Entire Range Of Operation Research Articles

Robust motor drive stabilization

Active stabilization of an induction motor drive fed through a poorly damped input LC filter is treated, explicitly addressing the design conflict of well damped filter quantities and small power modifications of the motors. On top of this, details of the closed-loop torque dynamics are used to assure robustness of stabilization over the entire range of operation. All this is achieved with a simple controller structure, consisting of a gain varying with the operating point and a bandpass filter. Derived results are verified through hardware-in-the-loop simulations of a traction motor drive using real control hardware.

PID system based on focusing aerogel RICH for the super C-[formula omitted] factory

A high performance particle identification (PID) system is essential for the successful realization of the broad physics program at the future Super C-τ Factory in Novosibirsk. The main requirements for the PID system are as follows: good π/K-separation in the entire operational momentum range and good μ∕π-separation in the momentum range from 0.3 to 1.2 GeV/c. The RICH detector based on focusing aerogel radiator (FARICH) and position-sensitive photon detector meets all these requirements. The FARICH method is described, and the beam test results are presented. The FARICH system design outline for the Super C-τ Factory project is presented. Most promising photon detector options are considered.

Modified Auxiliary-Resonant Commutated Pole Applied in a Three-Phase Dual-Active Bridge DC/DC Converter

The purpose of this study is to present the concept and properties of a dual-active bridge dc–dc converter with a modified auxiliary-resonant commutated (MARC) pole concept, and to discuss preliminary test results of a high-power setup. In this approach, the dual-active bridge based on IGCT is considered. First, the soft-switching boundaries for the converter with lossless snubbers and high switching delays are introduced. Second, the MARC pole is presented to overcome this border to receive full soft-switching capability in the entire operation range of the dc–dc converter. This is of crucial importance since IGCTs will be destroyed in case of a snubber dump. The advantage of the modified circuit is the guaranteed switching under zero-voltage conditions without applying an additional boost current as needed in the classic auxiliary-resonant commutated pole (ARCP) approach. Thus, complexity is reduced and reliability is increased. Measurement results of the MARC are presented from a mega-watt dc–dc converter where the concepts are fully implemented. The results of large-scale systems impressively show how the ARCP reduced the impact of parasitic elements, which would normally affect the switching transitions tremendously.

Modified Single-Carrier Multilevel SPWM and Online Efficiency Enhancement for Single-Phase Asymmetrical NPC Grid-Connected Inverter

In this paper, a modified single-carrier and multimodulation sine pulse width modulation (MSCMM-SPWM) is proposed to simplify the implementation of the single-phase asymmetrical neutral-point clamped grid-connected inverter (ANPC-GCI) for the PV generation system application. Furthermore, the expressions of the total switching loss and grid current total harmonic distortion (THD) of ANPC-GCI controlled by the proposed MSCMM-SPWM are derived. Then taking the grid current THD meet the grid-connected standard in the entire operational range as the constraint, an efficiency enhancement scheme for ANPC-GCI based on online adjusting the carrier frequency and the obtained THD expression is proposed. The control configuration of ANPC-GCI, including the proposed MSCMM-SPWM and online efficiency enhancement scheme, is designed. The detailed experimental results verify the correctness and feasibility of the proposed MSCMM-SPWM and the efficiency enhancement scheme.

Equilibrium Core Design of Reaktor Daya Eksperimental

A prototype of a high temperature gas-cooled reactor for electric and cogeneration application, called Reaktor Daya Eksperimental (RDE) is being developed at BATAN. RDE is developed to fulfill the huge yet distributed Indonesian energy demand, in particular for the eastern part of Indonesia. As a moving fuel core, analysis of the fuel management of PBR can be divided into the analysis of the start-up phase where the core composition, neutron flux, and power density profile still changing and equilibrium core. Equilibrium core design usually represent the general performance over the entire range of reactor operation. As part of the design development, current paper presents the equilibrium core design of RDE and depressurized-loss-of-forced-cooling (DLOFC) accident analysis. PEBBED code is utilized for the equilibrium core analysis. Results of this study include several possible equilibrium designs for RDE which then the design with 123 fuel pebble recirculated per day with equilibrium keff 1.02571, discharge burnup of 79.36 and maximum power generation 0.66kW per pebble fuel is chosen. Maximum fuel temperature of this design under the DLOFC accident is 1015.9°C which occurred 8.5h after the initiation of the accident. Results of DLOFC accident shows the strong passive safety features of RDE.

Creating a Model for Scientific Research Monitoring

A model developed by the staff of the Library for Natural Sciences of the Russian Academy of Sciences for evaluating the activities of scientific institutions based on the analysis of bibliometric data is described. An original integrated methodology is proposed that covers the entire range of operation of scientific organizations, including publishing, innovative and educational activities, international relations, and contributions from scientific schools and diasporas. The analysis criteria are universal and applicable for determining the scientific level of both individual scientists or laboratories and entire scientific centers.

Single longitudinal mode external cavity blue InGaN diode laser

We present a 445-nm InGaN blue diode laser in wavelength-tunable Littrow-type external cavity with a single longitudinal mode output, and a linewidth of 4.7 MHz. Its tuning range was estimated at 4 nm. The maximum output power was up to 20 mW, and the slope efficiency was approximately 0.36 W/A. The external cavity-diode laser linewidth was measured as 4.7 MHz with a lasing threshold to 8.1 MHz at higher applied current. The slope of the linewidth broadening with applied currents was calculated as 57 kHz/mA. And the wavelength tuning range was approximately 4.3 nm at low applied current and narrowed to approximately 2.6 nm at high applied current. A blue external cavity diode laser can deliver a single frequency beam within entire operation range.

MEMS capacitive accelerometer: dynamic sensitivity analysis based on analytical squeeze film damping and mechanical thermoelasticity approaches

In this work, we adopt a semi-analytical model to study a capacitive MEMS accelerometer based in silicon (Si). Such model takes into account the thermoelastic stiffness and linear expansion coefficients of anisotropic bulk Si. In addition, an analytical damping model, derived from the Reynolds equation, is incorporated in the model, in order to study dynamical characteristics of a MEMS capacitive accelerometer. Such approach takes into account the inertial effects on squeeze film damping in air, argon and helium gases, assumed as being ideal gases. The simulation model was compared with experimental measurements. The main figure of merit adopted is the electromechanical sensitivity (SEM), assuming frequency response and considering the effect of gas pressure, as well as temperature, on the damping loss mechanisms in such devices. The resulted model implementation shows a good agreement with the experimental data. For all gases, the sensitivity at 20 Pa presents less variation than at 200 Pa. At 20 Pa, the linear response of the device reaches up to 300 Hz, approximately, for air and helium, assuming variation of ≈ 0.5 dB, no matter which temperature. For 200 Pa, the linear response drops down to about 150 Hz. Also, for the three gases, the variation of SEM as a function of temperature is below 0.17 dB in the entire operational range, for both evaluated pressures, depending only on the silicon mechanical properties at low frequencies.

Variable-speed operation and pressure pulsations in a Francis turbine and a pump-turbine

The paper presents result from model measurements of the efficiency and pressure pulsation intensities for two low-specific-speed hydraulic turbines operated at variable speed, namely, one splitter-bladed Francis turbine marked with “F99” and one reversible pump-turbine marked with “RPT” and operated in a turbine mode. Both turbines have similar specific speeds, i.e. and , and for their best efficiency points, both have similar guide-vane opening angles but different operating parameters (i.e., speed factor and discharge factor). Pressure pulsation measurements were conducted for a wide operating range and at specific locations in the (1) vaneless space and (2) draft tube. Histogram method was used to obtain the peak-to-peak amplitudes of the fluctuating pressure for all operating points used to construct the performance hill-charts of the turbines. To the best of the authors’ knowledge, very little or no effort has been made so far to explore the amplitudes of pressure pulsations in the turbine when operated at rotational speeds specifically optimized for maximization of the hydraulic efficiency. Results show that operation of Francis turbines at optimized rotational speeds can increase the hydraulic efficiency of the turbine, while decreasing or maintaining the same pressure pulsation amplitudes in the entire operational range. Also, it was found that the level of efficiency gain and reduction of the pressure pulsations is greatly dependent on the hydraulic design of the turbine and should be investigated individually for each case.

Experimental investigation and numerical simulation of flow in the draft tube elbow of a Francis turbine over its entire operating range

Hydraulic power plants are increasingly required to extend their operating range, enabling the seamless large scale integration of renewable energy sources into the electrical grid. In Francis turbines, the complex cavitation patterns appearing in the draft tube cone at off-design operation cause a decline in turbine performance and cyclic pressure pulsations that may lead to dangerous hydro-acoustic instabilities. The accurate prediction of the velocity distribution and the pressure pulsations by numerical simulation in the design phase is important for manufacturing stable and more efficient hydraulic machines over a wide operating range. This work seeks to improve the accuracy of numerical flow models for predicting the dynamic turbine characteristics through a systematic comparison of the velocity fields simulated with CFD and measured with Laser Doppler Velocimetry (LDV) in the draft tube cone. The numerical simulation and experimental measurements are performed in flow conditions for six values of discharge factor, four part load comprised 40%, 60%, 80%, 90% of the discharge value at the Best Efficiency Point (BEP), at the BEP, and one full load of 110%. The steady Reynolds-Averaged Navier-Stokes (RANS) simulation are performed for numerical analysis by the commercial flow solver ANSYS CFX. The LDV measurements are performed on a reduced scale model with a specific speed of nQE=0.20, installed the test rig of EPFL Laboratory for Hydraulic Machines.

Fractional order PID control of steam generator water level for nuclear steam supply systems

Abstract The main part of nuclear powered system is the nuclear steam supply system (NSSS) to produce the steam needed for electricity or cogeneration. The NSSS mainly contains the fission reactor, based on pressurized water reactors or small modular reactors, and the steam generator. One of the most important control strategies in the NSSS is water level regulation to keep the water level of the steam generator around programmed setpoint because violation of the level jeopardizes the plant availability in making the electricity and supplying the heat for industrial applications. The appearance of fractional calculus made it possible to realize the control design requirements in optimum and efficient ways. In this paper, we proposed a gain scheduled Fractional order PID (FOPID) control system for steam generator level control system in entire operating range. Nelder-Mead tuning strategy which takes into account the desired gain- and phase- margin with integral time absolute error (ITAE) performance index has been devoted to adjust the FOPID parameters. Simulation results indicate that the new control system can enhance the transient response in contrast to the conventional PID. The performance comparison of the FOPID regulator with the classical PID shows that the fractional controller has huge superiority which is comparable with the advanced quantitative feedback theory (QFT) controller. The Nyquist stability analysis is also provided to demonstrate the favorable robust stability of the gain scheduled FOPID controller over the wide range of operating conditions.

Maintaining Continuous ZVS Operation of a Dual Active Bridge by Reduced Coupling Transformers

A major advantage of the dual active bridge (DAB) dc–dc converter is its ability to operate under zero voltage switching (ZVS) conditions to reduce switching losses. However, when the ac link coupling transformer is conventionally designed to minimize its magnetizing current, nonideal switching conditions almost invariably lead to hard switching operation at particular power transfer levels and dc–dc voltage ratios. This paper presents a mathematically based design approach for a coupling transformer with a reduced magnetizing inductance that creates just sufficient ac link circulating current to maintain continuous ZVS operation over the converter's entire specified operating range without incurring significant additional losses. The required magnetizing inductance reduction is found to be a function of the inherent transformer leakage inductances, switching dead-time, and device parasitic capacitances. The analysis approach is validated by matching experimental results.

Analysis and control of offboard bidirectional plug - in electric vehicle (PEV) charger for vehicle to grid operation

This paper presents an analysis of off board bidirectional Plug in Electric Vehicle (PEV) Charger. Since, normally, the control command for such chargers are given in terms of desired real and reactive power, a model of the system is formulated directly in terms of these variables. A detailed steady state analysis of the system is presented for the entire possible range of operation and for a given battery state of charge (SOC) rather than selecting points of operation a priori. This result shows the various possibilities of the system and informs further structural studies of the system and the design of controllers to meet the desired control objectives. Keywords: Battery charger, electric vehicle, natural variables, vehicle to grid

Advanced Soft- and Hard-Magnetic Material Models for the Numerical Simulation of Electrical Machines

Accurate modeling of soft- and hard-magnetic materials for the numerical simulation of rotating electrical machines is required to allow predictions on the operational characteristics along the torque-speed map, already in the design stage. The full potential of most appropriate material selection and concurrent geometry adaption can only be utilized if models can represent actual material behavior. The accurate prediction of iron losses of soft-magnetic materials for various frequencies and magnetic flux densities, as well as the degradation due to manufacturing is eminent for the design of electrical machines. Therefore, advanced material models need to be adapted and their accuracy examined to further improve the modeling and enable progression. This paper will give an overview of the current modeling approaches applied at the Institute of Electrical Machines for soft- and hard-magnetic materials in the simulation of rotating electrical machines. A case example in the form of a traction drive is presented to which the models are applied. For the machine modeling, the inhouse solver pyMOOSE is utilized. In order to determine the losses with regard to manufacturing processes, the iron-loss model with material degradation is used in combination with a machine simulation scheme of the entire operating range of the machine. Here, various simulation approaches are combined to form the entire computational toolchain to obtain accurate results in the entire operational range.

A Novel Frequency Beam-Steering Antenna Array for Submillimeter-Wave Applications

This paper describes design and development of a novel frequency beam-scanning array antenna operating at Y-band (220–325 GHz). The proposed antenna is a traveling-wave antenna, with a meandered rectangular waveguide structure as the propagating medium. The array generates a very narrow beamwidth of about 2.5° with ±25° beam steering capability as the frequency sweeps from 230 to 245 GHz. The antenna beam in elevation is about 10°, which is generated with a slot-coupled cavity-backed patch array antenna along the elevation direction. The proposed antenna provides an overall gain of over 29 dBi and exhibits a radiation efficiency of more than 55% over the entire frequency range of operation. The antenna topology is designed to present a very low-profile structure to meet a very low volume and low mass requirements. The antenna consists of over 600 patch elements and is confined within a volume of 45 mm × 8.5 mm × 1.25 mm and weighs less than 4.5 g. A prototype of the antenna is fabricated using silicon micromachining with a high level of accuracy and is characterized using a special near-field measurement setup. The antenna exhibits a measured scanning range of over 48° with a gain of over 28.5 dBi, all of which are in close agreements with simulation results.

Development of a physics-based model to predict the performance of pumps as turbines

This paper presents the development of a physics-based simulation model, aimed at predicting the performance curves of pumps as turbines (PATs) based on the performance curves of the respective pump. The simulation model implements the equations to be used for the estimation of head, power and efficiency for both direct and reverse operation. Model tuning on a given machine is performed by using loss coefficients and specific parameters identified by means of an optimization procedure, which is first applied to the considered pumps and subsequently to the same machine running in PAT mode.The simulation model is calibrated on data taken from literature, reporting both pump and PAT performance curves for head, power and efficiency over the entire range of operation. The performance data were acquired experimentally from four different centrifugal pumps, running in both pump and PAT mode and characterized by specific speed values in the range of 1.53–5.82. The accuracy of the predictions of the physics-based simulation model is quantitatively assessed against both pump and PAT experimental performance curves. Prediction consistency from a physical point of view is also evaluated.The results presented in this paper highlight that all the performance curves predicted by the simulation model are physically consistent over the entire range of operation. In general, the prediction error on the head of PATs is acceptable, while the accuracy of the prediction of PAT power, and thus of PAT efficiency, is more case-sensitive and usually higher. The relative deviation of model prediction with respect to the field data regarding head and power at the PAT best efficiency point always seems acceptable compared to the uncertainty of the original experimental data and to typical deviations of other methods available in literature.As a conclusion, the physics-based simulation model developed in this paper represents a powerful and reliable tool for estimating PAT performance curves over the entire range of operation based on pump characteristics.

Modified High-Efficiency LLC Converters With Two Split Resonant Branches for Wide Input-Voltage Range Applications

This paper proposes a novel modified LLC converter with two split resonant branches for wide input-range applications. It can operate in low-gain (LG) mode or medium-gain (MG) mode. The voltage gain of MG mode is 1.5 times that of LG mode, while they have same range of voltage gain $M_{{\rm{tank\_range}}}$ , i.e., the ratio of maximum voltage gain to minimum one. Therefore, the input voltage can be regulated in a wide range by operating the converter in different modes. To achieve the transition between modes, the required $M_{{\rm{tank\_range}}}$ of the proposed converter is as low as 1.5, resulting in lower magnetizing current and higher efficiency within the entire operation range. Smooth transition can be achieved by adjusting the duty cycles of switches gradually. The proposed LLC converter with primary dual-bridge is analyzed in detail as an example. To verify the theoretical analysis and performance of proposed solution, a 1-kW 400-V output prototype with input voltage ranging from 80 to 200 V is built, tested, and compared with two existing full-bridge LLC converters. Analysis and experimental results indicate that smaller volume of transformers, reduced rectifying diodes, and higher overall efficiency are achieved with the proposed converter.

A Photonic Switch Based on a Hybrid Combination of Metallic Nanoholes and Phase-change Vanadium Dioxide

A photonic switch is an integral part of optical telecommunication systems. A plasmonic bandpass filter integrated with materials exhibiting phase transition can be used as a thermally reconfigurable optical switch. This paper presents the design and demonstration of a broadband photonic switch based on an aluminium nanohole array on quartz utilising the semiconductor-to-metal phase transition of vanadium dioxide. The fabricated switch shows an operating range over 650 nm around the optical communication C, L, and U band with maximum 20%, 23% and 26% transmission difference in switching in the C band, L band, and U band, respectively. The extinction ratio is around 5 dB in the entire operation range. This architecture is a precursor for developing micron-size photonic switches and ultra-compact modulators for thin film photonics.

Development of Adaptive Variable Boundary based Real Coded Genetic Algorithm for online optimization of beam excitation level for Indus-2 tune measurement system

Indus-2 is a synchrotron radiation source which is operational at Raja Ramanna Centre for Advanced Technology (RRCAT), Indore, India. The betatron tune measurement system is an essential beam diagnostic system for smooth beam operation of Indus-2 which is based on swept frequency excitation method. In this method, a lookup table is used for adjustment of excitation signal level in the drive system and selection of reciver parameters such as sweep rate and bandwidth. It is observed that, beam excitation levels are required to be calibrated regularly due to change in the operating parameters of Indus-2. To cater this problem of re-calibration, a new tune measurement system for Indus-2 is developed based on optimal control method using genetic algorithm. Multiple parameters and multi-objective control were required to develop this system. A variant of genetic algorithm (GA) is developed for online control of this system. In this algorithm, real valued variables are used and their boundaries are adaptively modified during the online optimization, hence this variant of GA is called as Adaptive Variable Boundary based Real Coded Genetic Algorithm (AVB-RCGA). This system provides comparatively better results as compared to the old tune measurement system. The new tune measurement system is faster with better signal to noise ratio (SNR) for entire range of machine operation.

Comparison of Different Approaches to Predict the Performance of Pumps As Turbines (PATs)

This paper deals with the comparison of different methods which can be used for the prediction of the performance curves of pumps as turbines (PATs). The considered approaches are four, i.e., one physics-based simulation model (“white box” model), two “gray box” models, which integrate theory on turbomachines with specific data correlations, and one “black box” model. More in detail, the modeling approaches are: (1) a physics-based simulation model developed by the same authors, which includes the equations for estimating head, power, and efficiency and uses loss coefficients and specific parameters; (2) a model developed by Derakhshan and Nourbakhsh, which first predicts the best efficiency point of a PAT and then reconstructs their complete characteristic curves by means of two ad hoc equations; (3) the prediction model developed by Singh and Nestmann, which predicts the complete turbine characteristics based on pump shape and size; (4) an Evolutionary Polynomial Regression model, which represents a data-driven hybrid scheme which can be used for identifying the explicit mathematical relationship between PAT and pump curves. All approaches are applied to literature data, relying on both pump and PAT performance curves of head, power, and efficiency over the entire range of operation. The experimental data were provided by Derakhshan and Nourbakhsh for four different turbomachines, working in both pump and PAT mode with specific speed values in the range 1.53–5.82. This paper provides a quantitative assessment of the predictions made by means of the considered approaches and also analyzes consistency from a physical point of view. Advantages and drawbacks of each method are also analyzed and discussed.