Nominal Load Conditions Research Articles

Dynamic Stability Enhancement of Power System Using Fuzzy Power System Stabilizer Under Different Loading Conditions

The power system is dynamic in nature and is constantly being subjected to disturbances. It enters into dynamic instability when there is an imbalance between generation and varying load demand which calls for use of Power System Stabilizer (PSS). PSS is a device which provides additional signal to the voltage regulator derived from speed deviation, excitation deviation and accelerating power for damping critical oscillations. The PSS used should be capable to produce appropriate stabilizing signals against a wide range of operating conditions and disturbances. For this purpose, a PSS based on fuzzy logic control under multi-operating conditions is proposed in this paper. The performance of Fuzzy Logic based PSS(FLPSS) applied to Single Machine Infinite Bus (SMIB) system is studied for three different operating conditions; nominal load, heavy load and fault condition in transmission line. For Fuzzy PSS, speed deviation and acceleration are taken as input. The system is simulated in SIMULINK platform and its dynamic response is analyzed for system without PSS and with PSS. The results are compared for system with Conventional PSS and Fuzzy Logic PSS.

A comparative study between parabolic trough and solar tower technologies in Solar Rankine Cycle and Integrated Solar Combined Cycle plants

Simulations were carried out to predict the performance of a Solar Rankine Cycle (SRC) and an Integrated Solar Combined Cycle (ISCC) when combined with two different solar field configurations based on parabolic trough and power tower systems. For the selected cases, yearly plant performance was computed under real operating conditions on a one hour basis. A computing procedure was developed by integrating two commercial softwares with in-house computer code. Thermodynamic performance was featured for every plant configuration both at nominal and part load conditions. A single reheat regenerative Rankine cycle was chosen for the SRC plant whereas a commercial gas turbine, i.e. Siemens SGT-800, with a dual pressure heat recovery steam generator (HRSG) was assumed for the ISCC plant. As far as the heat transfer fluid (HTF) is concerned, molten salt was chosen to transfer heat to the water loop in the SRC. Synthetic oil was considered in the ISCC plant. Plants were assumed to be located in a Southern Spain site.The comparative analysis was mainly focused on the influence of CSP technology on global solar energy conversion efficiency of both SRC and ISCC plants. Special attention was devoted to assess trough collectors (PTCs) against the solar tower (ST) system in terms of intercepted radiation and thermal power sent to the power block. The ISCC coupled with a ST was found to assure the highest annual solar-to-electric efficiency of 21.8%. This is the result of both higher collection efficiency of ST compared to PTCs and higher conversion efficiency of solar energy introduced into the combined cycle, as compared to SRC.

Magnetic Simulation and Analysis of Radial Flux Permanent Magnet Generator using Finite Element Method

This paper discusses magnetic simulation and analysis of radial flux permanent magnet generator (PMG) using finite element method (FEM) by utilizing open source software FEMM 4.2. The specification of generator is 25 V, 28 A, 3 phase, 300 rpm. The analyzed magnetic flux was in the air gap, stator teeth and slots to find out the distribusian pattern and its fluctuation. The simulations were conducted in no-load and nominal load (28 A) conditions. Furthermore the maximum flux density of simulation (B g(sim) ) was used to calculate phase voltage E ph to find out the magnitude of generated electromotive force (EMF). The calculation results were presented as voltage vs. rotation graph in no-load condition and voltage vs. current graph in nominal load condition. Both graphs were validated with E ph of experiment result (E ph(exp) ) and E ph that the value of B g obtained from analytical calculation (E ph(calc) ). The final results showed that in no-load condition, E ph graph with B g(sim) (E ph(sim) ) was close to E ph(exp) and E ph(calc). The error rate with respect to the experiment was 6,9%. In nominal load condition, E ph(sim) graph almost coincides with E ph(calc.) graph, with the voltage drop of both was 0,441 V. Both graphs however were far different from E ph(exp) graph, which has 9 V of voltage drop. The overall results demonstrated that magnetic distribution pattern presented by FEM was very helpful to avoid magnetic flux accumulation in a particular segment. Besides B g(sim) facilitated to predict the value of E ph .

A Permanent Magnet Generator for Energy Conversion from Marine Currents: No Load and Load Experiments

This paper presents experiments and measurements on a low speed permanent magnet cable wound generator for marine current energy conversion. Measurements were made for no load and nominal load (4.44 Ω/phase) conditions at nominal speed (10 rpm). For either load condition, the magnetic fields in the air gap were also measured. The measurements on the generator were compared with the corresponding finite element method simulations used to design the machine. It is shown in the paper that measurements and corresponding case simulations show good agreement. At nominal speed, the measured and simulated load voltages (nominal load) differ less than 1% for the rms values and less than 5% for peak values. At no load, measured and simulated voltages had larger differences, that is, <9% for rms values and <5% for peak values. Harmonic analyses of measured and simulated phase voltages and currents show only the presence of third harmonics. The percentage of harmonics in the measured data was comparable with the corresponding predictions of the simulations. The discussions and results presented in the paper could be beneficial for future design of efficient and reliable marine current energy converter systems.

A scaling approach to model history effects in fatigue crack growth under mixed mode I + II + III loading conditions for a 316L stainless steel

Plastic deformation introduces internal stresses in the crack tip region that modify crack growth (direction and kinetics). Therefore, fatigue crack propagation models for metallic materials have to care about history effects. A model was developed for mode I fatigue crack growth under variable amplitude loading conditions. The purpose of this work is to extend it to account for I+II+III mixed mode loadings and for a 316L steel which displays both isotropic and kinematic non-linear hardening. The approach aims at establishing a model reasonably precise (compared with elastic–plastic FE computations) but condensed into a set of partial derivative equations so as to avoid huge elastic–plastic FE computations. For this purpose, the kinematics of the crack tip region is characterized by a set of condensed variables: to identify the parameters of the model, a scaling approach is used to transpose local results obtained using elastic–plastic FE simulations of crack tip cyclic plastic deformation to the global scale. In LEFM, the displacement field is approached by the product of spatial reference fields u̲Ie,u̲IIe and u̲IIIe and nominal stress intensity factors KI∞,KII∞ and KIII∞. Three condensed variables only, KI∞,KII∞ and KIII∞, fully define the kinematics in the crack tip region. So as to generalize this approach to mixed mode cyclic elastic–plastic conditions, the velocity field at crack tip is approached using first the intensity factors K˜˙I,K˜˙II and K˜˙III of the elastic spatial reference fields u̲Ie,u̲IIe and u̲IIIe and three additional spatial reference fields u̲Ic,u̲IIc and u̲IIIc and their intensity factors ρ˙I,ρ˙II and ρ˙III to account for plastic deformation within the crack tip region. Such an approximation is shown to be reasonably precise using finite element computations. The velocity field in the crack tip region is fully defined using only six condensed variables (K˜˙I,K˜˙II,K˜˙III,ρ˙I,ρ˙II,ρ˙III). Using the scaling approach proposed herein, evolutions of ρI, ρII and ρIII for various nominal mixed mode loading conditions defined by KI∞,KII∞ and KIII∞ were generated using the finite element method. It was shown that we can model these evolutions scale through a yield locus, a flow rule and a kinematics hardening rule. Fatigue crack growth experiments were performed in mode I (with or without overloads) using potential drop and digital image correlation as a measurement of crack tip propagation. SEM fractographies were also performed to determine the fatigue crack growth rate at the local scale from striations. The 316L steel displays a very significant cyclic hardening effect, which is expected to contribute to history effects in fatigue crack growth. In mode I, the model yields satisfactory results. Experiments have to be performed to be compared with model predictions in mixed mode conditions.

매립가스 마이크로가스터빈 배가스 분석에 관한 실험적 연구

MGT fuelled by landfill gas was tested to asses feasibility of its exhaust gas application for <TEX>$CO_2$</TEX> enrichment. The exhaust gas was analyzed during start-up and normal operation with different MGT load conditions. Due to the changes of air/fuel ratio and combustion mode, <TEX>$O_2$</TEX>, <TEX>$CO_2$</TEX>, CO and NOx concentration were varied within wide ranges during the MGT start-up. Especially, NOx emissioin level was increased up to 20.01 ppmv. Different tendencies of <TEX>$O_2$</TEX>, <TEX>$CO_2$</TEX>, CO and NOx concentrations were observed with MGT output changes. <TEX>$O_2$</TEX> and CO concentrations were shown to be decreased and NOx and <TEX>$CO_2$</TEX> concentrations were shown to have opposite trends. NOx emission level (0.8~1.88 ppmv) was very low compared to other types of combustion based power generation equipment. Unburned hydrocarbon emission level was substantially decreased with MGT load increase. Especially, <TEX>$C_2H_4$</TEX> concentration was below the detection limit(0.2 ppmv) around the nominal load condition. The exhaust gas from landfill gas fuelled MGT system was shown to be feasible for <TEX>$CO_2$</TEX> fertilization. Concentrations of major components were within or below the maximum allowable ranges.

Automatic generation control of interconnected power system with diverse sources of power generation

In this paper, automatic generation control (AGC) of two area interconnected power system having diverse sources of power generation is studied. A two area power system comprises power generations from hydro, thermal and gas sources in area-1 and power generations from hydro and thermal sources in area-2. All the power generation units from different sources are equipped with speed governors. A continuous time transfer function model of the system for studying dynamic response for small load disturbances is presented. A proportional-integral-derivative (PID) automatic generation control scheme is applied only to power generations from thermal and gas sources and power generation from hydro source is allowed to operate at its scheduled level with only speed governor control. The two area power system is simulated for different nominal loading conditions. Genetic algorithm (GA) is used to obtain the optimal PID gains for various cases using integral squared error plus integral time absolute error (ISE+ITAE) performance index for fitness evaluation. Some of the transient responses are shown for different nominal loading conditions due to step load disturbances in the system. Keywords: Two area power system, Diverse sources of power generation, Automatic generation Control , Genetic algorithm, PID controller

Thermal–mechanical and thermal–hydraulic integrated study of the Helium-Cooled Lithium Lead Test Blanket Module

The Helium-Cooled Lithium Lead Test Blanket Module (HCLL-TBM) is one of the two TBM to be installed in an ITER equatorial port since day 1 of operation, with the specific aim to investigate the main concept functionalities and issues such as high efficiency helium cooling, resistance to thermo-mechanical stresses, manufacturing techniques, as well as tritium transport, magneto-hydrodynamics effects and corrosion. In particular, in order to show a DEMO-relevant thermo-mechanical and thermal–hydraulic behavior, the HCLL-TBM has to meet several requirements especially as far as its coolant thermofluid-dynamic conditions and its thermal–mechanical field are concerned. The present paper is focused on the assessment of the HCLL-TBM thermal–mechanical performances under both nominal and accidental load conditions, by adopting a computational approach based on the Finite Element Method. A realistic 3D finite element model of the whole HCLL-TBM, in the horizontal first wall design has been set up, consisting of about 597,000 elements and 767,000 nodes. In particular, since the thermal fields of both the module and the coolant are strictly coupled, the helium flow domain has been modeled too and a thermal contact model has been set up to properly simulate the convective heat transfer between the structure wall and the coolant. Pure conductive heat transfer has been assumed within the Pb–Li eutectic alloy of the breeder units. The volumetric density of the nuclear deposited power, recently calculated at Department of Nuclear Engineering of the University of Palermo by the MCNP 4C code, has been applied as distributed thermal load in order to assess the potential influence on the module thermo-mechanical performances of the markedly non-uniform poloidal and toroidal distributions that have been predicted within the Segment Box. Different loading scenarios have been considered as to the heat flux onto the module First Wall. Steady state and transient thermal–mechanical analyses have been carried out and the detailed spatial distributions of the thermal and mechanical fields obtained as to the considered loading scenarios are reported, together with a critical analysis intended to verify their compliance with the agreed design criteria and the DEMO relevance requirements.

Thermo-hydraulical and thermo-mechanical analysis of the HCLL-TBM breeding unit

This paper concerns the latest design of the Helium Cooled Lithium-Lead (HCLL)-Test Blanket Module (TBM) according to the new dimensions of the space available for the module in the ITER equatorial ports. The performances of the proposed design are evaluated by means of new FE models of one breeding unit and the corresponding box structure. Detailed temperature and stress field distributions in each part of the structure have been obtained for nominal and accidental load conditions. The results of the FE calculations are analyzed with respect to thermal-hydraulics and thermo-mechanical stresses in order to verify the compliance with the established design criteria (maximum temperature in the structural material and SDC-IC rules). Also, the operating parameters are discussed in view of the DEMO-relevance of the proposed TBM design. Finally, possible improvements and modifications of the current design are proposed.

A new phenomenological criterion for pellet–cladding interaction rupture

This study is concerned with structural integrity assessment of Pressure Water Reactor's (PWR) fuel rods under pellet–cladding interaction (PCI) loading condition. An important experimental and research cooperative program between EDF, AREVA-NP and the Atomic Energy Commission CEA is achieved in order to get a better understanding of the mechanisms possibly leading to PCI failure, as well as to qualify a PCI resistant rod design. The objectives of this work are: first, to improve the understanding of the pellet mechanical properties impact on cladding local loading with 3D simulations results, and second, to propose a new phenomenological rupture criterion for a better assessment of the failure risk. In this study fuel behaviour modelling under nominal and transient loading conditions is achieved with a multi-dimensional simulation tool called ALCYONE, included in the new fuel software PLEIADES currently co-developed by the CEA and EDF. Cladding loading due to mechanical interaction during power transient stage is first analysed through pellet–cladding interfacial stresses computed in the 3D simulation. Then, a 2D model is proposed in order to establish a correlation between interfacial loading and stress concentration in the cladding. In order to assess the failure risk under PCI a phenomenological criterion based on the membrane circumferential stress in the cladding and shear stresses at pellet–cladding interface is proposed. To compute the shear loading at pellet–cladding interface a new parameter (called W rθ ) is introduced. Based on 3D calculations of PCI, it is shown in this paper that pellet fracture properties can have a significant effect on PCI loading.

A model predictive control approach for the Italian LBE–XADS

In this paper, model predictive control (MPC) is applied to the Italian 80 MW th experimental accelerator driven system (XADS), referring to a simple, non-linear model for the dynamic simulation of the plant, which has been developed and described in a previous work [A. Cammi, L. Luzzi, A.A. Porta, M.E. Ricotti, Prog. Nucl. Energ. 48 (2006) 578], in order to describe the interactions among the different subsystems: i.e., the accelerator-core coupling, the lead bismuth eutectic (LBE) primary system, the secondary system with diathermic oil and air coolers batteries, which reject the thermal power to the environment. Hereinafter, a model predictive controller is proposed, with the objective to minimize the difference between the average temperature of the diathermic oil and its reference value, while also minimizing the variations of the control input, which is the air coolers mass flow rate. The dynamic response of the LBE–XADS has been evaluated with reference to a reduction of 20% in the reactor power from nominal load conditions: this transient is very demanding for the overall plant, nevertheless the obtained results indicate the effectiveness of the proposed controller.

Magnetic emission ranking of electrical appliances. A comprehensive market survey

Over the last decades emissions of magnetic fields from electric appliances have considerably changed. Based on a comprehensive market survey it could be shown that today magnetic emissions are usually characterised by complex frequency spectra while single-frequency emissions have become rare. Therefore, spectral assessment procedures play a critical role. Compared to frequency-weighted equivalent magnetic induction, rms values may underestimate emissions up to two orders of magnitudes. Therefore, rms measurements are not suitable and emission-ranking lists of devices need revision. Surface hot-spot measurements at nominal load conditions and 230 V/50 Hz supply involved 1146 new electrical devices of 166 different categories. High emissions were not rare. Magnetic emissions of devices of 73 different categories exceeded reference levels up to almost two orders of magnitudes above reference levels. Maximum values were higher than reported so far. Magnetic emissions were high enough to make even conformity with existing basic restrictions not self-evident.

Bicycle helmet retention system testing and evaluation

Bicycle helmet testing is conducted under laboratory conditions, which do not always reflect real-world conditions. This paper reports on a survey of chin strap use among a test group of bicycle riders and the results of three tests: (1) a retention harness system static test to determine elongation properties; (2) a loop and position device test to determine the effects of the combination of the webbing positioner and the elongation properties of the webbing; and (3) a dynamic test to demonstrate the compatibility of the helmet retention system under real-world type dynamic impact loading conditions. The survey showed that bicyclists wear their helmets with an average of 4.76 cm of strap clearance when tested with a 500 gram load. Tests of chin strap shows that substantial motion and elongation can occur under nominal loading conditions. Comparative dynamic testing resulted in a bicycle helmet rotating forward significantly and exposing the back of the dummy head, while an equestrian helmet with a different retention system design rotated only slightly forward and remained on the dummy head. These tests demonstrate that effective helmet retention testing must take into account consumers’ normal use of helmets, and how all the elements in the helmet and its retention system work together.

Torque ripple reduction in exterior-rotor permanent magnet synchronous motor

The paper presents torque ripple reduction in permanent magnet synchronous motor with exterior-rotor. The influence of the magnet pole arc width and the influence of the supply current waveform on the torque ripple are considered in the analysis. The results of the analysis are obtained by the finite element method simulation and are verified experimentally as well. The reduction of total torque ripple at nominal load conditions less than 2% is achieved by proper motor magnet pole arc design and by applying the optimal stator current waveform control.

Improvement in Cable Rating Calculations by Consideration of Dependence of Losses on Temperature

In this paper a new method is proposed that allows estimation of conductor temperature and cable losses as a function of conductor current and some parameters corresponding to the nominal loading conditions. Such parameters include cable rating and loss factors computed by the cable manufacturer for the laying conditions specified by the user. There are two major applications of the proposed approach: one relates to rating of power cables with current measurements alone and the other to the computation of the external thermal resistance with a nonunity load factor used in the Neher/McGrath approach. Both applications are examined in this paper.

Balancing Pulverized Coal Flows in Parallel Piping

The distributions of the two-phase (pulverized coal in air) fuel inputs through the 24 parallel coal transport pipes of a coal-fired power plant are determined with a computer code. The orificing which would provide balanced fuel inputs through these coal transport pipes under nominal load conditions is also calculated with the code. Over the entire range of loading, the orificing determined with the code provides much smaller fuel imbalances than the imbalances which result with the previously installed orificings.

Channel Performance for Potential Early Commercial MHD Power Plants

The commercial viability of full and part load early commercial MHD power plants is examined. The load conditions comprise a mass flow of 472 kg/sec in the channel, Rosebud coal, 34% by volume oxygen in the oxidizer preheated to 922 K, and a one percent by mass seeding with K. The full load condition is discussed in terms of a combined cycle plant with optimized electrical output by the MHD channel. Various electrical load parameters, pressure ratios, and magnetic field profiles are considered for a baseload MHD generator, with a finding that a decelerating flow rate yields slightly higher electrical output than a constant flow rate. Nominal and part load conditions are explored, with a reduced gas mass flow rate and an enriched oxygen content. An enthalpy extraction of 24.6% and an isentropic efficiency of 74.2% is predicted for nominal operation of a 526 MWe MHD generator, with higher efficiencies for part load operation.