Simulating dynamic behavior of a grid-linked wind farm power system in Taiwan

Dynamic behavior of a directory combined binary turbine system using a mixture of R 134 a and R 123 is investigated experimentally and theoretically. Our previous binary turbine system, which employs steam as the primary working fluid, used R 11 as the secondary working fluid because R 11 has good characteristics as a working fluid in power plants. However, substitute LBMs (Low Boiling temperature Medium) are being developed because of the ozone layer depletion by CFCs (Chloro Fluoro-Carbons). We investigated the system using R 123 in the second stage. Because R 123 is also controlled, in this paper, the steady state characteristics and dynamic behavior of the system using a mixture of R 134 a and R 123 are investigated taking into account the mole fraction of the mixture. In addition to the investigation using the experimental system, the following are clarified using our model : In the steady-state characteristics, there are remarkable differences in pressure based on the thermodynamic properties and in the load allotment of the two turbines. However, in the dynamic characteristics, the effect of the mole fraction could hardly be observed on the response characteristics of the rotating components to the load change.

Aero-engine rotor system contains a variety of connectors such as bolts and bearings. However, the dynamic behaviors of the connection are complex in actual engineering. In this paper, the dynamic behavior of the rotor-bearing system with bolted joints and the influence of the parameters of the joints on it are clarified. The parameters include the bearing clearance and the deflection caused by the uneven bolt preload. A rotor-bearing model with bolted joints is established by using Lagrange equations. The bifurcation diagram is solved to explore the tendency of vibration of the system at different speeds by considering the Hertz contact force. Furthermore, the phase diagram, Poincaré map, time-domain steady-state response curve, and spectrum diagram are used to discuss the dynamic behaviors of the system specifically. The influence of the bearing clearance change and uneven bolt preload on the dynamic behaviors is investigated by using the bifurcation diagram. The result shows that the motion of the system is extremely complex, which includes chaotic motion. The Lyapunov exponent is then calculated to verify whether the system enters chaos. The correctness of the model is verified by comparing the result in this work with those in the literature. The model can clarify the dynamic behaviors of the system well and has high accuracy, which can provide the theoretical guidance for the design of rotor-bearing systems with bolted joints.

The present work deals with the dynamics of a generic mechanical linkage that is an integral part of many mechanical systems which require manual or automated control. It is necessary to include the dynamics of the control linkage in the model while modeling a system with such control for obtaining realistic dynamic behavior of the overall system. A typical application of the control linkages is to move an inertia element in a controlled manner, while keeping the motion as smooth as possible. Presence of inertia and elasticity in the form of a spring makes such system a second-order system, with a tendency to undergo oscillatory motion during such controlled motion. Presence of friction further introduces irregularities and nonlinearities in the motion of the target inertia element. Under these conditions, the trajectory of the controlling force has to be optimized to achieve smooth controlled motion. The present paper deals with these issues, by using a pedal-operated lever arrangement used in applications requiring controlled release or controlled engagement in mechanical systems. The computer tool used for simulation is MATLAB. The dynamic behavior of the system is assessed on the basis of total settling time of the target mass, computation time, time period of oscillation of the target mass, maximum amplitude, and amplitude decay. The present study can be useful in design of actuators and mechatronic systems involving similar dynamics.

Dynamical behaviors of a class-B laser system with dissipative strength are analyzed for a model in which the polarization is adiabatically eliminated. The results show that the injected signal has an important effect on the dynamical behaviors of the system. When the injected signal is zero, the dissipative term of the class-B laser system is balanced with external interference, and the quasi-periodic flows with conservative phase volume appear. And when the injected signal is not zero, the stable state in the system is broken, and the attractors (period, quasi-period, and chaos) with contractive phase volume are generated. The numerical simulation finds that the system has not only one attractor, but also coexisting phenomena (period and period, period and quasi-period) in special cases. When the injected signal passes the critical value, the class-B laser system has a fold-Hopf bifurcation and exists torus “blow-up” phenomenon, which will be proved by theoretical analysis and numerical simulation.

Gear systems are commonly used in vehicles, and the vibration of the gear system was paid more attention in recent years. In this paper, the dynamic behavior of gear system with stochastic perturbation of system parameters was analyzed. A stochastic nonlinear dynamic model of gear system, with consideration of the stochastic perturbation of system parameters, was established. The influences of stochastic perturbation of system parameters, such as excitation frequency, damping ratio, and backlash, on the dynamic behavior of the system were discussed. It was found that when the perturbation intensity is weak, the topological structure of the system solutions will not change, and there is no transition of the attractors. But if the perturbation intensity increases further, there will be transition between the attractors. In general, for single-DOF gear system, the multi-periodic attractor will jump to the quasi-period-1 attractor. But the quasi-period-1 attractor will not jump to other attractors. If the perturbation intensity is considerable great, bi-directional transition will occur. Yet, the probability of transition from multi-periodic attractor to quasi-period-1 attractor is greater than the probability of transition from multi-periodic attractor to other attractors. Which provide theoretical basis for effective vibration control of gear system.

SummaryHigh penetration of renewable energy in a power system may cause the problem of power dispatching and stability. The detailed dynamic behavior analysis for such a system is therefore important to the planning and operation of the power system. This study discussed the dynamic characteristics of an island power system with variable‐pitch wind turbines under high wind speed and high small hydraulic output power. The system primarily consisted of three diesel engine power generation systems, three constant‐speed variable‐pitch wind turbines, a small hydraulic induction generation system, and lumped static loads. The maximum penetration of renewable energy in this system could reach almost 60%. Detailed models based on MATLAB/Simulink were developed to cater for the dynamic behavior of the system. The results suggested that this island power system can operate stably in this operational mode with the help of variable‐pitch wind turbines. This study can serve as an important reference for planning, operation, and further expansion of island power systems. Copyright © 2014 John Wiley & Sons, Ltd.

(English) Dynamic behavior of modern power system is increasingly influenced by the dynamics of power converters. At the generation level, a high volume of wind and solar energy with their large-scale power converters are replacing conventional synchronous generators. At the transmission level, many High Voltage Direct Current (HVDC) projects based on Modular Multilevel Converter (MMC) technology are commissioned to transfer offshore wind to the load centers, interconnect two non-synchronous AC grids, or two different nodes of the same AC grid (as an embedded link) to enhance the security of supply. The consumption level also faces such high integration of power converters since the modern flexible loads, such as electric vehicles, industrial motor drives, and recent hydrogen electrolyzers, are connected to the power system via power converters. Such transformation in generation, transmission, and consumption levels leads to the power dynamics that have never been experienced before in the conventional power systems. The high penetration of power converters may cause several challenges: reduction in the system total inertia and short-circuit current, excitation of undesirable interactions among control loops, reduction in stability margin, and loss of devices in the context of fault-ride through (FRT). Such challenges can be addressed by appropriate adjustments in the control systems of power converters. At the transmission level, this thesis focuses on improving the dynamic behavior of HVDC systems. A methodology is suggested to study the small-signal stability and evaluate potential interactions that may happen among control loops of two HVDC converter stations. Next, a multivariable controller based on H-inf design practice is developed to optimize the dynamic behavior of the system. As a follow-up study, mu-synthesis control approach is adopted to make HVDC control resilient against AC grid impedance variation. In the context of FRT performance, the fault operation of the HVDC system is improved by appropriate modification of the MMC control loops. Finally, a brief study on the DC voltage droop control design is conducted on a multi-terminal HVDC system. At the generation level, this thesis investigates the dynamic behavior of grid-forming control during fault events in a low-strength power system. It investigates the complication related to the existing grid codes and suggests two FRT controls for AC voltage support during fault recovery. As the last step, this thesis evaluates the feasibility of modern flexible loads to provide grid-forming services to the low-strength power grid. A hydrogen electrolyzer is used as an example and the operational constraints related to the hydrogen production are linked to the grid-forming functionalities. (Català) El comportament dinàmic del sistema de potència modern està cada vegada més influenciat per la dinàmica dels convertidors de potència. A nivell de generació, un gran volum d'energia eòlica i solar amb els seus convertidors de potència a gran escala està substituint els generadors síncrons convencionals. A nivell de transmissió, molts projectes de corrent continu d'alta tensió (HVDC) basats en la tecnologia Modular Multilevel Converter (MMC) s'encarreguen de transferir l'eòlica marina als centres de càrrega o interconnectar dues xarxes de CA per millorar la seguretat del subministrament. El nivell de consum també s'enfronta a una integració tan alta dels convertidors de potència, ja que les càrregues flexibles modernes, com ara vehicles elèctrics, accionaments de motors industrials i electrolitzadors d'hidrogen recents, es connecten al sistema elèctric mitjançant convertidors de potència. Aquesta transformació en els nivells de generació, transmissió i consum condueix a una dinàmica de potència que mai s'havia experimentat abans en els sistemes de potència convencionals. L'elevada penetració dels convertidors de potència pot provocar diversos reptes: reducció de la inèrcia total del sistema i de la potència de curtcircuit, excitació d'interaccions indesitjables entre llaços de control, reducció del marge d'estabilitat i pèrdua de dispositius en el context de fallada (FRT). Aquests reptes es poden abordar mitjançant ajustos adequats en els sistemes de control dels convertidors de potència. A nivell de transmissió, aquesta tesi se centra en la millora del comportament dinàmic dels sistemes HVDC. Es proposa una metodologia per estudiar l'estabilitat del senyal petit i avaluar les interaccions potencials que poden passar entre els bucles de control de dues estacions convertidores HVDC. A continuació, es desenvolupa un controlador multivariable basat en la pràctica de disseny H-inf per optimitzar el comportament dinàmic del sistema. Com a estudi de seguiment, s'adopta un enfocament de control de sintetització-mu per fer que el control HVDC sigui resistent a les variacions en la impedància de la xarxa de CA. En el context del rendiment FRT, el funcionament de falla del sistema HVDC es millora mitjançant les modificacions adequades als bucles de control MMC. Finalment, es realitza un breu estudi sobre el disseny de control de caiguda de tensió de CC en un sistema HVDC multiterminal. A nivell de generació, aquesta tesi investiga el comportament dinàmic del control de formació de xarxa durant esdeveniments de falla en un sistema d'energia de baixa inèrcia. Investiga la complicació relacionada amb els codis de xarxa existents i suggereix dos controls FRT per al suport de la tensió de CA durant la recuperació de fallades. Com a darrer pas, aquesta tesi avalua la viabilitat de càrregues flexibles modernes per proporcionar serveis de formació de xarxa a la xarxa elèctrica de baixa resistència. Com a exemple s'utilitza un electrolitzador d'hidrogen i les limitacions operatives relacionades amb la producció d'hidrogen estan vinculades a les funcionalitats de formació de la xarxa. (Español) El comportamiento dinámico de los sistemas eléctricos modernos está cada vez más influido por la dinámica de los convertidores de potencia. A nivel de generación, un gran volumen de energía eólica y solar con sus convertidores de potencia a gran escala están sustituyendo a los generadores síncronos convencionales. A nivel de transmisión, se están encargando muchos proyectos de corriente continua de alta tensión (HVDC) basados en la tecnología de convertidores multinivel modulares (MMC) para transferir la energía eólica marina a los centros de carga, interconectar dos redes de CA no síncronas o dos nodos diferentes de la misma red de CA (como enlace integrado) para mejorar la seguridad del suministro. El nivel de consumo también se enfrenta a una integración tan elevada de los convertidores de potencia, ya que las cargas flexibles modernas, como los vehículos eléctricos, los accionamientos de motores industriales y los recientes electrolizadores de hidrógeno, se conectan al sistema eléctrico a través de convertidores de potencia. Esta transformación en los niveles de generación, transmisión y consumo da lugar a una dinámica de potencia nunca antes experimentada en los sistemas eléctricos convencionales. La alta penetración de los convertidores de potencia puede causar varios retos: reducción de la inercia total del sistema y de la corriente de cortocircuito, excitación de interacciones indeseables entre los bucles de control, reducción del margen de estabilidad y pérdida de dispositivos en el contexto de la conmutación por fallo (FRT). Estos retos pueden abordarse mediante ajustes adecuados en los sistemas de control de los convertidores de potencia. A nivel de transmisión, esta tesis se centra en mejorar el comportamiento dinámico de los sistemas HVDC. Se propone una metodología para estudiar la estabilidad de pequeña señal y evaluar las posibles interacciones que pueden producirse entre los lazos de control de dos estaciones convertidoras HVDC. A continuación, se desarrolla un controlador multivariable basado en la práctica de diseño H-inf para optimizar el comportamiento dinámico del sistema. Como estudio complementario, se adopta un enfoque de control mu-síntesis para que el control HVDC sea resistente a la variación de la impedancia de la red de CA. En el contexto del rendimiento FRT, se mejora el funcionamiento en fallo del sistema HVDC mediante la modificación adecuada de los bucles de control MMC. Por último, se realiza un breve estudio sobre el diseño del control de droop de tensión de CC en un sistema HVDC multiterminal. A nivel de generación, esta tesis investiga el comportamiento dinámico del control de formación de red durante eventos de fallo en un sistema eléctrico de baja tensión. Investiga la complicación relacionada con los códigos de red existentes y sugiere dos controles FRT para el soporte de tensión de CA durante la recuperación de fallos. Como último paso, esta tesis evalúa la viabilidad de las cargas flexibles modernas para proporcionar servicios de formación de red a la red eléctrica de baja potencia. Se utiliza como ejemplo un electrolizador de hidrógeno y se relacionan las restricciones operativas relacionadas con la producción de hidrógeno con las funcionalidades de formación de red.

As a nonlinear dynamic system, the dynamic equation of triboelectric nanogenerator system is not only difficult to accurately establish, but also difficult to solve. The output signals of triboelectric nanogenerator system depends on the initial conditions of the system, which reflects the dynamic behavior of the system. Currently, there is little research on using the output signals to study the dynamic behavior of triboelectric nanogenerator system. Therefore, a dynamic simulation model of a freestanding triboelectric nanogenerator (F-TENG) system was established using COMSOL software. The mathematical model of the F-TENG system was fitted. Using chaos theory and its phase-space reconstruction technology, the phase-space trajectories of the F-TENG system were reconstructed through voltage signals under external factors, and the dynamic behavior of the F-TENG system was discussed and studied. Finally, validation experiments were carried out. The research shows that with the variation of internal factors and operating frequency, the mathematical model of the F-TENG system remains basically unchanged, and the variation law of output characteristics also remains basically unchanged. The F-TENG system is in periodic motion; with the variation of external factors such as resistance and friction layer spacing, the mathematical model of the F-TENG system will evolve in a complex direction, and the output characteristics will gradually distort. The F-TENG system will evolve from periodic motion to chaotic motion. The research results not only reveal the dynamic behavior and enrich the nonlinear dynamic theory of triboelectric nanogenerator system, but also provide theoretical guidance for increasing the working bandwidth and stability of triboelectric nanogenerator system.

Effects of load modelling on the behaviour of power systems

00/02640 Tape casting—a versatile method of making fuel cell components and their characterization

In this paper, an attempt is made for effective application of energy storage unit to improve the transient behavior of the system in automatic generation control of interconnected power systems. For the investigation, we have considered thermal-hydal two area systems. This model is investigated with and without considering energy storage unit (CES and SMES) in the presence of Proportional Integral Derivative controller with a derivative filter for different cases. Results were compared for different cases and it demonstrates the effectiveness of energy storage devices for improving the dynamic behavior of the interconnected power system. Here instead of conventional controllers like I, PI and PID we have used PIDF controller and results shows that it is better than a conventional controller. The model is stimulated under MATLAB-2010 simulink environment.

We propose a new methodology based on modularity clustering of synchronization coefficient, to identify coherent groups of generators in the power grid in real-time. The method uses real-time integrity indices, i.e., the Generators Connectivity Index (GCI) that represents how generators are coherently strong within the groups, the Generator Splitting Index (GSI) that reveals to what extent the generators in different groups tend to swing against the other groups, and the System Separation Index (SI) which discloses the overall system separation status. We demonstrate how these integrity indices can be used to study the dynamic behavior of the power system. Furthermore, a comparison analysis is conducted between the synchronization coefficient (KS) and the generator rotor angle correlation coefficient (CC). The proposed indices demonstrate the dynamic behavior of power system following occurrence the faults and thus represent a promising approach in power system islanding studies. Our methodology is simple, fast, and computationally attractive. Simulation case performed on IEEE 118-bus systems demonstrates the efficacy of our approach.

The dc symmetrical component method is introduced for the analysis and control of bipolar dc distribution systems under asymmetrical operation. This method is an extension of the classical symmetrical component theory in three-phase ac power systems. The asymmetrical voltage and current in the positive and negative poles are decomposed into symmetrical components in common and differential modes. The equivalent circuit for each mode is derived, which forms decoupled mode networks. Consequently, it allows for independent investigation of each mode, and provides an insightful view of the static and dynamic behavior of a bipolar dc power system. The dc symmetrical component method is a general approach which is applicable to different aspects of system design. As an example, an enhanced common-mode voltage regulation scheme is described. It suppresses common-mode LC resonance by adding active damping control, and reduces common-mode impedance to improve power quality and voltage stability. The major theoretical conclusions are verified by experimental results.

The need for real-time simulation stems from the fact that in many practical situations it is desirable to analyze the dynamic behavior of a large power system with advanced equipment that has complex and high-speed performance. Analog simulators are effective, however they impose serious limitations on the size of the system that is being modeled. The authors have studied and developed a real-time digital simulator using a hypercube computer, and realized a real-time performance available for the analysis of large power systems. Now as the second step of their study, they developed a digital/analog conversion interface for testing actual power instruments. The interface exchanges the variables of fundamental frequency domain in the real-time digital simulator, and the variables of exact time domain in the analog equipment connected to the simulator. In this paper, the authors describe the detail of their developed digital/analog conversion interface of the real-time digital simulator for testing advanced power instruments. Its conversion algorithm, the system configuration of the simulator with the interface, and experimental results are also presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An innovative method to develop power system equivalents is presented in this paper. The purpose is the representation of system inertia, inter-area oscillations and primary control of large interconnected power systems by means of publicly available information. The approach to reach this target is based on a systematically developed load-flow model and the representation of system dynamics by means of standard dynamic models for generation units, their appropriate control and loads. The initial parameters of the standard dynamic models are tuned with regard to frequency measurements and published power system characteristics. The developed method allows general analysis of extensive influences on the dynamic behavior of a particular power system. Conceivable applications of the developed method are proposed for further system analysis. Finally an employment of the method is shown for the Continental Europe synchronous area (CESA).