The Experts below are selected from a list of 9810 Experts worldwide ranked by ideXlab platform

Naoyuki Uchida - One of the best experts on this subject based on the ideXlab platform.

  • Fast computation and stable convergence technique for unbalanced load flow calculation in large‐scale systems
    Electrical Engineering in Japan, 2010
    Co-Authors: Keisuke Shirasaki, Naoyuki Uchida
    Abstract:

    This paper presents a new method of unbalanced load flow calculation to improve complexity by the method of advanced symmetrical coordinates. Usually, the electric power system has been calculated only by the positive Phase Sequence Component on the assumption that three-Phase transmission lines and loads are balanced. However, many ultrahigh-voltage transmission lines are not transposed, and therefore mutual inductances cause negative Sequence currents in the trunk transmission system. Negative Sequence currents cause heating of generators and transformers, and therefore the three-Phase Sequence Component should be calculated accurately. We examined the fast computation and good convergence performance of unbalanced load flow calculation by models of three-Phase transmission lines, transformers, and loads. The proposed method is not the Phase coordinate system but the method of symmetrical coordinates. This technique decreases numerical complexity by the use of a simplified Jacobian matrix. The convergence performance of this method is inferior to that of the usual Newton–Raphson method. As a conSequence, the problem of poor convergence performance is alleviated by a technique for the newly developed deceleration Newton method. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(1): 17–24, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21034

  • Fast Computation and Stable Convergence Technique for Unbalanced Load Flow Calculation in the Large Scale System
    IEEJ Transactions on Power and Energy, 2008
    Co-Authors: Keisuke Shirasaki, Naoyuki Uchida
    Abstract:

    This paper presents a new method of unbalanced load flow calculation to improve complexity by the method of advanced symmetrical coordinates. Usually, the electric power system has been calculated only by positive Phase Sequence Component on the assumption that three Phase transmission lines and loads are balanced. However, many ultra high voltage transmission lines are not transposed, therefore mutual inductances cause negative Sequence current in trunk transmission system. Negative Sequence current causes the heating of the generators and transformers. Therefore, the three Phase Sequence Component should be calculated accurately.We examined fast computation and good convergence performance of unbalanced load flow calculation by the models of three Phase transmission lines, transformers and loads. The proposed method is not the Phase coordinate system but the method of symmetrical coordinates. This technique decreases numerical complexity by the use of simplified jacobian matrix. The convergence performance of this method is inferior to usual Newton-Raphson method. In conSequence, the problem of poor convergence performance is improved by the technique for newly developed deceleration Newton method.

R Gretsch - One of the best experts on this subject based on the ideXlab platform.

  • generalized theory of instantaneous reactive quantity for multiPhase power system
    IEEE Transactions on Power Delivery, 2004
    Co-Authors: R Gretsch
    Abstract:

    A new generalized definition of instantaneous reactive quantity in the multiPhase system is proposed in this paper, and an attempt is made to seek its unity in value as well as in meaning between in sinusoidal and in nonsinusoidal situations. By directly taking the instantaneous multiPhase voltage and multiPhase current as two vectors with multiComponents each, the instantaneous reactive quantity is considered as the second asymmetrical tensor resulting from the outer-product operation of voltage and current vectors. In this way, the so-called zero-Phase Sequence Component problem is solved. With its concise and direct expression, the theory can be applied to any kind of three-Phase systems, and can also be easily extended to any n-Phase systems without any additional transformation, in which the instantaneous quantities will have similar properties to those in a steady sinusoidal three-Phase system. Therefore, it may find wide application in many fields.

  • generalized theory of instantaneous reactive quantity for multiPhase power system
    2003 IEEE Power Engineering Society General Meeting (IEEE Cat. No.03CH37491), 2003
    Co-Authors: R Gretsch
    Abstract:

    A new generalized definition of instantaneous reactive quantity in the multiPhase system is proposed in this paper and an attempt is made to seek its unity, in value as well as in meaning, between in sinusoidal and in nonsinusoidal situations. By directly taking the instantaneous multiPhase voltage and multiPhase current as two vectors with multiComponents each, the instantaneous reactive quantity is considered as the 2nd asymmetrical tensor resulting from the outer-product operation of voltage and current vectors. In this way, the so-called zero-Phase Sequence Component problem is solved. With its concise and direct expression, the theory can be applied to any kind of 3-Phase systems, and can also be easily extended to any n-Phase systems without any additional transformation, in which the instantaneous quantities will have similar properties to those in a steady sinusoidal 3-Phase system. So it may find wide application in many fields.

Keisuke Shirasaki - One of the best experts on this subject based on the ideXlab platform.

  • Fast computation and stable convergence technique for unbalanced load flow calculation in large‐scale systems
    Electrical Engineering in Japan, 2010
    Co-Authors: Keisuke Shirasaki, Naoyuki Uchida
    Abstract:

    This paper presents a new method of unbalanced load flow calculation to improve complexity by the method of advanced symmetrical coordinates. Usually, the electric power system has been calculated only by the positive Phase Sequence Component on the assumption that three-Phase transmission lines and loads are balanced. However, many ultrahigh-voltage transmission lines are not transposed, and therefore mutual inductances cause negative Sequence currents in the trunk transmission system. Negative Sequence currents cause heating of generators and transformers, and therefore the three-Phase Sequence Component should be calculated accurately. We examined the fast computation and good convergence performance of unbalanced load flow calculation by models of three-Phase transmission lines, transformers, and loads. The proposed method is not the Phase coordinate system but the method of symmetrical coordinates. This technique decreases numerical complexity by the use of a simplified Jacobian matrix. The convergence performance of this method is inferior to that of the usual Newton–Raphson method. As a conSequence, the problem of poor convergence performance is alleviated by a technique for the newly developed deceleration Newton method. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(1): 17–24, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21034

  • Fast Computation and Stable Convergence Technique for Unbalanced Load Flow Calculation in the Large Scale System
    IEEJ Transactions on Power and Energy, 2008
    Co-Authors: Keisuke Shirasaki, Naoyuki Uchida
    Abstract:

    This paper presents a new method of unbalanced load flow calculation to improve complexity by the method of advanced symmetrical coordinates. Usually, the electric power system has been calculated only by positive Phase Sequence Component on the assumption that three Phase transmission lines and loads are balanced. However, many ultra high voltage transmission lines are not transposed, therefore mutual inductances cause negative Sequence current in trunk transmission system. Negative Sequence current causes the heating of the generators and transformers. Therefore, the three Phase Sequence Component should be calculated accurately.We examined fast computation and good convergence performance of unbalanced load flow calculation by the models of three Phase transmission lines, transformers and loads. The proposed method is not the Phase coordinate system but the method of symmetrical coordinates. This technique decreases numerical complexity by the use of simplified jacobian matrix. The convergence performance of this method is inferior to usual Newton-Raphson method. In conSequence, the problem of poor convergence performance is improved by the technique for newly developed deceleration Newton method.

D M Vilathgamuwa - One of the best experts on this subject based on the ideXlab platform.

  • a generalized voltage compensation strategy for mitigating the impacts of voltage sags swells
    IEEE Transactions on Power Delivery, 2005
    Co-Authors: S S Choi, D M Vilathgamuwa
    Abstract:

    Dynamic restoration of load voltage achieved through the application of voltage-injection technique is considered. The injected voltage is generated from a voltage-source-inverter-based series compensator. It is shown that during a voltage sag, the restoration process almost inevitably requires the injection of energy from the compensator to the external system. Conversely, a voltage swell event could cause the compensator to absorb energy from the external system which would then result in a rise in the dc-link voltage of the inverter. By permitting Phase adjustment in the injected voltage, a generalized compensation method is proposed. The new voltage injection technique allows the magnitude of the positive Phase-Sequence Component of the compensated load voltage to be restored to its pre-sag/swell level. It also exercises simultaneous control on the dc-link voltage. The efficacy of the proposed technique is illustrated by numerical examples.

  • A generalized voltage compensation strategy for mitigating the impacts of voltage sags/swells
    IEEE Transactions on Power Delivery, 2005
    Co-Authors: S S Choi, D M Vilathgamuwa
    Abstract:

    Dynamic restoration of load voltage achieved through the application of voltage-injection technique is considered. The injected voltage is generated from a voltage-source-inverter-based series compensator. It is shown that during a voltage sag, the restoration process almost inevitably requires the injection of energy from the compensator to the external system. Conversely, a voltage swell event could cause the compensator to absorb energy from the external system which would then result in a rise in the dc-link voltage of the inverter. By permitting Phase adjustment in the injected voltage, a generalized compensation method is proposed. The new voltage injection technique allows the magnitude of the positive Phase-Sequence Component of the compensated load voltage to be restored to its pre-sag/swell level. It also exercises simultaneous control on the dc-link voltage. The efficacy of the proposed technique is illustrated by numerical examples.

T. Kawabata - One of the best experts on this subject based on the ideXlab platform.

  • A control method of active power filter where system voltage contains negative-Phase-Sequence Component or zero-Phase-Sequence Component
    Proceedings of 1995 International Conference on Power Electronics and Drive Systems. PEDS 95, 1995
    Co-Authors: Y. Komatsu, T. Kawabata
    Abstract:

    The usual instantaneous reactive power q has been defined by using /spl alpha/, /spl beta/ Components of the voltage and current. The current from the power source contains higher harmonic Components when q is used for the control method of an active power filter in an unsymmetrical three Phase system. The higher harmonic current Components are bad for telecommunication and so on. Therefore, the authors have defined a new instantaneous reactive power whose mean value is equal to the three Phase reactive power. By the use of this value. The authors have clarified a new calculation method for compensating current command which solves the defects of the conventional pq method.