Suppression of numerical oscillations in the EMTP power systems
TL;DR: In this article, a critical damping adjustment (CDA) was proposed to solve the problem of sustained numerical oscillations that occur when the trapezoidal rule has to act as a differentiator.
Abstract: The integration scheme in the electromagnetic transients program EMTP has been modified to solve the problem of sustained numerical oscillations that occur when the trapezoidal rule has to act as a differentiator. These oscillations appear, for instance, on the voltage across an inductance after current interruption. The technique presented prevents these oscillations by providing critical damping of the discontinuity within one Delta t of the simulation. The critical damping adjustment (CDA) is achieved by means of two Delta t/2 integration steps using the backward Euler rule. With the CDA scheme the trapezoidal rule can still be used throughout the entire simulation without the problem at discontinuities. The effectiveness of the scheme is illustrated with simulation results. >
Citations
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01 Jan 2010
TL;DR: An overview of dynamic average-value modeling techniques for representing static switching converters for the system-level studies and desirable properties of averaged models for conducting large-Signal time-domain transient studies and small-signal frequency-domain analysis for control design tasks are discussed.
Abstract: Modeling and analysis of power and power-electronic systems' transients using digital programs enables testing new de- sign concepts in modern electric grid and many industrial and com- mercial products and applications. This paper gives an overview of dynamic average-value modeling techniques for representing static switching converters for the system-level studies. Concepts and de- sirable properties of averaged models for conducting large-signal time-domain transient studies and small-signal frequency-domain analysis for control design tasks are discussed. Basic approaches for developing average models for dc/dc and dc/ac converters are briefly reviewed and summarized. Finally, the desirable properties of the average-value models are demonstrated through an example system.
216Â citations
TL;DR: In this article, the authors give an overview of dynamic average-value modeling techniques for representing static switching converters for the system-level studies of power and power-electronic systems' transients using digital programs.
Abstract: Modeling and analysis of power and power-electronic systems' transients using digital programs enables testing new design concepts in modern electric grid and many industrial and commercial products and applications. This paper gives an overview of dynamic average-value modeling techniques for representing static switching converters for the system-level studies. Concepts and desirable properties of averaged models for conducting large-signal time-domain transient studies and small-signal frequency-domain analysis for control design tasks are discussed. Basic approaches for developing average models for dc/dc and dc/ac converters are briefly reviewed and summarized. Finally, the desirable properties of the average-value models are demonstrated through an example system.
201Â citations
TL;DR: This paper presents an enhanced implementation methodology for the associated discrete circuit model of a power-electronic converter in a field-programmable gate array-based real-time power systems simulator, which eliminates the need for corrective measures to reduce error and provides scalability.
Abstract: This paper presents an enhanced implementation methodology for the associated discrete circuit model of a power-electronic converter in a field-programmable gate array-based real-time power systems simulator. The simulator is intended for the testing and performance evaluation of digital control/protection platforms based on the hardware-in-the-loop concept. The salient features of the proposed implementation are: 1) It eliminates the need for corrective measures to reduce error due to the lack of synchronization between the simulation time-grid and output signals of the control/protection platform; 2) it provides scalability, that is, it maintains calculation time, within each simulation time step, nearly fixed irrespective of the system size; and 3) it enables the use of a small simulation timestep, for example, a couple of hundreds of nanoseconds for the overall system, in contrast to the microseconds range time-steps used in the existing simulators. Thus, it is also able to provide a wide frequency bandwidth for the simulation results. This paper also reports the implementation results and their verifications corresponding to real-time simulation of two converter units based on less than 60-ns calculation time within each simulation time step. The scalability property is also verified based on real-time simulation of six converter units.
173Â citations
TL;DR: An ultracapacitor model with automatic order selection of complexity and automatic scaling of capacity is created in Virtual Test Bed platform for complex system simulation and prototyping.
122Â citations
TL;DR: A method is developed to reduce large power systems to single- and multiport frequency-dependent equivalents, which consist of simple RLC modules that faithfully reproduce the frequency characteristics of the network.
Abstract: A method is developed to reduce large power systems to single- and multiport frequency-dependent equivalents. These equivalents consist of simple RLC modules that faithfully reproduce the frequency characteristics of the network. The method is implemented in the EletroMagnetics Transient Program (EMTP) and has been tested at Ontario Hydro. The implementation involves a preprocessor program, the Frequency Dependent Equivalent (FDNE), to generate the model and a EMTP time step loop module to calculate the transient response. The use of the FDNE results in major reductions in computer time and is especially beneficial for multicase statistical EMTP studies. An example showing the accuracy and efficiency of the FDNE when used to reduce a large 500 kV network is presented. >
112Â citations
References
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TL;DR: Electromagnetic transients in arbitrary single- or multiphase networks are solved by a nodal admittance matrix method based on the method of characteristics for distributed parameters and the trapezoidal rule of integration for lumped parameters.
Abstract: Electromagnetic transients in arbitrary single- or multiphase networks are solved by a nodal admittance matrix method. The formulation is based on the method of characteristics for distributed parameters and the trapezoidal rule of integration for lumped parameters. Optimally ordered triangular factorization with sparsity techniques is used in the solution. Examples and programming details illustrate the practicality of the method.
1,578Â citations
TL;DR: The methods presented in this paper are aimed to overcome numerical difficulties of closed mathematical solutions of the frequency-dependent line equations in the time domain.
Abstract: The parameters of transmission lines with ground return are highly dependent on the frequency. Accurate modelling of this frequency dependence over the entire frequency range of the signals is of essential importance for the correct simulation of electromagnetic transient conditions. Closed mathematical solutions of the frequency-dependent line equations in the time domain are very difficult. Numerical approximation techniques are thus required for practical solutions. The oscillatory nature of the problem, however, makes ordinary numerical techniques very susceptible to instability and to accuracy errors. The, methods presented in this paper are aimed to overcome these numerical difficulties.
876Â citations
TL;DR: A mathematical model for the simulation of electromagnetic transients in underground highvoltage cables is presented in this paper, where the solution is carried out in the time domain and is compatible with time-domain solution algorithms such as the one used in the EMTP (Electromagnetic Transients Program).
Abstract: A mathematical model for the simulation of electromagnetic transients in underground high-voltage cables is presented The solution is carried out in the time domain; therefore, this model is compatible with time-domain solution algorithms, such as the one used in the EMTP (Electromagnetic Transients Program) The frequency dependence of the cable parameters and of the modal transformation matrices is taken into account Comparisons with analytical and measured results are included >
221Â citations
TL;DR: In this paper, a variation of trapezoidal integration (called trapezoid integration with damping) for the solution of dynamic equations is described and tested using a transmission line model response to a voltage step function and the response of a HYDC converter with its controllers.
Abstract: A variation of trapezoidal integration (called trapezoidal integration with damping) for the solution of dynamic equations is described and tested. This method has several advantages over ordinary trapezoidal integration for the simulation of transients in power systems. The method is compared to ordinary trapezoidal integration, backward Euler and Gear 2nd order. The comparison is based upon local truncation error and upon performance of each method as a differentiator. The method is tested using a transmission line model response to a voltage step function, and the response of a HYDC converter with its controllers. Trapezoidal integration with damping is free from numerical problems, even when used as a differentiator; it provides a ready means for obtaining the "average behavior" of a simulator; it is fully compatible with trapezoidal; and it is very accurate.
72Â citations
TL;DR: Algorithmic passivity shows the overall stability--or lack thereof--inherent in forward Euler, backward Euler and trapezoidal one-step integration approximations as well as Gear's two-step method.
Abstract: In this paper we introduce the concept of algorithmic passiv- in in ity and indicate its role in circuit and timing simulation programs Algorithmic passivity shows the overall stability--or lack thereof--inherent in forward Euler, backward Euler, and trapezoidal one-step integration approximations as well as Gear's two-step method Passivity can be applied to - Vi_ _ Vn-i+ i integration algorithms to provide sufficient conditions for the overall stability of simulation programs that may employ them on an intermixed basis
64Â citations