20 MW Compressor LCI Drive: Modeling, Simulation and Measurements.

The LCI (Load commutated Inverter) is still today a suitable solution for supplying high power variable speed drive systems. The following main topics are described in this contribution: The modeling of a 20 MW LCI synchronous drive system for a compression train. The numerical simulation of the complete drive system. An original real time measurement of the air gap torque. A comparison between simulation results and measurement performed on the test shop of the manufacturer.

Étude du tomographe de haute résolution pour petits animaux ClearPET par la méthode de Monte Carlo

Martin Rey

The Lausanne ClearPET demonstrator is one of the new generation of high resolution small animal PET scanners. A high resolution PET scanner aims to maximize the signal-to-noise ratio measured in pixels for a given time without compromising spatial resolution. In order to achieve it, ClearPET scanners are based on phoswich technology : two different crystals (LSO and LuYAP) are aligned one behind the other and coupled to the same channel of a multichannel photo-detector. Depth-of-interaction is determined by a pulse shape analysis. To improve the prototype design, a Monte Carlo simulation toolkit dedicated to emission tomography – GATE – was created. The accurate description of time-dependent phenomena such as source or detector movement and source decay kinetics represents the most important feature of this software. The first part of this work presents the demonstrator built in Lausanne, mainly the DAQ process and the libraries for the data treatment, and the GATE functionality. In the second part, the measurements obtained with the ClearPET demonstrator combined with simulations are presented. The simulations allow estimation of the performance of a final scanner and refinement of the detector head design. Measurements as well as simulations give a spatial resolution of 1.3 mm on the scanner axis and 2.5 mm at 4 cm from the axis. Temporal resolution for two modules with the same sampling phase is about 4.3 ns for LSO and 4.9 ns for LuYAP. For a standard acquisition, the energy resolution at 511 keV is about 31 ± 4 % for LSO and 33 ± 8 % for LuYAP. The peaks at full energy before calibration are about 480 ± 50 keV1 for LSO and 470 ± 40 keV1 for LuYAP. These variations, coupled with hardware threshold, are one of the main reasons for the sensitivity and count rate performance limitations. A sensitivity of 4.37 ± 0.05 is estimated for a full ring design with four rings of detector modules. The large systematic errors are induced by the variability previously mentioned. ------------------------------ 1 As spectra are not normalized, keV unities are inappropriate. Channel numbers are more accurate.

EPFL2007

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

Alain Sapin, Jean-Jacques Simond

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.

1995

12-Pulse LCI Synchronous Drive for a 20 MW Compressor - Modeling, Simulation and Measurements.

Alain Sapin, Jean-Jacques Simond, Mai Tu Xuan, Roland Wetter

The current source thyristor inverter is still today a suitable choice for supplying high power adjustable speed drives for pumps or compressors. This paper presents a 12-pulse LCI (load commutated inverter) synchronous drive for a 20 MW compressor, it focuses on the following main aspects: modeling of the complete drive system, numerical simulation and comparison between calculated and measured values of the pulsating torque components in steady-state operations. The modeling of the six-phase synchronous motor is obtained by using a new virtual test-platform for large electrical machines. The pulsating torque components are measured in real time with a digital transient torque measurement device.

2005

Étude du tomographe de haute résolution pour petits animaux ClearPET par la méthode de Monte Carlo

Martin Rey

EPFL2007