Modelling and simulation of a gas turbine

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(1)Examensarbete LITH-ITN-ED-EX--05/009--SE. Modelling and simulation of a gas turbine Henrik Klang Andreas Lindholm 2005-04-22. Department of Science and Technology Linköpings Universitet SE-601 74 Norrköping, Sweden. Institutionen för teknik och naturvetenskap Linköpings Universitet 601 74 Norrköping.

(2) LITH-ITN-ED-EX--05/009--SE. Modelling and simulation of a gas turbine Examensarbete utfört i Elektronikdesign vid Linköpings Tekniska Högskola, Campus Norrköping. Henrik Klang Andreas Lindholm Handledare Tomas Strömberg Examinator Måns Östring Norrköping 2005-04-22.

(3) Datum Date. Avdelning, Institution Division, Department Institutionen för teknik och naturvetenskap. 2005-04-22. Department of Science and Technology. Språk Language. Rapporttyp Report category. Svenska/Swedish x Engelska/English. Examensarbete B-uppsats C-uppsats x D-uppsats. ISBN _____________________________________________________ ISRN LITH-ITN-ED-EX--05/009--SE _________________________________________________________________ Serietitel och serienummer ISSN Title of series, numbering ___________________________________. _ ________________ _ ________________. URL för elektronisk version http://www.ep.liu.se/exjobb/itn/2005/ed/009/. Titel Title. Modelling and simulation of a gas turbine. Författare Author. Henrik Klang, Andreas Lindholm. Sammanfattning Abstract In this. thesis, a gas turbine simulator for the Siemens GT10C was developed and implemented.. It concerns everything from the theory behind the simulator; both the hardware and software involved, to how the actual simulator was built using these tools. The theory concerns itself with basic automatic control concepts, as well as basic turbine theory. The simulator setup is being discussed concerning both technical and economic issues. A robust hardware solution is then selected, using the basic requirements, which the simulator then is built around. The tools used are the Siemens SIMATIC automatic control system and the Siemens SIMIT real-time simulator using a SIMBA Pro PCI card to interface with the PLC:s in the SIMATIC system. Matlab are also used to a lesser extent to build the simulator behavior in SIMIT. In the end, a fully featured simulator is presented that can be used for various purposes such as training operators, trying out new concepts and testing the automatic control system used to control the turbine. Further development that could be done, by other engineers, in the future, is also discussed.. Nyckelord Keyword. Automatic control, fieldbus, gas turbine, modelling, S7, Siemens, SIMATIC, SIMBA, SIMIT, PLC, PROFIBUS, simulation.

(4) Upphovsrätt Detta dokument hålls tillgängligt på Internet – eller dess framtida ersättare – under en längre tid från publiceringsdatum under förutsättning att inga extraordinära omständigheter uppstår. Tillgång till dokumentet innebär tillstånd för var och en att läsa, ladda ner, skriva ut enstaka kopior för enskilt bruk och att använda det oförändrat för ickekommersiell forskning och för undervisning. Överföring av upphovsrätten vid en senare tidpunkt kan inte upphäva detta tillstånd. All annan användning av dokumentet kräver upphovsmannens medgivande. För att garantera äktheten, säkerheten och tillgängligheten finns det lösningar av teknisk och administrativ art. Upphovsmannens ideella rätt innefattar rätt att bli nämnd som upphovsman i den omfattning som god sed kräver vid användning av dokumentet på ovan beskrivna sätt samt skydd mot att dokumentet ändras eller presenteras i sådan form eller i sådant sammanhang som är kränkande för upphovsmannens litterära eller konstnärliga anseende eller egenart. För ytterligare information om Linköping University Electronic Press se förlagets hemsida http://www.ep.liu.se/ Copyright The publishers will keep this document online on the Internet - or its possible replacement - for a considerable time from the date of publication barring exceptional circumstances. The online availability of the document implies a permanent permission for anyone to read, to download, to print out single copies for your own use and to use it unchanged for any non-commercial research and educational purpose. Subsequent transfers of copyright cannot revoke this permission. All other uses of the document are conditional on the consent of the copyright owner. The publisher has taken technical and administrative measures to assure authenticity, security and accessibility. According to intellectual property law the author has the right to be mentioned when his/her work is accessed as described above and to be protected against infringement. For additional information about the Linköping University Electronic Press and its procedures for publication and for assurance of document integrity, please refer to its WWW home page: http://www.ep.liu.se/. © Henrik Klang, Andreas Lindholm.

(5) Preface. i. Preface This thesis is a result of about 20 weeks of analysis and implementation at Siemens Industrial Turbomachinery AB, Finsp˚ ang, Sweden. It is a compulsory part of the education for the authors to receive their Master of Science degree in Electronics Design Engineering from the Department of Technology and Natural Sciences (ITN) at Linköping Institute of Technology. The work was carried out in between June and November of 2004. The exam¨ iner at Linköping Institute of Technology was M˚ ans Ostring and the instructor at Siemens Industrial Turbomachinery AB, Thomas Strömberg. The thesis was done in co-operation with another thesis worker, Daniel Wigren, which also is a student at Linköping Institute of Technology studying to receive a degree as a Master of Science in Applied Physics and Electrical Engineering. Henrik Klang and Andreas Lindholm. Stockholm and Finsp˚ ang, February 2005..

(6) ii. Thank you! To everyone who deserves it..

(7) Mandatory quotes from (in)famous persons. Mandatory quotes from (in)famous persons “ ‘Students?’ barked the Archchancellor. ‘Yes, Master. You know? They’re the thinner ones with the pale faces? Because we’re a ∗university∗? They come with the whole thing, like rats’ ” - Terry Pratchett (author, Moving Pictures) “Sometimes a scream is better than a thesis.” - Ralph Waldo Emerson (US essayist & poet, Journals). iii.

(8) iv. Abstract In this thesis, a gas turbine simulator for the Siemens GT10C was developed and implemented. It concerns everything from the theory behind the simulator; both the hardware and software involved, to how the actual simulator was built using these tools. The theory concerns itself with basic automatic control concepts, as well as basic turbine theory. The simulator setup is being discussed concerning both technical and economic issues. A robust hardware solution is then selected, using the basic requirements, which the simulator then is built around. The tools used are the Siemens SIMATIC automatic control system and the Siemens SIMIT real-time simulator using a SIMBA Pro PCI card to interface with the PLC:s in the SIMATIC system. Matlab are also used to a lesser extent to build the simulator behavior in SIMIT. In the end, a fully featured simulator is presented that can be used for various purposes such as training operators, trying out new concepts and testing the automatic control system used to control the turbine. Further development that could be done, by other engineers, in the future, is also discussed. Keywords: Automatic control, fieldbus, gas turbine, modelling, S7, Siemens, SIMATIC, SIMBA, SIMIT, PLC, PROFIBUS, simulation..

(9) CONTENTS. v. Contents Abstract 1 INTRODUCTION 1.1 Purpose . . . . . . . . . . . . . . . . 1.2 Background . . . . . . . . . . . . . . 1.3 Questions at hand . . . . . . . . . . 1.4 Limitations . . . . . . . . . . . . . . 1.5 History of the Finsp˚ ang development 1.6 The structure of this thesis . . . . .. iv . . . . . .. . . . . . .. . . . . . .. 1 1 1 1 2 2 2. 2 THEORY 2.1 Overview of fieldbus technology . . . . . . . . . . . . . . . . . R 2.2 PROFIBUS° . . . . . . . . . . . . . . . . . . . . . . . . . . . R 2.3 PROFIBUS-DP° . . . . . . . . . . . . . . . . . . . . . . . . 2.4 MPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 The Siemens SIMATIC totally integrated automation system 2.6 SIMATIC hardware . . . . . . . . . . . . . . . . . . . . . . . 2.7 Engineering and operator stations . . . . . . . . . . . . . . . 2.7.1 S7 PLC’s . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.2 DP-slaves explained . . . . . . . . . . . . . . . . . . . 2.8 SIMATIC software . . . . . . . . . . . . . . . . . . . . . . . . 2.8.1 SIMATIC manager . . . . . . . . . . . . . . . . . . . . 2.8.2 Hardware config . . . . . . . . . . . . . . . . . . . . . 2.8.3 SFC editor . . . . . . . . . . . . . . . . . . . . . . . . 2.8.4 CFC editor . . . . . . . . . . . . . . . . . . . . . . . . 2.8.5 NetPro . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8.6 Fail-safe versus non fail-safe . . . . . . . . . . . . . . . 2.8.7 WinCC . . . . . . . . . . . . . . . . . . . . . . . . . . 2.9 The Siemens SIMIT simulation system . . . . . . . . . . . . . 2.9.1 SIMBA Pro . . . . . . . . . . . . . . . . . . . . . . . . 2.9.2 Using SIMIT . . . . . . . . . . . . . . . . . . . . . . . 2.10 The Siemens GT10C gas turbine . . . . . . . . . . . . . . . . 2.10.1 Compressor . . . . . . . . . . . . . . . . . . . . . . . . 2.10.2 Combustion chamber . . . . . . . . . . . . . . . . . . . 2.10.3 Power turbine . . . . . . . . . . . . . . . . . . . . . . . 2.11 Turbine regulators . . . . . . . . . . . . . . . . . . . . . . . . 2.11.1 STC - starting control . . . . . . . . . . . . . . . . . . 2.11.2 NGGL - gas generator speed limiter . . . . . . . . . . 2.11.3 SC - speed controller . . . . . . . . . . . . . . . . . . . 2.11.4 T7L - exhaust average temperature limiter . . . . . . 2.11.5 T7Li - exhaust inner temperature limiter . . . . . . . 2.11.6 MPC - maximum servo position control . . . . . . . . 2.11.7 GAC - gas generator acceleration control . . . . . . . 2.11.8 GDC - gas generator deceleration control . . . . . . . 2.11.9 PAC - power turbine acceleration control . . . . . . . 2.11.10 LLD - loss of load detection . . . . . . . . . . . . . . . 2.12 Automated start of turbine . . . . . . . . . . . . . . . . . . . 2.12.1 Unit sequence . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4 4 5 6 7 7 7 7 8 9 9 10 11 11 12 12 12 13 13 13 14 15 16 17 18 19 19 19 20 20 20 20 20 21 21 21 21 21. . . . . . . . . . . . . site . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . ..

(10) vi. CONTENTS. 2.12.2 Gas fuel sequence . . . . . . . . 2.12.3 Turbine sequence . . . . . . . . 2.12.4 A start of the turbine using the 2.13 Summary . . . . . . . . . . . . . . . .. . . . . . . . . . . . . sequences . . . . . .. 3 DECIDING THE SIMULATOR SETUP 3.1 Different solutions . . . . . . . . . . . . . . . . . 3.1.1 Solution I - PLC—PLC . . . . . . . . . . 3.1.2 Solution II - Simulator and control system 3.1.3 Solution III - PLC—PC/C/C++ (Java) . 3.1.4 Solution IV - PLC—PC/Simulink . . . . 3.1.5 Solution V - PLC–SIMIT (chosen) . . . . 3.1.6 Conclussions . . . . . . . . . . . . . . . .. . . . .. . . . .. . . . .. . . . .. . . . .. . . . .. . . . .. . . . .. . . . .. 21 23 23 24. . . . . . . . . . . . . . . . . in same PLC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . .. 25 25 26 27 27 28 29 29. 4 IMPLEMENTING THE SIMULATOR AND THE MODEL 32 4.1 Setting up the simulator . . . . . . . . . . . . . . . . . . . . . . . 32 4.2 Closed and open loop control . . . . . . . . . . . . . . . . . . . . 32 4.3 Building HMI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 4.4 The development cycle . . . . . . . . . . . . . . . . . . . . . . . . 34 4.5 A simulation diagram example (calculating heat flow) . . . . . . 35 4.5.1 Using performance data . . . . . . . . . . . . . . . . . . . 35 4.5.2 Heat flow versus speed, temperature and pressure . . . . . 38 4.5.3 The pilot flame . . . . . . . . . . . . . . . . . . . . . . . . 38 4.5.4 Necessary adjustments . . . . . . . . . . . . . . . . . . . . 38 4.5.5 A run with the model . . . . . . . . . . . . . . . . . . . . 38 5 RESULT 41 5.1 Conclusions and discussion . . . . . . . . . . . . . . . . . . . . . 41 5.2 Future development . . . . . . . . . . . . . . . . . . . . . . . . . 42 References. 43.

(11) LIST OF FIGURES. vii. List of Figures 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9. 2.10 3.11 3.12 3.13. 4.14 4.15. 4.16 4.17 4.18 4.19. Old fieldbus network. . . . . . . . . . . . . . . . . . . . . . . . . . Modern fieldbus network. . . . . . . . . . . . . . . . . . . . . . . Two Siemens SIMATIC S7 PLC boxes (back) connected to DPslaves (front). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Basic configuration with a DP-rack in the hardware config editor Two typical CFC-blocks, normal (left) vs. fail-safe (right). . . . . SIMIT and SIMBA Pro interaction scheme (OS and ES computers connected to the S7 PLC are not included). . . . . . . . . . . SIMBA Pro list of configured DP-slaves. . . . . . . . . . . . . . . Example of a SIMIT diagram/modell. . . . . . . . . . . . . . . . The GT10C gas turbine is a turbine with two rotors, the compressor rotor and the power turbine rotor. This type is known as a double shaft turbine. The three main parts of the turbine is enclosed in red. . . . . . . . . . . . . . . . . . . . . . . . . . . . . The compressor valves locations of the turbine. . . . . . . . . . . Solution I, PLC to PLC communication (simplified schematic). . Solution III & IV, PLC to PC (C/C++/SimuLink) communication (simplified schematic). . . . . . . . . . . . . . . . . . . . . . Final hardware setup with the turbine PLC’s containing the control program and the PC containing the turbine simulation program. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The HMI of a turbine system (operator screen). . . . . . . . . . . Grouping of diagram and operating screens in SIMIT. The different alphanumeric codes are an internal Siemens scheme for naming different systems in the turbine. . . . . . . . . . . . . . . Simple development process flowchart of the simulator model. . . Data from performance tests used when developing the model. . The relation between the curve taken from SCADA Pro (blue) and the polygon curve done with Matlab (red). . . . . . . . . . . The SIMIT model to calculate the heat flow value. . . . . . . . .. 6 6 10 11 12 14 14 15. 16 17 27 29. 31 33. 34 36 37 37 39.

(12) viii. LIST OF TABLES. List of Tables 2.1 2.2 2.3 2.4 2.5 2.6 3.7. Comparison between PROFIBUS and older fieldbus standards . . Speed versus pressure ratio in the compressor. . . . . . . . . . . . Valve characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . The unit sequence which starts up turbine. . . . . . . . . . . . . Gas fuel sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . Turbine sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . Quick recap of investment costs for each solution. Notes: 1 A more powerful PLC might be needed. 2 If implemented. . . . . . .. 5 17 18 22 22 23 30.

(13) ABBREVIATIONS. ix. Abbreviations AI API AO CC CFC CP CPU DI DIP DO DOS DP ES FAT GDC GUI HMI I[/]O I 2C IGV IPX MAC MPI NIC OLE OPC OS OSI PCI PCS PID PLC PROFIBUS PS[U] PT RAM SCADA SCL SFC TCP/IP UR2. Analogue In Application Programming Interface Analogue Out Control Center Continuous Function Chart Communication Peripheral Central Processing Unit Digital In Dual-Inline Package Digital Out Disk Operating System Decentralized Peripheral Engineering Station Factory Acceptance Test Gas generator Deceleration Control Graphical User Interface Human Machine Interface Input/Output Inter-Integrated Circuit Inlet Guide Vane Internetwork Packet Exchange Media Access Control Multipoint Interface Network Interface Card Object Linking and Embedding OLE for Process Control Operator Station Open System Interconnection [Reference Model] Peripheral Component Interconnect Process Control System Proportional Integration Derivation Programmable Logic Controller PROcess FIeld BUS Power SUpply Power Turbine Random Access Memory Supervisory Control and Data Acquisition Structured Control Language Sequential Function Chart Transmission Control Protocol/Internet Protocol Universal Rack Type 2.

(14) 1 INTRODUCTION. 1. 1. INTRODUCTION. 1.1. Purpose. The primary purpose of this thesis is to develop a simulator and model for a specific gas turbine, the GT10C; which uses the Siemens SIMATIC system (“SIMATIC”, also referred to as “S7” where 7 is the latest version of SIMATIC). When this is done the model of the gas turbine will be implemented in the system which has been devised. Secondary purpose are to include more additions to the simulator, such as simulating the next coming stages in the turbine system; compressors, and other loads. More wanted additions is to be able to simulate other turbine models in the same family. The first goal of the thesis is to analyze what kind of system that would be needed to build and implement the simulator itself, both hard- and soft wise. When this is done, the actual simulator will be implemented in the developed system, and finally, at the end, tested against the actual turbine automation and control system located in multiple S7 PLC boxes. This thesis is being carried out at Siemens Industrial Turbomachinery AB (“Siemens”) located in Finsp˚ ang, Sweden which is a part of the Siemens group.. 1.2. Background. Siemens Industrial Turbomachinery AB is about to adopt the S7 system, thus replacing the currently used one developed by ABB. The current project at hand (as of June 2004) is to install a GT10C gas turbine in Eischleben, Germany. This is the first project, in Finsp˚ ang, to use the S7 system from Siemens, thus the development of a simulator would be helpful in the entire development cycle of a turbine and its systems. The simulator will be used for system testing, training new operators and simulating new additions to the automatic control system, before the system is tested in an actual turbine on site. This will help reduce, both development cost, and time to market, for new additions to the system. Moreover, it will shorten the time spent training operators for a specific turbine thus increasing total profit per installed turbine and project.. 1.3. Questions at hand. A number of questions were formulated to use during the entire thesis process. Each one of these questions will be answered in this thesis report. Primary, • What kind of system should be used for the simulator? • How should the communication work in between the simulator and the PLC. Is there any ready-made solutions to use? • What system is feasible to use concerning cost, training, and implementation time? • In which way should the human machine interface of the simulator be implemented and designed to be as easy as possible?.

(15) 2. Secondary, • How should other turbine models be implemented in the simulator and can it be done in a reasonable time frame?. 1.4. Limitations. The initial limitations will be to devise a simulator for only one turbine, the GT10C. Although extending the simulator for other turbine types such as the GTX100 would be favorable. At first the model of the turbine shall be static, that is, no dynamic signals shall be modeled. Static signals in this report refers to such ones that does not use any feedback when calculating the output signals of the system. If, and when, the static modeling is done, a half dynamic model should be developed. In this report a half dynamic model is a model where analogue and digital signals can be triggered by other signals, but not as a closed loop, such as a PID (for further discussion of these concepts please refer to Section 4). Furthermore, an external unit (load) of the turbine, shall be modeled if there is any time.. 1.5. History of the Finsp˚ ang development site. The Finsp˚ ang site has been developing and producing power generation equipment approximately 100 years. In 1913 Svenska Turbinfabriksaktiebolaget Ljungström (Swedish turbine factory Ljungström) was formed (known as STAL). In the 1950’s they merge with DeLaval and formes STAL-Laval. In the middle of the 1980’s ASEA buys the entire company which later becomes ABB STAL AB. In 1999 ABB Alstom Power Sweden AB is formed and in the same year the gas turbine GT10C is developed. This is the turbine that the simulator in this thesis simulates. Finally in 2003 Siemens buys the company and renames it Demag DeLaval Industrial Turbomachinery AB which in October of 2004 became Siemens Industrial Turbomachinery AB.. 1.6. The structure of this thesis. In the first chapter, THEORY, an explanation of automation control concepts and turbine theory will be introduced. This is the perquisites to understand the reasoning behind, both the model, and how the simulation system was developed. This chapter also explains the programs used and how they work together and individually. In the chapter DECIDING THE SIMULATOR SETUP the entire simulator hardware will be explained. Why and how the hardware and software was chosen and how the system was put together. Both technical and economic issues are taken into consideration here. In IMPLEMENTING THE SIMULATOR AND THE MODEL logic behind the actual turbine model will be explained in detail. Also the HMI will be shortly discussed and some other important aspects concerning the simulator implementation itself..

(16) 1.6. The structure of this thesis. 3. Last, the chapter RESULT discusses the results, and what could have been done differently. Also future improvement that would be possible is discussed here..

(17) 4. 2. THEORY. To be able to understand the next coming chapters some explanations of the terms and concepts, in this thesis, will be discussed below. A simple overview of the programs used will also be presented to give the reader a more in depth view of the problems the authors faced and measures taken to solve these. This chapter also explains, on a very low level, how a turbine works, and especially the turbine which the simulator in this thesis is developed for.. 2.1. Overview of fieldbus technology. Fieldbus[1][2] technology is a major step in the process control industry. In older systems, signals sent used to be unidirectional and traditionally 4 − 20mA analogue. Fieldbus technology on the other hand is a replacement for this type of older systems and extends the entire process control concept from the bottomup approach to a more sophisticated top-down thinking. The modern fieldbus of today acts as an entire network; much like the Internet. It connects everything from PLC’s, engineering and operator stations to low level field devices on the factory floor such as actuators, sensors, transducers and drives. The fieldbus networks makes use of modern communication standards such as TCP/IP, IPX and Ethernet. These networks interconnect over large areas where the operator can be in Australia and the process which the operator controls could be located somewhere in Europe (in theory, but not very likely used in practise). This in turn opens for entirely new possibilities such as remotely developing and upgrading systems, monitoring factory processes and supporting on site operators within the accessible process network. Optimizing processes and finding possible bottle necks more rapidly are other benefits. Down sides to the modern fieldbus networks could be speed and congestion problems due to the large amount of traffic being sent on the same network (cable) and over other “unknown” networks such as Internet cables which the engineer does not have control over. Older[2] technologies relied on several hundred of cables (Figure 2.1), one for each signal, up to the PLC’s and operator/engineering stations, while modern fieldbus networks interconnects the process objects with each other at central access points. The objects are often connected in a serial fashion thus creating bottle necks along the way if much traffic and information exchange is needed between the process objects and the process control itself. Although this can be helped with new technologies such as fiber cables sending information using light instead of electrical signals or installing a second cable so that the objects are connected in parallel; though this would require another PLC box. For an easy overlook of the difference between older network properties and modern such as fieldbus, see Table 2.1. Going more extensively into the positive properties of fieldbus technology some are, • Design and engineering - Building the networks around well defined and known standards and concepts both reduce design and planing time, as well as helps minimize the documentation needed..

(18) R PROFIBUS°. 2.2. Signals Cables. older standards Analogue Unidirectional One for each signal.. Networking. Multiplexing of signals needed at a central hub.. Diagnosis. Basic diagnosis information.. Commissioning. More expensive due to complex networks and more cables.. 5. profibus Digital (packet based) Bidirectional Multiple signals can share a cable. Signal information can be easily relayed to multiple end points both local and global. More extensive information can be provided (“intelligent slaves”). Less cables, easier layout of the network.. Table 2.1: Comparison between PROFIBUS and older fieldbus standards • Installation and commissioning - Since the fieldbus I/O’s can be more diverse with less cables required in the process, both cost and time is reduced during commissioning and installation of the network and its surrounding process objects, PLC’s and higher monitoring tools. • Easier operation and maintenance - The data being transferred on the network can be more diverse than traditional analogue process networks since the standards is built around packet sending services similar to TCP/IP. This means that, not only digital and analogue signal information can be sent, but also extensive diagnostic information from each process object located in the system process. The information can also be easily sent to several endpoints in the factory network as well as larger networks such as the Internet. This makes it easier co-operating and finding the actual errors or solutions to the problems at hand. There are several fieldbus standards such as PROFIBUS, INTERBUS, MPI and Industrial Ethernet. Some are proprietary while others are open. Common for all is that they are used by industrial applications and are certified to work under the very different environment of a plant versus an office. The difference are mostly in how the software protocol is implemented, as well as physical properties of the cables and signal levels.. 2.2. R PROFIBUS°. PROFIBUS[3] specifies everything from the medias electrical properties (the cable) to the protocol specifications over the cables. PROFIBUS is a simple two-wire buss (much like Phillips I 2 C), built to be robust in rugged environments, using a minimal and easy to implement protocol, with a minimal overhead. Thus reducing down time and need for maintenance. PROFIBUS is an open standard1 and was developed as a research project, involving several major corporations and research institutes, between 1987−1990. 1 IEC. 61158-1 through IEC 61158-6.

(19) 6. Location A PLC. Location B. Location C. Figure 2.1: Old fieldbus network. Location A PLC. Fieldbus Cable. I/O device. I/O device. Location B. Location C. Figure 2.2: Modern fieldbus network.. PROFIBUS is the leader of fieldbus communication with over 20 per cent of the world market. Approximately 500.000 plants and factories use PROFIBUS, with over 5 million nodes2 installed.. 2.3. R PROFIBUS-DP°. PROFIBUS-DP[3] is a extension of the PROFIBUS standard which is designed for fast data exchange at field level. The distribution is cyclic. It works much like “token ring”, where a token is “passed” between the different stations and “taken” by a particular station if information is to be sent by it. There are three different DP-protocols. The one used in the SIMATIC system is DP-V1 which supports features such as fail-safe (more about fail-safe in Section 2.8.5). Each object connected to the PROFIBUS-DP network has a unique id in between 1-127 where 0 is reserved for so called broadcast operations (sending information to several nodes at once). 2 A node is a PROFIBUS station with a unique PROFIBUS address such as PLC’s, sensors and actuators..

(20) 2.4. 2.4. MPI. 7. MPI. MPI[4], Multipoint Interface, is a closed Siemens standard. It is used as a programming interface for S7 PLC’s (see Section 2.7 for information on S7 PLC’s), but can also be used as a interface to operator panels simultaneously. Each MPI interface, or node, is identified by an address.. 2.5. The Siemens SIMATIC totally integrated automation system. The Siemens SIMATIC concept (“SIMATIC”) is a product line of both hardware and software products for plant control applications. The SIMATIC system itself is independent of the medium used to transport information, but it supports both MPI (proprietary of Siemens) and PROFIBUS standards, as well as Industrial Ethernet. The various communication interfaces can be used at the same time, combining them, depending on the configuration and system needed. A core product of the SIMATIC system is PCS7 which is a software suite (Process Control System 7) that is needed to build the programs used in the process plant control. Each control system is then loaded onto a S7 PLC box. The S7 PLC is set in run mode and then starts to interchange information with the surrounding objects through the various interfaces available (a more detailed description is provided in the next coming sub chapters). It can be discussed if the software or hardware should be explained first in this thesis, since they are so closely related. The reader should be advised, however, that there is no clear distinction between the hardware and software.. 2.6. SIMATIC hardware. The SIMATIC hardware suite consists of a line of hardware modules used to build the entire plant control system, from top to bottom. At the core is the S7 PLC boxes which are used to control the plant process. Around these S7 PLC boxes the network is built, both using Ethernet, PROFIBUS and MPI interfaces, depending on what, and where to connect peripheral equipment such as operating stations and engineering stations DP-slaves and even other PLC’s. Another integral part of the systems are, as already mentioned above, DPslaves. The DP-slaves controls the process objects of the plant, and communicates to the S7 PLC’s via a network.. 2.7. Engineering and operator stations. A operator station is a computer were the turbine is controlled and monitored. There usually exist more than one of these so the engineer can see several processes simultaneously. At the engineering stations the service personnel can make change to the control program and test these news changes. There usually exists only one of these..

(21) 8. 2.7.1. S7 PLC’s. The S7 PLC’s differ in function, speed and memory capacity. The configuration needed is dependent upon the application. Processes such as conveyor belt systems with few stations could settle with a simpler S7 PLC’s, while more complex systems such as turbines and paper machines could need several powerful S7 PLC’s working together as a cluster or separate, dividing the handling of DP-slaves and the calculations needed to run the plant process. The most basic S7 PLC hardware configuration consists of the following: • Rack (“UR2”) - Where the hardware components are mounted. • PS - Supplies power and provides battery backup if the system should happen to lose power. • CPU - The central unit which runs the PLC program stored on a memory card. • CP - The communication processor module used to interface with Ethernet. The PS, CPU and communication process modules are placed in a UR2 rack. The UR2 rack is both a mechanical and electrical “backplane”. The rack lets the different components communicate with each other as well as provides a mechanically stable platform for use in harsh industrial environments. Depending on the type of the rack it can mount multiple “PLC cells”, where each group consists of a power supply, CPU and communication processor. The PS supplies power to the rack through the backplane. The PS also consists of two batteries (rechargeable), which are used if the regular power from the grid is lost, thus creating redundancy. The S7 PLC program itself is stored on a flash memory card, which holds the information, even during a power loss. Although, the configuration data which holds information of what kind of components that is mounted on the rack, is stored in a volatile RAM thus making PS redundancy important via the batteries. Another source of redundancy can be created by adding a extra PS to the rack. For these purposes, and depending on the saftey needed, there are different types of PS such as redundant and non-redundant. Obviously, creating a nonredundant solution is a solution with low initial costs, but could be proven a fatal decision afterwards, due to production loss caused by downtime of the PLC-system. The CP modules is in many ways like a normal network interface card (“NIC”) found in any modern PC, thus having connections for ethernet wiring. Since Industrial Ethernet (a subset of Ethernet) is very much like normal Ethernet the wiring can be connected to switches and hubs like any other computer network. The engineer can then program the PLC through the CP cards interfaces as well as through the MPI interface as mentioned earlier. Also, the ethernet interfaces are often connected to the ES and OS stations where the operator can control the plant through the S7 PLC. There are CP modules which holds fiber optic connectors thus handling fiber optic nets if the S7 PLC needs to process time critical data and process objects. At the heart of the plant control is the CPU module(s). It consists of a CPU, and a memory module. The memory module size needed depends on the size of.

(22) 2.8. SIMATIC software. 9. the plant control program it needs to store. Also, depending on the model type of the CPU module it can be exchanged for larger modules (varying between 1-16MB). The CPU module also holds a DP interface and a combined DP/MPI interface. The MPI can be used to programme the CPU modules flash card via an expansion card in a PC. Usually, though, the memory card is programmed through the CP modules Ethernet connection (that is via a network). It is through the DP interface that the DP-slaves are connected. That is, the DP interface handles the process objects communication (see next sub chapter for a more throughout description). As with the other kinds hardware modules detailed above there are different types of CPU’s available, varying in speed and capabilities such as redundancy and fail-safe (see Section 2.8.5 for an explanation of fail-safe). 2.7.2. DP-slaves explained. A DP-slave is a hardware process object which handles the communication in between the S7 PLC and the sensor, actuator, drive or any other type of measurement point located in the plant or process hierarchy. Each DP-slave has a unique PROFIBUS node id, between 1-127, as mentioned before. The id itself can usually be set by DIP-switches directly on the device. The name itself R is derived from the fact that the objects use the PROFIBUS-DP° protocol to communicate with one or more master (S7 PLC box(es)). Each PLC box are also considered to be a node in the system and is therfore assigned a node number. By default a S7 PLC usually assigned node id 2 (id 0 is reserved for broadcast packets). The DP-slaves are connected via a PROFIBUS interface (cable) to a S7 PLC. Each slave can hold a variable number of I/O’s and types such as a 16 analog signals input or 4 input digital signals output matrix. The slaves can be connected in serial to the same S7 PLC using the same cable and interface. As with the S7 CPU there are fail-safe, redundant and fiber-optic versions of most DP modules. Industrial processes, such as a turbine may involve more than twenty DPslaves in the plant network containing hundreds of signals, while even more complex plant processes such as a paper machine may contain thousands of signals and an even larger amount of slaves.. 2.8. SIMATIC software. With the hardware explained briefly, one should note that the software of the SIMATIC suite is just as important and, sometimes, overly complex. The SIMATIC software suite consists of a plethora of components. While some are a integral part in this thesis, other, are not, thus these are excluded. Only the most important programs which the authors has used, are explained below, to make the thesis as easy as possible to grasp. SIMATIC software has been developed and used since the DOS days (late 80:s), before Windows. Since each new revision of the system, it has been updated, upgraded and reworked. Although, not from the bottom and up, rather, the other way around. This has created a non-modern suite of components which are not very easy to use. SIMATIC and the components are, to say the.

(23) 10. Figure 2.3: Two Siemens SIMATIC S7 PLC boxes (back) connected to DPslaves (front). least, software built on old concepts which the developers have tried to fusion with new ones such as drag and drop and GUI. Therfore, SIMATIC is relatively hard to work with initially, creating a steep learning curve for beginners. A summary of the programs explained are included in the list, • SIMATIC manager - All-in-one control center for the SIMATIC suite of programs. • WinCC - OS and ES station development and usage. • Hardware config - Configuration of the hardware setup, used in the factory process, at all levels. • Continuous function chart editor - Drag and drop editor where function blocks are interconnected to create the PLC functions (i.e. PID regulators, logic blocks et.c.). • Sequential function chart editor - Program used to build sequences using function blocks (very much like flow charts). • PG\PC interface - Sets the interface used when programming the CPU module. • NetPro - Program to set up communication between PLC’s and OS. 2.8.1. SIMATIC manager. SIMATIC manager is the control center in SIMATIC used to organize, set up and develop the software projects from a central point. Each and one of the other programs in the SIMATIC suite is started from the manager itself. Since building a control system often needs a team of people collaborating SIMATIC manager makes use of multi-project concepts which enables engineers to simultaneously develop the models and control systems, also known as concurrent engineering..

(24) 2.8. SIMATIC software. 11. The manager shows projects currently open, a summary of the hardware configured for the projects, and the different components included in the control program. The manager also shows connected DP nodes (masters and slaves) for an easy overview of the connected devices, making diagnosis and detection of error more manageable. Since most plant applications include more than one PLC controlling the process, more than one PLC program, at a time, can be loaded in the manager. 2.8.2. Hardware config. The hardware config editor is reached from the SIMATIC manager. This is where the engineer sets up the entire hardware network, concerning everything from what kind of PLC to use to the type of media interconnections between the nodes and where the OS and ES stations should be connected in the automatic control system network.. Figure 2.4: Basic configuration with a DP-rack in the hardware config editor In Figure 2.4 a hardware setup can be seen as defined by the hardware configuration editor. The window to the left in Figure 2.4 represents the components which the engineer have physically mounted on the UR2 rack. Since there are different kinds of S7 CPU’s, CP’s and PS’s the correct version must be configured. Each number in the window corresponds to the slot on the rack. As seen, the CPU and the PS is mounted in two slots each. To the right, on the “PROFIBUS cable”, a DP-slave is mounted. In this case a IM153-2 slave, which holds 16 analog out signals (cannot be seen in the figure). This example illustrates a minimal system with very few signals but is nevertheless a good example of how a plant network could be built using the hardware config interface. 2.8.3. SFC editor. In the sequential function editor the engineer builds the sequences in which the turbine should be started. In other words, in which order the CFC charts should be executed in order to start up the turbine in a controlled way. The editor also includes transition steps which has to be fulfilled before the sequence continues. The sequences, which is mentioned more in detail in the sub chapters of chapter 2.11, is built in the SFC editor..

(25) 12. 2.8.4. CFC editor. The continuous function chart editor is where the engineer builds the actual control program. Components such as PID-regulators, OR-blocks and timer functions can be dragged-and-dropped into the editor. The components can then be configured and connected to their respective I/O ports. There are two kinds of fundamental “low-level” blocks in the editor; fail-safe and normal blocks. The fail-safe blocks have a distinct yellow color while the others are grey as seen in Figure 2.5. The blocks seen in Figure 2.5 has the function of being out and input blocks out and into the PLC itself. The blocks are thus the “boundaries” of the PLC program.. Figure 2.5: Two typical CFC-blocks, normal (left) vs. fail-safe (right).. 2.8.5. NetPro. This program is used to set up the communication in between the PLC’s and the operator station(s). In addition to hardware config where the communication is initially set up, this program modifies the necessary “blocks” to ensure that the communication in between the PLC and OS works correctly concerning message and alarms sent between the process, PLC’s and OS. 2.8.6. Fail-safe versus non fail-safe. A fail-safe block differs from the non fail-safe ones in a few important aspects. First of all fail-safe blocks needs special CPU’s known as H-series modules. If this is not the case the control program cannot be loaded, at all, into the CPU’s memory module. Typically, fail-safe-able modules are more expensive than their non fail-safe counterparts, this is why the engineer should consider the pro’s and con’s of using fail-safe versus a more low-cost setup. A fail-safe block switches to an alternate value and sets the output of the block (that is, a value going into the process to a DP-slave) if a fail-safe mode should happen to be enabled. The fail-safe mode can be set for a number of reasons, such as the DP-slave failing electrically or if the cable is failing to deliver the signals to the CPU’s DP-interface (i.e. no acknowledgement is received from the DP-slave of the packets safe delivery). Fail-safe is mainly used in plant processes with sensitive components which could be damaged if the signals are lost. For example mechanical systems such as gas turbines. Fail-safe are also used in explosively classified environments such as oil and gas platforms..

(26) 2.9. 2.8.7. The Siemens SIMIT simulation system. 13. WinCC. WinCC, or Windows Control Center, is the program where the operator pictures are built in. The connections to the signals from the CFC-editor is connected to GUI components in WinCC such as buttons, diagrams, pictures and sliders. WinCC can be run on multiple PC’s known as operator stations (“OS”) which makes it easier to have an overview of the gas turbine process and to control it through the GUI.. 2.9. The Siemens SIMIT simulation system. The Siemens SIMIT simulation system is a program suite used for plant simulation and modelling. It has an easy to use interface, in many ways similar to Mathworks Simulink (included in Mathworks Matlab). SIMIT is a real time simulation system, that is; simulation of the models and analysis of the data is done in real time (although the data generated can be saved), while programs such as Simulink can simulate the entire model instantly and let the engineer analyze the model and its results at once. Clearly, this has its pro’s and con’s. It’s harder to know and estimate how the simulation is expected to develop and expand as time increases since SIMIT and SIMATIC has to interact and calculate values such as PID-controller settings dynamically as the process evolves. SIMIT has been designed for less complex models in mind, as the user would notice rather quickly. Still, more advanced programs are possible, as seen by this thesis.. 2.9.1. SIMBA Pro. The SIMIT suite can be extended with a SIMBA Pro PCI card (“SIMBA”). The card itself is fitted into a PCI slot in a PC and accessed via a special software which SIMIT uses to relay its information flow through to the PCI card itself (through the use of a hardware driver). The schematic view of SIMIT combined with the SIMBA Pro PCI card is seen in Figure 2.6. SIMBA Pro has two connectors. Each can be connected to a PROFIBUS network, which means the card can handle two networks at the same time. SIMBA Pro does not need SIMIT to function as it is a self-reliant system. SIMIT should be seen as an add on containing more advanced graphical GUI and better analysis tools. SIMBA Pro holds several tools and components to be able to simulate simpler processes. The values of the I/O ports of the DP-slave can also be set individually if needed. Since SIMBA Pro is built for S7 communication through PROFIBUS the DP-slave configuration can be easily imported into SIMBA Pro from the SIMATIC hardware config program. A list of a imported DP-slave configuration can be seen in Figure 2.7. SIMBA Pro also handles fail-safe DP-slaves by adding extra signals for the fail-safe to be turned on or off for each signal in the hardware config configured in the fail-safe mode..

(27) 14. x86 Simulator PC with Windows 2000. Driver. SIMBA Pro PCI card. PROFIBUS-DP S7 PLC. SW Interface. SIMBA Pro Software. SIMIT. Figure 2.6: SIMIT and SIMBA Pro interaction scheme (OS and ES computers connected to the S7 PLC are not included).. Figure 2.7: SIMBA Pro list of configured DP-slaves. 2.9.2. Using SIMIT. Although the GUI has not been designed with ease of use in mind, managing SIMIT is fairly simple. SIMIT consists of basic component types such as tanks, PID-regulators and digital logic which simply is dragged, dropped and connected together to achieve the needed function (as in for example Simulink). The components can then be connected to signals coming from the S7 PLC, through the SIMBA Pro card, via input and output elements known as peripheral blocks. The signal list in SIMIT can be imported from the PLC program in the SIMATIC system, thus not needing to enter the signals by hand. Since there can be hundreds of signals this is a very convenient feature..

(28) 2.10. The Siemens GT10C gas turbine. 15. Each signal has a hardware address and an alias assigned to it (this is done during the development cycle of the PLC program in SIMATIC). The alias is a name used when connecting I/O ports in SIMIT to simplify the process since only a hardware address would be confusing and rather cumbersome. A very simple example is shown in Figure 2.8 where two input signals, INPUT SIGNAL 1 and INPUT SIGNAL 2, is added together. The result is sent through a sin block, and finally output to the OUTPUT SIGNAL port. More complex concepts such as feedback (PID-regulators) are also available to the engineer.. Figure 2.8: Example of a SIMIT diagram/modell. SIMIT differentiates between what it calls operator screens and diagram screens. This is very much like the concept of SIMATIC. The logic and functions of the simulation is built in the diagram view, using, as explained, components of various types. The components are then connected to the operator screens which displays and presents the values the diagram screen produces during the simulation. The DISPLAY component seen in Figure 2.8 is such a component. The DISPLAY component is simply dragged to a operator screen and the output is then displayed at this screen during the simulation. Interactive switches and buttons can also be added to the operator screens to control and influence the diagrams, yet, analogous to SIMATIC. Custom components can be made in SIMIT thus reducing the need to connect large clusters of blocks to achieve the desired functionality. The programming language is proprietary to SIMIT but very similar to object oriented syntax.. 2.10. The Siemens GT10C gas turbine. The theory explained here is in no way meant to be a comprehensive description of how an actual turbine works down to the very core, rather, it should be seen as an overview. Some concepts, tables and formulas in the following sub chapters are taken from internal Siemens documents, thus there are no reference to these in the text. A gas turbine core engine can be decomposed into three different parts; compressor, combustion chamber and power turbine. This can be seen in Figure 2.9..

(29) 16. Figure 2.9: The GT10C gas turbine is a turbine with two rotors, the compressor rotor and the power turbine rotor. This type is known as a double shaft turbine. The three main parts of the turbine is enclosed in red. 2.10.1. Compressor. The function of the compressor is to compress the surrounding air. When the air is compressed the temperature and pressure increase. To avoid surge3 in the compressor, two bleed valves, are used as well as an inlet guide vane (IGV). These elements can be seen in Figure 2.10(BV1 and BV2). The IGV controls the amount of air that flows into the compressor. The bleed valves are used to level out the pressure in the compressor to avoid fluctuation in the pressure, which is an unwanted effect. BV1 is just an ordinary on/off valve and BV2 is a control4 valve. BV2 is connected to the air inlet through piping, this to be able to control the temperature in the combustion chamber. At a higher flame temperature the emissions are lower. The CO and N Ox values decrease and the turbine is in that way more environment friendly. BV1 is used only during the start of the compressor and closes when the speed Nnorm of the compressor reaches 6800rpm. BV1 is fully closed between 6950rpm and when stopping the turbine it remains closed until 400rpm. r 288 Nnorm = N · (2.1) t2 + 273 The relation Eq. 2.1 between the valves position and speed is later used in the SIMIT modell to verify a stable operation mode of the compressor. That is, if the simulated values is out of range, the turbine control system would trip5 since the model is not working as expected. To ensure stable operations and required engine performance, the compressor guide vanes must be controlled according to Table 2.2. P3 is the compressor discharge pressure (M P a) is calculated as an average of three different pressure transmitters. 3 When. a surge occurs the compressor stalls, that is, stops to work. control valve lets the PLC control the exact position of the valve, that is, how much it should open. 5 A trip of a turbine is when the control program shuts the turbine down because of errors (signals outside the safety limits set up by the control program). 4A.

(30) 2.10. The Siemens GT10C gas turbine. 17. Figure 2.10: The compressor valves locations of the turbine. P1 is the compressor inlet pressure (M P a). The surge protection is activated when the speed exceeds 6000rpm. Nnorm (rpm) ≤ 6000 6500 7500 8700 9800 ≥ 10500. P3/P1 1.0 2.5 4.8 7.6 13.8 14.2. Table 2.2: Speed versus pressure ratio in the compressor.. To detect compressor surges, the compressor operating line is supervised. If the compressor pressure ratio is lower than in Table 2.2, a surge is likely to have occurred and a trip will be initiated. When the compressed air has passed through the compressor it reaches the combustion chamber. 2.10.2. Combustion chamber. In the combustion chamber the compressed air and the ignited fuel help increase the pressure even more. The combustion chamber contains a ring with fuel burners which are constructed in such a way that the flame is rotating. This is to maintain a flame that keeps the same shape, if not a pulsation effect could occur, when the flame flickers. This in turn result in high vibrations, high axial displacement and damage to the turbine. The amount of fuel inserted into the combustion chamber is controlled by two gas fuel control valves. The primary gas fuel control valve is used in the start sequence and split range controlled with the main gas fuel control valve. The primary gas fuel valve is at nominal speed closed to a minimum of “stayalive” percentage opening, this to avoid flame extinction if the gas generator.

(31) 18. main pos. (%) 0 8 15 20 25 30 40 45 50 55 60 65 70 75 80. heatflow (M J/s) -2 0 4.9 10.5 17.6 25.7 43.9 53.2 62 70.2 77.2 82.8 87 92.1 97.2. primary pos. (%) 0 20.5 25 30 35 40 50 55 60 65 70 75 80 90 100. low load heatflow (M J/s) -2 0 2.7 5.46 9 13.78 20.8 25.3 30.18 32.98 36.19 38.89 40.98 42.98 45.2. primary pos. (%) 0 20.5 25 30 35 40 50 55 60 65 70 75 80 90 100. high load heatflow (M J/s) -2 0 1.48 3.86 7.98 12.47 20.8 25.3 30.18 32.98 36.19 38.89 40.98 42.98 45.2. Table 2.3: Valve characteristics.. deceleration control (GDC) goes active. The GDC is activated if the load6 on the turbine is lost due to an malfunction. When the high pressurized warm air expands through the compressor the kinetic energy is transformed to mechanical energy by the turbine blades and increase the speed of the compressor, thus if the air and heat flow through the turbine is not controlled the compressor would accelerate rapidly. The heat flow value can be derived from the fuel gas valves characteristics when a certain percentage opening generates a certain heat flow. The characteristics of the gas fuel valves can be seen in Table 2.3. The valve characteristics is used in the control program of the turbine (that is, in the SIMATIC system) and also in the SIMIT model to obtain the heat flow value. The heat flow now expands and continues through the power turbine. 2.10.3. Power turbine. Because the exhaust pressure is lower than the pressure in the combustion chamber the warm air now expands further through the turbine blades. The energy of the heat flow is once again transformed from kinetic energy to mechanical energy thus the speed of the power turbine increase in correlation to the heat flow value. The power turbine has an inertia which has to be conquered in order for the power turbine to start accelerating. As the power turbine is now turning the only thing missing is the actual load which can be a generator or a mechanical drive. Usually the mechanical drive application is a compressor used for compressing gas in pipelines, but there is also mechanical drives, as mentioned 6 The load is the equipment which the turbine drives, such as a water jet in a boat (this is not entirely accurate since it does not drive the water jet directly, rather it uses something called a mechanical drive in between)..

(32) 2.11. Turbine regulators. 19. before, connected to water jet propulsion systems like the Stena Carisma ferry ¨ over Oresund.. 2.11. Turbine regulators. The regulators role is to ensure that the turbine never reach a damageable operation mode. In normal operation the following regulators are used, 1. STC 2. NGGL 3. SC 4. T7L The other controllers are used to monitor that this happens in a controlled way. What the different regulators monitor can be found under the respective regulator heading in the text bellow. These regulators are, 1. STC - starting control 2. NGGL - gas generator speed limiter 3. SC - speed controller 4. T7L- exhaust average temperature limiter 5. T7Li - exhaust inner temperature limiter 6. MPC - maximum servo position control 7. GAC - gas generator acceleration control 8. GDC - gas generator deceleration control 9. PAC - power turbine acceleration control 10. LLD - loss of load detection 2.11.1. STC - starting control. In order to accelerate the gas generator at a limited rate, the starting control produces a set point for the desired heat flow as a function of time. It thereby prevents too rapid acceleration and thermal stress of the turbine. The set points is ramped from ignition level with a certain speed. The STC function controls the gas fuel servos until the NGGL function takes over. 2.11.2. NGGL - gas generator speed limiter. The NGGL controls the gas generator speed from 5600rpm and up to a certain speed where the speed controller takes over. It also controls that the gas generator does not exceed maximum allowed speed. When the gas generator speed is more than 5600rpm the set point is ramped with a max setting of 40rpm/s. The set point has no manual mode and the operator is not able to change it..

(33) 20. 2.11.3. SC - speed controller. The speed controller takes over at minimum speed of the power turbine at 3250rpm. The set point to the controller is set by the operator in automatic mode or received from the compressor performance controllers. This controller is normally in operation until full load is achieved when T7L (or NGGL) takes over. The feedback to the speed controller is the power turbine speed. The SC controller also makes sure that the power turbine maintains the correct speed. This to ensure that the correct flow and pressure in the pipelines are maintained. 2.11.4. T7L - exhaust average temperature limiter. T7L controller monitors the exhaust temperature so that the temperature does not get to high and damages the turbine. As the load increase the exhaust temperature increase. The T7L controller limits the exhaust temperature which is the normal maximum load limiter. The set point is a function of ambient temperature, ambient humidity, compressor delivery pressure, exhaust gas pressure and compressor inlet pressure. If the operator selects peak load the set point is automatically adjusted to a higher value. The feedback to the T7L controller is the turbine exhaust average temperature. In an ideal world it should be sufficient with these controllers but in the real world it is also necessary to make sure that other operating modes which is damageable in the long run never occurs. This is why there are six additional controllers. 2.11.5. T7Li - exhaust inner temperature limiter. The T7Li controller monitors the inner temperature so that the temperature does not get to high and damage the turbine. T7Li limits the inner exhaust temperature. This protects the turbine from high exhaust temperature if the combustion chamber bypasses malfunctions. 2.11.6. MPC - maximum servo position control. MPC limits the maximum fuel input. The operator sets the set point in M J/s. Normally the set point corresponds to more than 100 per cent load. MPC is as mentioned earlier not used at normal operation but the operator can manually limit the maximum amount of fuel fed to the combustion chamber. It is also used as backup control upon feedback error. The error freezes the actual desired heat flow signal and it becomes the set point for the MPC controller. 2.11.7. GAC - gas generator acceleration control. GAC shall prevent the turbine from surging and from transient over temperatures in the gas generator during loading. The set point is a function of normalized gas generator speed. The operator is not able to change the set point. To avoid overheating and compressor surge, there is an upper limit of the fuel flow, set by the actual normalized compressor speed. To prevent damage on the engine in mechanical drive applications there is a loading limitation on compressor discharge pressure increase, as a function of.

(34) 2.12. Automated start of turbine. 21. power turbine speed variation. The register is valid for all matching options; the points in between are linear interpolated. 2.11.8. GDC - gas generator deceleration control. To avoid flame out, there is a lower limit of the fuel flow, set by the actual normalized compressor speed. This is also valid for power generation. It is also necessary to increase the GDC level for mechanical drive applications. It is increased with required fuel flow to match the base load at minimum speed, after that the minimum speed has been reached. 2.11.9. PAC - power turbine acceleration control. In order to accelerate the power turbine at a limited rate, the power turbine acceleration control limits the set point for the desired heat flow as a function of power turbine acceleration. It thereby prevents too rapid acceleration and thermal stress of the power turbine. The set point is fixed during start up and put aside during operation. The feedback to the PAC limiter is the power turbine speed. 2.11.10. LLD - loss of load detection. The function of the loss of load detection is to sense the power turbine speed value, and calculate the rate of change over one sample. If it exceeds a certain level the fuel level is set to GDC level at maximum speed and BV2 is opened to brake the gas generator speed/load.. 2.12. Automated start of turbine. Because of the complexity of the turbine different start up sequences is used to ensure that all systems are started and set to their operation levels. There are three different sequences which a mechanical drive turbine has to go through before it is up and running. 2.12.1. Unit sequence. The unit sequence is a start/ stop sequence with 26 steps. The main purpose of this sequence is to start up different systems: such as lube oil, ventilation etc. Table 2.4 shows the steps included in the sequence. Some of the steps are enclosed in a function group which in turn uses a lot of signals. As an example the lube oil function group has to start two of three pumps, the function group also monitor that the lube oil has the correct temp, pressure and level. 2.12.2. Gas fuel sequence. The gas fuel sequence is used for leakage test of the two gas shut off valves. It also controls that each one of the gas fuel control valves is working properly with different set points which the valve has to reach in a certain time. The sequence also sets the start position for the gas fuel valves. The gas fuel sequence includes nine steps. Table 2.5 shows the complete gas fuel sequence..

(35) 22. Unit Sequence (step) Start Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Step 7 Step 8 Step 9 Step 10 Step 11 Step 12 Step 13 Step 14 Step 15 Step 16 Step 17 Step 18 Step 19 Step 20 Step 21 Step 22 Step 23 Step 24 End. Type off description Start of unit sequence Start preparation FG Cooling water on Lube oil FG on Ventilation FG on Reset trip system Prepare compressor Jump to step 9 if trip system reset Reset trip system Compressor piping pressurized Start turbine sequence, continue at turbine in service Spare Spare Unit in service until ordered off Start preparation FG off Spare Stop gas turbine Stop compressor Deactivate turbine and compressor sequence Unit standby Compressor unprepared Deactivate ventilation Deactivate lube oil Deactivate water cooling Spare End of unit sequence. Table 2.4: The unit sequence which starts up turbine.. Gas fuel sequence (step) Start Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Step 7 Step 8 Step 9 Step 10 End. Type off description Start of gas fuel sequence Primary fuel gas control valve check Main fuel gas control valve check Start position of fuel valves check Ventialtion position check Isolation valve leak test Open shut off valve ignition burner 6 Start position check Main ignition Gas in operation Close isolation valve End of gas fuel sequence. Table 2.5: Gas fuel sequence..

(36) 2.12. 2.12.3. Automated start of turbine. 23. Turbine sequence. This sequence initiates the purging of the turbine. The turbine needs to do a purging before start to ensure that there is no gas trapped inside it. The sequence is also used for accelerating the turbine with help of the start motor after ignition. After 5400rpm the start motor is disengaged and the turbine is now accelerating by itself, by controlling the gas fuel valves. This sequence also monitor when the ignition starts and ignites the fuel gas by looking at pilot flame and main flame indicators. The turbine sequence includes nine steps. Table 2.6 displays a complete list of all the steps included in the turbine sequence. Turbine sequence (step) Start Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Step 7 End. Type off description Start purge FG, fuel prep FG, stop cooling Start pilot ignition Start startmotor, main ignition, stop purge Acclerate with startmotor, start emergency lube oil, stop pilot ignition Acclerate without start motor, stop start motor Turbine in service Stop gas turbine, flame out, stop fuel stop emergency lube oil, start cooling Reset turbine sequence End of turbine sequence Table 2.6: Turbine sequence.. 2.12.4. A start of the turbine using the sequences. In the start of the gas turbine the unit sequence is activated first, the sequence executes each step when the transition criteria are fulfilled. When the sequence enter step 10, ventilation and lube oil systems are activated and running, the compressor is ready for start. The trip system is also reset and operative. Now the turbine sequence starts at step 1. This step also starts the gas fuel sequence which runs through the valve check and leakage test. At the same time the compressor turbine has purged the turbine for 75 seconds at 2300rpm and also increased the speed to 2600rpm which is the speed of ignition. Pilot ignition is initiated and the compressor turbine accelerates with help of the start motor until 5400rpm where the start motor is disengaged, in the mean time the main ignition also has been activated. The turbine exhaust temperature increases rapidly to 400 degrees centigrade. The gas fuel sequence has now reached step 9 and will maintain this step until a stop is initiated. Now the turbine accelerates by itself only using the gas fuel valves, the turbine sequence now reaches step 5 and the turbine is in service. When the heat flow value is over 17.77M J/s the power turbine starts rotating and accelerates controlled by the turbines ten controllers to a speed of 3250rpm. The unit is now in service and the unit sequence has reached step 13. It is now up to the operator to set the appropriate speed of the power turbine or use the set point set from the compressor PLC..

(37) 24. 2.13. Summary. A short summary, and quick facts list follows. It is not meant to be comprehensive; rather it should be used as a reminder on what the chapter is about. Since the THEORY part is very important to get a firm grasp of the details explained and discussed the reader should feel that he or she is somewhat familiar with the words and concepts in this summary before proceeding. • PROFIBUS is the medium used to send information from and to DP-slaves in the plant. • PROFIBUS connects through the DP interface of a S7 CPU module. • S7 and PROFIBUS is a distributed system built on modern network technologies. • A S7 rack (UR2) typically consists of PS, CPU and CP modules. • The CPU module holds two DP and one MPI interface (shared with one of the DP interfaces). • The CP module communicates via Ethernet (fiber optics or electrical signals). • The CP module handles communication with OS and ES stations. • There are two fundamental types of building blocks in the CFC-editor, fail-safe and non fail-safe. • DP slaves controls the process objects (such as motors and sensors) and sends the information through the DP interface (cables) to the S7 PLC. • Each signal in the PCS7 system have a unique address’ depending on the DP-slave address. • Each unique address has a signal name alias to make it easier looking up and working with signals rather then using the address’. • The engineer can program the CPU from both the MPI and Ethernet interface depending on the situation. • The SIMBA Pro card holds two PROFIBUS interfaces which can be directly connected to the S7 CPU’s DP interfaces. • The SIMIT simulation system is a real time system and the GUI is very similar to Mathworks Simulink. • SIMIT uses SIMBA Pro and the PCI-card through a software interface to communicate to a S7 PLC..

(38) 3 DECIDING THE SIMULATOR SETUP. 3. 25. DECIDING THE SIMULATOR SETUP. The following chapter describes how the simulator was developed. This includes initial analysis of what system and solution to use and how to build the simulator itself both soft- and hardware wise.. 3.1. Different solutions. The first steps of the initial analysis was to devise what kind of solution to use for the simulator. A number of conditions had to be met, • The investment costs had to be reasonable. • The simulator hardware had to be fast enough to be able to simulate a gas turbine. • PROFIBUS communication between the simulator and the turbine PLC boxes should be simulated if possible. • It should be easy to modify and develop in future engineering projects. This thesis revolves around the GT10C gas turbine, but since there is a need to extend it to other models, one of perquisites would be to make the simulator easy to modify and re-engineer when needed. Each delivered turbine comes with “options”, that is, specific parts which the customer decides. This makes each turbine unique thus the simulator should be able to be modified to handle all these different “options” as they are ordered by the customer. Therfore it should be easy to understand and change the simulation system itself, although the basic knowledge of automatic control and the SIMATIC system should be known. If the PROFIBUS communication between the PLC and the simulator should be tested, the simulator cannot be in the same PLC as the control program. As it is now a test can be done using the program in the PLC to try out different parts of the control system. But since this is only local, the communication in the cables will not be tested, thus, propagation time, delay and other factors will be left out of the test making the results inconclusive compared to a real test of the control program against a turbine. If the PROFIBUS communication could be included, somehow, all the important PROFIBUS factors mentioned above could be taken into account to check if the control program is feasible and also making the simulator more accurate. Making sure that the hardware used for the simulator is fast enough to handle all the signals is also an important factor. Although, it is very difficult to conclude if the simulator setup finally chosen will be able to handle the load done by the control program, therfore, one have to do an estimation if it is possible. Another important feature of the simulator is to be able to use the original OS pictures which the engineers at site uses to control an actual turbine with. That is, it is not just enough to simulate the signals the control program excepts. It’s also important to be able to use these operating pictures to “control” the simulator as one does with a turbine. Thus, if both the turbine and the simulator.

(39) 26. is seen as two black boxes the engineers should be able to “switch” these and the person operating the turbine should notice no difference at all. Initially there were discussions between four different solutions (as the supervisor of this thesis suggested). These were devised before the actual thesis work begun, thus it was not known if they were possible to implement or not; which is the first thing this thesis will discuss. The fifth solution was developed at a later stage after tips by SIMATIC consultants at Siemens. 3.1.1. Solution I - PLC—PLC. The first solution involved two PLC’s connected to each other via the proper interfaces. The first S7 PLC is the turbine PLC where the control automation program is located. The second one holds the actual simulator of the turbine. Therfore, the simulator would be built in the same environment as the turbine control program by using SIMATIC tools. A few questions involving this idea could be asked, • Can there be two masters on the same buss (cable)? • Cost of having the simulator in another PLC • Can the S7 PLC handle a simulation program in respect to memory available and the speed of the internal CPU of the PLC itself? The cost of another PLC is a major disadvantage. Since the PLC’s are designed to work in rugged industrial conditions they are more expensive. A PLC costs somewhere around 100KSEK and would thus result in large expenses. One could argue, however, that the PLC being used to develop the simulator software latter could be used in a turbine project where it is actually needed, that is; reused. Thus, just pushing back the investment cost to an earlier date than needed for an actual turbine project (which would lie forward in time). If the simulator is to be sold to a third party (as a product) the expense of the entire setup cost would be to large if a dedicated PLC is to be used for the simulation. After some more research into this solution the authors of this thesis came to the conclusion that it is not feasible. This is mainly due to one single reason; one have to change the control program itself. Adding and removing features from the control program would be dangerous and could cause unnecessary confusion. Obviously, simulating the turbine without changing the control program is the only solution accepted (that is, if there is no other possible ones, but since there are this condition can be set). To bypass this, a possible fix could be to somehow connect the S7 PLC’s to a PC and program a software which would act as a “switch” and change the packets being sent and reroute them to the simulator and the other way around. This is certainly possible but would take extensive time to implement, surpassing well over 20 weeks, which is the time frame that the simulator should be developed within. Thus this solution was discarded at an early stage. See Figure 3.11 for an schematic of this solution..

(40) 3.1. Different solutions. 27. Turbine Control System. CP. DP. S7. PSU. CP. PSU. S7. DP. Cable. Simulator. Figure 3.11: Solution I, PLC to PLC communication (simplified schematic). 3.1.2. Solution II - Simulator and control system in same PLC. • Would both the control program and turbine program fit? • Is the PLC fast enough to handle both programs at once? • Would the solution mirror an actual turbine in real life since no communication on physical mediums is used. Certainly, from an economic perspective this solution would be the best; to use the same PLC for both the turbine control system and the simulator itself would result in no direct investment costs for extra PLC’s. In reality, though, this is not the case. The control program and the simulator program would require extra memory. And because the PLC used for the control program itself has a limit on how large memory cards it can handle one have to invest in a PLC that can handle larger memory. This way this solution would actually result in the need to invest in more expensive PLC’s. Also, the PLC can not be reused in a latter turbine project because it can handle more memory than needed (the customer would not accept investing in a better PLC than needed, creating a more expensive turbine). Finally, this solution excludes any PROFIBUS communication. This makes the simulation less real life like and non accurate. 3.1.3. Solution III - PLC—PC/C/C++ (Java). The questions that should be discussed concerning this solution is, • What kind of PC would be needed, how fast? • Is there a possibility (in reasonable time) to make a gateway between Simulink and the simulator? • How should the PROFIBUS network, connected to the simulator PLC, be interfaced to the PC? The third alternative, using a PLC to communicate with the simulator on a normal PC would require minimal investment. An ordinary PC have to be bought, nothing over the top; today’s PC’s are high performance work tools certainly surpassing even the processor power of a SIMATIC PLC. Thus creating a simulator program that could respond in adequate time to the PLC software would be a non-trivial problem..

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