A Novel Three Phase Three Leg AC/AC Converter Using Nine IGBTS

Transcription

1 nineerin and Technoloy (An ISO 3297: 2007 ertified Oranization) Website: A Novel Three Phase Three Le A/A onverter Usin Nine IGBTS Abdul Quawi 1, Prof. Md Haseeb Khan 2 Asst. Professor Departent of, Alhabeeb ollee of nineerin and Technoloy, Hyderabad, Telanana, India 1 Professor, Departent of lectrical nineerin, Muffakha Jah ollee of nineerin and Technoloy, Hyderabad, Telanana, India 2 ABSTRAT: This paper proposes a three-phase nine-switch A/A converter topoloy. This converter features sinusoidal inputs and outputs, unity input power factor, and ore iportantly, low anufacturin cost due to its reduced nuber of active switches. The operatin principle of the converter is elaborated; its odulation schees are discussed. Siulated seiconductor loss analysis and coparison with the back-to-back two-level voltae source converter are presented. The ost popular confiuration uses voltae source inverter with a diode rectifier as a front end for adjustable speed drives, uninterruptible power supplies and other industrial applications. The back to back two level voltae source converter requires a relatively hih nuber (12)of active switches such as insulated ate bipolar transistors(igbts).it also needs a dc-link capacitor that is responsible for a liited life span and increased cost. To reduce the device count and iniized/eliinate a dc-capacitor filter, various converter topoloies have been proposed with the help of MATLAB / SIMULINK.. KYWORDS: A/A converter, pulse width odulation (PWM), reduced switch count topoloy. I. INTRODUTION THR-PHAS ac/dc/ac and ac/ac converters with variable frequency (VF) and variable voltae operation have found wide applications in the industry. The ost popular confiuration uses voltae source inverter (VSI) with a diode rectifier as the front end for adjustable speed drives (ASDs), uninterruptible power supplies (UPS), and other industrial applications. This confiuration features low cost and reliable operation due to the use of a diode rectifier, but it enerates hihly distorted input line currents and does not have reenerative or dynaic brakin capability. These probles can be itiated by usin a back-to back two-level voltae source converter (B2B 2L-VS), shown in Fi.1.1, where a pulse width odulation (PWM) voltae source rectifier is used to replace the diode rectifier. opyriht to IJIRST DOI: /IJIRST

2 nineerin and Technoloy (An ISO 3297: 2007 ertified Oranization) Website: Fiure 1.1: Back to Back two level Voltae Source converter In addition, cobined use of dc idpoint connection and phase le sharin has been proposed in, where only four les are needed to perfor three-phase ac to ac conversion with bidirectional power flow and power factor control. Althouh all the earlier references achieve the oal of reducin the nuber of switches and thus reducin the cost, they unexceptionally have liits or involve coplex control due to their unbalanced topoloical structure. For unidirectional applications, diodes can be used in place of active switches in the rectifier part, such as the VINNA rectifier, threephase three-switch buck-type rectifier, and three-phase three-switch two-level rectifier. These converters ay also be rearded as topoloies with a saved nuber of switches, despite their eployent of a lare nuber of diodes. Unlike VSs that inevitably require the dc-link stae, the atrix converter presents a radical chane in topoloy and directly converts a fixed ac input voltae to an adjustable ac output voltae. It features sinusoidal input output, controllable power factor, and is capable of bidirectional enery transfer fro the supply to the load or vice versa. Since there is no dc link circuit, the dc capacitor in the VS is not necessary here, leadin to cost reduction as well as iproved reliability and lonevity. However, the conventional atrix converter (M) norally requires 18 active switches and its switchin schee is coplex. The hih seiconductor cost and coplex control have ade this topoloy less attractive. Siilar to the situation of VSs, efforts to reduce the nuber of active switches for a atrix converter have been ade in recent publications, where a couple of topoloical variants such as the sparse atrix converter (SM) were proposed. The SM provides equivalent functionality to the M. It eploys 15 switches with the seiconductor cost still hiher than that of the B2B 2 L-VS. In this project, a novel one-stae three-phase ac/ac converter topoloy is proposed. Different fro all other existin topoloies, this converter has only three les with only nine active switches for bidirectional ac/ac power conversion. opyriht to IJIRST DOI: /IJIRST

3 nineerin and Technoloy (An ISO 3297: 2007 ertified Oranization) Website: II. PROPOSD TOPOLOGY A. THR PHAS NIN SWITH A/A ONVRTR Fiure 2.1:Three phase nine switch converter Fi. 2.1 shows the proposed three-phase nine-switch converter topoloy. This converter has only three les with three switches installed on each of the. The novelty herein is that the iddle switch in each individual le is shared by both the rectifier and the inverter, thereby reducin the switch count by 33% and 50% in coparison to the B2B 2L- VS and M, respectively. The input power is delivered to the output partially throuh the iddle three switches and partially throuh a quasi-dc-link circuit. For the convenience of discussion, we can consider that the rectifier of the nine-switch converter is coposed of the top three and iddle three switches, whereas the inverter consists of the iddle three and botto three switches. The converter has two odes of operation: 1) constant frequency (F) ode, where the output frequency of the inverter is constant and also the sae as that of the utility supply, while the inverter output voltae is adjustable; and 2) VF ode, where both anitude and frequency of the inverter output voltae are adjustable. The F-ode operation is particularly suitable for applications in UPS, whereas the VF ode can be applied to variable-speed drives by switches S1 and S2 in the rectifier, whereas the inverter le voltae vxn can be controlled by S3 and S4 in the inverter. This eans that the rectifier and inverter le voltaes can be controlled independently. The B2B 2L-VS has four switchin states per phase, as defined in Table I. For the nine-switch topoloy, the control of the input and output voltaes has to be accoplished throuh the three switches on each le. Because the iddle switches are shared by the rectifier and inverter, the proposed converter has only three switchin states per phase, as listed in Table I. It can be observed that switchin state 4 for the B2B 2L-VS does not exist in the nine-switch converter, which iplies that the inverter le voltae vxn cannot be hiher than the rectifier le voltae van at any instant. This is, in fact, the ain constraint for opyriht to IJIRST DOI: /IJIRST

4 nineerin and Technoloy (An ISO 3297: 2007 ertified Oranization) Website: the switchin schee desin of the nine-switch converter. arrier-based continuous PWM schees for odulatin the 2L-VS, such as sinusoidal PWM (SPWM), space vector PWM (SVPWM), and third-haronic injection PWM(THIPWM), are well established in the literature [15]. The principles of these ethods can all be applied to the nine-switch converter but a little odification would be necessary, because when desinin the switchin pattern for the nine-switch converter, the switchin constraint discussed earlier ust be satisfied. Fi. 2.2 illustrates the eneralized carrier-based odulation schee in a sinle switchin period for the nine-switch converter. The rectifier odulatin wave vr and the inverter odulatin wave vi are arraned such that vr is not lower than vi at any instant of tie. These two odulatin wavefors are copared with a coon trianular carrier vc. The enerated rectifier and inverter le voltaes van and vxn are also shown in the fiure. This arraneent uarantees that switch state 4 in the B2B 2L-VS is eliinated here for the nine-switch converter. TABL I SWITHING STATS AND ONVRTR LG VOLTAGS B. MODULATION SHM FOR F-MOD OPRATION Takin SPWM as an exaple, Fi. 2.2 illustrates the odified schee for F-ode operation, where r and i are the rectifier and inverter odulation indexes (defined as the peak-to-peak anitude of the sinusoid divided by the peak-to-peak anitude of the carrier), respectively. The difference between this schee and the traditional SPWM for 2L-VS is that here the odulatin waves of the rectifier (solid line) and the inverter (dashed line) are placed in a sinle dc plane and copared to a coon trianular carrier wave. The ate sinals are enerated at the wavefors intersections with the carrier. To prevent the odulatin waves fro intersectin each other, the rectifier s odulatin waves are lifted to the top of the dc plane whereas the inverter s are pushed to the botto by addin proper dc offsets. In this way, the switchin constraint of the nine-switch converter can be satisfied. In practice, the rectifier side odulation can be synchronized to the rid via a phase-locked loop (PLL) The freedos of choosin its odulation index r and firin anle α between the odulatin wave and the rid can be eployed to control the dc voltae and the input power factor opyriht to IJIRST DOI: /IJIRST

5 nineerin and Technoloy (An ISO 3297: 2007 ertified Oranization) Website: Fiure 2.2: Pw wave for eneration,where switichin state 4 B2B 2L-VS is eliinated.. The inverter-side odulation index i can be freely selected to adjust the output anitude. If the inverter s odulatin wave is set in phase with the rectifier s, as in the case shown in Fi. 2.2, both the rectifier and inverter s odulation indexes can siultaneously reach a axiu of unity.. MODULATION SHM FOR VF-MOD OPRATION Fi. 2.3 shows the SPWM odulation schee for the VF ode of operation. In this case, the inverter s odulation index and Fi.2.3. SPWM schee for VF-ode operation. Fi Rectifier input voltae wavefor, spectru, and THD. Fiure 2.3:. SPWM Schee for VF-Mode operation. phase anle can both be adjusted independently fro the rectifier s. In order to satisfy the switchin constraint discussed earlier, the su of the two odulation indexes r and i of the rectifier and inverter ust not exceed 1. For atchin the input and output ratins, we liit both of their axius to 0.5. It can be observed fro the fiure that both the rectifier and inverter s odulatin waves can only be adjusted within half of the carrier s anitude (which represents the dc voltae); therefore, the dc voltae vd of the converter is twice as hih as the rated dc voltae of a B2B 2L-VS with the sae ac ratins. This is different fro the situation of the F ode with identical input and output phases, in which the dc voltae of the converter can be tihtly controlled and aintained at around its rated value. opyriht to IJIRST DOI: /IJIRST

6 nineerin and Technoloy (An ISO 3297: 2007 ertified Oranization) Website: Fiure 2.4: Rectifier input voltae wavefors Fiure 2.5: Siulated wavefors of the rectifier and inverter (VF-ode operation). (a) Rectifier Input wavefors at 60 Hz.(b) Inverter output wavefors at 30 Hz. It should be pointed out that althouh the added dc offsets uarantee that the instant value of vr is always hiher than that of vi, they are of zero sequence in the three phases and have no effect on the input/output ac anitudes. In fact, opyriht to IJIRST DOI: /IJIRST

7 nineerin and Technoloy (An ISO 3297: 2007 ertified Oranization) Website: if the inverter s odulation index is selected to be hiher than the rectifier s, e.., i = 0.5 and r = 0.2, the fundaental coponent of the inverter output voltae vxy will be hiher than that of the rectifier input voltae vab. III.SIMULATION RSULTS onventional back to back converter 1 onn 1 s1 s7 s2 s8 s3 s9 A B Three -Phase Source load s4 s10 s5 s11 s6 s12 1 Out 1 50/3Hz syste Input voltae = 415 volts Output voltae with 50 Hz opyriht to IJIRST DOI: /IJIRST

8 ISSN(Online) : nineerin and Technoloy (An ISO 3297: 2007 ertified Oranization) Website: Proposed circuit of nine switch ac/ac converter Scope 4 Discrete, Scope 3 Ts = 5e-005 s powerui i + - Io S1 S4 S7 VR LR A Vabc Iabc B a Scope 2 VY VB LB LY Scope 1 b c Three -Phase V-I Measureent 1 d + v - Vo Scope S2 S5 S8 PWM Generator Three -Phase V-I Measureent Pulses Vabc Iabc a b c A B S3 S6 S9 Input frequency = 50 Hz Output frequency = 100 Hz IV. ONLUSION A nine switch PWM ac/ac converter topoloy was proposed in this project. The topoloy uses only nine IGBT devices for ac to ac conversion throuh a quasi dc-link circuit. opared with the conventional back-to-back PWM VS usin 12 switches and the atrix converter that uses 18, the nuber of switches in the proposed converter is reduced by 33% and 50% respectively. The proposed converter features sinusoidal inputs and outputs, unity input power factor, and low anufacturin cost. The operatin principle of the converter was elaborated, and odulation schees for constant and variable frequency operations were developed. Siulation results includin a seiconductor loss analysis and coparison were provided, which reveals that the proposed converter, while workin in constant frequency ode, has an overall hiher efficiency than the B2B 2L-VS at the expense of uneven loss distribution. opyriht to IJIRST DOI: /IJIRST

9 nineerin and Technoloy (An ISO 3297: 2007 ertified Oranization) Website: RFRNS [1] B. Wu, Hih-power onverters and A Drives. Piscataway, NJ: I/Wiley, [2] B. Sinh, B. N. Sinh, A. handra, K. Al-Haddad, A. Pandey, and D. P. Kothari, A review of three-phase iproved power quality A D converters, I Trans. Ind. lectron., vol. 51, no. 3, pp , Jun [3] F. Blaabjer, S. Freysson, H. H. Hansen, and S. Hansen, A new optiized space-vector odulation stratey for a coponent-iniized voltae source inverter, I Trans. Power lectron., vol. 12, no.4, pp , Jul [4] R. L. A. Ribeiro,. B. Jacobina,. R.. da Silva, and A. M. N. Lia, A/A converter with four switch three phase structures, in Proc. I PS, 1996, vol. 1, pp [5] K. Gi-Taek and T. A. Lipo, VSI-PWM rectifier/inverter syste with a reduced switch count, I Trans. Ind. Appl., vol. 32, no. 6, pp , Nov./Dec [6] A. Bouscayrol, B. Francois, P. Delarue, and J. Niiranen, ontrol ipleentation of a five-lea A converter to supply a three-phase induction achine, I Trans. Power lectron., vol. 20, no. 1, pp , Jan [7]. B. Jacobina, I. S. de Freitas,. R.. da Silva, A. M. N. Lia, and R. L. A. Ribeiro, Reduced switch count D-link A A five-le converter, I Trans. Power lectron., vol. 21, no. 5, pp , Sep [8]. B. Jacobina, I. S. de Freitas, and A. M. N. Lia, D-link three-phaseto- three-phase four-le converters, I Trans. Ind. lectron., vol. 54,no. 4, pp , Au [9] J. Minibock and J. W. Kolar, Novel concept for ains voltae proportional input current shapin of a VINNA rectifier eliinatin controller ultipliers, I Trans. Ind. lectron., vol. 52, no. 1, pp , Feb [10] T. Nussbauer, M. Bauann, and J.W. Kolar, oprehensive desin of a three-phase three-switch buck-type PWM rectifier, I Trans. Power lectron., vol. 22, no. 2, pp , Mar opyriht to IJIRST DOI: /IJIRST