Top PDF SELF TUNING CONTROLLERS FOR DAMPING LOW FREQUENCY OSCILLATIONS

SELF TUNING CONTROLLERS FOR DAMPING LOW FREQUENCY OSCILLATIONS

SELF TUNING CONTROLLERS FOR DAMPING LOW FREQUENCY OSCILLATIONS

Abstract: This paper presents a new control methods based on adaptive Neuro-Fuzzy damping controller and adaptive Artificial Neural Networks damping controller techniques to control a Unified Power Flow controller (UPFC) installed in a single machine infinite bus Power System. The objective of Neuro-Fuzzy and ANN based UPFC controller is to damp power system oscillations.Phillips-Herffron model of a single machine power system equipped with a UPFC is used to model the system. In order to damp power system oscillations, adaptive neuro-fuzzy damping controller and adaptive ANN damping controller for UPFC are designed and simulated. Simulation is performed for various types of loads and for different disturbances. Simulation results demonstrate that the developed adaptive ANN damping controller has an excellent capability in damping electromechanical oscillations which exhibits a superior damping performance in comparison to the neuro-fuzzy damping controller as well as conventional lead-lag controller.
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Robust Decentralized Control of Unified Power Flow Controller

Robust Decentralized Control of Unified Power Flow Controller

Using the schauder fixed point theorem [14] the synthesis and analysis of the Multi-Input Multi-output (MIMO) control system under study is translated into a set of equivalent Multi-Input Single-Output (MISO) control system. It is shown that each decentralized controller can be designed independently such that performance of the overall closed loop systems is guaranteed. Based on this framework, a new decentralized controller is designed for satisfying UPFC performance based on µ-synthesis technique to mitigate low frequency oscillations. The µ-synthesis technique not only minimizes the maximum error energy for all command disturbance input, but also stabilizes the closed loop system for structured plant uncertainties with limited H norm. This especially is desirable when designing controllers for plants with unmodeld high frequency dynamics, or when the plants under go faulty operating conditions or plant parameters vary due to aging such as power system. The proposed control strategy is compared with the classical PID controllers to illustrate its robust performance under different operation conditions for damping low frequency oscillation and load disturbances. Finally, several three- phase fault and nonlinear time simulation results are shown to highlight the effectiveness of the proposed µ- based UPFC controller.
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Improvement of Small Signal Stability of SMIB System Using PSO and CSO based Power System Stabilizer

Improvement of Small Signal Stability of SMIB System Using PSO and CSO based Power System Stabilizer

In this paper, Heffron-Phillips model is developed for Single Machine Infinite Bus (SMIB) system using MATLAB/SIMULINK. SMIB system is simulated for a step change in reference voltage without and with optimized PSS. Without PSS, both torque angle and speed deviation are subjected to low frequency oscillations with increasing amplitude. This is because of negative damping torque provided by AVR. For providing necessary damping torque, Power System Stabilizer (PSS) is installed. The PSS parameters are tuned using Particle Swarm Optimization (PSO) and Cat Swarm Optimization (CSO) techniques. Both of the tuning methods produced the same effect of damping of low frequency oscillations. From Fig. 8 and Fig. 9, it is clearly observed that the both optimization techniques are effective in tuning PSS parameters.
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GAPOD and GA DC-voltage regulator based UPFC supplementary cont roller for damping low frequency oscillations in Multi-machine power  systems

GAPOD and GA DC-voltage regulator based UPFC supplementary cont roller for damping low frequency oscillations in Multi-machine power systems

with these objectives. Gyugyi proposed the Unified Power Flow Controller which is the new type generation of FACTS devices in the year 1991 [5]. Unified Power Flow Controller (UPFC), being one the member of the FACTS device thus emerged as one of the effective controllers for controlling and optimization of the power flow in the electrical power transmission systems [7]. This device was formed due to the combination of the two other FACTS devices, namely Static Synchronous Compensator (STATCOM) and the Static Synchronous Series Compensator (SSSC). These are connected to each other by a common DC link, which is a typical a storage capacitor. The all parameters of the power transmission line (impedance, voltage and phase angle) can be control simultaneously by UPFC [6,8]. In the modern day power system stability, operation & control (PSOC), FACTS (Flexible AC Transmission Systems) plays a very important role. Usage of FACTS in the power systems not only enhances the dynamic performance, but also increases the stability of the power systems, enhances the controllability and increases its power transfer capability. Some of the devices used in the control of FACTS are the SVC, TCSC, STATCOM, UPFC, and the IPFC [1]. The FACTS controllers utilize power electronics based technology and can provide dynamic control on line power flows, bus voltages, line impedance & phase angles. One of the controllers being used in the work presented in this paper is the GAPOD and GA DC- voltage regulator scheme for the damping of power system oscillations. The FACTS initiative was originally launched in 19 80‟s to solve the emerging problems faced due to restrictions on transmission line construction, and to facilitate growing power export/import and wheeling transactions among
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Damping Of Low Frequency Oscillations In Power System Using  Device Upfc With Fuzzy Logic

Damping Of Low Frequency Oscillations In Power System Using Device Upfc With Fuzzy Logic

The problem of poorly damped low frequency oscillations associated with generator rotor swings has been a matter of concern to power system stabilizer (PSS). In addition, HVDC, SVC controllers have also been used to damp these low frequency oscillations. The advent of high power equipments to improve the utilization of transmission capacity provides system planers with additional leverage to improve stability of the system. Traditionally, power system stabilizers are being used to damp low frequency oscillations effectively through direct control of voltage and power.
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Robust state feedback controller design of STATCOM using chaotic optimization algorithm

Robust state feedback controller design of STATCOM using chaotic optimization algorithm

In this paper, COA is used for robust tuning of the STATCOM based state feedback damping controller in order to enhance the damping of the power systems low frequency oscillations. Chaos is a kind of characteristic of nonlinear systems which is a bounded unstable dynamic behavior, which exhibits sensitive dependence on the initial conditions and includes infinite unstable periodic motions. The COA is based on the ergodicity, stochastic properties and regularity of the chaos. It is not like some stochastic optimization algorithms that escape from the local minima by accepting some bad solutions according to a certain probability, but COA searches on the regularity of the chaotic motion to escape from the local minima [7-13].
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J. Braz. Soc. Mech. Sci. & Eng.  vol.26 número1

J. Braz. Soc. Mech. Sci. & Eng. vol.26 número1

correspond to mean values collected from different references. The USM experiments were carried out in a stationary Sonic- Mill machine with a power output of 1790 W. An electrostrictive PZT transducer converts the electric oscillations into mechanical vibrations in the frequency range of 20 kHz. The amplitude of vibration was set at the minimum value and was close to 25 µm in the tip of the cutting tool. The static load applied on the sonotrode was kept at 25 N throughout the experiments. The abrasive slurry was made with silicon carbide (SiC) with mean grain size of 15 µm (600 mesh) and water in the ratio 1:2.5 by volume. E, H and K 1c
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History-dependent excitability as a single-cell substrate of transient memory for information discrimination.

History-dependent excitability as a single-cell substrate of transient memory for information discrimination.

In this article we considered an idealized scenario in which the neuron sits at its stable point, receives a train of instantaneous EPSPs with constant amplitude, and it is then free to evolve according to its intrinsic dynamics alone. The adoption of linear models guarantees that the presented results also hold if the input histories include fluctuating currents (‘‘frozen noise’’), as long as they are equal among different input histories. Furthermore, intrinsic discriminability does not depend upon the neuron state at the moment of input arrival in linear models. Nevertheless, it is not clear whether intrinsic discriminability could still serve as a reliable indicator of the current context in a complex, non-linear neuron as the input histories include unknown time-varying components. From a dynamical perspective, the consistent encoding of incoming information could still be achieved if the neuron state is driven to a restricted portion of its state space before receiving its temporally-structured inputs. This task could be accomplished by network oscillations [30,65]: periodic inhibition could format the continuous stream of incoming synaptic events in blocks of fixed temporal duration, by driving the neuron to a restricted portion of its state space at each peak of the total inhibitory drive [66]. This periodic ‘‘reset’’ would allow the consistent contextualization of the EPSPs on a cycle-by-cycle basis. Periodic excitation could play a similar role. For networks operating in an asynchronous, irregular firing regime, results from random dynamical system theory [67] reveal that in certain conditions a neuron injected with a pseudo-random stimulus will soon forget its initial state and converge to a stochastic, time-varying attractor [68,69]. Hence, temporally structured inputs time-locked to the stochastic attractor might be consistently encoded through the proposed mechanism even in non-linear neurons. In this case, the transient memory trace induced by the external stimulus would gradually wane as the neuron trajectory converges to the stochastic attractor corresponding to a given noise realization. Nevertheless, more work is needed in the field in order to clarify the interplay between sensitivity and reliability in neuronal network dynamics [70–72].
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Efficiency of biparental crossing in sugarcane analyzed by SSR markers

Efficiency of biparental crossing in sugarcane analyzed by SSR markers

Sugarcane has hermaphrodite flowers, and pollination is accomplished by cross-pollination. However, either self-pollination or cross-pollination with foreign pollen can occur in breeding programs (Ferreira et al. 2005), resulting in selfing or foreign progenies (McIntyre and Jackson 2001, Chen et al. 2009). To minimize self-pollination in progeny numbers, maternal flowers are immersed in heated water at 50 °C for 4.5 min to sterilize them before crossings are carried out (Machado Jr et al. 1995). However, Pan et al. (2003) showed that complete pollen sterility has not been efficient, suggesting the occurrence of hybrid and selfing progenies in the F 1 population.
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Implementation of Self-Tuning Fuzzy PI Controller on DCS for Flow Control System

Implementation of Self-Tuning Fuzzy PI Controller on DCS for Flow Control System

Abstract —In case of changing a communication between field instruments and controller from analog signal into digital signal or of changing a model of plant, performance of controller is degraded because of the fixed controller parameters such as PID controller. To solve this problem, a self-tuning PID controller is proposed. One of a popular self- tuning method is self-tuning fuzzy. Many researchers have been presented the self-tuning fuzzy PID controller. In this paper, we present implementing of self-tuning fuzzy PI controller for flow control system. Both fuzzy and PI controller is implemented on distributed control system (DCS) as controller at which communication between field instruments and distributed control system is via both the analog input and output modules as analog signal in range of 4-20mA and digital signal as Profibus PA. The PI controller parameters, proportional gain and integral time, from auto-tuning method is used to control plant, flow control system, by using analog signal at which result shows that flow process variable reaches to flow set point. The same PI controller parameters is applied for PROFIBUS PA at which results shows that flow process variable oscillates because of effect of delay-time taken place from communication between field instruments and distributed control system.
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LOW-FREQUENCY DIELECTRIC RELAXATION IN SILVER STEARATE LAYERS

LOW-FREQUENCY DIELECTRIC RELAXATION IN SILVER STEARATE LAYERS

Silver stearate is produced by the exchange reaction of sodium substitution under the excess concentration of silver nitrate particles of about one micron. Thus, in electrophysical research monolithic samples of this substance are used, press-formed into a tablet shape. Films with thickness of 0.5 mm and diameter of 10 mm were used. Specific features of the dielectric rОХКбКЭТШЧ prШМОЬЬОЬ аОrО ЬЭЮНТОН Лв ЭСО НТОХОМЭrТМ ЬpОМЭrШЬМШpв ЦОЭСШН аТЭС “CШЧМОpЭ 81” ЬвЬЭОЦ (NШЯШМШЧЭrШХ Technologies). This method has been applied successfully in the recent studies of electronic processes in systems of varying structural disorder [8-10]. Spectra of the complex dielectric permittivity were calculated from the impedance data. The temperature and frequency dependences of dielectric parameters were measured in a wide frequency range (10 -2 …10 2 Hz) and temperature band (273- 353 K). The operating voltage was 1.0 V. The error of measurements and calculations of physical parameters did not exceed 3%.
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Gravity as an Ultra-Low Frequency Scattering Effect

Gravity as an Ultra-Low Frequency Scattering Effect

Under the weak gravitational field approximation, and, for the 00-component of the stress-energy tensor, Einstein’s field equations reduce to Newton’s model for a gravitational field which is compounded in the Poisson equation for the gravitational potential. By considering Newton’s field equation to be the result of an ultra-low frequency scattering effect (in the limiting case), this work introduce a model where a gravitational field is taken to be the result of an ultra-low frequency gravitational wave (propagating in a near-Cartesian Minkowski space) scattering from an object (a mass). Further, by using a scalar wave-field model for the propagation of an electromagnetic wave, the effect of a light wave with wavelength λ scattering from a gravitational potential is investigated from which a scaling relation for the inten- sity of the resulting diffraction pattern is derived. It is shown that the intensity associated with the diffraction pattern is proportional to λ − 6 which may provide an
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High-frequency atmospherically-induced oscillations in the middle Adriatic coastal area

High-frequency atmospherically-induced oscillations in the middle Adriatic coastal area

waves are not necessarily detected at the sea surface. They could be trapped in a stable lower troposphere (up to approx- imately 4 km) with an unstable reflecting layer (Richardson number lower than 0.25, Lindzen and Tung, 1976) above. These conditions enable the non-dispersive characteristic of the waves visible on the surface air pressure series, allowing them to travel over a long distance without dissipating much of their energy (Monserrat and Thorpe, 1996). However, the proof for this “ducting theory” should be supplied by addi- tional numerical studies rather than analytical theory. An- other propagation mechanism seems to be the “self-feeding convective cell”, which was recently reproduced by the MM5 mesoscale model (Beluˇsi´c et al., 2006) for the 2003 Adriatic case. This means that a gravity perturbation, once it is gen- erated and advected over the warm sea, is fed by the large influx of moisture on its front, resulting in a strong uplift in the whole troposphere. As the Adriatic Sea was heated quite anomalously in May/June 2003 (e.g. Orli´c et al., 2006), resulting in a sea surface temperature of about 26–27 ◦
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Wesley Augusto Conde Godoy

Wesley Augusto Conde Godoy

The mathematical analysis performed in this study reveals that C. albiceps shows a dynamic behavior represented by a limit cycle of two points, since λ = -1,0398 (larger than one in module). This behavior was also observed in C. megacephala and C. putoria (Godoy et al. 1993, Von Zuben et al. 1993), but it differs from the native species, C. macellaria, that shows damping oscillations in population size leading to one fixed point equilib- rium (Reis et al. 1996). We noted, however, that the value of λ obtained for C. albiceps is very close to one if compared to the other values observed for C. megacephala, λ = -1.3761 and C. putoria, λ = -1.2399 (Godoy et al. 1996). This result sug- gests that C. albiceps is a species apparently more susceptible to changes in its dynamic behavior than C. megacephala and C. putoria.
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ISSN 0100-879X CLINICAL INVESTIGATION

ISSN 0100-879X CLINICAL INVESTIGATION

The objective of this study was to use linear and non-linear methods to investigate cardiac autonomic modulation in healthy elderly men and women in response to a postural change from the supine to the standing position. Fourteen men (66.1 ± 3.5 years) and 10 women (65.3 ± 3.3 years) were evaluated. Beat-to-beat heart rate was recorded in the supine and standing positions. Heart rate variability was studied by spectral analysis, including both low (LFnu-cardiac sympathetic modulation (CSM) indicator) and high (HFnu-cardiac vagal modulation (CVM) indicator) frequencies in normalized units as well as the low frequency/high frequency (LF/HF) ratio. Symbolic analysis was performed using the following indexes: 0V% (CSM indicator), 1V% (CSM and CVM indicators), 2LV% (predominantly CVM indicator) and 2ULV% (CVM indicator). Shannon entropy was also calculated. Men presented higher LFnu and LF/HF ratio and lower HFnu and 1V% symbolic index (57.56, 4.14, 40.53, 45.96, respectively) than women (24.60, 0.45, 72.47, 52.69, respectively) in the supine position. Shannon entropy was higher among men (3.53) than among women (3.33) in the standing position, and also increased according to postural change in men (3.25; 3.53). During postural change, the LFnu (24.60; 49.85) and LF/HF ratio (0.45; 1.72) increased, with a concomitant decrease in HFnu (72.47; 47.56) and 2LV% (14.10; 6.95) in women. Women presented increased CSM in response to postural change and had higher CVM and lower CSM than men in the supine position. In conclusion, women in the age range studied presented a more appropriate response to a postural change than men, suggesting that cardiac autonomic modulation may be better preserved in women than in men.
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Input parameters self-tuning on the SNN algorithm (Shared Nearest Neighbour)

Input parameters self-tuning on the SNN algorithm (Shared Nearest Neighbour)

José Guilher me da Cr uz Mor eir a outubro de 2013 UMinho | 2013 In put P arame ter s Self-tuning on t he SNN Algor it hm (Shar ed Near es t Neighbour) Universidade do Minho Escola de En[r]

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RESEARCH ON HYDRAULIC SERVO AMPLIFIERS USED IN  MARINE SYSTEMS

RESEARCH ON HYDRAULIC SERVO AMPLIFIERS USED IN MARINE SYSTEMS

The functioning principle consists in a stagger between the opening of the admission and exposal slots, so that the fluid in the cell out of which the exposal takes place, to be comprised and to take over the pressure impulses that appear at the opening of the admission slots. This way the possibility of movement of the piston is reduced and the high frequency oscillations, which will further propagate in the chain of commands, will have the amplitude lowered to the value determined by the compressibility of the fluid, a value which is lower than the one obtained in the case of the distributor with rectangular slots with perfect coverage.
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Developing Digital Control System Centrifugal Pumping Unit

Developing Digital Control System Centrifugal Pumping Unit

In the synthesis of ACS CPU must consider several system requirements, determined by the characteristics of the controlled object and features of its operation. One such requirement is the frequency of the time discretization (sampling), which is mainly determined by the response time to emergencies. Frequency of issuing solutions of ACS is

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EFFECTS OF LOW FREQUENCY ELECTROMAGNETIC FIELDON THE HUMAN BODY

EFFECTS OF LOW FREQUENCY ELECTROMAGNETIC FIELDON THE HUMAN BODY

Currently, according to ICNIRP-Guidelines for exposure to time limiting electric and magnetic fields varying (1Hz-100 kHz), 2010, the commercial frequency 50/60 Hz limits for exposure criteria used is the electric field inside the body. For the assessment of exposure to frequencies below 100 kHz is recommended electric field strength of the tissues because the physical quantity is correlated with biological effects and itself is linked to the current density. For higher frequencies are used SAR (Specific Absorption Rate) which correlates with the square of the electric field strength in the tissue. SAR is the rate at which the wave energy is absorbed in a tissue mass m and is measured in watts / kg (W / kg). This physical quantity varies punctually in the body, because the electric field changes with body position and conductivity of tissue is different. In Tables 1 and 2 are shown the limits of electric and magnetic field strenght and magnetic flux density and for controlled and uncontrolled environments.
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DATA ACQUISITION AND ANALYSIS OF LOW FREQUENCY ELECTROMAGNETIC FIELD

DATA ACQUISITION AND ANALYSIS OF LOW FREQUENCY ELECTROMAGNETIC FIELD

For assessing the human exposure to electromagnetic field, measurements will especially aimed strength(power, amplitude) field as the most relevant parameter. Since the exposure comes from many sources, environmental and occupational, its power will be a resultant of powers fields that propagate in several directions. In this respect, can be performed two types of measurements with specific devices: measuring broadband (with devices that detect signals in a wide range of frequencies) and measuring the selected frequency.

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