A coordinated design of power system stabilizer and power oscillation damping controller for generator and STATCOM voltage regulators is presented. Because fuzzy logic has the potential to overcome the inherent limitations of conventional and analytical model-based design approaches, simple fuzzy logic controllers operating as power system stabilizer and power oscillation damping controller are used in this work to enhance power system stability. The coordinated design of these fuzzy supplementary controllers (FSCs) is formulated as a constrained optimization problem with a time-domain based cost function. The optimal set of controller parameters is determined by applying a simultaneous tuning approach based on bat algorithm optimization. Simulations of a two-area power system under several operating conditions and perturbations are carried out to validate the effectiveness of the proposed alternative in damping system oscillations. Performance of the proposed coordinated FSCs is compared with other coordinated and uncoordinated design approaches, including coordinated FSCs using genetic algorithm and particle swarm optimization. Traditionally, power system stabilizers (PSSs) providing a supplementary signal through the generator voltage regulators have been extensively used by electric power utilities around the world to resolve oscillatory instability problems [4]. However, the operation and control requirements of today's power systems frequently make the damping contribution from PSSs alone insufficient [5]. Despite the fact that FACTS devices offer new opportunities for improving the damping of electromechanical oscillations through supplementary controllers, it is generally recognized that installing them for the sole purpose of power system stability enhancement is not a cost-effective solution [6]. However, when installed to satisfy their primary purpose, a power oscillation damping controller (PODC) can be incorporated into the existing devices.With the deployment of an increasing number of FACTS controllers in the systems, the potential for adverse interaction with one another and other controllers such as PSSs increases. Therefore, in order to provide maximum system benefit, it is important to coordinate the controllers of the various dynamic devices installed in a power system [1]. In this regard, various approaches have been reported in the literature to design PSSs and PODCs [7][8][9][10][11][12][13][14][15]. Because of the nonlinear nature of power system dynamics, any design based on linear analysis is often questionable and has to be extensively checked by nonlinear simulation [9,16,17]. On the other hand, despite that nonlinear design methods offer attractive features for the controller synthesis, a more complicated design procedure is also involved in this case [8,14,18]. In general, it is important to highlight that any analytical model-based approach presents some inherent shortcomings in the design and performance of the controller [17,18]. As for this, alternative synthesis techniques like ...
Undergraduate power engineering students find difficult to apply modal analysis to characterize the dynamical behavior of a power system, although they know some basic concepts of modal analysis from courses such as linear algebra and differential equations. This paper presents an educational software tool for the identification of dominant oscillatory modes from time domain responses. It is aimed to help power engineering systems students to understand and to gain experience on the application of modal analysis for assessing the system dynamics from measured signals of a power system, in terms its dynamic properties such as oscillation frequency and its associated damping.
ABSTRACT:There is a typical dynamical performance associated with every system.Oscillations are phenomena inherent to dynamical systems and the analysis of such phenomena is a fundamental issue for understanding the dynamical behavior of a particular system. Knowledge of the system natural modes, frequencies and its associated damping ratio, provide valuable information regarding the system performance after being subjected to a disturbance. Due to the operational requirements, topological changes in the transmission network of the electrical power systems are quite common. This causes modification in both frequency and damping values of the natural system modes. In the past, normal changes in the operating condition have kicked up undamped power oscillations in the Mexican system, thus assessing the damping of critical oscillation modes of the system is of utmost importance. This paper reports on the application of modal analysis and time domain simulations for computing and tracking the most dominant low frequency oscillations, also known as interarea modes, in the Mexican power system under different operating conditions. As a result, the most influential system variables on the low frequency oscillations have been identified. RESUMEN:Existe un comportamiento dinámico típico asociado a todo sistema. Las oscilaciones son fenómenos inherentes a los sistemas dinámicos, por lo que el análisis de estos resulta fundamental para entender el comportamiento dinámico de un sistema en particular. El conocimiento de la frecuencia de oscilación y su correspondiente razón de amortiguamiento, asociados con los modos naturales del sistema, resulta fundamental para inferir el comportamiento dinámico del sistema después de que ha experimentado un disturbio. En un sistema eléctrico de potencia los cambios topológicos en la red de transmisión son bastante comunes debido a los requerimientos operativos. Esto ocasiona cambios en los valores tanto de la frecuencia de oscilación como el amortiguamiento de los modos naturales del sistema. En el pasado, cambios normales en la condición de operación del sistema mexicano han dado como resultado la aparición de oscilaciones de potencia no amortiguadas, por esta razón el conocer el amortiguamiento asociado con los modos críticos del sistema resulta de vital importancia. Este artículo reporta la aplicación del análisis modal y simulaciones en el dominio del tiempo para el rastreo de las oscilaciones de baja frecuencia dominantes, también conocidas como modos inter-área, en el sistema eléctrico mexicano durante diferentes condiciones de operación. Los resultados obtenidos permiten identificar a las variables del sistema de potencia más importantes sobre las oscilaciones de baja frecuencia.
Large-scale integration of converter-based renewable energy sources into power systems, such as wind generation, can lead to frequency stability issues due to the variable nature and lack of inertia of these technologies in combination with the gradual replacement of conventional generating units. However, wind turbine generators (WTGs) can be exploited to provide frequency support and keep system frequency stability requirements. A case study considering the Mexican Electric Power System is presented in this study to highlight both the impact of large-scale deployment of inverter-interfaced wind energy generation on system frequency response, and the participation of WTGs in inertial and primary frequency control (IPFC) as a mitigation approach. By incorporating synthetic inertia and droop control functions into the active power control loop of WTG converters, IPFC by wind generation is assessed for several wind shares, different active power modulation strategies based on the rate of change of frequency and frequency deviation, and several IPFC contribution levels under critical contingencies for generation outage. Simulation results show the combination of increasing share of wind energy generation in the study system and retirement of conventional generation has a clearly negative impact on system frequency dynamics. However, the incorporation of IPFC functions into wind power generators of the sample system, with appropriate control gain values, may contribute to effectively achieve an improved system performance in terms of grid frequency response under high wind power penetration scenarios.
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