Research on Application of 36-Pulse Phase-Shifting Transformer to High-Voltage Frequency Converter

Transcription

1 Research on Applicaion of 36-Pulse Phase-Shifing Transformer o High-olage Frequency Converer 1 Jianchao Zhang, Wei Xu, 3 Jun Wang 1, Engineering Training Cener, Shijiazhuang Tiedao Universiy, zhang.jianchao@yahoo.cn *,Corresponding Auhor Universiy of Macau, Jerryxw@live.com 3, School of Mechanical Engineering, Shijiazhuang Tiedao Universiy Absrac The power cell series muli-level high-volage frequency converer is one of presen elecric power elecron area research ho spos. This paper seleced he power uni andem ype srucure o realize he high-pressured frequency conversion, one of is bigges superioriy was he inpu end uses he phase-shifing ransformer o realize inpus he muli-densificaion, hus served he inpu oupu overone small purpose. This paper also sudies phase-shifing ransformer's phase shifing principle emphaically, and designs 36 pulse wave phase-shifing ransformer's relaed parameer, will provide he heory and he compuaion basis for he presen phase-shifing ransformer's design. Therefore, his paper provided he imporan reference and he insrucion for nex high pressure frequency changer's engineering design. Keywords: Phase-Shifing Transformer, High-olage Frequency Converer, Power Uni, Harmonic 1. Inroducion AC variable frequency speed regulaion echnology is a main means of power saving and echnical process improvemen so as o improve he qualiy of producs nowadays. ariable frequency speed regulaion is generally recognized as he mos promising speed regulaion way due o is numerous advanages such as good speed regulaion and sarup performances, high efficiency, high power facor and power saving effec and wide scope of applicaion. Manjrekar e al.[1] invesigae a hybrid mulilevel power conversion sysem ypically suiable for high-performance high-power applicaions. In addiion, performance of a mulilevel curren-regulaed dela modulaor as applied o he single-phase full-bridge IGBT recifier is discussed. A new opology for a hybrid mulilevel inverer is presened,[] which significanly increases he level number of he oupu waveform and hereby dramaically reduces he low-order harmonics and oal harmonic disorion. Rodriguez e al.[3]presen a swiching sraegy for mulilevel cascade inverers, based on he space-vecor heory. This new conrol mehod is an aracive alernaive o he classic mulilevel pulsewidh modulaion echniques. An improved carrier-based SPWM scheme, which is fully suiable for cascaded mulilevel inverer opologies are inroduced.[4] Zhong and Tolber[5] presen a programmed PWM mehod o eliminae specific higher order harmonics of mulilevel converers. Zhou and Wang[7] analyze he relaionship beween space-vecor modulaion and hree-phase carrier-based pulse widh modulaion(pwm). Furhermore, he implemenaions of boh space-vecor modulaion and carrier-based PWM in a closed-loop feedback converer are discussed. ariable frequency speed regulaion echnology has been widely used in low-volage AC moor ransmission field. Due o various reasons, inverer hasn' been widely used in high-volage moor. Using high-volage inverer, high-volage moor can realize sepless speed regulaion and mee he requiremen of producion process for speed conrol of moor. The applicaion of high-volage inverer has imporan meanings for improving he oupu and qualiy of producs, saving energy drasically and reducing he producion cos. As a resource-saving produc, high-volage inverer has inegraed power echnology, ransmission echnology, mecharonics echnology and communicaion inerne echnology. In paricular, by adoping mulipliciy echnology, high-volage inverer has realized significan decrease of inpu and oupu harmonic conens. I will cerainly mee he requiremen of human beings for produc and environmenal proecion in he 1s cenury. Wih he consan developmen of power elecronic echnologies, consan improvemen of producs, deepening of he concep and expansion of he marke, i will show a grea echnical developmen prospec and marke demand. Inernaional Journal of Digial Conen Technology and is Applicaions(JDCTA) olume7,number5,march 013 doi: /jdca.vol7.issue

2 . Applicaion of phase-shifing ransformer in high-volage inverer One of he major advanages of high-volage inverer (Fig.1 shows is srucure) adoping power uni andem-ype mulilevel echnology is he use of phase-shifing ransformer o realize he inpu of mulipliciy echnology so as o decrease inpu harmonic. Phase-shifing ransformer has he following hree funcions: 1. Realize phase deviaion of line volages on he primary side and secondary side so as o eliminae harmonic;. Obain he required line volage on he secondary side hrough ransformaion; 3. Realize elecric isolaion beween recifier and power grid. Wha follows is he research on phase shif principles of phase-shifing ransformer and he design of 36-pulse phase-shifing ransformer. The following assumpions are made for he purpose of clear undersanding: 1. The phase-shifing ransformer is an ideal ransformer wihou he influence of impedance and leakage reacance ec.;. Power elecronic devices such as diode are ideal devices wihou a swich ime ec.; 3. DC side afer recificaion adops LC filering and he filer inducance L is large enough. The direc curren is a consan value. Figure 1. Srucure char of high-volage inverer 139

3 3. Phase shif echnology of dela of phase-shifing ransformer According o differen connecion modes of winding, phase-shifing ransformer can be classified ino and non- ransformers, i.e. he phase of winding line volage on he secondary side of ransformer is one angle ahead or lagging han he winding line volage on is primary side Exended phase-shifing ransformer Fig. shows he winding connecion diagram and phasor diagram of phase-shifing ransformer respecively. The winding on is primary side is sar connecion, wih he number of urns of each winding as N1; each winding on he secondary side is composed of wo coils, wih he number of urns respecively as N and N3. According o he analysis of phasor diagram, he phase-shifing angle of phase-shifing ransformer has he following relaion: Where, ab AB (1) AB and ab respecively refer o phasors of line volages AB and ab on he primary side and secondary side. A B C N1 X Y Z x N N3 a v P v Q AX y b 10 z c BY CZ 30 AB cz 30 by P Figure. Exended Exended phase-shifing ransformer Q ax ab 30 AB The side volage on he primary side AB is used as he reference volage and he phase-shifing angle by which ab is ahead of AB is posiive. To calculae he urns raio of he ransformer, he following can be obained from he riangle composed of Q, by and ab and in he phasor diagram: Q by () sin 30 sin 30 Where, 0 30 ; Q is he effecive volage value of N3 coil; by is he effecive volage value beween b and y. For a hree-phase symmerical sysem, volages by and ax have he same value. Equaion () can be rewrien as: Q ax sin 30 sin 30 (3) The winding facor k on he secondary side can be obained from he equaion above: 140

4 N3 sin 30 Q k N N3 sin 30 ax (4) Similarly, he following can be inferred from he phasor diagram ab by (5) sin10 sin(30 ) Tha is sin(30 ax by ) ab, The urns raio of ransformer is 3 n N N N 3 1 AX (6) ax The following can be obained by subsiuing equaion (6) wih equaion ax, N1 1 n N N3 sin(30 ) AB ab (7) Where, 3 AB AX Boh exremes can be verified. Assuming ha N=0, he winding on he secondary side in Fig. urns ino sar connecion. Thus volages on he secondary side and primary side have he same phase, i.e. =0 ; if N3=0, he winding on he secondary side urns ino riangular connecion. A his ime, =30. Therefore, he phase-shifing angle of phase-shifing ransformer is wihin 0 ~ Non- phase-shifing ransformer Fig.3 shows he winding connecion diagram and phasor diagram of non- phase-shifing ransformer respecively, where he winding on he primary side is sar connecion and he winding connecion order of riangle on he secondary side is opposie o ha of phase-shifing ransformer. I can hus be seen ha ab lags behind AB and is herefore negaive. Similar o he analysis of phase-shifing ransformer, he winding facor k and urns raio n on he secondary side can be obained as follows. k N 3 sin( 30 N N 3 sin( 30 ) ) (8) N1 1 n N N3 sin(30 ) AB ab (9) Where,

5 CZ cz A B N1 X Y x N N3 a AX v P v Q 10 y b AB P AB ax C Z z BY c 30 Q Figure 3. Non- phase-shifing ransformer by ab Table 1. Turns raio of and non- phase-shifing ransformers Phase-shifing angle k n Applicaion Exended Non AB ab 1, 18 and 4-pulse recifiers AB ab 4-pulse recifier AB ab 18-pulse recifier AB ab 1 and 4-pulse recifiers Table 1 shows ypical values of phase-shifing angle and urns raio of muli-pulse recifier when using phase-shifing ransformer wih he wo kinds of connecion above. For 1, 18 and 4-pulse recifiers, he volage raio AB ab is generally, 3 and 4 respecively. The principle of and non- phase-shifing ransformers has been described above and wha follows is specific design calculaion of 36-pulse phase-shifing ransformer Srucural design of 36-pulse phase-shifing ransformer I is known from design requiremens ha he nework volage is 6K 10%, he frequency is 50HZ and he oupu power of inverer is 370KW. Then, he compuaional formula of ransformer capaciy is: S / cos (10) TN P CN CN Where: S TN refers o he ransformer capaciy and P CN refers o he oupu power of ransformer. cos CN refers o he inpu power facor of inverer and refers o he efficiency of inverer. Where, he power facor of inverer is beween 0.8 and 0.85 wih inpu AC reacor. Therefore, cos CN =0.85, =0.9 and P CN =370KW. Then, cos 370 / 0.85/ KA STN PCN / CN 7 Wha's move, he reference value of ransformer capaciy recommended by he inverer manufacurer is ofen 130% of he inverer capaciy based on experience. Tha is, he capaciy of phase-shifing ransformer is 630KA. The compuaional formula of phase-shifing angle of wo adjacen windings is: 60 / N (11) Where, is he phase-shifing angle of wo adjacen windings; N is he number of power unis in series 14

6 This design adops he program of 6 power unis in series. Therefore, he phase-shifing angle of wo adjacen windings in phase-shifing ransformer is: 60 / N 60 / 6 10 (1) Therefore, he phase-shifing angle of inpu ransformer is:+5,+15,+5,-5,-15,-5. The winding on he primary side is pu on he inner side close o he iron core and ha on he secondary side is pu on he mos exernal side. Hea resising and insulaing cable is used beween he winding on he secondary side and phase-shifing winding o connec ino an dela. A recangular winding srucure is adoped on he primary side, in which an air passage for hea dissipaion is insalled in he middle of muliple layers. I is winded wih core limb by copper wire wrapped by Nomex paper wih urn insulaion resising 0 C. The winding on he secondary side is divided ino 18 independen small windings. The capaciy of each small winding is 1/18 of he raed ransformer capaciy. Each phase winding is divided ino hree major groups on average and each major group is designed ino 6 small windings. The phase-shifing angle of each winding is realized hrough differen modes of exernal connecion, i.e. dela, as shown in Fig. and Fig.3. The phase-shifing angle beween adjacen windings is 10 and he sor order of phase-shifing angles of small windings is: The phase-shifing angle of No.1, No.7 and No.13 windings is -5 ; The phase-shifing angle of No., No.8 and No.14 windings is -15 ; The phase-shifing angle of No.3, No.9 and No.15 windings is -5 ; The phase-shifing angle of No.4, No.10 and No.16 windings is +5 ; The phase-shifing angle of No.5, No.11 and No.17 windings is +15 ; The phase-shifing angle of No.6, No.1 and No.18 windings is +5 ; No.1 o No.6 are in one group; No.7 o No.1 are in one group and No.13 o No.18 are in one group. H class insulaion srucure is used among secions and groups for secion fixaion and insulaion. The lead of each secion is drawn forh wih copper bar and secondary winding is winded on primary winding wihou any addiional die, making primary and secondary windings an enirey. 4. Elecromagneic design of 36-pulse phase-shifing ransformer 4.1. Selecion of number of urns of winding The relaional expression of winding facor and urns raio of 36-pulse phase-shifing ransformer is obained from he analysis of equaions (6), (7), (8) and (9). According o he design requiremens, he primary side of ransformer is Y connecion; he inpu line volage is 6000; 18 windings on he secondary side is divided ino 6 major groups and he phase difference of each group is 10. Table shows relevan parameers. 1. Calculaion of he number of urns on he primary side The raed capaciy of phase-shifing ransformer P=630KA; inpu raed volage U 1 =6000; volage of each urn of phase-shifing ransformer e =10. Therefore, he number of urns in sar connecion on he primary side is: W1 U1 e 600. Calculaion of he number of urns on he secondary side The number of urns of winding on he secondary side is analyzed as follows, aking phase-shifing ransformer for example. Table. The relevan parameers of 6 groups of phase shif in phase-shifing ransformer Basic Turns raio Winding winding Connecion mode n facor k facor (1-k) n Phase difference of primary and secondary volages urns Phase-shifing winding facor Kn 143

7 5 Exended Exended Exended Non Non Non Figure 4. Exended + phase-shifing connecion diagram In Fig.4, he number of urns of winding in he secion of phase-shifing ransformer: W =AZ=BX=CY The number of urns of winding in he basic secion of phase-shifing ransformer: W basic =ZX=XY=YZ Moreover, AC=AB=BC=U/ e ; CZ=CY+YZ=AZ+ZX= W + W basic. In ACZ, he following can be obained according o he sine rule: AZ AC sin a sin10 W ( U e ) ; CZ AC sin(60 a) sin10 ( W W ) ( U e ) basic The following can hus be obained, W U sin a sin10 e U Wbasic [sin(60 a) sin a] sin10 (13) e Where, U refers o he line volage on valve side and e refers o he volage of each urn of phase-shifing ransformer. The number of urns in riangular connecion on he secondary side can be obained by subsiuing equaion (13) wih he inpu raed volage U =550 and he volage of each urn of phase-shifing ransformer e =10, as shown in able Deerminaion of winding curren 1.Curren on primary side Raed capaciy of phase-shifing ransformer P=630KA and inpu raed volage U 1 =6000. Therefore, he phase curren in sar connecion on he primary side is: 144

8 3 I1 P / 3U /( ) 61A Table 3. The number of urns in riangular connecion on he secondary side of 36-pulse phase-shifing ransformer (uni: urn) W basic W Curren on secondary side Each small winding on he secondary side is divided ino basic winding and phase-shifing winding. The capaciy of a single small winding is 1/18 of he raed capaciy of ransformer. Therefore, he raed curren I of phase-shifing winding is: I P /18 3U Where, he raed capaciy of phase-shifing ransformer is P=630KA and he raed oupu volage U = I P /18 3U / A The curren relaionship beween basic winding and phase-shifing winding on he secondary side is analyzed hereinafer. The following can be obained a node Z according o he node curren law: I AZ I ZX I YZ 30 Figure 5. Curren phasor diagram a node Z The following can be obained from analysis of Fig.5: 1 I AZ I ZX cos30 As I I I I ; I I I I, herefore AZ BX CY basic ZX XY YZ I 3I (14) basic Magneic poenial balance equaion: IW IbasicWbasic IW 1 1 Subsiue i wih equaion (15): 3I basic W I basic W basic IW 1 1 The following can be obained: Ibasic IW 1 1 ( 3 W Wbasic ) (15) Where, I refers o he curren in he secion of winding on valve side; I basic refers o he curren in he basic secion of winding on valve side; I 1 refers o he phase curren of winding on grid side; W 1 refers o he number of urns of winding on grid side. The curren of basic winding and phase-shifing winding can be obained based on equaions (14) and (15) and he number of urns of 145

9 winding calculaed above, as shown in able 4. Table 4. Curren value on secondary side of 36-pulse phase-shifing ransformer (uni: A) I basic I Conclusion This paper firs analyzes he principle of and non- phase-shifing ransformers and designs 36-pulse phase-shifing ransformer, mainly including he capaciy of phase-shifing ransformer, he calculaion of phase-shifing angle, he design of phase-shifing ransformer and insulaion design, and he calculaion of he number of urns of winding, winding curren, phase-shifing volage and shor-circui impedance of phase-shifing ransformer, which provide basis for he design of phase-shifing ransformer in he fuure. 6. Acknowledgmen This research is suppored by he Naural Science Foundaion of Hebei Province, China (E ) and he Research Foundaion of Educaion Bureau of Hebei Province, China (Q01113). 7. References [1] M.D.Manjrekar,P.K.Seimer,T.A.Lipo. Hybrid mulilevel power conversion sysem: a compeiive soluion for high-power applicaions[j]. IEEE Trans. on Indusry Applicaions, 000,36(3): [] Y.S.Lai,F.S.Shyu. Topology for hybrid mulilevel inverer[j].ieee Proceedings-Elecric Power Applicaions, 00,149(6): [3] Jose Rodriguez,L.Moran,P.Correa,C.Silva. A vecor conrol echnique for medium volage mulilevel inverers[j].ieee Transacions on Indusrial Elecronics, 00,49(4): [4] D.W.Kang,Y.H.Lee,B.S.Suh,C.H.Choi,D.S.Hyun. An improved carrier-based SPWM mehod using leg volage redundancies in generalized cascaded mulilevel inverer opology[j]. IEEE Transacions on Power Elecronics, 003,18(1): [5] D.Zhong, L.M.Tolber,J.N.Chiasson. Harmonic eliminaion for mulilevel converer wih programmed PWM mehod[j].ieee Conference Proceedings of IAS'004,004, [6] JIANG You-hua,CAOYi-long, GONG You-min, A Novel Topology of Hybrid Mulilevel In verer wih Minimum Number of Separaed DC Sources[J]. Journal of Shanghai Universiy(English Ediion), NO,004: [7] Zhou K, Wang D. Relaionship Beween Space-vecor Modulaion and Three-phase Carrier-based PWM A Comprehensive Analysis[J]. IEEE Trans on Indusry Elecronics, 00.49(1): [8] Wang F. Sine-riangle ersus Space-vecor Modulaion for Three-level PWM olage-source Inverers[J]. IEEE Trans on Indusry Applicaions,00,38():