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2008 - A PC-based Hardware-In-the-Loop Simulator for the Integration Testing of Modern Train and Ship Propulsion Systems.pdf

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444 A PC-based Hardware-In-the-Loop Simulator for the Integration Testing of Modern Train and Ship Propulsion Systems Christian Dufour, Guillaume Dumur, Jean-Nicolas Paquin, Jean Bélanger Opal-RT Technologies, 1751 Richardson, suite 2525, Montreal, Canada Abstract - Today, the development and integration of train and ship controllers is a more difficult task than ever. Emergence of high-power switching devices has enabled the development of new solutions with improved control
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  444 A PC-based Hardware-In-the-Loop Simulator for the Integration Testing of Modern Train and Ship Propulsion Systems Christian Dufour, Guillaume Dumur, Jean-Nicolas Paquin, Jean Bélanger  Opal-RT Technologies, 1751 Richardson, suite 2525, Montreal, Canada  Abstract   -  Today, the development and integration of train and ship controllers is a more difficult task thanever.Emergence of high-power switching deviceshasenabledthedevelopment of new solutions with improved controllability andefficiency.Ithasalso increased the necessity for more stringent test and integration capabilities since these newtopologies come with less design experience on thepartof thesystemdesigners. To address this issue, a real-time simulator can be a very useful tool to test, validate andintegrate the various subsystems of modernrailvehicledevices. This paper presents such a real-time simulator,based on commercial-off-the-shelf PC technology,suitablefor the simulation of train and ship propulsion devices.Therequirementsfor rail/water vehicle test and integrationreachesseveral levels on the control hierarchyfromlow-levelpower electronic converters used for propulsion and auxiliary systems to high-level supervisory controls.Thispaper places great emphasis on the real-time simulation of several high-power drives used for train andship propulsion, including a multi-induction machine drive,a three-level GTO - PMSM drive and a high-powerthyristor-basedconverter - synchronous machine drive. All models are designedfirstwith the SimPowerSystemsblockset and then automatically compiled and runoncommercial PCs under RT-LAB. Interfaces to I/O are also madeattheSimulink model level without any low-levelcodingrequiredby the user. Supervisory control integrationandtestingcan also be made using the RT-LAB real-time simulator.Theother objective of this paper is to demonstrate thatHIL testing of complex drives, such as thethosefoundontrains, can be done using commercial-off-the-shelf (COTS)software and hardware and model-based design techniquesthat only require high-level system modelssuitableforsystem specifications down to controller test andfinalsystem integration. I. I  NTRODUCTION The integration, test and verificationofmoderntrainand ship systems represent a serious challenge. Currently, because of the risks involved, it is not conceivable to integrate these kinds of systems with direct subsysteminterconnection.Modern design approaches mitigatetheserisksthroughthe extensive use of technologieslikeHardware-In-the-Loop (HIL) simulation. HIL simulationtechnologiesenablemore gradual integration, while diminishing therisk and costs of such projects. Also, more elaborate test coverage can be conducted thanispossibleusinganalog prototypes because of the safety operational limitsofrealdevices.Model-based design is an approach that putsthesystemmodel at the center of the design process[7].Withthisapproach,thespecification, controller prototype design,codingandintegrationtests are based on a set of reference models.At the integration stage, this approach makesextensive use of HIL simulators, with a numberof objectives that are directlyrelated to the control hierarchyof the complete train system. The control hierarchy of a train system is given in Figure 1. Figure 1 Train control hierarchy  A.Individual Train Actuators and Circuits ControllersTests: ThefirststageofHIL controller test is to individuallyverifythecontrollers. At this stage, a detailed model of thesubsystem is used to which the controller under testisattached,whilea simplified model is made of the rest of the system. Two types of tests are then conducted:1) Open-looptests: this kind of test is usedtoverifythefunctionality of the I/O of the controller by simpleexcitation/monitoringofthe I/Os. It is also used to verifythe behavior of the controller incaseofshort-circuitoftheI/Os. In this last case, the controller should detectsuchconditions and output proper code tothesupervisorycontroller.2) Closed-looptests:controller behavior is testedfor its control action on thepowerdevices.Thecontroller isconnectedto the HIL-simulated power devices in theexactsamemanner as the real device (IGBT gate signals, current sensors, etc.) For example, the acceleration/deceleration behavior of the induction traction units [4] can be tested with a simplifiedDC-link model. 978-1-4244-1668-4/08/$25.00 ©2008 IEEE  445  B. Multi-subsystem Integration Tests: The different subsystems (generation, propulsion, auxiliary) are electrically connected and may therefore interact with each other. Consequently, the next stage of test/integration is to verify the functionality of the controllers with all system interactions. Basic Supervisory control law can be tested at this stage. The scalability of the simulator is very important in this regard[8]. C. Main Supervisory Control Tests: The main supervisory control algorithm is tested at this stage. This includes testing in normal conditions with a human operator command (start and accelerate, stopping the train) and in abnormal conditions (communication bus fault or electric fault).  D. User Control Tests: The real-time simulator can be used to verify the overall conductibility of the train by a human operator, in normal and faulty modes, as well as for operator training. At this point, the user graphical interface becomes important because the human operator’s ‘I/Os’ are mainly their eyes and hands. II.C HALLENGES AND S OLUTIONS IN R  EAL - TIME S IMULATION OF C OMPLEX E LECTRIC D RIVES There are several challenges to achieve real-time simulation of large electric drives. The global challenge is to obtain good accuracy using fixed time step solvers and methods. Furthermore, the calculation time of all   time steps must always be kept under a prescribed value to enable HIL interface of the simulator with external equipment or controllers. The last challenge consists of finding the right simulation platform. Challenge 1) Keeping the accuracy of simulation with high-frequency power converter.Given that the simulator is a sampled system, the accuracy of simulation of high-frequency PWM inverter may be compromised if the ratio of simulator sampling frequency to the PWM frequency is too low. Interpolation-capable inverter models are the solution to this problem. These inverter models are part of the RTeDRIVE[5] package from Opal-RT Technologies. This challenge notably exists in the Three-Level GTO-Inverter PMSM Drive of section IV.A. Challenge 2) Keeping the calculation time of all time steps almost constant to achieve HIL. The SimPowerSystems default solver takes more time to iterate whenever a switch changes position because it recalculates circuit mode on-line. The ARTEMIS plug-in for SimPowerSystems makes pre-computation of all system state-space matrices in advance to solve this  problem Challenge 3) Keeping the calculation time of large systems relatively low. Power systems are typically simulated with a time step objective typically near 25-50  s. This objective may be difficult to reach for large networks or drives (a bigger system implies bigger set of equations to solve). The ARTEMIS[5] package provides nice solutions to this problem with distributed parameter line and stublines models that enable the decoupling of the underlying system equations. The stubline model is particularly interesting in electric drives. The stubline is the equivalent of a distributed  parameter line with an exact 1-time step propagation delay and a fully tunable inductance value[2]. It can effectively replace inductances and provide decoupling of the system equations. The stubline can be used to model transformer leakage inductance (section IV.A) or current converter chokes (section IV.B) and increases simulation speed by splitting the system equations into 2 parts. III.HILS IMULATION P LATFORM (RT-LAB). RT-LAB is the real-time simulation software from Opal-RT Technologies. RT-LAB runs almost entirely on commercial-off-the-shelf hardware. The only exception,  because of the extreme I/O requirements for electric drives and system applications, is the Opal-RT FPGA-based I/O card. RT-LAB supports distributed simulation through shared memory with 2/4/8/16-CPU (including multi-core CPU technology), AMD- or Intel-based systems, or through PC clusters with InfiniBand or FireWire communication links[8]. The RT-LAB real-time operating system, running on the actual simulation targets, is either QNX from QNX Software System Corp. or RedHawk-Linux from Concurrent Computer Corp. Most commercial I/O cards are supported with RT-LAB, including cards from Acromag, DDC, Kontron, Measurement Computing, National Instruments, Quanser, RTD, Sensoray, and Softing. However, Opal-RT FPGA cards are preferred for electrical applications because such applications have unusually high switching frequencies. Opal-RT FPGA I/O cards feature 10-ns digital I/O, 1-microsecond D/A converters, and 2-microsecond A/D converters with integrated signal conditioning. XSG support enables users to fully customize I/Os for Opal-RT FPGA cards using the standard Simulink diagram editor. IV.T RAIN AND S HIP P ROPULSION D EVICES In this section, we give examples of common train and ship propulsion drive configurations for which low-level  power electronic controls are to be tested. The first model is a four-induction machine traction unit that can be driven  by either an on-board synchronous generator or AC-single  phase catenary system. A high-power three-level GTO- based PMSM drive is shown next. The dual-voltage DC-link of the drive is made of a 12-pulse rectifier connected to the grid by a three-phase three-winding transformer. The last drive is a very-high power current converter made of back-to-back thyristor converters (12-pulse rectification and 6-pulse inversion). The converter drives a synchronous machine. Except for the catenaries power feeds, all topologies can be studies in the context of either train or train studies. In some cases, the generator model is replaced by a simple 3-phase source. The description of the various systems is given next:  446  A. High-Power Three-level GTO-Based PMSM Drive  Propulsion System Thistype of system involves a power converter feed from a 20-kV three-phase power system whichistransformed to lower voltage by 3-winding transformers.A 12-pulse thyristor rectifier is then usedtocontroltheDC-linkvoltages.From the bipolar DC-bus, a three-levelneutral-clamped GTO inverter drives a permanentmagnetsynchronousmachine. The machine is rated at 1 MVAwith magnet flux of 2.5 Weber. Figure 2 Three-level GTO inverter motor drive Figure 3 shows the PMSMmotorterminalvoltages,currents, electric torque and speed during the drive start-up from zero speed to 4 Hz rotation frequency.Figure4shows the DC-link voltage and transformer secondarycurrents during the start-up. A systemengineermightwant to investigate a method toreducetheDC-link voltage oscillations during the accelerationphaseofthetest.Interpolation method requirements of theRTeDRIVE package for the accurate simulation of the PMSM drivecan be seen in Figure 5. For the test,thePWMfrequencyof the drive is 1 kHz, no dead time is appliedandthesamplingfrequencyof the model is 40 kHz (Ts=25  s).Forthepurposeofthe test, interpolation is disabled duringthesimulation.OnFigure5, one can clearly observe theincreaseddistortion in the current and torque values when interpolation is disabled. Figure 3 PMSM motor voltages, currents, electric torque and speed Figure 4 DC-link voltage and transformer currents.Figure 5 Effect of interpolation on the PMSM Drive accuracy  B.Very-High-Power   C  urrent   C  onverter   S   ystem This type of propulsion systeminvolvesadirectAC-AC converter based on thyristor switchingdevices.Froman AC primary feed, a step-down transformer feeds a 12- pulse thyristor rectifier. The thyristorrectifier is connectedtoa 6-pulse inverter through a simple smoothing reactor. The inverter drives a synchronous machine used for  propulsion.This type of drive can handle more power than itsIGBTor GTO counterparts. It is however moredifficulttocontrol. For example, special techniques must be used todrive a motor at very low speed because the back-EMF is not sufficient to enable inverter thyristor commutation.Atesthasbeen made on this model which consisted of rising the commanded DC-linkcurrent from a steady-state valueof 0.5 pu to 0.8 pu. For the test, the SM machineworksatafixed speed of 50 Hz and a constant fieldexcitationvoltageis applied to the machine. Testing thisdevice in constant speed mode is something rather difficultwithreal devices (requiring a test bench), but isveryeasytoachieve in simulation. It enables theverification of torque and current controls. The resultof the test is shown in Figure 7. The test showsthatthesystem takes less than 0.1 sec toreachthecommandedcurrent.  447 Figure 6 Thyristor-based current converter SM propulsion systemFigure 7 Current converter response to a commanded current step C.Diesel-based   P  ower   G  eneration  S   ystem Synchronous machine Exciter armature DieselEngineDiode rectifiersBreakers Fieldwinding +V1-V1+V2-V2  Actuator  Diesel Power Generation System Figure 8 Diesel-based power generation systems This system is composed of adiesel-engine-drivenalternatorconnectedtotwo 6-pulses diode rectifiers. The diode rectifiers produce 2 DC-linkvoltages.Thealternator fieldwinding is fed with the rectified voltage of an armature voltage induced by an external DC-winding.This approach avoids slip ringsastherectificationcircuitis physically inside the alternatorrotor.Thesystemis protected by several breakers that control the alternator connection to the DC-links.  D.Catenary-based   P  ower   G  eneration  S   ystems For externally powered trainfrom an AC-catenary, this circuit uses two active-front end rectifiers to generatethe2 DC-link voltages. Breakers control theconnectionsof the IGBTs to the catenary’s transformer. =2~ CatenaryPento =2~ +V1-V1+V2-V2 Catenary-fed power generation system Figure 9 Caterany-based power generation system  E.Four Induction Motor Traction  S   ystem Thissystemis composed of 4 induction motors, two on each DC-link, driven by IGBTinverters. Each DC-link also has a chopper to control overvoltages and anadditional inverter to feed the auxiliarysystems.Thechallenges of conducting real-time simulation of inductionmotor drives are describedin[2], especially with regards to the correct simulation of high-frequency PWMtypically found in these applications. Thistypeoftractionsystem can be connected to eithera Diesel-based power generation system or catenary-basedpowergenerationsystems. +V2-V2 =3~=3~=1~=1~  AUXsystem =1~=1~ 3~=3~= Chopper Chopper Tractioninduction motorsIM 1 IM 2   IM 3 IM 4+V1-V1-V1-V2+Vx1+Vx2 Traction system Figure 10 Induction machine traction system 1)Validation against EMTP-RV   S  imulation Inthissub-section, we compare the simulation resultsofSimPowerSystemsand RTeDRIVE inverter modelsagainsta well-known reference, EMTP-RV. The modelunder test is a simple induction machine driven by an IGBT-inverter.Themachineis driven in open loop from a DC voltage source of 700V and the inverterismodulated

Roshni Issue 68

Jul 28, 2017

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