Swing Modes Research Articles

Coupled modes of the torsion pendulum

The coupling of the swing modes of a torsion pendulum to the torsional mode has been solved analytically. Our solution provides a clear explanation of why a magnetic damper is effective in suppressing unwanted modes in most gravitational experiments. The analytic solution also shows that the amplitude of the mode coupling is greatest at the lowest frequencies. This explains why mode coupling at the lowest frequency is all that is observed in the experiments reported here.

An abnormal mode of torsion pendulum and its suppression

The numerical solution of non-linear equations shows that the abnormal mode observed in our torsion pendulum experiments is an intrinsic mode of the pendulum. Further analysis shows that the amplitude of abnormal mode increasing with of swing modes can be suppressed with a magnetic damper effectively.

Power swing damping control by HVDC power modulation in an ac/dc hybrid transmission system

This paper describes power swing damping control by HVDC power modulation. In a hybrid system (where the ac transmission system and the HVDC system compose a loop transmission system), damping control of power swing by control of HVDC power is called power modulation control. The new HVDC link between the Shikoku and Kansai power systems forms a loop transmission system consisting of the existing ac transmission system and the new HVDC transmission system; therefore, power modulation control can be applied for stabilization of the ac system. This paper deals with a newly developed power modulation control system to damp two power-swing modes occurring in a 60-Hz interconnected system and the neighboring power system to the HVDC converter station. Characteristics of power swings in an ac system, principles of power swing damping control by power modulation, the control system design method, and the results of verification tests by digital and analog simulators are described. It is shown that the developed power modulation system applied to the HVDC link is effective for damping two power swing modes. © 1998 Scripta Technica, Electr Eng Jpn, 124(3): 10–18, 1998

Power system reduction to simplify the design of damping controllers for interarea oscillations

This paper describes the application of a reduction method to power systems to obtain simplified models that facilitate the design of damping controllers. The reduced system retains the lightly damped swing of interest and exhibits modal characteristics similar to the unreduced system in the frequency range associated with swing modes. A power system damping controller is designed using a reduced system. The modal characteristics of the reduced and unreduced system with the damping controller included, are compared. The validity of the control design is assessed via nonlinear simulations. The reduction method is simple to implement and is based on the computation of the observability and controllability Gramians.

Robust redesign of power system damping controllers

This paper presents a model-matching robustness design procedure based on H/sub /spl infin//-optimization theory for the robust redesign of nominal controllers. The approach directly uses a control law designed for the nominal operating condition and tunes the nominal control law to enhance the robustness with respect to the off-nominal operating conditions. The procedure is applied to the design of a power system stabilizer (PSS) for a single-machine infinite-bus system which has a range of possible operating conditions. The results show that the redesigned controller contains features similar to the nominal controller, but yet improves significantly the damping of the machine swing modes at the off-nominal conditions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Stability investigation of a longitudinal power system and its stabilization by a coordinated application of power system stabilizers

This paper presents the results of a stability investigation of a power system with longitudinal structure and its stabilization by coordinated power system stabilizers (PSSs). The effects of the existing controllers on system stability are studied. If no PSSs are present, the damping of various swing modes in the system will be very poor and low frequency oscillations present. Eigenvalue analysis shows that the undamped modes are sensitive to excitation control while speed governors have little influence on damping. In order to enhance the overall system stability through excitation control, a coordinated design procedure for power system stabilizers has been developed based on generation coherency, total coupling factor and nonlinear simulation. A PSS designed using this procedure is robust to different operating conditions and very effective for damping oscillations. Comprehensive simulation studies were conducted and results are presented. >

電力動揺特性に着目した電力系統の等価縮約モデル

電力動揺特性に着目した電力系統の等価縮約モデル

Two reduced-order methods for studies of power system dynamics

The authors present two reduced-order methods, namely second-order aggregation and external system partition, for the analysis of power system dynamics. These methods are developed by the combination of the machine mode associate property with the aggregated model of multimachine systems. An 18-machine and a 9-machine power system are employed to numerically verify the basic concept and the methods. The verification results show that the first method is suited for the computation of all swing modes, while the second method is suited for computing the modes associated with a selected machine group.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Exact solutions of the autonomous Duffing equation and their computation. 2nd Report. Some improvements of accuracy.

In the previous paper, exact solutions of the autonomous Duffing equation were obtained in terms of the Fourier series making use of the so-called q-expansion of the elliptic functions. A characteristic parameter which plays a central role in calculating the Fourier coefficients, must be determined as a root of the modulus equation essentially by a trial method. As for some algorithms as well as approximation formulae proposed in the previous Saper, a few extensions of the discussions are presented here to improve the accuracy. A new trial algorithm and a revised approximation formula are proposed for a case of ultra low frequency (strongly nonlinear square wave and pulse train), and a new expression of the Fourier coefficient is also discussed, which is suitable in particular for the case of quasi-linear oscillation. Some salient features of the solution are illustrated for the case of a snap-through spring system in a full swing as well as in half swing modes.

A new design method for power modulation of dc transmission

A new design method for a PM (power modulation) controller is proposed. It is based on the eigenvalue assignment method combined with frequency response method. The proposed method is as systematic as the eigenvalue assignment method and as simple as the frequency response method. Generally speaking, the eigenvalue assignment method makes it possible to design the control system more systematically than the frequency response method. However, an observer is required to observe all state variables and a complicated matrix calculation is required. The proposed method requires no complicated matrix calculation nor the trial and error calculation. It is applicable to a large scale system and measured frequency response characteristics of the system can be used for more accurate design. In the second part of this paper, we discuss how to find the most appropriate input signal. As a result of this discussion, we show that PM is not always effective for all swing modes and the effect of PM on each swing mode varies depending upon the power flow we choose as the input signal.

The role of hybrid construction techniques on sealed moisture levels : D. T. Somerville. 5th A. Proc. Reliab. Phys. IEEE (1977) Nevada. p. 107

This chapter emphasizes on the analysis of small-signal stability problems in a multimachine power system. A detailed description of the method of multimachine modeling, simulations, and case studies is illustrated. Two-axis multimachine model with IEEE type I exciter considering all network bus dynamics is taken into consideration. A detailed step-by-step procedure to construct multimachine system matrix has been presented. This model has been employed in different chapters throughout this book. The initial conditions of the state variables are computed by systematically solving the standard load-flow equations of the network and then computing the other algebraic and state variables. The method of identification of electromechanical swing modes and computation of participation factor has been described through numerical examples, illustration, and case study.