SIMSEN : A MODULAR SOFTWARE PACKAGE FOR THE ANALYSIS OF POWER NETWORKS AND ELECTRICAL MACHINES

Transcription

1 SIMSEN : A MODULA SOFTWAE PACKAGE FO THE ANALYSIS OF POWE NETWOKS AND ELECTICAL MACHINES Dr A. Sapin, Prof. Dr J.J. Simond Swiss Federal Institte of Technology Electrical Engineering Dept CH1015 EcblensLasanne (Switzerland) 1. Abstract This paper deals with a software package for the nmerical analysis in transient and steadystate modes of power electrical networks or variable speed drives with arbitrary topologies. The package is composed of a series of nits, each representing a specific cell in the network : voltage spply, electrical machine, mechanical system, transmission line, circitbreaker, phase shifting transformer, static converter with control and command organ, reglator, etc. SIMSEN is highly flexible and efficient. It is implanted on microcompter or on workstation. The network or the variable speed drive to be simlated is assembled sing a graphic inpt interface by adeqatly choosing and linking the bilding nits, so as to flfill a desired topology. An existing system may be easily extended or modified. A simple procedre can be sed in order to define a new nit or to modify an existing one. The initial conditions of operation can be partly or entirely specified by the ser. A transient mode of operation may inclde several sccessive pertrbations. The simlation reslts are displayed throgh an efficient graphic interface. An original featre of SIMSEN is its ability to analyse electrical networks involving semicondctors (diodes rectifiers, thyristor or GTO crrent converters, voltage inverters, etc.). Ths, systems having a complex strctre can be simlated. Practical examples of applications to sch systems constitte the main part of this paper : constant or variable speed grops involving indction and synchronos machines, HVDC networks, reactive power static converter SVC. These examples show how SIMSEN can be sed for an optimized design of complex networks. 2. Introdction The nmerical simlation is an essential tool for the conception, design and exploitation of power networks or systems. An efficient nmerical software package mst have the following properties : high modelling level, wide application field, precision, qickness, flexibility and conviviality. Voltage spply, line, transformer, circitbreaker, load MS 3 ~ MAS 3 ~ Machines with mechanical systems diodes rectifier, crrent converter, crrent variator crrent inverter, voltage inverter M 1

2 Fig. 1 List of available nits reglators, singlephase nits The modlar software package SIMSEN for the nmerical simlation in transient or steadystate modes of power networks and electrical machines joins these whole properties. Its two main targets are on the one hand the application to the power electrical networks with arbitrary topologies, involving semicondctors nits [1] and reglators [2], and on the other hand, the possibility to analyse rapid transient phenomena [3] (shortcircits, onoff switching of circitbreakers, starting of motors, semicondctor commtations). Another featre of SIMSEN is its open strctre which allows newly developped nits to be easily implemented. It is ths possible to widen the applications field frthermore in the ftre. In comparison with two well known simlation packages, EMTP [4] and EUOSTAG [5], the following remarks can be formlated. EMTP is sitable for the simlation of rapid transient phenomena in complex electrical networks, also in those having elements with semicondctors. However, in order to define his network, the EMTP ser mst start with the basic elements (resistance, condenser, diodes, thyristors, etc.) which, depending on the complexity of the system stdied, may become long and tedios. EUOSTAG is a very modern system, highly interactive and based on a reliable macrolangage sing an atomatic and variable stepsize managed by the dynamic behavior of the power system. The fact that the EUOSTAG macrolangage does'nt contain elements with semicondctors represents a restriction in relation with the possible field of applications. modified or extended by adding or retrieving nits. The main devices of SIMSEN are shown in figre 2. Each of the networks nits shown in figre 1 incldes a set of differential eqations based on the nits modelling. An original algorithm has been developed in order to generate atomatically the main set of differential eqations, written in phase vales and resolved by nmerical integrations. The soltion takes into accont the whole interaction between the different nits of the power system. The integration system works with a variable stepsize [6]. This method allows to detect exactly all the events in time as the onoff switching of a semicondctor [7] or the onoff switching of a phase of a circitbreaker. The strctre of SIMSEN allows newly developed nits to be easily implemented, an existing nit can also be modified easily. The only restriction on the size of the power network to simlate is prescribed by the available memory of the microcompter. SIMSEN administrates its memory with dynamic variables and can, in this way, simlate large networks size. TOPOLOGY SIMSEN PAAMETES 3. Strctre and properties of SIMSEN SIMSEN is based on a modlar strctre which enables the nmerical simlation of the behavior in transient or steadystate modes of a power network with an arbitrary topology. The ser bilds its power network by choosing and linking adeqately the nits shown in figre 1 in order to create the desired TOPOLOGY. This operation is made by sing a graphical inpt interface. Then, the ser has to introdce the PAAMETES of each nit. The initial conditions of operation can be partly or entirely specified by the ser. The SIMULATION of a transient mode can involve a lot of sccessive pertrbations. All the simlation reslts are displayed throgh an efficient graphic OUTPUT interface. A specified network topology can be easily 2 SIMULATION 4. Application examples OUTPUT Fig. 2 Main devices of SIMSEN In addition to the examples shown below, other applications of SIMSEN are described in [8, 9]. Example 1 : HVDC transmission with reactive power static converter The system stdied is shown in figre 3. It consists of a synchronos machine MS1 with its mechanical system ME1. The voltage and the speed of

3 this machine are tned by the reglators U1 and N1. The stator of this machine is connected to a HVDC transmission constitted by 4 crrent converters CONV1 CONV4 and 4 transformers T1 T4 with phase shifting Yy0 and Yd11. Both AC sides of the transmission are eqipped with filters C1 C4 for the elimination of the 12 th and the 24 th harmonics. The capacitor effect of the DC line is taken into accont h by the condenser CCC1. The DC transmission line is tned T1 T2 G1 L2 L1! cons C 1 C 2 T5! CONV1 i1 CONV2 C5 DC P1 CCC1 i D C p cons C6 CONV4 Q1 CONV3 i2 C7 C 3 C 4 T3 T4 T6 VA1 ME1 MS1 N 1 n by 2 crrent reglators i1 and i2, a power reglator P1 and an extingishing angle reglator G1 for the inverters CONV1 and CONV2. At the inverters side, the voltage is tned by a reactive power static converter. It is constitted by 2 transformers T5 T6, 3 filters C5 C7 for the elimination of the 5 th, 7 th, 11 th and 13 th U1 n cons harmonics and the prodction of reactive power, a crrent variator VA1 and a reactive power reglator Q1. All the system is connected to the AC network S1 throgh the line L1. This example is an academical one in order to show the ability of SIMSEN to simlate complex networks. The aim of the stdy is to analyse the dynamic behavior of the system after a sdden change of the power set vale p cons of the power reglator P1. In this simlation, the extingishing angle set vale of the reglator G1 keep a constant vale of 30. Figres 4 to 11 show the reslts of the simlation. All these reslts are referred to the rating vales of the synchronos machine MS1. Therefore SIMSEN is a sitable tool for the determination of optimal reglators and filters parameters relative to a complex strctre as presented in figre 3. S1 Fig.3 Power network stdied in example 1 : HVDC transmission with reactive power static converter (SVC) Fig. 4 Power set vale "pcons" of the power reglator P1 and power "pg" of the HVDC transmission Fig.5 Voltage "DC" and crrent "idc" in the DC link of the HDVC transmission 3

4 Fig. 6 Electromagnetic torqe "tem" of the synchronos machine MS1 Fig. 9 Firing angle "!" of the crrent variator VA1 Fig. 7 Voltage set vale "cons" and voltage "mg" of the synchronos machine MS1 Fig. 10 eactive power "Q1" of the transformer T5 (prodced by the SVC) Fig. 8 Voltage set vale "cons" and voltage "f" of the transformer T5 (SVC) Example 2 : Static slipenergy recovery drive with indction machine and cycloconverter Fig. 11 Active power "P1" and reactive power "Q1" of the AC network S1 4

5 S1 T1 L1 i3 T2 T3 T4 C5 i2 C6 C4 SU1 i cons MAS1 N1 C3 MAS P n m i1 ME1 ME2 n cons C2 C1 is connected to the AC network S1 by 4 transformers T1 T4. The rotor phase crrents are tned by 3 crrent reglators i1 i3. The crrent set vale of these 3 reglators are given by the stator crrents reglator SU1. The stategy of reglation is based on the voltage stator oriented method and depends on the rotor position. The aim of this method is to separate the active and reactive stator crrents. So, it is possible to garantee a high power factor for this electrical drive. The speed of the machine is tned by the speed reglator N1. The indction machine MAS1 drives the pmp P. Figres 13 to 18 presents reslts of a variation of the speed from 0.9 [p..] to 1.1 [p..] with a constant mechanical torqe of 0.5 [p..]. All the reslts are given in the rating vales of the indction machine MAS1 : 80 MVA, 12.5 kv, 50 Hz, p = 6. Fig.12 Electrical drive stdied in example 2 : Slipenergy recovery drive with indction machine and cycloconverter The system stdied is shown in figre 12. It consists of an indction machine MAS1 with a rotor winding connected to a cycloconverter constitted by 6 crrent converters C1 C6. All the system Fig. 13 Electromagnetic torqe "tem" and speed "nm" of the indction machine MAS1 Fig. 15 Firing angle "!" of the crrent converter C1 Fig. 14 Crrent set vale "icons" and rotor phase crrent "ig" of the indction machine MAS1 Fig. 16 Crrent set vale "idscons" and crrent "idsg" in the d axis of the indction machine (reactive power) 5

6 Fig. 17 Crrent set vale "iqscons" and crrent "iqsg" in the q axis of the indction machine (active power) Fig. 18 Active power "P1" and reactive power "Q1" of the main transformer T1 Example 3 : Shaft train torsional oscillations of large trbogenerators MS1 T1 L1 S1 The system stdied is shown in figre 20. It consists of 4 grops inclding : a synchronos machine MS, a mechanical shaft train ME, a voltage reglator U and a transformer T. The 4 grops are connected to the AC network S1 throgh the line L1. A circitbreaker D1 allows to generate a three phase defalt on the high voltage side of each transformer. The main field satration in the d and q axis of the synchronos machine have been taken into accont as well as the complete shaft train (slip rings, large trbogenerator and 4 trbines) of the mechanical system as represented in figre 19. U1 U2 ME1 MS2 ME2 MS3 T2 T3 D1 [p.] Fd U3 ME3 Fq i [p.] S GEN LP3 LP2 LP1 HP MS4 T4 Fig. 19 Satration of the synchronos machine and shaft train for the mechanical system U4 ME4 Fig. 20 Power network stdied in example 3 : Shaft train torsional oscillations of large trbogenerators The aim of the stdy is to analyse the dynamic behavior of the system with 1 or 4 machines after a onoff switching of the circitbreaker D1. The operating point of the first trbogenerator MS1 is the same in both cases. Figres 21 and 22 show the reslts of the two simlations. All the reslts are given in the rating vales : 1200 MVA, 28.5 kv, 50 Hz, p = 1. 6

7 Fig. 21 Electromagnetic torqe of the synchronos machine MS1 ("tem" : 1 machine, "tem' " : 4 machines) [6] J.J. Simond : "Nachbildng eines Systems as Synchronmaschine, Freqenzmrichter nd Drehstromnetz mit Simlation instationärer Vorgänge". ETZ Archiv, Bd. 10, [7] A. Sapin, J.J. Simond, B. Kawkabani : "Freqency converterfed synchronos machines : Interactive simlation system", ICEM [8] A. Sapin, J.J. Simond, B. Kawkabani : "SIMSEN : a modlar software package for the analysis of power networks and electrical machines", ICEM 94. [9] A. Sapin, J.J. Simond : "SIMSEN : a modlar software package for the analysis of power networks and variable speed drives", EPE Lasanne, Fig. 22 Torsional torqe between the generator and the trbine ("tk"" : 1 machine, "tk"' " : 4 machines) 5. Conclsion A modlar software package for the analysis of power networks and electrical machines SIMSEN has been described. This package is a flexible, convivial and evoltive tool for the conception, design and exploitation of complex power systems with an arbitrary topology inclding also elements with semicondctors. The field of applications of SIMSEN is very wide, the nmerical simlation is possible nder steadystate or transient conditions. A possibility exists for the ser to introdce in a simple manner a new nit or to modify an existing one. 6. eferences [1] H. Bühler : "Convertissers statiqes". Presses polytechniqes romandes, Lasanne [2] H. Bühler : "Electroniqe de réglage et de commande". Traité d'electricité, vol XVI, 1 ère édition, Presses polytechniqes romandes, Lasanne [3] I. M. Canay : "Extended synchronos machine model for the calclation of transient processes and stability", Electr. Mach. a. Electromech. No 2, pp , [4] EMTP le book. Bonneville Power Administration. Portland Oregon [5] EUOSTAG, Software for the Simlation of Power Systems Dynamics. Electricité de France, Tractebel