FACTS, which advantages for the modern electrical networks?

The energy market liberalization requires using the actual transportation network in a more flexible and more efficient way. What is needed are strategies and facilities that will improve the energy flux sharing, as well as the maintaining of the node voltages. These goals can only be partially reached in the conventional networks. However, the FACTS are offering a very promising solution. The UPFL (Unified Power Flow Controller) will be briefly presented as an example of FACTS, and its behaviour will be illustrated with simulations

A modular software package for the analysis of power networks and electrical drives

This paper deals with a software package for the numerical analysis in transient and steady-state modes of power electrical networks or variable speed drives with arbitrary topologies. The package is composed of a series of units, each representing a specific cell in the network : voltage supply, electrical machine, mechanical system, transmission line, circuit-breaker, phase shifting transformer, static converter with control and command organ, regulator, etc. SIMSEN is highly flexible and efficient. It is implanted on microcomputer or on workstation. The network or the variable speed drive to be simulated is assembled using a graphic input interface by adequatly choosing and linking the building units, so as to fulfill a desired topology. An existing system may be easily extended or modified. A simple procedure can be used in order to define a new unit or to modify an existing one. The initial conditions of operation can be partly or entirely specified by the user. A transient mode of operation may include several successive perturbations. The simulation results are displayed through an efficient graphic interface. An original feature of SIMSEN is its ability to analyse electrical networks involving semi-conductors (diodes rectifiers, thyristor or GTO current converters, voltage inverters, etc.). Thus, systems having a complex structure can be simulated. Practical examples of applications to such systems constitute the main part of this paper : constant or variable speed groups involving induction and synchronous machines, HVDC networks, reactive power static converter SVC. These examples show how SIMSEN can be used for an optimized design of complex networks

Improved modeling of three-phase transformer analysis based on nonlinear BH curve and taking into account zero-sequence flux

Abstract The present paper deals with a new approach for the study of the steady-state and transient behavior of three-phase transformers. This approach based on magnetic equivalent circuit-diagrams, takes into account the nonlinear BH curve as well as zero- sequence flux. The nonlinear BH curve is represented by a Fourier series, based on a set of measurement data. For the numerical simulations, two methods have been developed, by considering the total magnetic flux respectively the currents as state variables. Numerical ..

Advantages for the electrical grid using a doubly fed asynchronous machine - Numerical simulations

The use of a static frequency converter which is inserted between the grid and the stator is a well known solution to achieve an adjustable speed machine. Adjustable speed drive systems have already been applied in the past to hydro power plants. Up to now they have mainly been used for start-up purposes of pumps or pump-turbines. The used converters were therefore rather small in respect of converter power output (250 MVA)

Test virtuel d'un code de régulation DSP pour réseaux et systèmes d'entraînements électriques

Cet article décrit une procédure pour tester un code destiné à un DSP prévu pour le contrôle- commande d’équipements industriels tels que les systèmes d’entraînements à vitesse variable ou les réseaux électriques. Cette procédure repose sur le logiciel SIMSENTM développé à l’EPFL lequel offre nouvellement la possibilité de traduire une stratégie de contrôle-commande non plus impérativement à l’aide d’un schéma-bloc de réglage, mais également au travers du code défini par l’utilisateur et destiné à être implémenté. Ce code doit simplement être compatible avec le DSP choisi pour l’application prévue (code C, assembler, pascal, fortran,...), il se substitue au schéma-bloc. Il est ainsi possible de procéder aux tests et à l’optimisation des performances de l’ensemble d’un équipement. Dès lors que cette étape est résolue, il suffit de procéder au « download » du code établi dans le DSP de l’équipement. Cette procédure est non seulement une aide précieuse à une conception optimisée, elle permet des tests sans aucun risque ni limitations et induit des économies substantielles par le gain de temps qu’elle génère

Adjustable speed asynchronous machine in hydro power plants and its advantages for the electric grid stability.

The use of a static frequency converter which is inserted between the grid and the stator is a well known solution to achieve an adjustable speed machine. Adjustable speed drive systems have already been applied in the past to hydro power plants. Up to now they have mainly been used for start-up purposes of pumps or pump- turbines. The used converters were therefore rather small in respect of converter power output (250 MVA)

Modeling of Multi-winding Phase Shifting Transformers : Application to DC and Multi-level VSI Supplies.

This paper deals with the modeling of multi-winding transformers. Based on the real example of a railway DC - supply, a modeling methodology is presented as the original part of the paper. Afterwards two application examples of multi-winding phase shifting transformers (18 and 24 pulse) are described, these applications have been simulated using the SIMSEN simulation software package [1,2]. Harmonics analysis of simulation results (elimination of low order harmonics 5, 7, 11, 13) has validated the proposed methodology

Voltage peaks of low voltage induction motors due to PWM inverter supply

In industrial variable speed drives, the supply of low voltage induction motors by IGBT-PWM inverters through screened cables may cause dangerous over-voltage surges at the motors terminals. These voltage peaks of about twice the de link voltage, with a short rise time of about 200 nsec, increase the armature insulation stress and may damage the motor insulation. The prsent study provides a theoretical approach to this matter and is completed by tests performed on two 3 and 7.5 kW drives, with different cable lengths. Its target is to define the properties of these voltage peaks, their dependency on the installation parameters, and to present two measures to reduce the voltage gradient du/dt or the peak voltages at the motor terminals in order to raise motor lifetime of such a.c motors

Modeling and Transient Simulation of Unified Power Flow Controllers (UPFC) in Power System Studies

The present paper describes the modeling of Unified Power Flow Controllers (UPFC) for studying the steady-state and transient behavior of electrical networks equipped with FACTS devices. Detailed time-domain simulations are carried out on four model power systems (single-machine system and multi-machine systems including the IEEE-14 bus test system), to illustrate the control features of these devices and their influence to increase power transfer and improve system stability. The interaction between the UPFC, the network and the machines are analyzed

Voltage stresses on PWM inverter fed induction motors : cable modeling and measurement.

The present paper deals with the determination of voltage stresses on PWM inverter fed induction motors by considering first the cable modeling and the measurement of different parameters. Then, based on this model, voltage stresses on the motor windings are determined precisely by an analytical approach, which takes into account the motor windings, and the filters. Different aspects related to such installations will be briefly described and discussed. hes will be discussed