Identification of SVC Dynamics Using Wide Area Signals in a Power System

This paper presents the design of a wide area monitor (WAM) using remote area signals, such as speed deviations of generators in a power network, for identifying online the dynamics of a static var compensator (SVC). The design of the WAM is studied on the 12 bus FACTS benchmark system recently introduced. A predict-correct method is used to enhance the performance of the WAM during online operation. Simulation results are presented to show that WAM can correctly identify the dynamics of SVC in a power system for small and large disturbances. Such WAMs can be applied in the design of adaptive SVC controllers for damping interarea oscillations in power networks

Dual-Function Neuron-Based External Controller for a Static Var Compensator

The use of wide-area measurements for power system stabilization has recently been given a lot of attention by researchers and the power industry to avoid cascading failures and blackouts, such as the one in North America in August 2003. This paper presents the design of a nonlinear external damping controller based on wide-area measurements as inputs to a single dual-function neuron (DFN)-based controller. This DFN controller is specifically designed to enhance the damping characteristics of a power system over a wide range of operating conditions using an existing static var compensator (SVC) installation. The major advantage of the DFN controller is that it is simple in structure with less development time and hardware requirements for real-time implementation. The DFN controller presented in this paper is realized on a digital signal processor and its performance is evaluated on the 12-bus flexible ac transmission system benchmark test power system implemented on a real-time platform-the real-time digital simulator. Experimental results show that the DFN controller provides better damping than a conventional linear external controller and requires less SVC reactive power. The damping performance of the DFN controller is also illustrated using transient energy calculations

Real-Time Implementation of a Dual Function Neuron Based Wide Area SVC Damping Controller

The use of wide area measurements for power system stabilization is recently given a lot of attention by researchers and the power industry to avoid cascading failures and blackouts such as the August 2003. This paper presents the design of a nonlinear external damping controller based on wide area measurements as inputs to a dual function neuron (DFN). This DFN controller is specifically designed to enhance the damping characteristics of a power system considering the nonlinearity in the system. The major advantage of the DFN controller is that it is simple in structure with less development time and hardware requirements for real-time implementation. The DFN controller is implemented on a digital signal processor and its performance is evaluated on the IEEE 12 bus FACTS benchmark power system implemented on a real time platform - real time digital simulator (RTDS). Experimental results show that the DFN controller provides better damping than a conventional linear controlle

Online Training of a Generalized Neuron with Particle Swarm Optimization

Neural networks are used in a wide number of fields including signal and image processing, modeling and control and pattern recognition. Some of the most common type of neural networks is the multilayer perceptrons and the recurrent neural networks. Most of these networks consist of large number of neurons and hidden layers, which results in a longer training time. A Generalized Neuron (GN) has a compact structure and overcomes the problem of long training time. Due to its simple structure and lesser memory requirements, the GN is attractive for hardware implementations. This paper presents the online training of a GN with the Particle Swarm Optimization (PSO) algorithm. A comparative study of the GN and the MLP online trained with PSO is presented for function approximations. The GN based identification of the Static VAR Compensator (SVC) dynamics in a 12 bus FACTS benchmark power system trained online with the PSO is also presented

Origin of left accessory hepatic artery from the left gastric artery in a South Indian cadaver: Its clinical importance.

In recent years there has been an increase in number of transplantation surgeries, especially live donor liver transplantation in the western countries. In view of this, anatomical variations of hepatobiliary vessels gained special attention from anatomists, gastroenterological surgeons and interventional radiologists. These variations are of concern in hepatobiliary surgical procedures so as to minimize risk of complications for optimal success rates. We report a case of accessory hepatic artery that arose from the left gastric artery, entered the liver at an independent site from the porta hepatis to supply the left lobe of the liver. Transplantation of such livers with multi vascular pedicles may pose a challenge during anastomosis of these accessory hepatic arteries of the donor liver to the nearby arteries of the recipient.Keywords: Hepatic artery; Liver transplantation; Hepato biliary surgeries; Multivascular pedicles;Clinical significance

Optimal Design of SVC Damping Controllers with Wide Area Measurements Using Small Population Based PSO

Static Var Compensator (SVC) are employed for providing better voltage regulation and transient stability especially for increased power transfer through the transmission lines. In this paper, two SVC damping controllers with single and dual inputs respectively are designed based on wide area measurements of generator speed deviations. A Small Population based Particle Swarm Optimization algorithm (SPPSO) is applied to determine the optimal parameters of the damping controllers for small and large disturbances. Simulation results are provided to show that the effectiveness of the optimal damping controllers on the Kundur\u27\u27s two-area benchmark power system. Results show the dual input controller further improves the damping provided by the single input controller

Fruit quality evaluation of strawberries (Fragaria ananassa) grown in California and Oregon

Five genotypes from California (Ventana, Caniarosa, San Miguel, 13G97, and Venice) and Oregon (Totem, Puget Reliance, Puget Summer, Hood and Independence) were evaluated for quality. The volatile compounds were analyzed using head space solid phase micro extraction-gas chromatography-flame ionization detection (GGFID) and gas chromatography-mass spectrometry (GC-MS). Odor activity values of the compounds were calculated to understand the contribution of the individual compounds to the overall aroma. Ethyl butanoate, furaneol, ethyl hexanoate, ethyl acetate, ethyl isovalerate, hexyl acetate and gamma dodecalactone have the highest odor activity values. The chemical results were correlated with the sensory data obtained from a trained panel of 10 members. Correlation was achieved for the floral, pineapple, banana, peach and caramel notes. The green notes did not correlate with the concentration and odor activity values of the corresponding compounds. This variation could be due to the very high odor activity of other compounds resulting in the masking of the green notes. The sugar, organic acid and ascorbic acid composition was investigated using F]PLC Anthocyanin content was determined by pH differential method. The color properties were studied by measuring tn-stimulus measurements. The average fructose, glucose, sucrose and the total sugar content in the ten cultivars were 2.24, 1.96, 0.92 and 5.13 g/100 g respectively. Total acid content ranged from 0.93 g/100 g to 2.01 g/100 g. Puget Summer had the highest total sugars and Independence had the highest acids and ascorbic acid content. The anthocyanin content varied from 7.1 mg/100 g fruit to 30.52 mg/ba g fruit. The sensory evaluation of the genotypes in terms of sweetness and sourness could be partially explained by sugar/acid ratio. A consumer preference test showed that 'Totem' and 'Puget Reliance' were preferred over 'Camarosa' and 'Ventana' for their aroma

Intelligent Integration of a Wind Farm to an Utility Power Network with Improved Voltage Stability

The increasing effect of wind energy generation will influence the dynamic behavior of power systems by interacting with conventional generation and loads. Due to the inherent characteristics of wind turbines, non-uniform power production causes variations in system voltage and frequency. Therefore, a wind farm requires high reactive power compensation. Flexible AC transmission systems (FACTS) devices such as SVCs inject reactive power into the system which helps in maintaining a better voltage profile. This paper presents the design of a linear and a nonlinear coordinating controller between a SVC and the wind farm inverter at the point of interconnection. The performances of the coordinating controllers are evaluated on the IEEE 12 bus FACTS benchmark power system where one of the generators is replaced by a wind farm supplying 300 MW. Results are presented to show that the voltage stability of the entire power system during small and large disturbances is improved

An anatomical variation of Superficial Palmar Arch and its clinical significance: A Case Report

The familiarity of variations in vascular architecture of hand is helpful to surgeons, in microsurgical procedures precipitated by crush injuries of hand and in amputations. The efficiency of collateral circulation in hand is essential in certain peripheral vascular diseases like Raynaud’s disease and in harvesting of the radial artery for coronary bypass graft. Variation in the formation of superficial palmar arch is common. We report a rare variation of equitable distribution of superficial palmar arch. Variations of the superficial palmar arterial arch are not uncommon. Allen’s test, doppler ultra sound, arterial angiography pulse oximetry should therefore be used to assess the efficiency of collateral circulation before surgical interventions.Keywords: Vascular anatomy; superficial palmar arc

Steering non-centrosymmetry into the third dimension: crystal engineering of an octupolar nonlinear optical crystal

The ability of CH3 groups to form helical chains of C-H…∏ interactions with phenyl rings leads to polar stacking of trigonal octupolar networks in a substituted triazine, and therefore to three-dimensional non-centrosymmetry