The use of supplementary controllers for mitigating subsynchronous control interaction (SSCI) in doubly-fed induction generator based wind parks is quite promising due to their low investment costs. These SSCI damping controllers are typically designed and tested using an aggregated wind turbine (WT) model that represents the entire wind park (WP). However, no research has been reported on their implementations in a realistic WP. This paper, first presents various implementation schemes for a linear-quadratic regulator based SSCI damping controller, and discusses the corresponding practical challenges. Then, an implementation scheme that obviates the need for high rate data transfer between the WTs and the WP secondary control layer is proposed. In the proposed implementation, the SSCI damping controller receives only the WT outage information updates from the WP controller, hence it is not vulnerable to the variable communication network latency. The SSCI damping controller parameters are also modified when there is a change in WT outage information for the ultimate performance. The effectiveness of the proposed implementation scheme is confirmed with detailed electromagnetic transient simulations, considering different wind speeds at each WT and WT outages due to sudden decrease in wind speeds.
This two-part paper proposes a modified version of the IEEE 118-bus benchmark, referred to as 118-GMD, for time-domain simulation of the impacts of a geomagnetic disturbance (GMD) on a power system within an electromagnetic transient program (EMT-type). The advantage of 118-GMD over existing GMD test cases in the literature is that it enables additional GMD studies including harmonic analysis, response of control and protection, and interaction between the dc geomagnetically-induced currents, transformer saturation, additional var consumption and voltage collapse due to a GMD. Part I has presented the network model and its parameters. Part II presents simulation results and identifies the influential modeling details that should be incorporated in an EMT-type GMD simulation study based on the type of simulation. The study includes modeling details such as line model, delta-winding resistance, over excitation limiter, on-load tap changer, and load model.
In June 2014 the French TSO (Réseau de Transport d'Électricité - RTE) performed a field test on a 64 km 225 kV XLPE underground cable. This paper presents the validation of the cable model from field test measurements. In the first part, the cable impedance and admittance calculations are compared to the per-unit-length parameters evaluated from field test results. In the second part the field tests are simulated in an Electromagnetic Transients Program (EMTP) to validate the cable model.
This paper presents experience in software engineering for recoding a large scale power system analysis application. The application is a transient analysis package named EMTP (Electromagnetic Transients Program). Although the presented material is related only to this software, ideas, tools and methods are applicable to other power system analysis applications. There are several software engineering considerations in recoding a large scale power system application. The most important considerations are the programming languages, software development tools, code documentation methods, validation tools and interfaces. This paper presents and discusses programming language and programming tool choices for the recoded software. Some basic code documentation methods are also discussed.
A detailed dynamic arc model may be used to roughly evaluate the interrupting capacity of a breaker and its influence on the deformation of the interrupted current. In some cases the correct computation of the actual arcing time is of crucial importance for assessing the first current-zero crossing of the breaker. Arc models in conjunction with surrounding network details are also used to understand complex arc instability problems. This paper recalls gas circuit breaker models and presents data requirement for such models. The document includes some illustrative examples and typical data.
This paper presents a simulation method that combines state-space analysis with a nodal method for the simulation of electrical systems. This paper extends the concept of a discrete companion branch equivalent of the nodal approach to state-space described systems, and enables natural coupling between them. The flexible clustering of state-space described electrical subsystems into a nodal method has the following advantages: first, the nodal admittance matrix can be constrained in size while still permitting the solution of a switched network by nodal admittance matrix on-line triangularisation. Also, each group can have a precalculation of all internal modes (caused by switches, for example) within itself, an important feature for real-time applications. Secondly, the state-space formulation enables the use of higher-level discretization methods with L-stability properties. Finally, the approach enables the coupling of complex nodal-based models like FD-line into a state-space based solver. The method is implemented in a commercial real-time simulation software tool, the Advanced Real-Time Electro-Magnetic Simulator (ARTEMiS).
In time-domain simulations of power system transients, trapezoidal integration with fixed step-size is the most common method due to its accuracy and ease of implementation. Discontinuities occurring within fixed time-step when simulating power electronics circuits, may cause numerical oscillations and errors. Several methods are available in the literature for interpolation and handling of discontinuities. This paper intends to analyze how accuracy is affected by existing techniques for handling discontinuities in time-domain simulations based on the trapezoidal integration method. New algorithms are proposed to improve accuracy.
La ferroresonance designe tous les phenomenes oscillatoires, le plus souvent harmoniques mais aussi pseudo-periodiques qui peuvent affecter les reseaux de transport et de distribution de l’electricite. Rencontres egalement en mecanique des fluides, thermique et mecanique, ces phenomenes non lineaires ont fait l’objet d’etudes mathematiques et de la mise au point de modelisation permettant l’etude et donc une meilleure comprehension de la ferroresonance. Par exemple, les phenomenes de surtensions en regime transitoire apparaissant a la mise sous tension de transformateurs sont modelises et expliques par la theorie des bifurcations.
This paper presents a sequential ac-dc load-flow method for parallel multiterminal dc networks. P.u.-expressed dc equations are treated separately from ac equations and an interface is used to check and adjust their mutual convergence. A dc converter acts like a load on its ac bus; when it is a rectifier P and Q powers are consumed, and when it is an inverter Q is consumed and P is a negative load, or a generation. This method distinguishes itself by its ability to handle a large variety of converter controls, by its capability to modify established controls to respect angle, transformer tap, voltage and current limits at the converters. The interface between the ac and dc equations is designed to increase ac-dc convergence possibilities. Standard characteristics such as fixed tap and discrete tap-steps at the converter transformer are also handled. Numerical examples which demonstrate several features of the described method are presented.
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