFLS based on a single-machine equivalent model. Then, an optimal model of the minimal area of the power system’s operation frequency trajectory is introduced, yielding the optimal frequency trajectory, and is used for obtaining the action frequency of the joint control strategy. A simulated annealing algorithm based on the perturbation analysis is proposed for solving the optimal model, and the optimal action frequency is obtained that satisfies the transient frequency offset safety constraint of the power system. Thus, the joint optimal control of the mode transition of the pumped storage units and UFLS is realized. Finally, the EPRI-36 bus system and China’s actual power grid are considered, for demonstrating the efficiency of the proposed strategy.

Frequency Modulation Method and System of Photovoltaic Virtual Synchronous Generator Based on Computer Technology

With people’s attention to environmental protection, clean energy has become an important research and development direction. Among them, photovoltaic power generation has many advantages, such as simple process, no fuel consumption, no noise, no pollution and so on. The power grid capacity is becoming larger and larger, and has a great impact on the environment. Therefore, the grid connection of photovoltaic power generation will cause major problems for the planning, operation and dispatching of power grid. Virtual synchronous generator (hereinafter referred to as VSG) technology can simulate the inertia, primary frequency regulation and voltage regulation characteristics of synchronous generator, which has become an important way to improve the dynamic frequency response ability of the system. Therefore, VSG technology has become an important research technology of photovoltaic grid connected system, among which FM method will also become an important research direction. Firstly, this paper analyzes the VSG algorithm and its basic characteristics. Finally, this paper analyzes the control scheme of overall primary frequency regulation of photovoltaic power station (hereinafter referred to as PPS).

Dynamic modeling and damping performance improvement of two stage ISD suspension system

In this paper, the dynamics of the vehicle suspension system under the random excitation and the periodic excitation are investigated. To improve the damping performance of the vehicle suspension system, a two stage ISD suspension with “Inerter-Spring-Damper” in each stage is proposed based on electromechanical similarity theory. A vehicle dynamic model with two stage ISD suspension is established in this paper. The dynamic equation is solved by the Runge-Kutta method and the dynamic response of the whole vehicle system is obtained. Taking the traditional suspension as the comparison object, the dynamic characteristics of the system under random excitation and periodic excitation are studied in the time domain, and the suppression effect of the suspension designed in this paper on the resonance peak is verified in the frequency domain. The influence of the inertia coefficient on the damping performance of the vehicle suspension system is analyzed. The effects of excitation amplitude and vehicle speed on ride comfort improvement of vehicle system with two stage ISD suspension are discussed respectively. The results show that, the resonance peak values of body acceleration, dynamic travel of rear suspension and rear tire dynamic load frequency response are reduced by 59.1%, 21.6%, and 60.3% respectively. With the increase of excitation amplitude in the range of 0.02–0.04 m, the ride comfort improvement of two stage ISD suspension system is always more than 61%. With the increase of vehicle speed in the range of 10–25m/s, the performance improvement rate of two stage ISD suspension system can reach more than 34.1%.

Analytical and Numerical Investigations of Mechanical Vibration in the Vertical Direction of a Human Body in a Driving Vehicle using Biomechanical Vibration Model

The main reason that affects the discomfort in a driving vehicle is the vibration response. The human body vibration leads to many malfunctions in both comfort and performance in human health. As a result, the human body’s simulation in sitting posture in the driving vehicle has a strategic relationship for all Tires and vehicles manufacturers. The digital process simulation of the human body seat vehicle vibration shows two significant advantages. The first advantage is the prevention of the high-cost modifications in the construction stage of the vehicle, while the second one describes the stability test during the undesirable vibrations. This study modelled the human body’s dynamic characterisations, natural frequency, and mechanical response when seated in the driving vehicle with vibration transmissibility in the vertical direction have been using the biomechanical vibration model. The vertical vibrations and the transmissibility of the human body dynamic response are presented in detail. Exciting results have been obtained, and they are significant for human health, which relates to sitting posture in the driving vehicle. It can assist in understanding the influences of low-frequency vibration on human health, comfort, and performance, and therefore it could be applied for ride comfort evaluation. An analytical solution to derive the general equations of motion for the human system was developed. Then, using the vibration analysis technique and the corresponding equations, the accurate dynamic response of the selected mode is identified. Furthermore, the mathematical modelling for free vibration using the finite element analysis has been performed to determine the appropriate values and set its description. Then, the comparison results of the two techniques have been carried out.

The Mathematical Model for Research of the UAV Longitudinal Moving

The paper presents one of the perspective directions of the development to modern aviation, which is connected with designing and producing unmanned aerial vehicles (UAV) of various functionalities for applying in both military and civilian spheres. The syntheses of UAV control systems, regardless of their type and purpose presumes creation of adequate mathematical models, first of all adequate aerodynamic mathematical models. In the paper results that forms and justify the aerodynamic mathematical model and as well as the results of building a general mathematical model of the longitudinal movement of the perspective UAV are presented. Also factors that forms the mathematical model on given aerodynamic, geometric, mass and inertial data for a hypothetical perspective altitude long-range UAV are submitted. Assessment of the impact of these data on the dynamic, temporal, and logarithmic frequency response UAV also has been given in this paper.

Development of vehicle noise-vibration-harshness analysis calculation method in order to improve NVH characteristics

The article presents a calculation method of Noise-Vibration-Harshness (NVH) analysis of a vehicle, the purpose of which is to reduce noise pollution. The results of calculations and experimental validations of calculations, natural frequencies and oscillation modes of the trimmed body internal volume, local dynamic stiffnesses and frequency response are provided. Also, contribution of the body panels to forming internal noise is defined.

Vehicle structural analysis calculation method development in order to improve noise-vibration-harshness characteristics

The article presents a calculation method of structural analysis of a vehicle through the example of a body, the purpose of which is to reduce noise pollution. The results of calculations and experimental validations of calculations, natural frequencies and oscillation modes of the body, local dynamic stiffnesses and frequency response are provided. Also, the body characteristics in natural frequencies are improved through topological and topographical optimization of the body element.

An optimal probabilistic spinning reserve quantification scheme considering frequency dynamic response in smart power environment

These frequency responses in tandem with spinning reserve are a prominent problem in the future smart grid environment due to the increase of non-dispatchable energy sources. However, this new environment allows incorporating new technologies, that is, distributed energy resource (DER), energy storage systems (ESSs), and shiftable loads, to prevent emergency situations and blackouts. This paper proposes a novel, energy reserve operational scheduling method for future smart grid frequency enhancement considering wind generation, ESSs, thermal generating units, shiftable loads, and power system frequency response characteristics. The proposed method divides the reserve into two different parts, that is, active power reserve, which is responsible for smoothing the frequency fluctuations due to load variations and the second part is essential to control the frequency after large disturbances. The spinning reserve required for safe operation of the power system is determined based on a reliability criterion, that is, total expected energy not supplied (TEENS). The proposed method aims to maintain the frequency response in a stable mode by incorporating active power reserve from both generation and demand-sides. IEEE 30-bus and RTS-96 systems are utilized to verify the proposed reserve scheduling methods using GAMS programming environment. The obtained results verify the superiority and usefulness of the proposed method over others.

An Electromagnetic Vibration Energy Harvester with a Tunable Mass Moment of Inertia.

This paper presents a vibration-based electromagnetic energy harvester whose resonance frequency can be adjusted to match that of the excitation. Frequency adjustment is attained by controlling a rotatable arm, with tuning masses, at the tip of a cantilever-type energy harvester, thereby changing the effective mass moment of inertia of the system. The rotatable arm is mounted on a servomotor that is autonomously controlled through a microcontroller and a photo sensor to keep the device at resonance for maximum power generation. A mathematical model is developed to predict the system response for different design parameters and to estimate the generated power. The system is investigated analytically by a distributed-parameter model to study the natural frequency variation and dynamic response. The analytical model is verified experimentally where the frequency is tuned from 8 to 10.25 Hz. A parametric study is performed to study the effect of each parameter on the system behavior.