Control and analysis of a unified power flow controller

This paper presents a control scheme and comprehensive analysis for a unified power flow controller (UPFC) on the basis of theory, computer simulation and experiment. This developed theoretical analysis reveals that a conventional power feedback control scheme makes the UPFC induce power fluctuation in transient states. The conventional control scheme cannot attenuate the power fluctuation, and so the time constant of damping is independent of active and reactive power feedback gains integrated in its control circuit. This paper proposes an advanced control scheme which has the function of successfully damping out the power fluctuation. A UPFC rated at 10 kVA is designed and constructed, which is a combination of a series device consisting of three single-phase pulsewidth modulation (PWM) converters and a shunt device consisting of a three-phase diode rectifier. Although the dynamics of the shunt device are not included, it is possible to confirm and demonstrate the performance of the series device. Experimental results agree well with both analytical and simulated results and show viability and effectiveness of the proposed control scheme </p

Dynamic regulation of erythropoiesis: A computer model of general applicability

A mathematical model for the control of erythropoiesis was developed based on the balance between oxygen supply and demand at a renal oxygen detector which controls erythropoietin release and red cell production. Feedback regulation of tissue oxygen tension is accomplished by adjustments of hemoglobin levels resulting from the output of a renal-bone marrow controller. Special consideration was given to the determinants of tissue oxygenation including evaluation of the influence of blood flow, capillary diffusivity, oxygen uptake and oxygen-hemoglobin affinity. A theoretical analysis of the overall control system is presented. Computer simulations of altitude hypoxia, red cell infusion hyperoxia, and homolytic anemia demonstrate validity of the model for general human application in health and disease

Optic Flow-Based Nonlinear Control and Sub-optimal Guidance for Lunar Landing

International audience— A sub-optimal guidance and nonlinear control scheme based on Optic Flow (OF) cues ensuring soft lunar land-ing using two minimalistic bio-inspired visual motion sensors is presented here. Unlike most previous approaches, which rely on state estimation techniques and multiple sensor fusion methods, the guidance and control strategy presented here is based on the sole knowledge of a minimum sensor suite (including OF sensors and an IMU). Two different tasks are addressed in this paper: the first one focuses on the computation of an optimal trajectory and the associated control sequences, and the second one focuses on the design and theoretical stability analysis of the closed loop using only OF and IMU measurements as feedback information. Simulations performed on a lunar landing scenario confirm the excellent performances and the robustness to initial uncertainties of the present guidance and control strategy

Control and analysis of a unified power flow controller”.

Abstract -This paper presents a control scheme and comprehensive analysis for a UPFC (unified power flow controller), on the basis of theory, computer simulation and experiment. This developed theoretical analysis reveals that a conventional power-feedback control scheme makes the UPFC induce power swings in transient states. The conventional control scheme has no capability of damping power swings, so the time constant of damping is independent of active and reactive power feedback gains integrated in its control circuit. This paper proposes a generalized control scheme which is characterized by successfully damping power swings in transient states. Experimental results obtained from a 10-kVA laboratory setup agree well with both analytical and simulated results. Moreover, it is shown that the proposed control scheme is viable and effective in damping of power swings in transient states

The Case for Joy in Learning: Teacher and Students\u27 Perceptions of Flow Experiences in Upper Elementary Classrooms

This dissertation focused on intrinsic motivation in elementary schooling, with Csikszentmihalyi’s flow theory and the conditions and dimensions leading to optimal learning, serving as the theoretical framework. This qualitative case study investigated: 1.) How do teachers create flow-producing learning experiences for upper elementary students and 2.) How do upper elementary students experience flow in their daily school lives. Fieldwork included observation, collection of work product, and interviews of thirteen students and two exemplary teachers. Students were also asked to take digital photos of artifacts or spaces that related to their learning, and that they were proud of or found exciting. This case study makes a significant contribution to the literature by providing evidence that enjoyable, flow-like learning can be experienced in upper elementary classrooms. Analysis of data indicated that teachers created flow-like conditions by modeling habits of the mind, providing challenges at student readiness levels, offering feedback, and modeling enjoyable learning experiences. Student participants reported enjoyment in the learning process under conditions that allowed them to move freely in the classroom, concentrate, yet have the opportunity to obtain immediate feedback, and become immersed in, with control over, learning tasks. Fueled by intrinsic motivation, flow-producing learning experiences in upper elementary classrooms also have the potential to put students on the path to lifelong learning before middle school. More research on intrinsic motivation in elementary schooling needs to be conducted to maximize learning experiences

Trapezoidal Current Modulation for Bidirectional High-Step-Ratio Modular DC–DC Converters

Modular dc-dc converter (MDCC) has been proposed for high step-ratio interconnection in dc grid applications. To further optimize the performance of MDCC, this paper presents a trapezoidal current modulation with bidirectional power flow ability. By giving all the sub-module (SM) capacitors an equal duty to withstand the stack dc voltage, their voltages are balanced without additional feedback control. Moreover, based on soft-switching performance and circulating current analysis, three-level and two-level operation modes featured with high efficiency conversion and large power transmission, respectively, are introduced. The control schemes of both modes are designed to minimize the conduction losses. Besides, the SM capacitor voltage ripples with different switching patterns are compared and the option for ripple minimization is presented. A full-scale case study is provided to introduce the design process and device selection of the MDCC. The experimental tests based on a downscaled prototype are finally presented to validate the theoretical analysis

Motorway tidal flow lane control

The expansion of road infrastructure, in spite of increasing congestion levels, faces severe restrictions from all sorts: economical, environmental, social, or technical. An efficient and, usually, less expensive alternative to improve mobility and the use of available infrastructure is the adoption of traffic management. A particular case of interest occurs when inbound and outbound traffic on a given facility is unbalanced throughout the day. This scenario may benefit of a lane management strategy called tidal flow (or reversible) lane control, in which case the direction of one or more contraflow buffer lanes is reversed according to the needs of each direction. This paper proposes a simple and practical real-time strategy for efficient motorway tidal flow lane control. A state-feedback switching policy based on the triangular fundamental diagram, that requires only aggregated measurements of density, is adopted. A theoretical analysis based on the kinematic wave theory shows that the strategy provides a Pareto-optimal solution. Microsimulations using empirical data from the A38(M) Aston Expressway in Birmingham, UK, are used to demonstrate the operation of the proposed strategy. The robustness of the switching policy to parameter variations is demonstrated by parametric sensitivity analysis. Simulation results confirm an increase of motorway throughput and a smooth operation for the simulated scenarios

Parametric resonance in the Rayleigh-Duffing oscillator with time-delayed feedback

We investigate the principal parametric resonance of a Rayleigh–Duffing oscillator with time-delayed feedback position and linear velocity terms. Using the asymptotic perturbation method, we obtain two slow flow equations on the amplitude and phase of the oscillator. We study the effects of the frequency detuning, the deterministic amplitude, and the time-delay on the dynamical behaviors, such as stability and bifurcation associated with the principal parametric resonance. Moreover, the appropriate choice of the feedback gain and the time-delay is discussed from the viewpoint of vibration control. It is found that the appropriate choice of the time-delay can broaden the stable region of the non-trivial steady-state solutions and enhance the control performance. Theoretical stability analysis is verified through a numerical simulation.The University of Pretoriahttp://www.elsevier.com/locate/cnsnsai201