PHASE-SHIFT SHIFT TRANSFORMER WITH IMPROVED CHARACTERISTICS

Transcription

1 PHASE-SHIFT SHIFT TRANSFORMER ITH IMPROVED CHARACTERISTICS Mihai TIRSU, PhD 1, Vladimir BERZAN, dr. 1, Lev CALININ, PhD 1, Dmitrii ZAITEV PhD 1 1 Institute of Power Engineering of Academy of Sciences of Moldova, Chisinau, Reublic of Moldova REZUMAT. Transformatoarele de reglare a decalajului de fază (TRDF) sunt comonente cruciale în luta ce se desfăşoară entru îmbunătăţirea eficienţei reţelei de curent alternativ şi eliminării congestiilor. Creşterea ermanentă a energiei electrice transortate aduce liniile la valoarea lor de limită, majorând riscul stabilităţii reţelei. TRDF sunt mijloace cost- eficiente entru a soluţiona controlul sigur şi eficient al fluxului de utere în liniile electrice de transort suraîncărcate. În această lucrare se rezintă o soluţie tehnică inovativă de realizare a instalaţiei de reglare a decalajului de fază Cuvinte cheie: PST, transformator de reglare a decalajului de fază, FACTS controler. ABSTRACT. Phase shifting transformers (PST) are crucial comonents in the ongoing strive for r imroved AC network efficiency and congestion elimination. Increasing amounts of transmitted energy ush the networks to the limit, increasing the risk of network instability. PSTs are a cost-effective means to ensure reliable and efficient ower flow control in overloaded transmission lines. In this aer, is resented a new PST design which is more cost-efficient technical solution. Keywords: PST, hase shift transformer, FACTS controllers 1. INTRODUCTION Imroved system oerating erformance and efficiency PSTs allow to control the ower flow in the transmission grid indeendently of the generation [1]. Total ower flow is influenced by modifying the load share of arallel lines. System reliability is imroved by mitigation of ost-contingency overloads and of unwanted ower transfer. By balancing the ower flow in the network and otimizing the electrical ower flow, grid owners can minimize the electrical losses in their system. On the other hand, tend to increase the share of renewable sources in the energy balance involves the need to use secialized euiment to solve roblems of bottlenecks and distribution. Euiment such as can serve hase-shift transformers and other euiment in this class. However, these are enormously exensive. Therefore, this issue is dedicated to a large number of scientific articles, authored with scientists from around the world. In addition to the ower unit has articular imortance and ower electronics used to change the hase shift. The hase shift installations, as rule, are realized on base of technical solution called Marcereau Connection [],[3],[4]. Installation based on this technical solution has rated ower of.1 higher than transmitted. This aer roosed an innovative technical solution of PST realization, which allows reducing rated ower of installation u to 1.61 comare to transmitted ower, what is about 33% less than traditional technical solution. At the same time, is roosed also an innovative technical solution for ower key system what connect in stes selected hase shift. DELTA/HEXAGON SCHEME OF PST Institute of Power Engineering of Academy of Sciences of Moldova has a large exerience in the field of elaboration of ower flow control euiment in electrical transort lines. Among these is the hase shift transformer (PST). As rule, PST consists of two transformers: exciting transformer and boosting transformer. Technical solution roosed in this aer also consists from two transformers (so called two-core installation). General scheme is resented on fig.1. From fig.1 it can be seen what the roosed technical solution is kind of hexagon (delta scheme). This kind of solution is also well used in ractice []. Excitation transformer is marked with index, and the boosting transformer is marked with index. Excitation transformer consists from 4 windings. Primary winding is marked with index and is consecutive connected 1 with winding of another transformer marked with 3. Relation between these windings is selected such to rovide a hase shift of 30 degrees than voltage on winding is missing. The secondary winding is Buletinul AGIR nr. 1/01 ianuarie-martie 1 Buletinul AGIR nr. 3/01 iunie-august 43

2 ORLD ORLD ENERGY ENERGY SYSTEM SYSTEM CONFERENCE CONFERENCE ESC - ESC 01 marked with and voltage and the winding and is divided in two eual windings. The winding constitute / of total constitute only /. At the same time, is rovided with intermediary outut what searate voltage of this winding in two eually arts. 3. COMPUTATION OF INSTALLATION TRANSFORMERS PARAMETERS In order to get ractical aroval of roosed technical solution was manufactured a samle of PST with rated ower of 10k and inut voltage 380V. For comutation of installation characteristics (transformers arameters) were established maximal arameters of all windings. Maximal load current is 1A. Obtained results are resented in table 1. Table 1 Maximal windings arameters of excitation and boosting transformers for roosed solution resented on fig U max, V 33 18, 6 13,8 6,8 13,4 I max, A.,, 1, 1 Fig.1. General scheme of technical solution of PST realization Boosting transformer is comosed from two windings: rimary winding marked as 1 and secondary winding, which is formed from two eually windings marked resectively as and ". The summary voltage of these two windings is eually to voltage of winding. 3 Inut voltage is alied at tas marked as U S and the outut voltage is taken across tas marked U r. Generally, they can be changed with the lace, but in this case hase shift will have negative values. Using arameters resented in table 1 we can calculate the rated ower of each winding, and as result the installation rated ower. Rated ower of boosting transformer searated on windings: S = 6.8. = rated ower of rimary 1 winding of boosting transformer; S = = rated ower of secondary windings of boosting transformer; S + S 1 S = = rated ower of boosting transformer; S = 33. = rated ower of rimary 1 winding of excitation transformer; S = 6. = 448.4, S = 18.. = , S 3 = = rated ower of secondary windings of excitation transformer. S + S + S + S 1 3 S = =. - rated ower of excitation transformer. S = S + S = rated ower of installation; PST Sr = U r Ir = 6. 1 = 18 - transmitted ower by installation; SPST = relation between rated ower of Sr installation and transmitted ower. Buletinul AGIR nr. 3/01 iunie-august 44 Buletinul AGIR nr. 3/01 iunie-august

3 PHASE-SHIFT TRANSFO RMER ITH IMPROVED CHARACTERISTICS The last relation is very imortant because show the erformance of roosed technical solution in comarison with traditional solution maintained the same arameters. This index can be imroved if we will use a caacitor connected in arallel with inut and outut of installation how it is shown in fig.1. In our case was selected a caacitor of 0 mkf. In this case we reduced this index u to 0.3. But for each case searately may be selected a caacitor deends of rated ower of installation and maximal hase shift and obtains a cost-efficient solution. 4. POER ELECTRONIC MODULE As rule, necessary hase shift selection is done by hel of mechanical ta. But, in modern conditions, then level of network integration is constantly growing it is reuest a more and more flexibility. This means a more uickly reaction (answer) of these installations to network fluctuations. For this reason, more freuently the mechanical switchers are relaced by ower electronic keys. Deending on alied switching scheme and realization scheme of installation the number of key are different. The rice of ower electronic keys is also different in function of voltage level on which they work. The technical solution roosed for realization of electronic commutation circuit allows reducing the cost with about 0% and additional reduces the level working voltage. The develoed scheme is resented on fig.. U sr C I c Us I s 3 I 3 I r a I 1 Ur a U r a I r a I c C ai 1 a I s a U s 1 1 U U I 1 ai r au r ai s ai c au s C Fig.. General scheme of ower electronic module On fig. is shown the extended scheme of electronic keys module which rovide commutation of needed hase shift. The advantage of electronic module consists in using of diodes instead of controlled keys, what allow reducing the cost of whole ower electronic module. On the other hand, this allows simlifying the control algorithm of ower electronic module. For this scheme was develoed control algorithm of hase shift in stes, each ste has a value of 4, degree (fig.3). Buletinul AGIR nr. 1/01 ianuarie-martie 3 Buletinul AGIR nr. 3/01 iunie-august 4

4 ORLD ORLD ENERGY ENERGY SYSTEM SYSTEM CONFERENCE CONFERENCE ESC - ESC 01 Psc, si Fig.4. Losses in installation for idle (first) and short-circuit modes (second) in function of hase shift Fig.3. ork diagram of ower electronic module From fig.3 it can be seen, what for any osition there is connected four keys. Number of stes is 14. Ste consists 4, degree and this value is selected in order to not exceed the allowed value of harmonics (3%) in electrical energy transort lines. From this figure it can be seen that losses in installation for both modes not exceed value of,% which is very well. For short-circuit the current mode was maintained at constant value of 1A. For additional verification was develoed both mathematical and simulink (MATLAB) models of installation. Result comarisons are resented on fig... TEST OF PST POER MODULE In order to verify correctness of roosed technical solution was manufactured a samle of 10k for which were done verification tests. During tests the ower key were relaced by mechanical switchers. The installation was verified for both idle mode and shortcircuit mode. Obtained characteristics a resented on fig. 4. P, si 4 Buletinul AGIR nr. 3/01 iunie-august 46 Buletinul AGIR nr. 3/01 iunie-august

5 PHASE-SHIFT TRANSFO RMER ITH IMPROVED CHARACTERISTICS 0% in comarison with existing ractically solutions was develoed. The control algorithm of ower keys which rovide change of hase shift in range of 0-60 degrees by ste of 4, degree was develoed. BIBLIOGRAPHY Fig.. The analytical and simulated result comarison for roosed solution 6. CONCLUSIONS In aer was roosed an innovative technical solution of two core PST realization, which allowing decrease the rated ower with about 33% in comarison with classical solution Marcereau Connection. The ower electronic module of hase shift switching which has a reduced rated ower with about [1] htt://www0.abb.com/global/scot/scot.nsf/veritydislay/ee e6e01c1ea ce04/$file/pst_low%0res.df. [] Luiz A. C. Loes, Geza Joos, Boon-Teck Ooi, A PM Quadrature Booster Phase-Shifter For FACTS, IEEE Transactions on Power Delivery, Vol.11, No.4, October 16. [3] D.Perco, Secial Transformer ill Control Power Flow between Ontario-Manitoba, Electrical News and Engineering, July, 1. [4] S.Nyati, J.Kaenman, N.Mohan, A.Edris, Design Issues For a Single Core Transformer Thyristor Controlled Phase-Angle Regulator, IEEE Transactions on Power Delivery, Vol.10, No.4, October 1 [] Michael J. Thomson, Hank Miller and John Burger., Innovative ower flow regulating ta-changer control installed on multile hase-shifting transformers, 008 Doble Engineering Comany th Annual International Doble Client Conference. About the authors Calinin Lev Pavel kalinin_lev@ie.asm.md He graduated from the Odessa Polytechnic Institute (Ukraine) in163. In 18 he defended his thesis for the degree of candidate of technical sciences in the NETI Novosibirsk (Russia). Research of interests related to the alication of FACTS controllers in ower systems. Zaitev Dmitrii Alexandru zaiats@ie.asm.md He graduated from the Polytechnic Institute of Chisinau (Moldova) in18, defended his thesis for the degree of candidate of technical sciences in 000 at the Institute of Energy Sciences of the RM. His research interests lie in the field of study modes of ower systems containing flexible interconnections. He is the head of "Electro-technical euiment and ower electronics Laboratory. Tirsu Mihai Stefan tirsu.mihai@gmail.com.0.1. He graduated from the Technical University of Moldova in 14, secialty "Automation and control of technical systems". In 003 he defended his thesis for the degree of candidate of technical sciences. He is deuty director of the Institute of Power Engineering of the Academy of Sciences of Moldova. Basic research in the field of transort networks control, diagnostics of high-voltage euiment, ower electronics, etc. Berzan Vladimir Petru berzan@ie.asm.md He graduated from the Technical University of Moldova in 11, secialty "Electrical machines and aaratus systems", activity at the Institute of Energy of ASM as an engineer, scientist, Head of Laboratory, Deuty Director for Science, Director. PhD thesis was suorted in 11 the State Technical Universityof Saint Petersburg (Russia), thesis Ph.D of science in 1 at the Institute of Energy of the ASM. Publications: all-over 1, including atents monograhs -1 and - 1. Buletinul AGIR nr. 1/01 ianuarie-martie Buletinul AGIR nr. 3/01 iunie-august 4

6 ORLD ORLD ENERGY ENERGY SYSTEM SYSTEM CONFERENCE CONFERENCE ESC - ESC 01 6 Buletinul AGIR nr. 3/01 iunie-august 48 Buletinul AGIR nr. 3/01 iunie-august