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Voltage Control (voltage + control)
Selected AbstractsA simple method for output voltage control of a three-phase multilevel inverter considering DC voltage fluctuationELECTRICAL ENGINEERING IN JAPAN, Issue 3 2010Kenji Amei Abstract Multilevel inverter circuit generates the stair-like voltage without using transformer and interphase reactor, and it is the circuit which realizes reduction in the harmonics and enlargement of the capacity. In addition, the application of PWM control improves the waveform, and reduces the switching component to the conventional half, and the filter capacity is reduced. In this paper, improvement on the voltage utilization factor and feedback control of output voltage are applied to multilevel inverter circuit. For the DC power supply with the intense fluctuation, it is necessary to construct inverter circuit which can supply stabilized AC voltage. One-chip microcomputer with various functions is used for the control equipment of this circuit, and miniaturization and cost reduction of the control equipment are realized. Here, the control principle and experimental results of this equipment are mainly reported. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(3): 40,47, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20906 [source] Active coordinated operation of a distribution network system for many connections of distributed generatorsELECTRICAL ENGINEERING IN JAPAN, Issue 3 2009Yasuhiro Hayashi Abstract Recently, the total number of distributed generators (DGs) such as photovoltaic generation system and wind turbine generation system connected to an actual distribution network has increased drastically. The distribution network connected to many distributed generators must be operated keeping reliability of power supply, power quality, and loss minimization. In order to accomplish active distribution network operation to take advantage of many connections of DGs, a new coordinated operation of distribution system with many connections of DGs is necessary. In this paper, the authors propose a coordinated operation of distribution network system connected to many DGs by using newly proposed sectionalizing switch control, sending voltage control, and computation of available DG connection capability. In order to check the validity of the proposed coordinated operation of distribution system, numerical simulations using the proposed coordinated distribution system operation are carried out in a practical distribution network model. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(3): 46,57, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20655 [source] Coordinated voltage control of transformer taps with provision for hierarchical structure in power systemELECTRICAL ENGINEERING IN JAPAN, Issue 4 2009Yoshiki Nakachi Abstract Participation of distributed generators (DGs), such as wind turbines, cogeneration systems, etc., is a natural trend from an ecological point of view and will continue to increase. The outputs of these DGs mainly depend on weather conditions but do not correspond to the changes of electrical load demand necessarily. On the other hand, due to deregulation of the electric power market, the power flow in a power system will uncertainly vary with several power transactions. Thus, complex power flow by DGs or transactions will cause voltage deviation. It will be difficult to sustain the voltage quality by using conventional voltage/reactive power control in the near future. In this paper, in order to avoid such voltage deviation and to decrease the frequency of transformer tap operations, the coordinated voltage control scheme of transformer taps on account of hierarchical structure in the power system is proposed. In the proposed scheme, integral of voltage deviation at each layer bus is applied to decide the timing of each transformer tap operation. Numerical simulations confirm that the proposed scheme is able to respond to every condition on voltage deviation. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(4): 48,55, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20531 [source] Vertical double-gate MOSFET device technologyELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 1 2008Meishoku Masahara Abstract Silicon device technology is facing several difficulties. Especially, explosion of power consumption due to short-channel effects (SCEs) becomes the biggest issue in further device scaling down. Fortunately, double-gate (DG) MOSFETs have promising potential to overcome this obstacle. The DG-MOSFET is recognized to be the most scalable MOSFET for its high SCE immunity. In addition, independent DG-MOSFET (4T-DG-MOSFET) has great advantage to enable the threshold voltage control for the flexible power management. Through this work, we have realized ideal DG-MOSFETs using newly developed vertical DG-MOSFET device technology. This article examines the effectiveness of the vertical DG-MOSFETs in future high-performance and ultralow-power CMOS circuits. © 2008 Wiley Periodicals, Inc. Electron Comm Jpn, 91(1): 46, 51, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10021 [source] Damping torque analysis for DC bus implemented damping control,EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2010W. Du Abstract Damping torque analysis is a well-developed technique for understanding and studying power system oscillations. This paper presents the applications of damping torque analysis for DC bus implemented damping control in power transmission networks in two examples. The first example is the investigation of damping effect of shunt voltage source converter (VSC) based flexible AC transmission systems (FACTS) voltage control, i.e. static synchronous compensator (STATCOM) voltage control. It is shown in the paper that STATCOM voltage control mainly contributes synchronous torque and hence has little effect on the damping of power system oscillations. The second example is the damping control implemented by a battery energy storage system (BESS) installed in a power system. Damping torque analysis reveals that when BESS damping control is realized by regulating exchange of active and reactive power between the BESS and power system, respectively, BESS damping control exhibits different properties. It is concluded by damping torque analysis that BESS damping control implemented by regulating active power is better with less interaction with BESS voltage control and more robust to variations of power system operating conditions. In the paper, all analytical conclusions obtained are demonstrated by simulation results of example power systems. Copyright © 2009 John Wiley & Sons, Ltd. [source] Local control of photovoltaic distributed generation for voltage regulation in LV distribution networks and simulation toolsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 6 2009Stefania Conti Abstract The increasing connection of distributed generation (DG) in distribution networks may affect the quality of power offered to customers. One of the most relevant issues is the possibility to have unacceptable voltage rise at the point of common coupling (PCC). This work focuses on the problem of voltage control in LV distribution networks in the presence of photovoltaic (PV) DG. The paper presents a local voltage control method based on PV generation curtailment as an alternative to ,on/off' operation, typically required by distribution operators to prevent overvoltage at the PCCs by means of overvoltage protections embedded in the PV unit. To show the effect of the proposed local voltage control, a simulation tool, developed in MATLAB®,Simulink® environment, is presented. Appropriate numerical models for network components and PV generators are provided in order to describe computer simulation implementation of the test system. The final results show that the control system is able to adjust the active power output of local generators to keep the voltage profile of the feeder, in which DG is installed, within the range allowed by Norm EN 50160. Copyright © 2008 John Wiley & Sons, Ltd. [source] A study on a new AVR parameter tuning concept using on-line measured data with the real-time simulatorEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2006Joong-Moon Kim Abstract Automatic voltage regulator (AVR) parameter tuning for voltage control of power system generators has generally been performed with the analytic methods and the simulation methods, which mostly depend on off-line linear mathematical models of power system. However, due to the nonlinear nature of power system, the mathematical models of the excitation system may not be correct. So the excitation control system performances with the parameter set that is tuned by using the mathematical model, may not be appropriate for some operating conditions. This paper presents an AVR parameter tuning method using on-line measured data of the excitation control system with parameter optimization technique. As this method utilizes on-line operating data, it can overcome the limitation of model uncertainty problems of conventional method. To validate the proposed tuning concept, a scaled model excitation system is connected to the real-time power system simulator, and the proposed tuning concept is tested. Copyright © 2006 John Wiley & Sons, Ltd. [source] Interactions and co-ordination of multiple-function FACTS controllersEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 1 2001H. F. Wang This paper presents two study cases of interaction analysis of multiple-function FACTS (flexible AC transmission systems) controllers: - the contradiction between the voltage and the damping control of a SVC (static VAr compensator); - the interaction between the voltage control of the DC link capacitor and the damping control of a UPFC (unified power-flow controller). In the paper, an algorithm is proposed for the co-ordinated design of these two multiple-function FACTS controllers. Examples are presented to confirm the analytical conclusions obtained and to demonstrate the effectiveness of the algorithm of the co-ordination proposed. [source] Steady-state power flow and voltage control by unified power-flow controllers, part 2: ApplicationsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 2 2000Y. H. Song The unifiedpower-flowcontroller(UPFC) isa powerfuldeviceforthe reliejroj'transmission constraints. Part 1 of the paper proposes novel steady-state modelling and control algorithms for the study of UPFC, which use power-injection models to derive control parameters for UPFC to achieve the required line active power control and bus-voltage support. The proposed method does not change the symmetrical structures of Jacobian matrix, avoids the initialisations of control parameters and can cover a wide control range of UPFC due to the characteristics of optimal multiplier power-flow algorithms employed. This paper describes in detail the applications of the proposed theory in a 28-node system. The convergence of controlled power flow is analysed. Control performance has been evaluated. The numerical results presented clearly illustrate the effectiveness of the proposed approach. [source] Co-ordinated control design of generator excitation and SVC for transient stability and voltage regulation enhancement of multi-machine power systemsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 9-10 2004L. Cong Abstract This paper presents a co-ordinated control scheme for generator excitation and a static var compensator (SVC) to achieve transient stability, adequate damping and voltage regulation enhancement of multimachine power systems. By using the feedback linearization technique, the nonlinearities of the generator and the SVC model are cancelled. With the help of robust control theory, the interconnection between controllers, the variation of system structure and the parameter uncertainties are taken into consideration in the controller design. Only local measurements are required. Simulation results obtained from a three-machine, one-SVC example system show that the proposed controllers can provide good stability, voltage control and damping over a wide range of operating conditions. Copyright © 2004 John Wiley & Sons, Ltd. [source] Robust control of multi-axis magnetic bearing systemsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 14 2001T.-J. Yeh Abstract This paper proposes robust control schemes for multi-axis magnetic bearing systems under current control and voltage control. The control schemes are based on a model which characterizes not only the electromagnetic interaction but also secondary effects such as flux leakage, fringing fluxes, and finite core permeance in the magnetic bearing. In the current control case, a sliding-mode-based robust controller, whose control parameters have to be deliberately chosen to account for the uni-directionality of magnetic forces, is proposed to provide robust performance against uncertain dynamics. In the voltage control case, a control scheme that combines the sliding methodology and the backstepping technique is used to provide robust performance under the influence of the electrical dynamics. It is demonstrated through simulations and experiments that, because the nonlinearity and the uncertainty inherently residing in the system behaviour are directly tackled, the proposed controllers achieve superior tracking performances compared to control lers based on linearization. Copyright © 2001 John Wiley & Sons, Ltd. [source] The Effect of Induction Method on Defibrillation Threshold and Ventricular Fibrillation Cycle LengthJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 4 2006ENDRE ZIMA M.D. Introduction: Since no clinical data are available on the comparison of the "shock on T-wave" and "high frequency burst" ventricular fibrillation (VF) induction modes during defibrillation threshold (DFT) testing, we aimed to compare these two methods during implantable cardioverter defibrillator implantation. Methods: The DFT was determined with a step-down protocol using biphasic, anodal polarity (100%, 40%, 20% voltage control) shocks. Patients were randomized: VF was induced by 50 Hz burst in group B (n = 45) and T-wave shock in group T (n = 41). The DFT was defined as the lowest energy level that terminated VF; confirmed DFT (DFTc) was defined as the minimal energy level that consecutively terminated VF twice. Success rate of DFTc was calculated during an intraindividual test for the alternate induction method. Results: A total of 546 episodes of VF were induced: n = 278 (B) vs n = 268 (T). Incidence of VT during inductions was 9.9% (B) vs 2.7% (T), P < 0.05. Neither the DFT, 8.8 ± 4.0 J (B) vs 9.7 ± 4.2 J (T), nor the DFTc, 10.6 ± 5.1 J (B) vs 10.8 ± 4.2 J (T), proved to be significantly different. A significant correlation was found between VF cycle length (CL) and the concomitant DFT (r = 0.298, P < 0.05) in group T only. Subgroup analysis of patients under chronic class III antiarrhythmic treatment showed no increase of the DFT in either group and significantly lower incidence of VT induction in group T regardless of antiarrhythmic treatment. Conclusion: The DFT and the VFCL proved to be independent of the VF induction method. The T-wave shock was more unlikely to induce VT during DFT testing. These results suggest that both methods are reliable in DFT determination, though T-wave shock application is a more reliable method for DFT testing. [source] | ||||||||||