Performance Study for High Power Density Three- Phase Vienna PFC Rectifier by Using SVPWM Control Method

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1 Perforance Study for High Power Density Three- Phase ienna PFC Rectifier by Using SPWM Control Method Ming Zhang, Bin Li, Lijun Hang, Leon M. Tolbert,Zhengyu Lu College of Electrical Engineering,Zhejiang University Power Electrical Research Institute Hangzhou,China University of Tennessee Electrical Engineering and Coputer Science Knoxville,United States ABSTRACT-This paper presents one non-regenerative front-end three-phase AC/DC power factor correction (PFC) rectifier, which is based on IENNA topology. At first, the space vector pulse width odulation ethod (SPWM) for this converter is theoretical analyzed and the control ethod based in d-q frae is given. Then the DC-link voltage utilization ratio is studied based on the SPWM strategy. The unbalance ability by applying SPWM ethod is theoretical analyzed. The theoretical analysis is well verified by the experiental results. I. INTRODUCTION The non-regenerative three-level boost (ienna-type) rectifiers have received considerable attention since they offer attractive advantages such as: high input power factor, reduced nuber of switching devices, and low device voltage stress [-]. Nowadays, thanks to the developent of seiconductors devices and passive coponents, these rectifiers reain as one of the preferred choices when power density is a design objective, such as vehicular applications, industrial otor drives, power supplies, and etc. [][4] Space ector Modulation (SM), which can increase the utilization of DC voltage and the quality of three-phase current, can solve the proble of unbalanced neutral point voltage by adjusting the effective tie of the redundant short-vectors [4 6]. Actually, the voltage level on the switch side is deterined both by the switch state and the current direction, which eans not all of the switching cobinations (or level states) can be achieved when SM is applied in this topology [7]. However, the reduction of DC voltage and unbalance control ability for this topology can both be greatly increased by applying SPWM ethod, which is very attractive for the industrial application. In Section II, vector odulation strategy for the ienna rectifier is theoretical analyzed based on the basic three-level SM. In section III, the DC-link voltage calculation is This work was supported by National Natural Science Foundation of China ( ). ipleented. In Section I, the unbalance control for the dual-output is analyzed, and further the corresponding ipleentation ethod is obtained. In section, the experiental results are given based on the theoretical analysis. II. ECTOR MODULATION STRATEGY FOR THE IENNA RECTIFIER As shown in Fig., the three wires three phase ienna topology is shown. It consists of six diodes and three bidirectional switching units. S a, S b and S c are the bidirectional switches which are connected to the neutral point of N. Since this type of rectifier is current force coutated, the rectifier pole voltage ( AN, BN, CN ) is deterined by not only the controlled switch state but also the polarity of the ac phase current. For exaple, if the switch S a is off and the phase current i a is positive, the phase leg A is claped to the positive dc link, and therefore, AN is equal to U o /. Siilarly, if S a is off and i a is negative, then AN will be U o /. If the S a is on, phase leg A will be claped to the dc-link neutral point and AN will be zero, regardless of i a polarity. The sae operation principle applies to phase B and phase C. Therefore statespace representation can be obtained, and then used to analyze the syste operation. As shown in Fig., three phase input grid side voltage A, B and C are shown. According to the current forced couted characteristic of ienna converter, there only one zero vector can be realized. Fig. shows the space vector representation of the 5 electrical states of ienna-type rectifiers. These 5 states are a subset of the 7 states of the NPC converter [8][9]. The ain constraint of this topology liits the nuber of active states that can be applied at any given tie to a subset of eight vectors depending on the instantaneous polarity of the converter phase currents. So the vector sector for this converter should be divided according to //$ IEEE 87

2 the synthesized current i αβ in the α-β plane. As shown in Fig., the phase currents of B and C cross zero fro -0 degree to 0 degree. When the equivalent current in α-β plane i αβ is located in this section, then it is naed as vector section I. Correspondingly, the α-β plane is divided into 6 equivalent sectors, as shown in Fig.. Whereas, the calculation tie of each vector should be based on the odulation reference. In reference [], the three-level vectors are equaled to the twolevel vectors, as shown in Fig.4. Therefore, a hexagonal region ade of the vectors of U, U, U 0,U 00,U 06 and U 6, can be used to calculate the activated vector iplantation tie. The hexagonal region can be regarded as a whole two level vector presentation. Corresponding, the total of six possible subsectors exist, {I, II,, I}, which activate six different set of space vectors foring six hexagonal regions. The active states of the vectors equivalently depend on the sector where the phase current vector lies in the α-β plane. O A B C C A C B C C i a i b ic D ap D bp D cp La A Lb B Lc C D an D bn D cn S a,b,c S asb S c i U o+ i N N i R o U o- Fig.Non-regenerative three-level bidirectional-switch IENNA rectifier C C U o U' = U U 0 U' = U U 0 U z = U 0 U 0 ' U r = Iref U 0 () Considering the syetry of the duty for the SPWM ethod, the following equation can be obtained: T c ' TU ' + TU ' = Ur () T c T = T T () Uα = U'cos r Uβ = U'sin r Wherein,. Fro the above equations, T, T and T c can be solved. III. DC-LINK OLTAGE CALCULATION It is supposed that the three-phase grid voltage is as follows, A=sinωt (4) π B =sin ωt π C =sin ωt+ Wherein, is the axiu of the phase voltage. Its corresponding vector in αβ coordinate can be obtained by ref =T abc/αβ *[ ABC ] = e j. So three-phase voltage signal can be replaced by the vector of ref in the the αβ coordinate with / / the aplitude of. Wherein, T abc/αβ =. 0 It is supposed that U o+ =U o- =U o /= dc. Therefore, the following odel can be concluded, dc vao = [ sgn( ia ) sgn( ib ) sgn( ic ) + sb sgn( ib ) + sc sgn( ic ) sa sgn( ia ) ] dc vbo = [ sgn( ib ) sgn( ia ) sgn( ic ) + sa sgn( ia ) + sc sgn( ic ) sb sgn( ib ) ] (5) dc vco = [ sgn( ic ) sgn( ib ) sgn( ia ) + sb sgn( ib ) + sa sgn( ia ) sc sgn( i C )] Fig. Three-phase input voltage It is supposed that the three-phase current are exactly in phase with the three-phase voltage. Due to the syetry of the six sectors, the first sector is used to calculate the ipleentation tie of each vector. As shown in Fig., in the first sector of -0 to 0, the vector of U 0 can realize (0,0,-) due to the polarity of the three phase current shown in Fig.. Correspondingly, (0,-,0) can be realized in the vector U 06. As shown in Fig.4, the hexagonal region of sector I is used to equal the three level vector to two level vector. The following equivalent should be ade [], Wherein, S i (i=a,b,c) is the switching function. When the switch of phase i is on, S i is, otherwise S i is zero. The whole stationary coordinate can be divided into 6 basic sections, as shown in Fig.. It can be obtained that the large vector of U can be expressed as U =( dc 4/)e 0*j. The other 5 basic large vectors U, U, U 4, U 5 and U 6 can be obtained as well. According to the above analysis, the aplitude of U can be 88

3 U 4 [- + 0] U I U 0 U 04 U 0 4 [00 0] I U [0 + +] [+ 0 0] [- + +] 60 [+- -] [- 0 0] [0- -] U 45 [- 0 +] U 00 ß III U [- + -] [-- +] U 5 U 0 III? I U 06 U [0 + -] U 0 [0 + 0] [- 0 -] [0- +] U 56 II U 0 ref U I I U 6 Fig.4 Hexagonal region for of the first Sector obtained as, U =. As shown in Fig., it is dc [+ + 0] [0 0 -] U 05 U 06 [00 +] [+ 0 +] [- - 0] [0-0] U [+ + -] U [+ 0 -] U 6 [+ - 0] [+- +] U 6 supposed the vector of ref belongs to the first section, i.e. - 0 to 0 and the subsection I. Therefore, the adjacent vectors are U, U and U 0, which can be used to synthesize the vector of ref. The ipleentation tie of above three vectors can be obtained as follows [5][6], T = Tccos T c sin Tc T = T c sin T = Tc T c cos Tcsin (6) Then T can be obtained as follows, π π T = Tc sin (7) Fro Eq.(), T should be larger than 0. Therefore, dc can be obtained as follows, dc. So the theoretical inial DC-link voltage is obtained. Due to the switch characteristic of the topology, the converter s dead-tie is reduced copared with the traditional PWM rectifier. So the dead-tie influence can be reduced and the DC-link U 0 II I Fig. Space vectors of three-level converter ß a utilization ratio can be increased without perforance deterioration. I. UNBALANCE CONTROL It is supposed that ref is located in the first section. When (00) works, the current of i N =i a +i b. Due to the direction of three phase current, (i a >0, i b <0 and i c <0), the neutral point N is discharged, correspondingly, U o+ is decreased and U o- is increased. However, when the vector of (0--) works, the neutral point N is charged, correspondingly, U o+ is increased and U o- is decreased. Therefore, U 0 is the redundant vector and it can be used to control the neutral point voltage. As shown in Fig.4, suppose 0.5<<, so ref is located in subsection I, II, and I. It is supposed that the charging and discharging tie for neutral point N is respective r and T -r during every switching period. Therefore, when the vector is located in the subsection I, the total current i N for the neutral point can be obtained as follows, T T T i = i + i = ri + ( T r)( i + i ) d N in out a b c t T 0 = r( i i i ) + T ( i + i ) d T 0 = ( r T ) ia d T 0 a b c b c t t Three phase current is supposed to be: π ib = Isin ωt π ia = Isinωt ic = Isin ωt, +,. It is supposed that the unbalanced load is paralleled connected with C and the unbalanced liitation is to ake the neutral point current be charged, therefore r=t, the current of i N is can be concluded as follows, π π π i + i = I sin+ I cos cos I sin in out ωt ωt + (9) Wherein, is supposed to be 0.748, then fro (6), φ can be obtained, which is π/0. On the other hand, ω=πf, T =φ/πf=/0f, T c =/f s. f is the line frequency and f s is the switching frequency. So finally, the total charged current can be obtained as iin + iout 0.6I. Correspondingly, if ref is located in other subsections, the unbalanced ability by using the SPWM ethod in ienna converter can be concluded. It will be given in the final paper. Fro the above analysis, when ref is located in the first section(-0 to 0 ), the average unbalanced charged current to the neutral point can be obtained as, pi pi pi pi pi pi IN = I / According to the power balance between the input and the (8) 89

4 output, the following relationship can be obtained I ( i+ i) dc = grid. i i = 0.504I Therefore, the unbalance output i and i can be obtained, and the factor of i /i can be used to evaluate the unbalance ability of the control ethod. The relationship of unbalance factor versus the odulation ratio is given in Fig.5. U o+ :50/div U o- :50/div Input voltage:00/div Input current:5a/div 8 Fig.8 Transient response of unbalanced load: tie,0s/div, input=0ac 6 ) Fig.5 Relation of odulation index and the ability of DC-link neutral voltage balancing U oref U o+ +U o- i a i b i c A B PLL? C PI regulator abc/dq i* dref U o+ -U o- i* qref u d u a DQ i d regulator u q dq/aß u ß i q? 0 PI regulator SPWM unbalance factor: f u d + a d a d b d c + + d b d c. EXPERIMENTAL RESULTS The above analysis is verified both by experiental result. The experiental prototype was ipleented in DSP board and whose syste controller is shown in Fig.6. Table. I, Fig.7, Fig.8 and Fig.9 show the experiental results. Fig.7 shows the input voltage and current when the DC output is reduced to 580. Fig.8 gives the transient response when the unbalanced load is paralleled with C. The test condition of Fig.8 is as follows: input voltage is 0AC, total output voltage is 60, the total load is 70.9Ω, unbalance load connected to C is 48.6Ω. This value is the axiu unbalance ability when =0.76, when T is assigned to charging vector for the neutral point. The unbalance control for this converter can be verified for different odulation ratio by theoretical analysis and experients. Fig.9 gives the tested PF value under different power odulation index. During wide odulation index range, the PF value can be larger than 0.998, which proves the advantage of the SM ethod. Table I gives the THD and different haronics coponents of input current at the rated power level for different output voltage. Fig.6 Controller for the syste Input voltage:500/div Fig.9 Relation between odulation index and power factor Input current:5a/div U o =580 Fig.7 Input voltage and current at different output: tie,0s/div TABLE I. INPUT CURRENT HARMONICS ANALYSIS ERSUS U O (INPUT=0AC) U o () THD rd 5 th 7 th Output power(w) %.78%.5%.5% %.0% 0.5% 0.9% %.6% 0.79% 0.%

5 I. CONCLUSIONS This paper presents one non-regenerative front-end three-phase AC/DC power factor correction (PFC) rectifier, which is based on IENNA topology. At first, the space vector pulse width odulation ethod (SPWM) for this converter is theoretical analyzed and the control ethod based in d-q frae is given. Then the DC-link voltage utilization ratio is studied based on the SPWM strategy. The unbalance ability by applying SPWM ethod is theoretical analyzed. Finally, the theoretical analysis is well verified by experiental results. ACKNOWLEDGMENT This work was supported by National Natural Science Foundation of China ( ): Research of the Real-tie Character of Network-controlled Power Electronics Syste. REFERENCES []. J. W. Kolar, H. Ertl, and F. Zach, Design and experiental investigation of a three-phase high power density high efficiency unity power factor PWM (IENNA) rectifier eploying a novel integrated power seiconductor odule, in Conf. IEEE APEC 96, vol., pp. 54-5, Mar []. J. Minibock, and J. Kolar, Coparative theoretical and experiental evaluation of bridge-leg topologies of a three-phase three-level unity power factor rectifier, in Conf. IEEE PESC 0, vol. 4 pp , June 00. []. Rolando Burgos, Rixin Lai, Yunqing Pei, Fei (Fred) Wang, Dushan Boroyevich, and Josep Pou, Space ector Modulator for ienna- Type Rectifiers Based on the Equivalence Between Two- and Three- Level Converters: A Carrier-Based Ipleentation, IEEE TRANSACTIONS ON POWER ELECTRONICS, OL., NO. 4, JULY 008,pp [4]. Rixin Lai, Fei (Fred) Wang, Rolando Burgos, Dushan Boroyevich, etc, Average Modeling and Control Design for IENNA-Type Rectifiers Considering the DC-Link oltage Balance, IEEE TRANSACTIONS ON POWER ELECTRONICS, OL. 4, NO., NOEMBER 009. Pp [5]. M. Malinowski, M. Jasinski, and M. P. Kazierkowski, Siple direct power control of three-phase PWM rectifier using space-vector odulation (DPC-SM), IEEE Trans. Ind. Electron., vol. 5, no., pp ,Apr [6]. D. G. Holes, The significance of zero space vector placeent for carrier-based PWM schees, IEEE Trans. Ind. Appl., vol., no. 5, pp. 9, Sep./Oct [7]. B. P. McGrath, D. G. Holes, and T. Lipo, Optiized space vector switching sequences for ultilevel inverters, IEEE Trans. Power Electron., vol. 8, pp. 9 0,Nov. 00. [8]. G. Carrara, S. Gardella, M. Marchesoni, R. Salutari, and G. Sciutto, A New Multilevel PWM Method: A Theoretical Analysis, IEEE Trans. Power Electron., vol. 7, pp , Jul. 99. [9]. J. K. Steinke, Switching Frequency Optial PWM Control of a Three-Level Inverter, IEEE Trans. Power Electron., vol. 7, pp , Jul